wok-current diff asterisk/stuff/rfc3951.txt @ rev 23176

openvpn: add conf2opvn (again)
author Pascal Bellard <pascal.bellard@slitaz.org>
date Wed Mar 18 11:14:38 2020 +0100 (2020-03-18)
parents
children
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     1.9 +
    1.10 +Network Working Group                                        S. Andersen
    1.11 +Request for Comments: 3951                            Aalborg University
    1.12 +Category: Experimental                                          A. Duric
    1.13 +                                                                   Telio
    1.14 +                                                               H. Astrom
    1.15 +                                                                R. Hagen
    1.16 +                                                               W. Kleijn
    1.17 +                                                               J. Linden
    1.18 +                                                         Global IP Sound
    1.19 +                                                           December 2004
    1.20 +
    1.21 +
    1.22 +                   Internet Low Bit Rate Codec (iLBC)
    1.23 +
    1.24 +Status of this Memo
    1.25 +
    1.26 +   This memo defines an Experimental Protocol for the Internet
    1.27 +   community.  It does not specify an Internet standard of any kind.
    1.28 +   Discussion and suggestions for improvement are requested.
    1.29 +   Distribution of this memo is unlimited.
    1.30 +
    1.31 +Copyright Notice
    1.32 +
    1.33 +   Copyright (C) The Internet Society (2004).
    1.34 +
    1.35 +Abstract
    1.36 +
    1.37 +   This document specifies a speech codec suitable for robust voice
    1.38 +   communication over IP.  The codec is developed by Global IP Sound
    1.39 +   (GIPS).  It is designed for narrow band speech and results in a
    1.40 +   payload bit rate of 13.33 kbit/s for 30 ms frames and 15.20 kbit/s
    1.41 +   for 20 ms frames.  The codec enables graceful speech quality
    1.42 +   degradation in the case of lost frames, which occurs in connection
    1.43 +   with lost or delayed IP packets.
    1.44 +
    1.45 +
    1.46 +
    1.47 +
    1.48 +
    1.49 +
    1.50 +
    1.51 +
    1.52 +
    1.53 +
    1.54 +
    1.55 +
    1.56 +
    1.57 +
    1.58 +
    1.59 +
    1.60 +
    1.61 +Andersen, et al.              Experimental                      [Page 1]
    1.62 +
    1.63 +RFC 3951              Internet Low Bit Rate Codec          December 2004
    1.64 +
    1.65 +
    1.66 +Table of Contents
    1.67 +
    1.68 +   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
    1.69 +   2.  Outline of the Codec . . . . . . . . . . . . . . . . . . . . .  5
    1.70 +       2.1.  Encoder. . . . . . . . . . . . . . . . . . . . . . . . .  5
    1.71 +       2.2.  Decoder. . . . . . . . . . . . . . . . . . . . . . . . .  7
    1.72 +   3.  Encoder Principles . . . . . . . . . . . . . . . . . . . . . .  7
    1.73 +       3.1.  Pre-processing . . . . . . . . . . . . . . . . . . . . .  9
    1.74 +       3.2.  LPC Analysis and Quantization. . . . . . . . . . . . . .  9
    1.75 +             3.2.1.  Computation of Autocorrelation Coefficients. . . 10
    1.76 +             3.2.2.  Computation of LPC Coefficients. . . . . . . . . 11
    1.77 +             3.2.3.  Computation of LSF Coefficients from LPC
    1.78 +                     Coefficients . . . . . . . . . . . . . . . . . . 11
    1.79 +             3.2.4.  Quantization of LSF Coefficients . . . . . . . . 12
    1.80 +             3.2.5.  Stability Check of LSF Coefficients. . . . . . . 13
    1.81 +             3.2.6.  Interpolation of LSF Coefficients. . . . . . . . 13
    1.82 +             3.2.7.  LPC Analysis and Quantization for 20 ms Frames . 14
    1.83 +       3.3.  Calculation of the Residual. . . . . . . . . . . . . . . 15
    1.84 +       3.4.  Perceptual Weighting Filter. . . . . . . . . . . . . . . 15
    1.85 +       3.5.  Start State Encoder. . . . . . . . . . . . . . . . . . . 15
    1.86 +             3.5.1.  Start State Estimation . . . . . . . . . . . . . 16
    1.87 +             3.5.2.  All-Pass Filtering and Scale Quantization. . . . 17
    1.88 +             3.5.3.  Scalar Quantization. . . . . . . . . . . . . . . 18
    1.89 +       3.6.  Encoding the Remaining Samples . . . . . . . . . . . . . 19
    1.90 +             3.6.1.  Codebook Memory. . . . . . . . . . . . . . . . . 20
    1.91 +             3.6.2.  Perceptual Weighting of Codebook Memory
    1.92 +                     and Target . . . . . . . . . . . . . . . . . . . 22
    1.93 +             3.6.3.  Codebook Creation. . . . . . . . . . . . . . . . 23
    1.94 +                     3.6.3.1. Creation of a Base Codebook . . . . . . 23
    1.95 +                     3.6.3.2. Codebook Expansion. . . . . . . . . . . 24
    1.96 +                     3.6.3.3. Codebook Augmentation . . . . . . . . . 24
    1.97 +             3.6.4.  Codebook Search. . . . . . . . . . . . . . . . . 26
    1.98 +                     3.6.4.1. Codebook Search at Each Stage . . . . . 26
    1.99 +                     3.6.4.2. Gain Quantization at Each Stage . . . . 27
   1.100 +                     3.6.4.3. Preparation of Target for Next Stage. . 28
   1.101 +       3.7.  Gain Correction Encoding . . . . . . . . . . . . . . . . 28
   1.102 +       3.8.  Bitstream Definition . . . . . . . . . . . . . . . . . . 29
   1.103 +   4.  Decoder Principles . . . . . . . . . . . . . . . . . . . . . . 32
   1.104 +       4.1.  LPC Filter Reconstruction. . . . . . . . . . . . . . . . 33
   1.105 +       4.2.  Start State Reconstruction . . . . . . . . . . . . . . . 33
   1.106 +       4.3.  Excitation Decoding Loop . . . . . . . . . . . . . . . . 34
   1.107 +       4.4.  Multistage Adaptive Codebook Decoding. . . . . . . . . . 35
   1.108 +             4.4.1.  Construction of the Decoded Excitation Signal. . 35
   1.109 +       4.5.  Packet Loss Concealment. . . . . . . . . . . . . . . . . 35
   1.110 +             4.5.1.  Block Received Correctly and Previous Block
   1.111 +                     Also Received. . . . . . . . . . . . . . . . . . 35
   1.112 +             4.5.2.  Block Not Received . . . . . . . . . . . . . . . 36
   1.113 +
   1.114 +
   1.115 +
   1.116 +
   1.117 +Andersen, et al.              Experimental                      [Page 2]
   1.118 +
   1.119 +RFC 3951              Internet Low Bit Rate Codec          December 2004
   1.120 +
   1.121 +
   1.122 +             4.5.3.  Block Received Correctly When Previous Block
   1.123 +                     Not Received . . . . . . . . . . . . . . . . . . 36
   1.124 +       4.6.  Enhancement. . . . . . . . . . . . . . . . . . . . . . . 37
   1.125 +             4.6.1.  Estimating the Pitch . . . . . . . . . . . . . . 39
   1.126 +             4.6.2.  Determination of the Pitch-Synchronous
   1.127 +                     Sequences. . . . . . . . . . . . . . . . . . . . 39
   1.128 +             4.6.3.  Calculation of the Smoothed Excitation . . . . . 41
   1.129 +             4.6.4.  Enhancer Criterion . . . . . . . . . . . . . . . 41
   1.130 +             4.6.5.  Enhancing the Excitation . . . . . . . . . . . . 42
   1.131 +       4.7.  Synthesis Filtering. . . . . . . . . . . . . . . . . . . 43
   1.132 +       4.8.  Post Filtering . . . . . . . . . . . . . . . . . . . . . 43
   1.133 +   5.  Security Considerations. . . . . . . . . . . . . . . . . . . . 43
   1.134 +   6.  Evaluation of the iLBC Implementations . . . . . . . . . . . . 43
   1.135 +   7.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 43
   1.136 +       7.1.  Normative References . . . . . . . . . . . . . . . . . . 43
   1.137 +       7.2.  Informative References . . . . . . . . . . . . . . . . . 44
   1.138 +   8.  ACKNOWLEDGEMENTS . . . . . . . . . . . . . . . . . . . . . . . 44
   1.139 +   APPENDIX A: Reference Implementation . . . . . . . . . . . . . . . 45
   1.140 +       A.1.  iLBC_test.c. . . . . . . . . . . . . . . . . . . . . . . 46
   1.141 +       A.2   iLBC_encode.h. . . . . . . . . . . . . . . . . . . . . . 52
   1.142 +       A.3.  iLBC_encode.c. . . . . . . . . . . . . . . . . . . . . . 53
   1.143 +       A.4.  iLBC_decode.h. . . . . . . . . . . . . . . . . . . . . . 63
   1.144 +       A.5.  iLBC_decode.c. . . . . . . . . . . . . . . . . . . . . . 64
   1.145 +       A.6.  iLBC_define.h. . . . . . . . . . . . . . . . . . . . . . 76
   1.146 +       A.7.  constants.h. . . . . . . . . . . . . . . . . . . . . . . 80
   1.147 +       A.8.  constants.c. . . . . . . . . . . . . . . . . . . . . . . 82
   1.148 +       A.9.  anaFilter.h. . . . . . . . . . . . . . . . . . . . . . . 96
   1.149 +       A.10. anaFilter.c. . . . . . . . . . . . . . . . . . . . . . . 97
   1.150 +       A.11. createCB.h . . . . . . . . . . . . . . . . . . . . . . . 98
   1.151 +       A.12. createCB.c . . . . . . . . . . . . . . . . . . . . . . . 99
   1.152 +       A.13. doCPLC.h . . . . . . . . . . . . . . . . . . . . . . . .104
   1.153 +       A.14. doCPLC.c . . . . . . . . . . . . . . . . . . . . . . . .104
   1.154 +       A.15. enhancer.h . . . . . . . . . . . . . . . . . . . . . . .109
   1.155 +       A.16. enhancer.c . . . . . . . . . . . . . . . . . . . . . . .110
   1.156 +       A.17. filter.h . . . . . . . . . . . . . . . . . . . . . . . .123
   1.157 +       A.18. filter.c . . . . . . . . . . . . . . . . . . . . . . . .125
   1.158 +       A.19. FrameClassify.h. . . . . . . . . . . . . . . . . . . . .128
   1.159 +       A.20. FrameClassify.c. . . . . . . . . . . . . . . . . . . . .129
   1.160 +       A.21. gainquant.h. . . . . . . . . . . . . . . . . . . . . . .131
   1.161 +       A.22. gainquant.c. . . . . . . . . . . . . . . . . . . . . . .131
   1.162 +       A.23. getCBvec.h . . . . . . . . . . . . . . . . . . . . . . .134
   1.163 +       A.24. getCBvec.c . . . . . . . . . . . . . . . . . . . . . . .134
   1.164 +       A.25. helpfun.h. . . . . . . . . . . . . . . . . . . . . . . .138
   1.165 +       A.26. helpfun.c. . . . . . . . . . . . . . . . . . . . . . . .140
   1.166 +       A.27. hpInput.h. . . . . . . . . . . . . . . . . . . . . . . .146
   1.167 +       A.28. hpInput.c. . . . . . . . . . . . . . . . . . . . . . . .146
   1.168 +       A.29. hpOutput.h . . . . . . . . . . . . . . . . . . . . . . .148
   1.169 +       A.30. hpOutput.c . . . . . . . . . . . . . . . . . . . . . . .148
   1.170 +
   1.171 +
   1.172 +
   1.173 +Andersen, et al.              Experimental                      [Page 3]
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   1.175 +RFC 3951              Internet Low Bit Rate Codec          December 2004
   1.176 +
   1.177 +
   1.178 +       A.31. iCBConstruct.h . . . . . . . . . . . . . . . . . . . . .149
   1.179 +       A.32. iCBConstruct.c . . . . . . . . . . . . . . . . . . . . .150
   1.180 +       A.33. iCBSearch.h. . . . . . . . . . . . . . . . . . . . . . .152
   1.181 +       A.34. iCBSearch.c. . . . . . . . . . . . . . . . . . . . . . .153
   1.182 +       A.35. LPCdecode.h. . . . . . . . . . . . . . . . . . . . . . .163
   1.183 +       A.36. LPCdecode.c. . . . . . . . . . . . . . . . . . . . . . .164
   1.184 +       A.37. LPCencode.h. . . . . . . . . . . . . . . . . . . . . . .167
   1.185 +       A.38. LPCencode.c. . . . . . . . . . . . . . . . . . . . . . .167
   1.186 +       A.39. lsf.h. . . . . . . . . . . . . . . . . . . . . . . . . .172
   1.187 +       A.40. lsf.c. . . . . . . . . . . . . . . . . . . . . . . . . .172
   1.188 +       A.41. packing.h. . . . . . . . . . . . . . . . . . . . . . . .178
   1.189 +       A.42. packing.c. . . . . . . . . . . . . . . . . . . . . . . .179
   1.190 +       A.43. StateConstructW.h. . . . . . . . . . . . . . . . . . . .182
   1.191 +       A.44. StateConstructW.c. . . . . . . . . . . . . . . . . . . .183
   1.192 +       A.45. StateSearchW.h . . . . . . . . . . . . . . . . . . . . .185
   1.193 +       A.46. StateSearchW.c . . . . . . . . . . . . . . . . . . . . .186
   1.194 +       A.47. syntFilter.h . . . . . . . . . . . . . . . . . . . . . .190
   1.195 +       A.48. syntFilter.c . . . . . . . . . . . . . . . . . . . . . .190
   1.196 +   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . .192
   1.197 +   Full Copyright Statement . . . . . . . . . . . . . . . . . . . . .194
   1.198 +
   1.199 +1.  Introduction
   1.200 +
   1.201 +   This document contains the description of an algorithm for the coding
   1.202 +   of speech signals sampled at 8 kHz.  The algorithm, called iLBC, uses
   1.203 +   a block-independent linear-predictive coding (LPC) algorithm and has
   1.204 +   support for two basic frame lengths: 20 ms at 15.2 kbit/s and 30 ms
   1.205 +   at 13.33 kbit/s.  When the codec operates at block lengths of 20 ms,
   1.206 +   it produces 304 bits per block, which SHOULD be packetized as in [1].
   1.207 +   Similarly, for block lengths of 30 ms it produces 400 bits per block,
   1.208 +   which SHOULD be packetized as in [1].  The two modes for the
   1.209 +   different frame sizes operate in a very similar way.  When they
   1.210 +   differ it is explicitly stated in the text, usually with the notation
   1.211 +   x/y, where x refers to the 20 ms mode and y refers to the 30 ms mode.
   1.212 +
   1.213 +   The described algorithm results in a speech coding system with a
   1.214 +   controlled response to packet losses similar to what is known from
   1.215 +   pulse code modulation (PCM) with packet loss concealment (PLC), such
   1.216 +   as the ITU-T G.711 standard [4], which operates at a fixed bit rate
   1.217 +   of 64 kbit/s.  At the same time, the described algorithm enables
   1.218 +   fixed bit rate coding with a quality-versus-bit rate tradeoff close
   1.219 +   to state-of-the-art.  A suitable RTP payload format for the iLBC
   1.220 +   codec is specified in [1].
   1.221 +
   1.222 +   Some of the applications for which this coder is suitable are real
   1.223 +   time communications such as telephony and videoconferencing,
   1.224 +   streaming audio, archival, and messaging.
   1.225 +
   1.226 +
   1.227 +
   1.228 +
   1.229 +Andersen, et al.              Experimental                      [Page 4]
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   1.231 +RFC 3951              Internet Low Bit Rate Codec          December 2004
   1.232 +
   1.233 +
   1.234 +   Cable Television Laboratories (CableLabs(R)) has adopted iLBC as a
   1.235 +   mandatory PacketCable(TM) audio codec standard for VoIP over Cable
   1.236 +   applications [3].
   1.237 +
   1.238 +   This document is organized as follows.  Section 2 gives a brief
   1.239 +   outline of the codec.  The specific encoder and decoder algorithms
   1.240 +   are explained in sections 3 and 4, respectively.  Appendix A provides
   1.241 +   a c-code reference implementation.
   1.242 +
   1.243 +   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   1.244 +   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   1.245 +   document are to be interpreted as described in BCP 14, RFC 2119 [2].
   1.246 +
   1.247 +2.  Outline of the Codec
   1.248 +
   1.249 +   The codec consists of an encoder and a decoder as described in
   1.250 +   sections 2.1 and 2.2, respectively.
   1.251 +
   1.252 +   The essence of the codec is LPC and block-based coding of the LPC
   1.253 +   residual signal.  For each 160/240 (20 ms/30 ms) sample block, the
   1.254 +   following major steps are performed: A set of LPC filters are
   1.255 +   computed, and the speech signal is filtered through them to produce
   1.256 +   the residual signal.  The codec uses scalar quantization of the
   1.257 +   dominant part, in terms of energy, of the residual signal for the
   1.258 +   block.  The dominant state is of length 57/58 (20 ms/30 ms) samples
   1.259 +   and forms a start state for dynamic codebooks constructed from the
   1.260 +   already coded parts of the residual signal.  These dynamic codebooks
   1.261 +   are used to code the remaining parts of the residual signal.  By this
   1.262 +   method, coding independence between blocks is achieved, resulting in
   1.263 +   elimination of propagation of perceptual degradations due to packet
   1.264 +   loss.  The method facilitates high-quality packet loss concealment
   1.265 +   (PLC).
   1.266 +
   1.267 +2.1.  Encoder
   1.268 +
   1.269 +   The input to the encoder SHOULD be 16 bit uniform PCM sampled at 8
   1.270 +   kHz.  It SHOULD be partitioned into blocks of BLOCKL=160/240 samples
   1.271 +   for the 20/30 ms frame size.  Each block is divided into NSUB=4/6
   1.272 +   consecutive sub-blocks of SUBL=40 samples each.  For 30 ms frame
   1.273 +   size, the encoder performs two LPC_FILTERORDER=10 linear-predictive
   1.274 +   coding (LPC) analyses.  The first analysis applies a smooth window
   1.275 +   centered over the second sub-block and extending to the middle of the
   1.276 +   fifth sub-block.  The second LPC analysis applies a smooth asymmetric
   1.277 +   window centered over the fifth sub-block and extending to the end of
   1.278 +   the sixth sub-block.  For 20 ms frame size, one LPC_FILTERORDER=10
   1.279 +   linear-predictive coding (LPC) analysis is performed with a smooth
   1.280 +   window centered over the third sub-frame.
   1.281 +
   1.282 +
   1.283 +
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   1.287 +RFC 3951              Internet Low Bit Rate Codec          December 2004
   1.288 +
   1.289 +
   1.290 +   For each of the LPC analyses, a set of line-spectral frequencies
   1.291 +   (LSFs) are obtained, quantized, and interpolated to obtain LSF
   1.292 +   coefficients for each sub-block.  Subsequently, the LPC residual is
   1.293 +   computed by using the quantized and interpolated LPC analysis
   1.294 +   filters.
   1.295 +
   1.296 +   The two consecutive sub-blocks of the residual exhibiting the maximal
   1.297 +   weighted energy are identified.  Within these two sub-blocks, the
   1.298 +   start state (segment) is selected from two choices: the first 57/58
   1.299 +   samples or the last 57/58 samples of the two consecutive sub-blocks.
   1.300 +   The selected segment is the one of higher energy.  The start state is
   1.301 +   encoded with scalar quantization.
   1.302 +
   1.303 +   A dynamic codebook encoding procedure is used to encode 1) the 23/22
   1.304 +   (20 ms/30 ms) remaining samples in the two sub-blocks containing the
   1.305 +   start state; 2) the sub-blocks after the start state in time; and 3)
   1.306 +   the sub-blocks before the start state in time.  Thus, the encoding
   1.307 +   target can be either the 23/22 samples remaining of the two sub-
   1.308 +   blocks containing the start state or a 40-sample sub-block.  This
   1.309 +   target can consist of samples indexed forward in time or backward in
   1.310 +   time, depending on the location of the start state.
   1.311 +
   1.312 +   The codebook coding is based on an adaptive codebook built from a
   1.313 +   codebook memory that contains decoded LPC excitation samples from the
   1.314 +   already encoded part of the block.  These samples are indexed in the
   1.315 +   same time direction as the target vector, ending at the sample
   1.316 +   instant prior to the first sample instant represented in the target
   1.317 +   vector.  The codebook is used in CB_NSTAGES=3 stages in a successive
   1.318 +   refinement approach, and the resulting three code vector gains are
   1.319 +   encoded with 5-, 4-, and 3-bit scalar quantization, respectively.
   1.320 +
   1.321 +   The codebook search method employs noise shaping derived from the LPC
   1.322 +   filters, and the main decision criterion is to minimize the squared
   1.323 +   error between the target vector and the code vectors.  Each code
   1.324 +   vector in this codebook comes from one of CB_EXPAND=2 codebook
   1.325 +   sections.  The first section is filled with delayed, already encoded
   1.326 +   residual vectors.  The code vectors of the second codebook section
   1.327 +   are constructed by predefined linear combinations of vectors in the
   1.328 +   first section of the codebook.
   1.329 +
   1.330 +   As codebook encoding with squared-error matching is known to produce
   1.331 +   a coded signal of less power than does the scalar quantized start
   1.332 +   state signal, a gain re-scaling method is implemented by a refined
   1.333 +   search for a better set of codebook gains in terms of power matching
   1.334 +   after encoding.  This is done by searching for a higher value of the
   1.335 +   gain factor for the first stage codebook, as the subsequent stage
   1.336 +   codebook gains are scaled by the first stage gain.
   1.337 +
   1.338 +
   1.339 +
   1.340 +
   1.341 +Andersen, et al.              Experimental                      [Page 6]
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   1.343 +RFC 3951              Internet Low Bit Rate Codec          December 2004
   1.344 +
   1.345 +
   1.346 +2.2.  Decoder
   1.347 +
   1.348 +   Typically for packet communications, a jitter buffer placed at the
   1.349 +   receiving end decides whether the packet containing an encoded signal
   1.350 +   block has been received or lost.  This logic is not part of the codec
   1.351 +   described here.  For each encoded signal block received the decoder
   1.352 +   performs a decoding.  For each lost signal block, the decoder
   1.353 +   performs a PLC operation.
   1.354 +
   1.355 +   The decoding for each block starts by decoding and interpolating the
   1.356 +   LPC coefficients.  Subsequently the start state is decoded.
   1.357 +
   1.358 +   For codebook-encoded segments, each segment is decoded by
   1.359 +   constructing the three code vectors given by the received codebook
   1.360 +   indices in the same way that the code vectors were constructed in the
   1.361 +   encoder.  The three gain factors are also decoded and the resulting
   1.362 +   decoded signal is given by the sum of the three codebook vectors
   1.363 +   scaled with respective gain.
   1.364 +
   1.365 +   An enhancement algorithm is applied to the reconstructed excitation
   1.366 +   signal.  This enhancement augments the periodicity of voiced speech
   1.367 +   regions.  The enhancement is optimized under the constraint that the
   1.368 +   modification signal (defined as the difference between the enhanced
   1.369 +   excitation and the excitation signal prior to enhancement) has a
   1.370 +   short-time energy that does not exceed a preset fraction of the
   1.371 +   short-time energy of the excitation signal prior to enhancement.
   1.372 +
   1.373 +   A packet loss concealment (PLC) operation is easily embedded in the
   1.374 +   decoder.  The PLC operation can, e.g., be based on repeating LPC
   1.375 +   filters and obtaining the LPC residual signal by using a long-term
   1.376 +   prediction estimate from previous residual blocks.
   1.377 +
   1.378 +3.  Encoder Principles
   1.379 +
   1.380 +   The following block diagram is an overview of all the components of
   1.381 +   the iLBC encoding procedure.  The description of the blocks contains
   1.382 +   references to the section where that particular procedure is further
   1.383 +   described.
   1.384 +
   1.385 +
   1.386 +
   1.387 +
   1.388 +
   1.389 +
   1.390 +
   1.391 +
   1.392 +
   1.393 +
   1.394 +
   1.395 +
   1.396 +
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   1.399 +RFC 3951              Internet Low Bit Rate Codec          December 2004
   1.400 +
   1.401 +
   1.402 +             +-----------+    +---------+    +---------+
   1.403 +   speech -> | 1. Pre P  | -> | 2. LPC  | -> | 3. Ana  | ->
   1.404 +             +-----------+    +---------+    +---------+
   1.405 +
   1.406 +             +---------------+   +--------------+
   1.407 +          -> | 4. Start Sel  | ->| 5. Scalar Qu | ->
   1.408 +             +---------------+   +--------------+
   1.409 +
   1.410 +             +--------------+    +---------------+
   1.411 +          -> |6. CB Search  | -> | 7. Packetize  | -> payload
   1.412 +          |  +--------------+ |  +---------------+
   1.413 +          ----<---------<------
   1.414 +       sub-frame 0..2/4 (20 ms/30 ms)
   1.415 +
   1.416 +   Figure 3.1. Flow chart of the iLBC encoder
   1.417 +
   1.418 +   1. Pre-process speech with a HP filter, if needed (section 3.1).
   1.419 +
   1.420 +   2. Compute LPC parameters, quantize, and interpolate (section 3.2).
   1.421 +
   1.422 +   3. Use analysis filters on speech to compute residual (section 3.3).
   1.423 +
   1.424 +   4. Select position of 57/58-sample start state (section 3.5).
   1.425 +
   1.426 +   5. Quantize the 57/58-sample start state with scalar quantization
   1.427 +      (section 3.5).
   1.428 +
   1.429 +   6. Search the codebook for each sub-frame.  Start with 23/22 sample
   1.430 +      block, then encode sub-blocks forward in time, and then encode
   1.431 +      sub-blocks backward in time.  For each block, the steps in Figure
   1.432 +      3.4 are performed (section 3.6).
   1.433 +
   1.434 +   7. Packetize the bits into the payload specified in Table 3.2.
   1.435 +
   1.436 +   The input to the encoder SHOULD be 16-bit uniform PCM sampled at 8
   1.437 +   kHz.  Also it SHOULD be partitioned into blocks of BLOCKL=160/240
   1.438 +   samples.  Each block input to the encoder is divided into NSUB=4/6
   1.439 +   consecutive sub-blocks of SUBL=40 samples each.
   1.440 +
   1.441 +
   1.442 +
   1.443 +
   1.444 +
   1.445 +
   1.446 +
   1.447 +
   1.448 +
   1.449 +
   1.450 +
   1.451 +
   1.452 +
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   1.456 +
   1.457 +
   1.458 +             0        39        79       119       159
   1.459 +             +---------------------------------------+
   1.460 +             |    1    |    2    |    3    |    4    |
   1.461 +             +---------------------------------------+
   1.462 +                            20 ms frame
   1.463 +
   1.464 +   0        39        79       119       159       199       239
   1.465 +   +-----------------------------------------------------------+
   1.466 +   |    1    |    2    |    3    |    4    |    5    |    6    |
   1.467 +   +-----------------------------------------------------------+
   1.468 +                                  30 ms frame
   1.469 +   Figure 3.2. One input block to the encoder for 20 ms (with four sub-
   1.470 +   frames) and 30 ms (with six sub-frames).
   1.471 +
   1.472 +3.1.  Pre-processing
   1.473 +
   1.474 +   In some applications, the recorded speech signal contains DC level
   1.475 +   and/or 50/60 Hz noise.  If these components have not been removed
   1.476 +   prior to the encoder call, they should be removed by a high-pass
   1.477 +   filter.  A reference implementation of this, using a filter with a
   1.478 +   cutoff frequency of 90 Hz, can be found in Appendix A.28.
   1.479 +
   1.480 +3.2.  LPC Analysis and Quantization
   1.481 +
   1.482 +   The input to the LPC analysis module is a possibly high-pass filtered
   1.483 +   speech buffer, speech_hp, that contains 240/300 (LPC_LOOKBACK +
   1.484 +   BLOCKL = 80/60 + 160/240 = 240/300) speech samples, where samples 0
   1.485 +   through 79/59 are from the previous block and samples 80/60 through
   1.486 +   239/299 are from the current block.  No look-ahead into the next
   1.487 +   block is used.  For the very first block processed, the look-back
   1.488 +   samples are assumed to be zeros.
   1.489 +
   1.490 +   For each input block, the LPC analysis calculates one/two set(s) of
   1.491 +   LPC_FILTERORDER=10 LPC filter coefficients using the autocorrelation
   1.492 +   method and the Levinson-Durbin recursion.  These coefficients are
   1.493 +   converted to the Line Spectrum Frequency representation.  In the 20
   1.494 +   ms case, the single lsf set represents the spectral characteristics
   1.495 +   as measured at the center of the third sub-block.  For 30 ms frames,
   1.496 +   the first set, lsf1, represents the spectral properties of the input
   1.497 +   signal at the center of the second sub-block, and the other set,
   1.498 +   lsf2, represents the spectral characteristics as measured at the
   1.499 +   center of the fifth sub-block.  The details of the computation for 30
   1.500 +   ms frames are described in sections 3.2.1 through 3.2.6.  Section
   1.501 +   3.2.7 explains how the LPC Analysis and Quantization differs for 20
   1.502 +   ms frames.
   1.503 +
   1.504 +
   1.505 +
   1.506 +
   1.507 +
   1.508 +
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   1.512 +
   1.513 +
   1.514 +3.2.1.  Computation of Autocorrelation Coefficients
   1.515 +
   1.516 +   The first step in the LPC analysis procedure is to calculate
   1.517 +   autocorrelation coefficients by using windowed speech samples.  This
   1.518 +   windowing is the only difference in the LPC analysis procedure for
   1.519 +   the two sets of coefficients.  For the first set, a 240-sample-long
   1.520 +   standard symmetric Hanning window is applied to samples 0 through 239
   1.521 +   of the input data.  The first window, lpc_winTbl, is defined as
   1.522 +
   1.523 +      lpc_winTbl[i]= 0.5 * (1.0 - cos((2*PI*(i+1))/(BLOCKL+1)));
   1.524 +               i=0,...,119
   1.525 +      lpc_winTbl[i] = winTbl[BLOCKL - i - 1]; i=120,...,239
   1.526 +
   1.527 +   The windowed speech speech_hp_win1 is then obtained by multiplying
   1.528 +   the first 240 samples of the input speech buffer with the window
   1.529 +   coefficients:
   1.530 +
   1.531 +      speech_hp_win1[i] = speech_hp[i] * lpc_winTbl[i];
   1.532 +               i=0,...,BLOCKL-1
   1.533 +
   1.534 +   From these 240 windowed speech samples, 11 (LPC_FILTERORDER + 1)
   1.535 +   autocorrelation coefficients, acf1, are calculated:
   1.536 +
   1.537 +      acf1[lag] += speech_hp_win1[n] * speech_hp_win1[n + lag];
   1.538 +               lag=0,...,LPC_FILTERORDER; n=0,...,BLOCKL-lag-1
   1.539 +
   1.540 +   In order to make the analysis more robust against numerical precision
   1.541 +   problems, a spectral smoothing procedure is applied by windowing the
   1.542 +   autocorrelation coefficients before the LPC coefficients are
   1.543 +   computed.  Also, a white noise floor is added to the autocorrelation
   1.544 +   function by multiplying coefficient zero by 1.0001 (40dB below the
   1.545 +   energy of the windowed speech signal).  These two steps are
   1.546 +   implemented by multiplying the autocorrelation coefficients with the
   1.547 +   following window:
   1.548 +
   1.549 +      lpc_lagwinTbl[0] = 1.0001;
   1.550 +      lpc_lagwinTbl[i] = exp(-0.5 * ((2 * PI * 60.0 * i) /FS)^2);
   1.551 +               i=1,...,LPC_FILTERORDER
   1.552 +               where FS=8000 is the sampling frequency
   1.553 +
   1.554 +   Then, the windowed acf function acf1_win is obtained by
   1.555 +
   1.556 +      acf1_win[i] = acf1[i] * lpc_lagwinTbl[i];
   1.557 +               i=0,...,LPC_FILTERORDER
   1.558 +
   1.559 +   The second set of autocorrelation coefficients, acf2_win, are
   1.560 +   obtained in a similar manner.  The window, lpc_asymwinTbl, is applied
   1.561 +   to samples 60 through 299, i.e., the entire current block.  The
   1.562 +
   1.563 +
   1.564 +
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   1.568 +
   1.569 +
   1.570 +   window consists of two segments, the first (samples 0 to 219) being
   1.571 +   half a Hanning window with length 440 and the second a quarter of a
   1.572 +   cycle of a cosine wave.  By using this asymmetric window, an LPC
   1.573 +   analysis centered in the fifth sub-block is obtained without the need
   1.574 +   for any look-ahead, which would add delay.  The asymmetric window is
   1.575 +   defined as
   1.576 +
   1.577 +      lpc_asymwinTbl[i] = (sin(PI * (i + 1) / 441))^2; i=0,...,219
   1.578 +
   1.579 +      lpc_asymwinTbl[i] = cos((i - 220) * PI / 40); i=220,...,239
   1.580 +
   1.581 +   and the windowed speech is computed by
   1.582 +
   1.583 +      speech_hp_win2[i] = speech_hp[i + LPC_LOOKBACK] *
   1.584 +               lpc_asymwinTbl[i];  i=0,....BLOCKL-1
   1.585 +
   1.586 +   The windowed autocorrelation coefficients are then obtained in
   1.587 +   exactly the same way as for the first analysis instance.
   1.588 +
   1.589 +   The generation of the windows lpc_winTbl, lpc_asymwinTbl, and
   1.590 +   lpc_lagwinTbl are typically done in advance, and the arrays are
   1.591 +   stored in ROM rather than repeating the calculation for every block.
   1.592 +
   1.593 +3.2.2.  Computation of LPC Coefficients
   1.594 +
   1.595 +   From the 2 x 11 smoothed autocorrelation coefficients, acf1_win and
   1.596 +   acf2_win, the 2 x 11 LPC coefficients, lp1 and lp2, are calculated
   1.597 +   in the same way for both analysis locations by using the well known
   1.598 +   Levinson-Durbin recursion.  The first LPC coefficient is always 1.0,
   1.599 +   resulting in ten unique coefficients.
   1.600 +
   1.601 +   After determining the LPC coefficients, a bandwidth expansion
   1.602 +   procedure is applied to smooth the spectral peaks in the
   1.603 +   short-term spectrum.  The bandwidth addition is obtained by the
   1.604 +   following modification of the LPC coefficients:
   1.605 +
   1.606 +      lp1_bw[i] = lp1[i] * chirp^i; i=0,...,LPC_FILTERORDER
   1.607 +      lp2_bw[i] = lp2[i] * chirp^i; i=0,...,LPC_FILTERORDER
   1.608 +
   1.609 +   where "chirp" is a real number between 0 and 1.  It is RECOMMENDED to
   1.610 +   use a value of 0.9.
   1.611 +
   1.612 +3.2.3.  Computation of LSF Coefficients from LPC Coefficients
   1.613 +
   1.614 +   Thus far, two sets of LPC coefficients that represent the short-term
   1.615 +   spectral characteristics of the speech signal for two different time
   1.616 +   locations within the current block have been determined.  These
   1.617 +   coefficients SHOULD be quantized and interpolated.  Before this is
   1.618 +
   1.619 +
   1.620 +
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   1.623 +RFC 3951              Internet Low Bit Rate Codec          December 2004
   1.624 +
   1.625 +
   1.626 +   done, it is advantageous to convert the LPC parameters into another
   1.627 +   type of representation called Line Spectral Frequencies (LSF).  The
   1.628 +   LSF parameters are used because they are better suited for
   1.629 +   quantization and interpolation than the regular LPC coefficients.
   1.630 +   Many computationally efficient methods for calculating the LSFs from
   1.631 +   the LPC coefficients have been proposed in the literature.  The
   1.632 +   detailed implementation of one applicable method can be found in
   1.633 +   Appendix A.26.  The two arrays of LSF coefficients obtained, lsf1 and
   1.634 +   lsf2, are of dimension 10 (LPC_FILTERORDER).
   1.635 +
   1.636 +3.2.4.  Quantization of LSF Coefficients
   1.637 +
   1.638 +   Because the LPC filters defined by the two sets of LSFs are also
   1.639 +   needed in the decoder, the LSF parameters need to be quantized and
   1.640 +   transmitted as side information.  The total number of bits required
   1.641 +   to represent the quantization of the two LSF representations for one
   1.642 +   block of speech is 40, with 20 bits used for each of lsf1 and lsf2.
   1.643 +
   1.644 +   For computational and storage reasons, the LSF vectors are quantized
   1.645 +   using three-split vector quantization (VQ).  That is, the LSF vectors
   1.646 +   are split into three sub-vectors that are each quantized with a
   1.647 +   regular VQ.  The quantized versions of lsf1 and lsf2, qlsf1 and
   1.648 +   qlsf2, are obtained by using the same memoryless split VQ.  The
   1.649 +   length of each of these two LSF vectors is 10, and they are split
   1.650 +   into three sub-vectors containing 3, 3, and 4 values, respectively.
   1.651 +
   1.652 +   For each of the sub-vectors, a separate codebook of quantized values
   1.653 +   has been designed with a standard VQ training method for a large
   1.654 +   database containing speech from a large number of speakers recorded
   1.655 +   under various conditions.  The size of each of the three codebooks
   1.656 +   associated with the split definitions above is
   1.657 +
   1.658 +      int size_lsfCbTbl[LSF_NSPLIT] = {64,128,128};
   1.659 +
   1.660 +   The actual values of the vector quantization codebook that must be
   1.661 +   used can be found in the reference code of Appendix A.  Both sets of
   1.662 +   LSF coefficients, lsf1 and lsf2, are quantized with a standard
   1.663 +   memoryless split vector quantization (VQ) structure using the squared
   1.664 +   error criterion in the LSF domain.  The split VQ quantization
   1.665 +   consists of the following steps:
   1.666 +
   1.667 +   1) Quantize the first three LSF coefficients (1 - 3) with a VQ
   1.668 +      codebook of size 64.
   1.669 +   2) Quantize the next three LSF coefficients 4 - 6 with VQ a codebook
   1.670 +      of size 128.
   1.671 +   3) Quantize the last four LSF coefficients (7 - 10) with a VQ
   1.672 +      codebook of size 128.
   1.673 +
   1.674 +
   1.675 +
   1.676 +
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   1.680 +
   1.681 +
   1.682 +   This procedure, repeated for lsf1 and lsf2, gives six quantization
   1.683 +   indices and the quantized sets of LSF coefficients qlsf1 and qlsf2.
   1.684 +   Each set of three indices is encoded with 6 + 7 + 7 = 20 bits.  The
   1.685 +   total number of bits used for LSF quantization in a block is thus 40
   1.686 +   bits.
   1.687 +
   1.688 +3.2.5.  Stability Check of LSF Coefficients
   1.689 +
   1.690 +   The LSF representation of the LPC filter has the convenient property
   1.691 +   that the coefficients are ordered by increasing value, i.e., lsf(n-1)
   1.692 +   < lsf(n), 0 < n < 10, if the corresponding synthesis filter is
   1.693 +   stable.  As we are employing a split VQ scheme, it is possible that
   1.694 +   at the split boundaries the LSF coefficients are not ordered
   1.695 +   correctly and hence that the corresponding LP filter is unstable.  To
   1.696 +   ensure that the filter used is stable, a stability check is performed
   1.697 +   for the quantized LSF vectors.  If it turns out that the coefficients
   1.698 +   are not ordered appropriately (with a safety margin of 50 Hz to
   1.699 +   ensure that formant peaks are not too narrow), they will be moved
   1.700 +   apart.  The detailed method for this can be found in Appendix A.40.
   1.701 +   The same procedure is performed in the decoder.  This ensures that
   1.702 +   exactly the same LSF representations are used in both encoder and
   1.703 +   decoder.
   1.704 +
   1.705 +3.2.6.  Interpolation of LSF Coefficients
   1.706 +
   1.707 +   From the two sets of LSF coefficients that are computed for each
   1.708 +   block of speech, different LSFs are obtained for each sub-block by
   1.709 +   means of interpolation.  This procedure is performed for the original
   1.710 +   LSFs (lsf1 and lsf2), as well as the quantized versions qlsf1 and
   1.711 +   qlsf2, as both versions are used in the encoder.  Here follows a
   1.712 +   brief summary of the interpolation scheme; the details are found in
   1.713 +   the c-code of Appendix A.  In the first sub-block, the average of the
   1.714 +   second LSF vector from the previous block and the first LSF vector in
   1.715 +   the current block is used.  For sub-blocks two through five, the LSFs
   1.716 +   used are obtained by linear interpolation from lsf1 (and qlsf1) to
   1.717 +   lsf2 (and qlsf2), with lsf1 used in sub-block two and lsf2 in sub-
   1.718 +   block five.  In the last sub-block, lsf2 is used.  For the very first
   1.719 +   block it is assumed that the last LSF vector of the previous block is
   1.720 +   equal to a predefined vector, lsfmeanTbl, obtained by calculating the
   1.721 +   mean LSF vector of the LSF design database.
   1.722 +
   1.723 +   lsfmeanTbl[LPC_FILTERORDER] = {0.281738, 0.445801, 0.663330,
   1.724 +                  0.962524, 1.251831, 1.533081, 1.850586, 2.137817,
   1.725 +                  2.481445, 2.777344}
   1.726 +
   1.727 +
   1.728 +
   1.729 +
   1.730 +
   1.731 +
   1.732 +
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   1.736 +
   1.737 +
   1.738 +   The interpolation method is standard linear interpolation in the LSF
   1.739 +   domain.  The interpolated LSF values are converted to LPC
   1.740 +   coefficients for each sub-block.  The unquantized and quantized LPC
   1.741 +   coefficients form two sets of filters respectively.  The unquantized
   1.742 +   analysis filter for sub-block k is defined as follows
   1.743 +
   1.744 +                ___
   1.745 +                \
   1.746 +      Ak(z)= 1 + > ak(i)*z^(-i)
   1.747 +                /__
   1.748 +             i=1...LPC_FILTERORDER
   1.749 +
   1.750 +   The quantized analysis filter for sub-block k is defined as follows
   1.751 +                 ___
   1.752 +                 \
   1.753 +      A~k(z)= 1 + > a~k(i)*z^(-i)
   1.754 +                 /__
   1.755 +             i=1...LPC_FILTERORDER
   1.756 +
   1.757 +   A reference implementation of the lsf encoding is given in Appendix
   1.758 +   A.38.  A reference implementation of the corresponding decoding can
   1.759 +   be found in Appendix A.36.
   1.760 +
   1.761 +3.2.7.  LPC Analysis and Quantization for 20 ms Frames
   1.762 +
   1.763 +   As previously stated, the codec only calculates one set of LPC
   1.764 +   parameters for the 20 ms frame size as opposed to two sets for 30 ms
   1.765 +   frames.  A single set of autocorrelation coefficients is calculated
   1.766 +   on the LPC_LOOKBACK + BLOCKL = 80 + 160 = 240 samples.  These samples
   1.767 +   are windowed with the asymmetric window lpc_asymwinTbl, centered over
   1.768 +   the third sub-frame, to form speech_hp_win.  Autocorrelation
   1.769 +   coefficients, acf, are calculated on the 240 samples in speech_hp_win
   1.770 +   and then windowed exactly as in section 3.2.1 (resulting in
   1.771 +   acf_win).
   1.772 +
   1.773 +   This single set of windowed autocorrelation coefficients is used to
   1.774 +   calculate LPC coefficients, LSF coefficients, and quantized LSF
   1.775 +   coefficients in exactly the same manner as in sections 3.2.3 through
   1.776 +   3.2.4.  As for the 30 ms frame size, the ten LSF coefficients are
   1.777 +   divided into three sub-vectors of size 3, 3, and 4 and quantized by
   1.778 +   using the same scheme and codebook as in section 3.2.4 to finally get
   1.779 +   3 quantization indices.  The quantized LSF coefficients are
   1.780 +   stabilized with the algorithm described in section 3.2.5.
   1.781 +
   1.782 +   From the set of LSF coefficients computed for this block and those
   1.783 +   from the previous block, different LSFs are obtained for each sub-
   1.784 +   block by means of interpolation.  The interpolation is done linearly
   1.785 +   in the LSF domain over the four sub-blocks, so that the n-th sub-
   1.786 +
   1.787 +
   1.788 +
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   1.792 +
   1.793 +
   1.794 +   frame uses the weight (4-n)/4 for the LSF from old frame and the
   1.795 +   weight n/4 of the LSF from the current frame.  For the very first
   1.796 +   block the mean LSF, lsfmeanTbl, is used as the LSF from the previous
   1.797 +   block.  Similarly as seen in section 3.2.6, both unquantized, A(z),
   1.798 +   and quantized, A~(z), analysis filters are calculated for each of the
   1.799 +   four sub-blocks.
   1.800 +
   1.801 +3.3.  Calculation of the Residual
   1.802 +
   1.803 +   The block of speech samples is filtered by the quantized and
   1.804 +   interpolated LPC analysis filters to yield the residual signal.  In
   1.805 +   particular, the corresponding LPC analysis filter for each 40 sample
   1.806 +   sub-block is used to filter the speech samples for the same sub-
   1.807 +   block.  The filter memory at the end of each sub-block is carried
   1.808 +   over to the LPC filter of the next sub-block.  The signal at the
   1.809 +   output of each LP analysis filter constitutes the residual signal for
   1.810 +   the corresponding sub-block.
   1.811 +
   1.812 +   A reference implementation of the LPC analysis filters is given in
   1.813 +   Appendix A.10.
   1.814 +
   1.815 +3.4.  Perceptual Weighting Filter
   1.816 +
   1.817 +   In principle any good design of a perceptual weighting filter can be
   1.818 +   applied in the encoder without compromising this codec definition.
   1.819 +   However, it is RECOMMENDED to use the perceptual weighting filter Wk
   1.820 +   for sub-block k specified below:
   1.821 +
   1.822 +      Wk(z)=1/Ak(z/LPC_CHIRP_WEIGHTDENUM), where
   1.823 +                               LPC_CHIRP_WEIGHTDENUM = 0.4222
   1.824 +
   1.825 +   This is a simple design with low complexity that is applied in the
   1.826 +   LPC residual domain.  Here Ak(z) is the filter obtained for sub-block
   1.827 +   k from unquantized but interpolated LSF coefficients.
   1.828 +
   1.829 +3.5.  Start State Encoder
   1.830 +
   1.831 +   The start state is quantized by using a common 6-bit scalar quantizer
   1.832 +   for the block and a 3-bit scalar quantizer operating on scaled
   1.833 +   samples in the weighted speech domain.  In the following we describe
   1.834 +   the state encoding in greater detail.
   1.835 +
   1.836 +
   1.837 +
   1.838 +
   1.839 +
   1.840 +
   1.841 +
   1.842 +
   1.843 +
   1.844 +
   1.845 +Andersen, et al.              Experimental                     [Page 15]
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   1.847 +RFC 3951              Internet Low Bit Rate Codec          December 2004
   1.848 +
   1.849 +
   1.850 +3.5.1.  Start State Estimation
   1.851 +
   1.852 +   The two sub-blocks containing the start state are determined by
   1.853 +   finding the two consecutive sub-blocks in the block having the
   1.854 +   highest power.  Advantageously, down-weighting is used in the
   1.855 +   beginning and end of the sub-frames, i.e., the following measure is
   1.856 +   computed (NSUB=4/6 for 20/30 ms frame size):
   1.857 +
   1.858 +      nsub=1,...,NSUB-1
   1.859 +      ssqn[nsub] = 0.0;
   1.860 +      for (i=(nsub-1)*SUBL; i<(nsub-1)*SUBL+5; i++)
   1.861 +               ssqn[nsub] += sampEn_win[i-(nsub-1)*SUBL]*
   1.862 +                                 residual[i]*residual[i];
   1.863 +      for (i=(nsub-1)*SUBL+5; i<(nsub+1)*SUBL-5; i++)
   1.864 +               ssqn[nsub] += residual[i]*residual[i];
   1.865 +      for (i=(nsub+1)*SUBL-5; i<(nsub+1)*SUBL; i++)
   1.866 +               ssqn[nsub] += sampEn_win[(nsub+1)*SUBL-i-1]*
   1.867 +                                 residual[i]*residual[i];
   1.868 +
   1.869 +   where sampEn_win[5]={1/6, 2/6, 3/6, 4/6, 5/6}; MAY be used.  The
   1.870 +   sub-frame number corresponding to the maximum value of
   1.871 +   ssqEn_win[nsub-1]*ssqn[nsub] is selected as the start state
   1.872 +   indicator.  A weighting of ssqEn_win[]={0.8,0.9,1.0,0.9,0.8} for 30
   1.873 +   ms frames and ssqEn_win[]={0.9,1.0,0.9} for 20 ms frames; MAY
   1.874 +   advantageously be used to bias the start state towards the middle of
   1.875 +   the frame.
   1.876 +
   1.877 +   For 20 ms frames there are three possible positions for the two-sub-
   1.878 +   block length maximum power segment; the start state position is
   1.879 +   encoded with 2 bits.  The start state position, start, MUST be
   1.880 +   encoded as
   1.881 +
   1.882 +      start=1: start state in sub-frame 0 and 1
   1.883 +      start=2: start state in sub-frame 1 and 2
   1.884 +      start=3: start state in sub-frame 2 and 3
   1.885 +
   1.886 +   For 30 ms frames there are five possible positions of the two-sub-
   1.887 +   block length maximum power segment, the start state position is
   1.888 +   encoded with 3 bits.  The start state position, start, MUST be
   1.889 +   encoded as
   1.890 +
   1.891 +      start=1: start state in sub-frame 0 and 1
   1.892 +      start=2: start state in sub-frame 1 and 2
   1.893 +      start=3: start state in sub-frame 2 and 3
   1.894 +      start=4: start state in sub-frame 3 and 4
   1.895 +      start=5: start state in sub-frame 4 and 5
   1.896 +
   1.897 +
   1.898 +
   1.899 +
   1.900 +
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   1.903 +RFC 3951              Internet Low Bit Rate Codec          December 2004
   1.904 +
   1.905 +
   1.906 +   Hence, in both cases, index 0 is not used.  In order to shorten the
   1.907 +   start state for bit rate efficiency, the start state is brought down
   1.908 +   to STATE_SHORT_LEN=57 samples for 20 ms frames and STATE_SHORT_LEN=58
   1.909 +   samples for 30 ms frames.  The power of the first 23/22 and last
   1.910 +   23/22 samples of the two sub-frame blocks identified above is
   1.911 +   computed as the sum of the squared signal sample values, and the
   1.912 +   23/22-sample segment with the lowest power is excluded from the start
   1.913 +   state.  One bit is transmitted to indicate which of the two possible
   1.914 +   57/58 sample segments is used.  The start state position within the
   1.915 +   two sub-frames determined above, state_first, MUST be encoded as
   1.916 +
   1.917 +      state_first=1: start state is first STATE_SHORT_LEN samples
   1.918 +      state_first=0: start state is last STATE_SHORT_LEN samples
   1.919 +
   1.920 +3.5.2.  All-Pass Filtering and Scale Quantization
   1.921 +
   1.922 +   The block of residual samples in the start state is first filtered by
   1.923 +   an all-pass filter with the quantized LPC coefficients as denominator
   1.924 +   and reversed quantized LPC coefficients as numerator.  The purpose of
   1.925 +   this phase-dispersion filter is to get a more even distribution of
   1.926 +   the sample values in the residual signal.  The filtering is performed
   1.927 +   by circular convolution, where the initial filter memory is set to
   1.928 +   zero.
   1.929 +
   1.930 +      res(0..(STATE_SHORT_LEN-1))   = uncoded start state residual
   1.931 +      res((STATE_SHORT_LEN)..(2*STATE_SHORT_LEN-1)) = 0
   1.932 +
   1.933 +      Pk(z) = A~rk(z)/A~k(z), where
   1.934 +                                   ___
   1.935 +                                   \
   1.936 +      A~rk(z)= z^(-LPC_FILTERORDER)+>a~k(i+1)*z^(i-(LPC_FILTERORDER-1))
   1.937 +                                   /__
   1.938 +                               i=0...(LPC_FILTERORDER-1)
   1.939 +
   1.940 +      and A~k(z) is taken from the block where the start state begins
   1.941 +
   1.942 +      res -> Pk(z) -> filtered
   1.943 +
   1.944 +      ccres(k) = filtered(k) + filtered(k+STATE_SHORT_LEN),
   1.945 +                                        k=0..(STATE_SHORT_LEN-1)
   1.946 +
   1.947 +   The all-pass filtered block is searched for its largest magnitude
   1.948 +   sample.  The 10-logarithm of this magnitude is quantized with a 6-bit
   1.949 +   quantizer, state_frgqTbl, by finding the nearest representation.
   1.950 +
   1.951 +
   1.952 +
   1.953 +
   1.954 +
   1.955 +
   1.956 +
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   1.959 +RFC 3951              Internet Low Bit Rate Codec          December 2004
   1.960 +
   1.961 +
   1.962 +   This results in an index, idxForMax, corresponding to a quantized
   1.963 +   value, qmax.  The all-pass filtered residual samples in the block are
   1.964 +   then multiplied with a scaling factor scal=4.5/(10^qmax) to yield
   1.965 +   normalized samples.
   1.966 +
   1.967 +   state_frgqTbl[64] = {1.000085, 1.071695, 1.140395, 1.206868,
   1.968 +                  1.277188, 1.351503, 1.429380, 1.500727, 1.569049,
   1.969 +                  1.639599, 1.707071, 1.781531, 1.840799, 1.901550,
   1.970 +                  1.956695, 2.006750, 2.055474, 2.102787, 2.142819,
   1.971 +                  2.183592, 2.217962, 2.257177, 2.295739, 2.332967,
   1.972 +                  2.369248, 2.402792, 2.435080, 2.468598, 2.503394,
   1.973 +                  2.539284, 2.572944, 2.605036, 2.636331, 2.668939,
   1.974 +                  2.698780, 2.729101, 2.759786, 2.789834, 2.818679,
   1.975 +                  2.848074, 2.877470, 2.906899, 2.936655, 2.967804,
   1.976 +                  3.000115, 3.033367, 3.066355, 3.104231, 3.141499,
   1.977 +                  3.183012, 3.222952, 3.265433, 3.308441, 3.350823,
   1.978 +                  3.395275, 3.442793, 3.490801, 3.542514, 3.604064,
   1.979 +                  3.666050, 3.740994, 3.830749, 3.938770, 4.101764}
   1.980 +
   1.981 +3.5.3.  Scalar Quantization
   1.982 +
   1.983 +   The normalized samples are quantized in the perceptually weighted
   1.984 +   speech domain by a sample-by-sample scalar DPCM quantization as
   1.985 +   depicted in Figure 3.3.  Each sample in the block is filtered by a
   1.986 +   weighting filter Wk(z), specified in section 3.4, to form a weighted
   1.987 +   speech sample x[n].  The target sample d[n] is formed by subtracting
   1.988 +   a predicted sample y[n], where the prediction filter is given by
   1.989 +
   1.990 +           Pk(z) = 1 - 1 / Wk(z).
   1.991 +
   1.992 +               +-------+  x[n] +    d[n] +-----------+ u[n]
   1.993 +   residual -->| Wk(z) |-------->(+)---->| Quantizer |------> quantized
   1.994 +               +-------+       - /|\     +-----------+    |   residual
   1.995 +                                  |                      \|/
   1.996 +                             y[n] +--------------------->(+)
   1.997 +                                  |                       |
   1.998 +                                  |        +------+       |
   1.999 +                                  +--------| Pk(z)|<------+
  1.1000 +                                           +------+
  1.1001 +
  1.1002 +   Figure 3.3.  Quantization of start state samples by DPCM in weighted
  1.1003 +   speech domain.
  1.1004 +
  1.1005 +   The coded state sample u[n] is obtained by quantizing d[n] with a 3-
  1.1006 +   bit quantizer with quantization table state_sq3Tbl.
  1.1007 +
  1.1008 +   state_sq3Tbl[8] = {-3.719849, -2.177490, -1.130005, -0.309692,
  1.1009 +                  0.444214, 1.329712, 2.436279, 3.983887}
  1.1010 +
  1.1011 +
  1.1012 +
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  1.1015 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.1016 +
  1.1017 +
  1.1018 +   The quantized samples are transformed back to the residual domain by
  1.1019 +   1) scaling with 1/scal; 2) time-reversing the scaled samples; 3)
  1.1020 +   filtering the time-reversed samples by the same all-pass filter, as
  1.1021 +   in section 3.5.2, by using circular convolution; and 4) time-
  1.1022 +   reversing the filtered samples.  (More detail is in section 4.2.)
  1.1023 +
  1.1024 +   A reference implementation of the start-state encoding can be found
  1.1025 +   in Appendix A.46.
  1.1026 +
  1.1027 +3.6.  Encoding the Remaining Samples
  1.1028 +
  1.1029 +   A dynamic codebook is used to encode 1) the 23/22 remaining samples
  1.1030 +   in the two sub-blocks containing the start state; 2) the sub-blocks
  1.1031 +   after the start state in time; and 3) the sub-blocks before the start
  1.1032 +   state in time.  Thus, the encoding target can be either the 23/22
  1.1033 +   samples remaining of the 2 sub-blocks containing the start state, or
  1.1034 +   a 40-sample sub-block.  This target can consist of samples that are
  1.1035 +   indexed forward in time or backward in time, depending on the
  1.1036 +   location of the start state.  The length of the target is denoted by
  1.1037 +   lTarget.
  1.1038 +
  1.1039 +   The coding is based on an adaptive codebook that is built from a
  1.1040 +   codebook memory that contains decoded LPC excitation samples from the
  1.1041 +   already encoded part of the block.  These samples are indexed in the
  1.1042 +   same time direction as is the target vector and end at the sample
  1.1043 +   instant prior to the first sample instant represented in the target
  1.1044 +   vector.  The codebook memory has length lMem, which is equal to
  1.1045 +   CB_MEML=147 for the two/four 40-sample sub-blocks and 85 for the
  1.1046 +   23/22-sample sub-block.
  1.1047 +
  1.1048 +   The following figure shows an overview of the encoding procedure.
  1.1049 +
  1.1050 +         +------------+    +---------------+    +-------------+
  1.1051 +      -> | 1. Decode  | -> | 2. Mem setup  | -> | 3. Perc. W. | ->
  1.1052 +         +------------+    +---------------+    +-------------+
  1.1053 +
  1.1054 +         +------------+    +-----------------+
  1.1055 +      -> | 4. Search  | -> | 5. Upd. Target  | ------------------>
  1.1056 +       | +------------+    +------------------ |
  1.1057 +       ----<-------------<-----------<----------
  1.1058 +                     stage=0..2
  1.1059 +
  1.1060 +         +----------------+
  1.1061 +      -> | 6. Recalc G[0] | ---------------> gains and CB indices
  1.1062 +         +----------------+
  1.1063 +
  1.1064 +   Figure 3.4.  Flow chart of the codebook search in the iLBC encoder.
  1.1065 +
  1.1066 +
  1.1067 +
  1.1068 +
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  1.1071 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.1072 +
  1.1073 +
  1.1074 +   1. Decode the part of the residual that has been encoded so far,
  1.1075 +      using the codebook without perceptual weighting.
  1.1076 +
  1.1077 +   2. Set up the memory by taking data from the decoded residual.  This
  1.1078 +      memory is used to construct codebooks.  For blocks preceding the
  1.1079 +      start state, both the decoded residual and the target are time
  1.1080 +      reversed (section 3.6.1).
  1.1081 +   3. Filter the memory + target with the perceptual weighting filter
  1.1082 +      (section 3.6.2).
  1.1083 +
  1.1084 +   4. Search for the best match between the target and the codebook
  1.1085 +      vector.  Compute the optimal gain for this match and quantize that
  1.1086 +      gain (section 3.6.4).
  1.1087 +
  1.1088 +   5. Update the perceptually weighted target by subtracting the
  1.1089 +      contribution from the selected codebook vector from the
  1.1090 +      perceptually weighted memory (quantized gain times selected
  1.1091 +      vector).  Repeat 4 and 5 for the two additional stages.
  1.1092 +
  1.1093 +   6. Calculate the energy loss due to encoding of the residual.  If
  1.1094 +      needed, compensate for this loss by an upscaling and
  1.1095 +      requantization of the gain for the first stage (section 3.7).
  1.1096 +
  1.1097 +   The following sections provide an in-depth description of the
  1.1098 +   different blocks of Figure 3.4.
  1.1099 +
  1.1100 +3.6.1.  Codebook Memory
  1.1101 +
  1.1102 +   The codebook memory is based on the already encoded sub-blocks, so
  1.1103 +   the available data for encoding increases for each new sub-block that
  1.1104 +   has been encoded.  Until enough sub-blocks have been encoded to fill
  1.1105 +   the codebook memory with data, it is padded with zeros.  The
  1.1106 +   following figure shows an example of the order in which the sub-
  1.1107 +   blocks are encoded for the 30 ms frame size if the start state is
  1.1108 +   located in the last 58 samples of sub-block 2 and 3.
  1.1109 +
  1.1110 +   +-----------------------------------------------------+
  1.1111 +   |  5     | 1  |///|////////|    2   |    3   |    4   |
  1.1112 +   +-----------------------------------------------------+
  1.1113 +
  1.1114 +   Figure 3.5.  The order from 1 to 5 in which the sub-blocks are
  1.1115 +   encoded.  The slashed area is the start state.
  1.1116 +
  1.1117 +
  1.1118 +
  1.1119 +
  1.1120 +
  1.1121 +
  1.1122 +
  1.1123 +
  1.1124 +
  1.1125 +Andersen, et al.              Experimental                     [Page 20]
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  1.1128 +
  1.1129 +
  1.1130 +   The first target sub-block to be encoded is number 1, and the
  1.1131 +   corresponding codebook memory is shown in the following figure.  As
  1.1132 +   the target vector comes before the start state in time, the codebook
  1.1133 +   memory and target vector are time reversed; thus, after the block has
  1.1134 +   been time reversed the search algorithm can be reused.  As only the
  1.1135 +   start state has been encoded so far, the last samples of the codebook
  1.1136 +   memory are padded with zeros.
  1.1137 +
  1.1138 +   +-------------------------
  1.1139 +   |zeros|\\\\\\\\|\\\\|  1 |
  1.1140 +   +-------------------------
  1.1141 +
  1.1142 +   Figure 3.6.  The codebook memory, length lMem=85 samples, and the
  1.1143 +   target vector 1, length 22 samples.
  1.1144 +
  1.1145 +   The next step is to encode sub-block 2 by using the memory that now
  1.1146 +   has increased since sub-block 1 has been encoded.  The following
  1.1147 +   figure shows the codebook memory for encoding of sub-block 2.
  1.1148 +
  1.1149 +   +-----------------------------------
  1.1150 +   | zeros | 1  |///|////////|    2   |
  1.1151 +   +-----------------------------------
  1.1152 +
  1.1153 +   Figure 3.7.  The codebook memory, length lMem=147 samples, and the
  1.1154 +   target vector 2, length 40 samples.
  1.1155 +
  1.1156 +   The next step is to encode sub-block 3 by using the memory which has
  1.1157 +   been increased yet again since sub-blocks 1 and 2 have been encoded,
  1.1158 +   but the sub-block still has to be padded with a few zeros.  The
  1.1159 +   following figure shows the codebook memory for encoding of sub-block
  1.1160 +   3.
  1.1161 +
  1.1162 +   +------------------------------------------
  1.1163 +   |zeros| 1  |///|////////|    2   |   3    |
  1.1164 +   +------------------------------------------
  1.1165 +
  1.1166 +   Figure 3.8.  The codebook memory, length lMem=147 samples, and the
  1.1167 +   target vector 3, length 40 samples.
  1.1168 +
  1.1169 +   The next step is to encode sub-block 4 by using the memory which now
  1.1170 +   has increased yet again since sub-blocks 1, 2, and 3 have been
  1.1171 +   encoded.  This time, the memory does not have to be padded with
  1.1172 +   zeros.  The following figure shows the codebook memory for encoding
  1.1173 +   of sub-block 4.
  1.1174 +
  1.1175 +
  1.1176 +
  1.1177 +
  1.1178 +
  1.1179 +
  1.1180 +
  1.1181 +Andersen, et al.              Experimental                     [Page 21]
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  1.1183 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.1184 +
  1.1185 +
  1.1186 +   +------------------------------------------
  1.1187 +   |1|///|////////|    2   |   3    |   4    |
  1.1188 +   +------------------------------------------
  1.1189 +
  1.1190 +   Figure 3.9.  The codebook memory, length lMem=147 samples, and the
  1.1191 +   target vector 4, length 40 samples.
  1.1192 +
  1.1193 +   The final target sub-block to be encoded is number 5, and the
  1.1194 +   following figure shows the corresponding codebook memory.  As the
  1.1195 +   target vector comes before the start state in time, the codebook
  1.1196 +   memory and target vector are time reversed.
  1.1197 +
  1.1198 +   +-------------------------------------------
  1.1199 +   |  3  |   2    |\\\\\\\\|\\\\|  1 |   5    |
  1.1200 +   +-------------------------------------------
  1.1201 +
  1.1202 +   Figure 3.10.  The codebook memory, length lMem=147 samples, and the
  1.1203 +   target vector 5, length 40 samples.
  1.1204 +
  1.1205 +   For the case of 20 ms frames, the encoding procedure looks almost
  1.1206 +   exactly the same.  The only difference is that the size of the start
  1.1207 +   state is 57 samples and that there are only three sub-blocks to be
  1.1208 +   encoded.  The encoding order is the same as above, starting with the
  1.1209 +   23-sample target and then encoding the two remaining 40-sample sub-
  1.1210 +   blocks, first going forward in time and then going backward in time
  1.1211 +   relative to the start state.
  1.1212 +
  1.1213 +3.6.2.  Perceptual Weighting of Codebook Memory and Target
  1.1214 +
  1.1215 +   To provide a perceptual weighting of the coding error, a
  1.1216 +   concatenation of the codebook memory and the target to be coded is
  1.1217 +   all-pole filtered with the perceptual weighting filter specified in
  1.1218 +   section 3.4.  The filter state of the weighting filter is set to
  1.1219 +   zero.
  1.1220 +
  1.1221 +      in(0..(lMem-1))            = unweighted codebook memory
  1.1222 +      in(lMem..(lMem+lTarget-1)) = unweighted target signal
  1.1223 +
  1.1224 +
  1.1225 +      in -> Wk(z) -> filtered,
  1.1226 +          where Wk(z) is taken from the sub-block of the target
  1.1227 +
  1.1228 +      weighted codebook memory = filtered(0..(lMem-1))
  1.1229 +      weighted target signal = filtered(lMem..(lMem+lTarget-1))
  1.1230 +
  1.1231 +   The codebook search is done with the weighted codebook memory and the
  1.1232 +   weighted target, whereas the decoding and the codebook memory update
  1.1233 +   uses the unweighted codebook memory.
  1.1234 +
  1.1235 +
  1.1236 +
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  1.1240 +
  1.1241 +
  1.1242 +3.6.3.  Codebook Creation
  1.1243 +
  1.1244 +   The codebook for the search is created from the perceptually weighted
  1.1245 +   codebook memory.  It consists of two sections, where the first is
  1.1246 +   referred to as the base codebook and the second as the expanded
  1.1247 +   codebook, as it is created by linear combinations of the first.  Each
  1.1248 +   of these two sections also has a subsection referred to as the
  1.1249 +   augmented codebook.  The augmented codebook is only created and used
  1.1250 +   for the coding of the 40-sample sub-blocks and not for the 23/22-
  1.1251 +   sample sub-block case.  The codebook size used for the different
  1.1252 +   sub-blocks and different stages are summarized in the table below.
  1.1253 +
  1.1254 +                              Stage
  1.1255 +                        1               2 & 3
  1.1256 +           --------------------------------------------
  1.1257 +                22     128  (64+0)*2     128 (64+0)*2
  1.1258 +   Sub-    1:st 40     256  (108+20)*2   128 (44+20)*2
  1.1259 +   Blocks  2:nd 40     256  (108+20)*2   256 (108+20)*2
  1.1260 +           3:rd 40     256  (108+20)*2   256 (108+20)*2
  1.1261 +           4:th 40     256  (108+20)*2   256 (108+20)*2
  1.1262 +
  1.1263 +   Table 3.1.  Codebook sizes for the 30 ms mode.
  1.1264 +
  1.1265 +   Table 3.1 shows the codebook size for the different sub-blocks and
  1.1266 +   stages for 30 ms frames.  Inside the parentheses it shows how the
  1.1267 +   number of codebook vectors is distributed, within the two sections,
  1.1268 +   between the base/expanded codebook and the augmented base/expanded
  1.1269 +   codebook.  It should be interpreted in the following way:
  1.1270 +   (base/expanded cb + augmented base/expanded cb).  The total number of
  1.1271 +   codebook vectors for a specific sub-block and stage is given by the
  1.1272 +   following formula:
  1.1273 +
  1.1274 +   Tot. cb vectors = base cb + aug. base cb + exp. cb + aug. exp. cb
  1.1275 +
  1.1276 +   The corresponding values to Figure 3.1 for 20 ms frames are only
  1.1277 +   slightly modified.  The short sub-block is 23 instead of 22 samples,
  1.1278 +   and the 3:rd and 4:th sub-frame are not present.
  1.1279 +
  1.1280 +3.6.3.1.  Creation of a Base Codebook
  1.1281 +
  1.1282 +   The base codebook is given by the perceptually weighted codebook
  1.1283 +   memory that is mentioned in section 3.5.3.  The different codebook
  1.1284 +   vectors are given by sliding a window of length 23/22 or 40, given by
  1.1285 +   variable lTarget, over the lMem-long perceptually weighted codebook
  1.1286 +   memory.  The indices are ordered so that the codebook vector
  1.1287 +   containing sample (lMem-lTarget-n) to (lMem-n-1) of the codebook
  1.1288 +
  1.1289 +
  1.1290 +
  1.1291 +
  1.1292 +
  1.1293 +Andersen, et al.              Experimental                     [Page 23]
  1.1294 +
  1.1295 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.1296 +
  1.1297 +
  1.1298 +   memory vector has index n, where n=0..lMem-lTarget.  Thus the total
  1.1299 +   number of base codebook vectors is lMem-lTarget+1, and the indices
  1.1300 +   are ordered from sample delay lTarget (23/22 or 40) to lMem+1 (86 or
  1.1301 +   148).
  1.1302 +
  1.1303 +3.6.3.2.  Codebook Expansion
  1.1304 +
  1.1305 +   The base codebook is expanded by a factor of 2, creating an
  1.1306 +   additional section in the codebook.  This new section is obtained by
  1.1307 +   filtering the base codebook, base_cb, with a FIR filter with filter
  1.1308 +   length CB_FILTERLEN=8.  The construction of the expanded codebook
  1.1309 +   compensates for the delay of four samples introduced by the FIR
  1.1310 +   filter.
  1.1311 +
  1.1312 +   cbfiltersTbl[CB_FILTERLEN]={-0.033691, 0.083740, -0.144043,
  1.1313 +                  0.713379, 0.806152, -0.184326,
  1.1314 +                  0.108887, -0.034180};
  1.1315 +
  1.1316 +                   ___
  1.1317 +                   \
  1.1318 +      exp_cb(k)=  + > cbfiltersTbl(i)*x(k-i+4)
  1.1319 +                   /__
  1.1320 +             i=0...(LPC_FILTERORDER-1)
  1.1321 +
  1.1322 +      where x(j) = base_cb(j) for j=0..lMem-1 and 0 otherwise
  1.1323 +
  1.1324 +   The individual codebook vectors of the new filtered codebook, exp_cb,
  1.1325 +   and their indices are obtained in the same fashion as described above
  1.1326 +   for the base codebook.
  1.1327 +
  1.1328 +3.6.3.3.  Codebook Augmentation
  1.1329 +
  1.1330 +   For cases where encoding entire sub-blocks, i.e., cbveclen=40, the
  1.1331 +   base and expanded codebooks are augmented to increase codebook
  1.1332 +   richness.  The codebooks are augmented by vectors produced by
  1.1333 +   interpolation of segments.  The base and expanded codebook,
  1.1334 +   constructed above, consists of vectors corresponding to sample delays
  1.1335 +   in the range from cbveclen to lMem.  The codebook augmentation
  1.1336 +   attempts to augment these codebooks with vectors corresponding to
  1.1337 +   sample delays from 20 to 39.  However, not all of these samples are
  1.1338 +   present in the base codebook and expanded codebook, respectively.
  1.1339 +   Therefore, the augmentation vectors are constructed as linear
  1.1340 +   combinations between samples corresponding to sample delays in the
  1.1341 +   range 20 to 39.  The general idea of this procedure is presented in
  1.1342 +   the following figures and text.  The procedure is performed for both
  1.1343 +   the base codebook and the expanded codebook.
  1.1344 +
  1.1345 +
  1.1346 +
  1.1347 +
  1.1348 +
  1.1349 +Andersen, et al.              Experimental                     [Page 24]
  1.1350 +
  1.1351 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.1352 +
  1.1353 +
  1.1354 +       - - ------------------------|
  1.1355 +    codebook memory                |
  1.1356 +       - - ------------------------|
  1.1357 +                  |-5-|---15---|-5-|
  1.1358 +                  pi  pp       po
  1.1359 +
  1.1360 +                      |        |                       Codebook vector
  1.1361 +                      |---15---|-5-|-----20-----|   <- corresponding to
  1.1362 +                          i     ii      iii            sample delay 20
  1.1363 +
  1.1364 +   Figure 3.11.  Generation of the first augmented codebook.
  1.1365 +
  1.1366 +   Figure 3.11 shows the codebook memory with pointers pi, pp, and po,
  1.1367 +   where pi points to sample 25, pp to sample 20, and po to sample 5.
  1.1368 +   Below the codebook memory, the augmented codebook vector
  1.1369 +   corresponding to sample delay 20 is drawn.  Segment i consists of
  1.1370 +   fifteen samples from pointer pp and forward in time.  Segment ii
  1.1371 +   consists of five interpolated samples from pi and forward and from po
  1.1372 +   and forward.  The samples are linearly interpolated with weights
  1.1373 +   [0.0, 0.2, 0.4, 0.6, 0.8] for pi and weights [1.0, 0.8, 0.6, 0.4,
  1.1374 +   0.2] for po.  Segment iii consists of twenty samples from pp and
  1.1375 +   forward.  The augmented codebook vector corresponding to sample delay
  1.1376 +   21 is produced by moving pointers pp and pi one sample backward in
  1.1377 +   time.  This gives us the following figure.
  1.1378 +
  1.1379 +       - - ------------------------|
  1.1380 +    codebook memory                |
  1.1381 +       - - ------------------------|
  1.1382 +                  |-5-|---16---|-5-|
  1.1383 +                  pi  pp       po
  1.1384 +
  1.1385 +                      |        |                       Codebook vector
  1.1386 +                      |---16---|-5-|-----19-----|   <- corresponding to
  1.1387 +                          i     ii      iii            sample delay 21
  1.1388 +
  1.1389 +   Figure 3.12.  Generation of the second augmented codebook.
  1.1390 +
  1.1391 +   Figure 3.12 shows the codebook memory with pointers pi, pp and po
  1.1392 +   where pi points to sample 26, pp to sample 21, and po to sample 5.
  1.1393 +   Below the codebook memory, the augmented codebook vector
  1.1394 +   corresponding to sample delay 21 is drawn.  Segment i now consists of
  1.1395 +   sixteen samples from pp and forward.  Segment ii consists of five
  1.1396 +   interpolated samples from pi and forward and from po and forward, and
  1.1397 +   the interpolation weights are the same throughout the procedure.
  1.1398 +   Segment iii consists of nineteen samples from pp and forward.  The
  1.1399 +   same procedure of moving the two pointers is continued until the last
  1.1400 +   augmented vector corresponding to sample delay 39 has been created.
  1.1401 +   This gives a total of twenty new codebook vectors to each of the two
  1.1402 +
  1.1403 +
  1.1404 +
  1.1405 +Andersen, et al.              Experimental                     [Page 25]
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  1.1407 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.1408 +
  1.1409 +
  1.1410 +   sections.  Thus the total number of codebook vectors for each of the
  1.1411 +   two sections, when including the augmented codebook, becomes lMem-
  1.1412 +   SUBL+1+SUBL/2.  This is provided that augmentation is evoked, i.e.,
  1.1413 +   that lTarget=SUBL.
  1.1414 +
  1.1415 +3.6.4.  Codebook Search
  1.1416 +
  1.1417 +   The codebook search uses the codebooks described in the sections
  1.1418 +   above to find the best match of the perceptually weighted target, see
  1.1419 +   section 3.6.2.  The search method is a multi-stage gain-shape
  1.1420 +   matching performed as follows.  At each stage the best shape vector
  1.1421 +   is identified, then the gain is calculated and quantized, and finally
  1.1422 +   the target is updated in preparation for the next codebook search
  1.1423 +   stage.  The number of stages is CB_NSTAGES=3.
  1.1424 +
  1.1425 +   If the target is the 23/22-sample vector the codebooks are indexed so
  1.1426 +   that the base codebook is followed by the expanded codebook.  If the
  1.1427 +   target is 40 samples the order is as follows: base codebook,
  1.1428 +   augmented base codebook, expanded codebook, and augmented expanded
  1.1429 +   codebook.  The size of each codebook section and its corresponding
  1.1430 +   augmented section is given by Table 3.1 in section 3.6.3.
  1.1431 +
  1.1432 +   For example, when the second 40-sample sub-block is coded, indices 0
  1.1433 +   - 107 correspond to the base codebook, 108 - 127 correspond to the
  1.1434 +   augmented base codebook, 128 - 235 correspond to the expanded
  1.1435 +   codebook, and indices 236 - 255 correspond to the augmented expanded
  1.1436 +   codebook.  The indices are divided in the same fashion for all stages
  1.1437 +   in the example.  Only in the case of coding the first 40-sample sub-
  1.1438 +   block is there a difference between stages (see Table 3.1).
  1.1439 +
  1.1440 +3.6.4.1.  Codebook Search at Each Stage
  1.1441 +
  1.1442 +   The codebooks are searched to find the best match to the target at
  1.1443 +   each stage.  When the best match is found, the target is updated and
  1.1444 +   the next-stage search is started.  The three chosen codebook vectors
  1.1445 +   and their corresponding gains constitute the encoded sub-block.  The
  1.1446 +   best match is decided by the following three criteria:
  1.1447 +
  1.1448 +   1. Compute the measure
  1.1449 +
  1.1450 +      (target*cbvec)^2 / ||cbvec||^2
  1.1451 +
  1.1452 +   for all codebook vectors, cbvec, and choose the codebook vector
  1.1453 +   maximizing the measure.  The expression (target*cbvec) is the dot
  1.1454 +   product between the target vector to be coded and the codebook vector
  1.1455 +   for which we compute the measure.  The norm, ||x||, is defined as the
  1.1456 +   square root of (x*x).
  1.1457 +
  1.1458 +
  1.1459 +
  1.1460 +
  1.1461 +Andersen, et al.              Experimental                     [Page 26]
  1.1462 +
  1.1463 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.1464 +
  1.1465 +
  1.1466 +   2. The absolute value of the gain, corresponding to the chosen
  1.1467 +      codebook vector, cbvec, must be smaller than a fixed limit,
  1.1468 +      CB_MAXGAIN=1.3:
  1.1469 +
  1.1470 +            |gain| < CB_MAXGAIN
  1.1471 +
  1.1472 +      where the gain is computed in the following way:
  1.1473 +
  1.1474 +            gain = (target*cbvec) / ||cbvec||^2
  1.1475 +
  1.1476 +   3. For the first stage, the dot product of the chosen codebook vector
  1.1477 +      and target must be positive:
  1.1478 +
  1.1479 +      target*cbvec > 0
  1.1480 +
  1.1481 +   In practice the above criteria are used in a sequential search
  1.1482 +   through all codebook vectors.  The best match is found by registering
  1.1483 +   a new max measure and index whenever the previously registered max
  1.1484 +   measure is surpassed and all other criteria are fulfilled.  If none
  1.1485 +   of the codebook vectors fulfill (2) and (3), the first codebook
  1.1486 +   vector is selected.
  1.1487 +
  1.1488 +3.6.4.2.  Gain Quantization at Each Stage
  1.1489 +
  1.1490 +   The gain follows as a result of the computation
  1.1491 +
  1.1492 +      gain = (target*cbvec) / ||cbvec||^2
  1.1493 +
  1.1494 +   for the optimal codebook vector found by the procedure in section
  1.1495 +   3.6.4.1.
  1.1496 +
  1.1497 +   The three stages quantize the gain, using 5, 4, and 3 bits,
  1.1498 +   respectively.  In the first stage, the gain is limited to positive
  1.1499 +   values.  This gain is quantized by finding the nearest value in the
  1.1500 +   quantization table gain_sq5Tbl.
  1.1501 +
  1.1502 +   gain_sq5Tbl[32]={0.037476, 0.075012, 0.112488, 0.150024, 0.187500,
  1.1503 +                  0.224976, 0.262512, 0.299988, 0.337524, 0.375000,
  1.1504 +                  0.412476, 0.450012, 0.487488, 0.525024, 0.562500,
  1.1505 +                  0.599976, 0.637512, 0.674988, 0.712524, 0.750000,
  1.1506 +                  0.787476, 0.825012, 0.862488, 0.900024, 0.937500,
  1.1507 +                  0.974976, 1.012512, 1.049988, 1.087524, 1.125000,
  1.1508 +                  1.162476, 1.200012}
  1.1509 +
  1.1510 +   The gains of the subsequent two stages can be either positive or
  1.1511 +   negative.  The gains are quantized by using a quantization table
  1.1512 +   times a scale factor.  The second stage uses the table gain_sq4Tbl,
  1.1513 +   and the third stage uses gain_sq3Tbl.  The scale factor equates 0.1
  1.1514 +
  1.1515 +
  1.1516 +
  1.1517 +Andersen, et al.              Experimental                     [Page 27]
  1.1518 +
  1.1519 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.1520 +
  1.1521 +
  1.1522 +   or the absolute value of the quantized gain representation value
  1.1523 +   obtained in the previous stage, whichever is larger.  Again, the
  1.1524 +   resulting gain index is the index to the nearest value of the
  1.1525 +   quantization table times the scale factor.
  1.1526 +
  1.1527 +        gainQ = scaleFact * gain_sqXTbl[index]
  1.1528 +
  1.1529 +   gain_sq4Tbl[16]={-1.049988, -0.900024, -0.750000, -0.599976,
  1.1530 +                  -0.450012, -0.299988, -0.150024, 0.000000, 0.150024,
  1.1531 +                  0.299988, 0.450012, 0.599976, 0.750000, 0.900024,
  1.1532 +                  1.049988, 1.200012}
  1.1533 +
  1.1534 +   gain_sq3Tbl[8]={-1.000000, -0.659973, -0.330017,0.000000,
  1.1535 +                  0.250000, 0.500000, 0.750000, 1.00000}
  1.1536 +
  1.1537 +3.6.4.3.  Preparation of Target for Next Stage
  1.1538 +
  1.1539 +   Before performing the search for the next stage, the perceptually
  1.1540 +   weighted target vector is updated by subtracting from it the selected
  1.1541 +   codebook vector (from the perceptually weighted codebook) times the
  1.1542 +   corresponding quantized gain.
  1.1543 +
  1.1544 +      target[i] = target[i] - gainQ * selected_vec[i];
  1.1545 +
  1.1546 +   A reference implementation of the codebook encoding is found in
  1.1547 +   Appendix A.34.
  1.1548 +
  1.1549 +3.7.  Gain Correction Encoding
  1.1550 +
  1.1551 +   The start state is quantized in a relatively model independent manner
  1.1552 +   using 3 bits per sample.  In contrast, the remaining parts of the
  1.1553 +   block are encoded by using an adaptive codebook.  This codebook will
  1.1554 +   produce high matching accuracy whenever there is a high correlation
  1.1555 +   between the target and the best codebook vector.  For unvoiced speech
  1.1556 +   segments and background noises, this is not necessarily so, which,
  1.1557 +   due to the nature of the squared error criterion, results in a coded
  1.1558 +   signal with less power than the target signal.  As the coded start
  1.1559 +   state has good power matching to the target, the result is a power
  1.1560 +   fluctuation within the encoded frame.  Perceptually, the main problem
  1.1561 +   with this is that the time envelope of the signal energy becomes
  1.1562 +   unsteady.  To overcome this problem, the gains for the codebooks are
  1.1563 +   re-scaled after the codebook encoding by searching for a new gain
  1.1564 +   factor for the first stage codebook that provides better power
  1.1565 +   matching.
  1.1566 +
  1.1567 +   First, the energy for the target signal, tene, is computed along with
  1.1568 +   the energy for the coded signal, cene, given by the addition of the
  1.1569 +   three gain scaled codebook vectors.  Because the gains of the second
  1.1570 +
  1.1571 +
  1.1572 +
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  1.1575 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.1576 +
  1.1577 +
  1.1578 +   and third stage scale with the gain of the first stage, when the
  1.1579 +   first stage gain is changed from gain[0] to gain_sq5Tbl[i] the energy
  1.1580 +   of the coded signal changes from cene to
  1.1581 +
  1.1582 +      cene*(gain_sq5Tbl[i]*gain_sq5Tbl[i])/(gain[0]*gain[0])
  1.1583 +
  1.1584 +   where gain[0] is the gain for the first stage found in the original
  1.1585 +   codebook search.  A refined search is performed by testing the gain
  1.1586 +   indices i=0 to 31, and as long as the new codebook energy as given
  1.1587 +   above is less than tene, the gain index for stage 1 is increased.  A
  1.1588 +   restriction is applied so that the new gain value for stage 1 cannot
  1.1589 +   be more than two times higher than the original value found in the
  1.1590 +   codebook search.  Note that by using this method we do not change the
  1.1591 +   shape of the encoded vector, only the gain or amplitude.
  1.1592 +
  1.1593 +3.8.  Bitstream Definition
  1.1594 +
  1.1595 +   The total number of bits used to describe one frame of 20 ms speech
  1.1596 +   is 304, which fits in 38 bytes and results in a bit rate of 15.20
  1.1597 +   kbit/s.  For the case of a frame length of 30 ms speech, the total
  1.1598 +   number of bits used is 400, which fits in 50 bytes and results in a
  1.1599 +   bit rate of 13.33 kbit/s.  In the bitstream definition, the bits are
  1.1600 +   distributed into three classes according to their bit error or loss
  1.1601 +   sensitivity.  The most sensitive bits (class 1) are placed first in
  1.1602 +   the bitstream for each frame.  The less sensitive bits (class 2) are
  1.1603 +   placed after the class 1 bits.  The least sensitive bits (class 3)
  1.1604 +   are placed at the end of the bitstream for each frame.
  1.1605 +
  1.1606 +   In the 20/30 ms frame length cases for each class, the following hold
  1.1607 +   true: The class 1 bits occupy a total of 6/8 bytes (48/64 bits), the
  1.1608 +   class 2 bits occupy 8/12 bytes (64/96 bits), and the class 3 bits
  1.1609 +   occupy 24/30 bytes (191/239 bits).  This distribution of the bits
  1.1610 +   enables the use of uneven level protection (ULP) as is exploited in
  1.1611 +   the payload format definition for iLBC [1].  The detailed bit
  1.1612 +   allocation is shown in the table below.  When a quantization index is
  1.1613 +   distributed between more classes, the more significant bits belong to
  1.1614 +   the lowest class.
  1.1615 +
  1.1616 +
  1.1617 +
  1.1618 +
  1.1619 +
  1.1620 +
  1.1621 +
  1.1622 +
  1.1623 +
  1.1624 +
  1.1625 +
  1.1626 +
  1.1627 +
  1.1628 +
  1.1629 +Andersen, et al.              Experimental                     [Page 29]
  1.1630 +
  1.1631 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.1632 +
  1.1633 +
  1.1634 +   Bitstream structure:
  1.1635 +
  1.1636 +   ------------------------------------------------------------------+
  1.1637 +   Parameter                         |       Bits Class <1,2,3>      |
  1.1638 +                                     |  20 ms frame  |  30 ms frame  |
  1.1639 +   ----------------------------------+---------------+---------------+
  1.1640 +                            Split 1  |   6 <6,0,0>   |   6 <6,0,0>   |
  1.1641 +                   LSF 1    Split 2  |   7 <7,0,0>   |   7 <7,0,0>   |
  1.1642 +   LSF                      Split 3  |   7 <7,0,0>   |   7 <7,0,0>   |
  1.1643 +                   ------------------+---------------+---------------+
  1.1644 +                            Split 1  | NA (Not Appl.)|   6 <6,0,0>   |
  1.1645 +                   LSF 2    Split 2  |      NA       |   7 <7,0,0>   |
  1.1646 +                            Split 3  |      NA       |   7 <7,0,0>   |
  1.1647 +                   ------------------+---------------+---------------+
  1.1648 +                   Sum               |  20 <20,0,0>  |  40 <40,0,0>  |
  1.1649 +   ----------------------------------+---------------+---------------+
  1.1650 +   Block Class                       |   2 <2,0,0>   |   3 <3,0,0>   |
  1.1651 +   ----------------------------------+---------------+---------------+
  1.1652 +   Position 22 sample segment        |   1 <1,0,0>   |   1 <1,0,0>   |
  1.1653 +   ----------------------------------+---------------+---------------+
  1.1654 +   Scale Factor State Coder          |   6 <6,0,0>   |   6 <6,0,0>   |
  1.1655 +   ----------------------------------+---------------+---------------+
  1.1656 +                   Sample 0          |   3 <0,1,2>   |   3 <0,1,2>   |
  1.1657 +   Quantized       Sample 1          |   3 <0,1,2>   |   3 <0,1,2>   |
  1.1658 +   Residual           :              |   :    :      |   :    :      |
  1.1659 +   State              :              |   :    :      |   :    :      |
  1.1660 +   Samples            :              |   :    :      |   :    :      |
  1.1661 +                   Sample 56         |   3 <0,1,2>   |   3 <0,1,2>   |
  1.1662 +                   Sample 57         |      NA       |   3 <0,1,2>   |
  1.1663 +                   ------------------+---------------+---------------+
  1.1664 +                   Sum               | 171 <0,57,114>| 174 <0,58,116>|
  1.1665 +   ----------------------------------+---------------+---------------+
  1.1666 +                            Stage 1  |   7 <6,0,1>   |   7 <4,2,1>   |
  1.1667 +   CB for 22/23             Stage 2  |   7 <0,0,7>   |   7 <0,0,7>   |
  1.1668 +   sample block             Stage 3  |   7 <0,0,7>   |   7 <0,0,7>   |
  1.1669 +                   ------------------+---------------+---------------+
  1.1670 +                   Sum               |  21 <6,0,15>  |  21 <4,2,15>  |
  1.1671 +   ----------------------------------+---------------+---------------+
  1.1672 +                            Stage 1  |   5 <2,0,3>   |   5 <1,1,3>   |
  1.1673 +   Gain for 22/23           Stage 2  |   4 <1,1,2>   |   4 <1,1,2>   |
  1.1674 +   sample block             Stage 3  |   3 <0,0,3>   |   3 <0,0,3>   |
  1.1675 +                   ------------------+---------------+---------------+
  1.1676 +                   Sum               |  12 <3,1,8>   |  12 <2,2,8>   |
  1.1677 +   ----------------------------------+---------------+---------------+
  1.1678 +                            Stage 1  |   8 <7,0,1>   |   8 <6,1,1>   |
  1.1679 +               sub-block 1  Stage 2  |   7 <0,0,7>   |   7 <0,0,7>   |
  1.1680 +                            Stage 3  |   7 <0,0,7>   |   7 <0,0,7>   |
  1.1681 +                   ------------------+---------------+---------------+
  1.1682 +
  1.1683 +
  1.1684 +
  1.1685 +Andersen, et al.              Experimental                     [Page 30]
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  1.1687 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.1688 +
  1.1689 +
  1.1690 +                            Stage 1  |   8 <0,0,8>   |   8 <0,7,1>   |
  1.1691 +               sub-block 2  Stage 2  |   8 <0,0,8>   |   8 <0,0,8>   |
  1.1692 +   Indices                  Stage 3  |   8 <0,0,8>   |   8 <0,0,8>   |
  1.1693 +   for CB          ------------------+---------------+---------------+
  1.1694 +   sub-blocks               Stage 1  |      NA       |   8 <0,7,1>   |
  1.1695 +               sub-block 3  Stage 2  |      NA       |   8 <0,0,8>   |
  1.1696 +                            Stage 3  |      NA       |   8 <0,0,8>   |
  1.1697 +                   ------------------+---------------+---------------+
  1.1698 +                            Stage 1  |      NA       |   8 <0,7,1>   |
  1.1699 +               sub-block 4  Stage 2  |      NA       |   8 <0,0,8>   |
  1.1700 +                            Stage 3  |      NA       |   8 <0,0,8>   |
  1.1701 +                   ------------------+---------------+---------------+
  1.1702 +                   Sum               |  46 <7,0,39>  |  94 <6,22,66> |
  1.1703 +   ----------------------------------+---------------+---------------+
  1.1704 +                            Stage 1  |   5 <1,2,2>   |   5 <1,2,2>   |
  1.1705 +               sub-block 1  Stage 2  |   4 <1,1,2>   |   4 <1,2,1>   |
  1.1706 +                            Stage 3  |   3 <0,0,3>   |   3 <0,0,3>   |
  1.1707 +                   ------------------+---------------+---------------+
  1.1708 +                            Stage 1  |   5 <1,1,3>   |   5 <0,2,3>   |
  1.1709 +               sub-block 2  Stage 2  |   4 <0,2,2>   |   4 <0,2,2>   |
  1.1710 +                            Stage 3  |   3 <0,0,3>   |   3 <0,0,3>   |
  1.1711 +   Gains for       ------------------+---------------+---------------+
  1.1712 +   sub-blocks               Stage 1  |      NA       |   5 <0,1,4>   |
  1.1713 +               sub-block 3  Stage 2  |      NA       |   4 <0,1,3>   |
  1.1714 +                            Stage 3  |      NA       |   3 <0,0,3>   |
  1.1715 +                   ------------------+---------------+---------------+
  1.1716 +                            Stage 1  |      NA       |   5 <0,1,4>   |
  1.1717 +               sub-block 4  Stage 2  |      NA       |   4 <0,1,3>   |
  1.1718 +                            Stage 3  |      NA       |   3 <0,0,3>   |
  1.1719 +                   ------------------+---------------+---------------+
  1.1720 +                   Sum               |  24 <3,6,15>  |  48 <2,12,34> |
  1.1721 +   ----------------------------------+---------------+---------------+
  1.1722 +   Empty frame indicator             |   1 <0,0,1>   |   1 <0,0,1>   |
  1.1723 +   -------------------------------------------------------------------
  1.1724 +   SUM                                 304 <48,64,192> 400 <64,96,240>
  1.1725 +
  1.1726 +   Table 3.2.  The bitstream definition for iLBC for both the 20 ms
  1.1727 +   frame size mode and the 30 ms frame size mode.
  1.1728 +
  1.1729 +   When packetized into the payload, the bits MUST be sorted as follows:
  1.1730 +   All the class 1 bits in the order (from top to bottom) as specified
  1.1731 +   in the table, all the class 2 bits (from top to bottom), and all the
  1.1732 +   class 3 bits in the same sequential order.  The last bit, the empty
  1.1733 +   frame indicator, SHOULD be set to zero by the encoder.  If this bit
  1.1734 +   is set to 1 the decoder SHOULD treat the data as a lost frame.  For
  1.1735 +   example, this bit can be set to 1 to indicate lost frame for file
  1.1736 +   storage format, as in [1].
  1.1737 +
  1.1738 +
  1.1739 +
  1.1740 +
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  1.1743 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.1744 +
  1.1745 +
  1.1746 +4.  Decoder Principles
  1.1747 +
  1.1748 +   This section describes the principles of each component of the
  1.1749 +   decoder algorithm.
  1.1750 +
  1.1751 +              +-------------+    +--------+    +---------------+
  1.1752 +   payload -> | 1. Get para | -> | 2. LPC | -> | 3. Sc Dequant | ->
  1.1753 +              +-------------+    +--------+    +---------------+
  1.1754 +
  1.1755 +              +-------------+    +------------------+
  1.1756 +           -> | 4. Mem setup| -> | 5. Construct res |------->
  1.1757 +           |  +-------------+    +-------------------   |
  1.1758 +           ---------<-----------<-----------<------------
  1.1759 +                     Sub-frame 0...2/4 (20 ms/30 ms)
  1.1760 +
  1.1761 +              +----------------+    +----------+
  1.1762 +           -> | 6. Enhance res | -> | 7. Synth | ------------>
  1.1763 +              +----------------+    +----------+
  1.1764 +
  1.1765 +              +-----------------+
  1.1766 +           -> | 8. Post Process | ----------------> decoded speech
  1.1767 +              +-----------------+
  1.1768 +
  1.1769 +   Figure 4.1.  Flow chart of the iLBC decoder.  If a frame was lost,
  1.1770 +   steps 1 to 5 SHOULD be replaced by a PLC algorithm.
  1.1771 +
  1.1772 +   1. Extract the parameters from the bitstream.
  1.1773 +
  1.1774 +   2. Decode the LPC and interpolate (section 4.1).
  1.1775 +
  1.1776 +   3. Construct the 57/58-sample start state (section 4.2).
  1.1777 +
  1.1778 +   4. Set up the memory by using data from the decoded residual.  This
  1.1779 +      memory is used for codebook construction.  For blocks preceding
  1.1780 +      the start state, both the decoded residual and the target are time
  1.1781 +      reversed.  Sub-frames are decoded in the same order as they were
  1.1782 +      encoded.
  1.1783 +
  1.1784 +   5. Construct the residuals of this sub-frame (gain[0]*cbvec[0] +
  1.1785 +      gain[1]*cbvec[1] + gain[2]*cbvec[2]).  Repeat 4 and 5 until the
  1.1786 +      residual of all sub-blocks has been constructed.
  1.1787 +
  1.1788 +   6. Enhance the residual with the post filter (section 4.6).
  1.1789 +
  1.1790 +   7. Synthesis of the residual (section 4.7).
  1.1791 +
  1.1792 +   8. Post process with HP filter, if desired (section 4.8).
  1.1793 +
  1.1794 +
  1.1795 +
  1.1796 +
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  1.1800 +
  1.1801 +
  1.1802 +4.1.  LPC Filter Reconstruction
  1.1803 +
  1.1804 +   The decoding of the LP filter parameters is very straightforward.
  1.1805 +   For a set of three/six indices, the corresponding LSF vector(s) are
  1.1806 +   found by simple table lookup.  For each of the LSF vectors, the three
  1.1807 +   split vectors are concatenated to obtain qlsf1 and qlsf2,
  1.1808 +   respectively (in the 20 ms mode only one LSF vector, qlsf, is
  1.1809 +   constructed).  The next step is the stability check described in
  1.1810 +   section 3.2.5 followed by the interpolation scheme described in
  1.1811 +   section 3.2.6 (3.2.7 for 20 ms frames).  The only difference is that
  1.1812 +   only the quantized LSFs are known at the decoder, and hence the
  1.1813 +   unquantized LSFs are not processed.
  1.1814 +
  1.1815 +   A reference implementation of the LPC filter reconstruction is given
  1.1816 +   in Appendix A.36.
  1.1817 +
  1.1818 +4.2.  Start State Reconstruction
  1.1819 +
  1.1820 +   The scalar encoded STATE_SHORT_LEN=58 (STATE_SHORT_LEN=57 in the 20
  1.1821 +   ms mode) state samples are reconstructed by 1) forming a set of
  1.1822 +   samples (by table lookup) from the index stream idxVec[n], 2)
  1.1823 +   multiplying the set with 1/scal=(10^qmax)/4.5, 3) time reversing the
  1.1824 +   57/58 samples, 4) filtering the time reversed block with the
  1.1825 +   dispersion (all-pass) filter used in the encoder (as described in
  1.1826 +   section 3.5.2); this compensates for the phase distortion of the
  1.1827 +   earlier filter operation, and 5 reversing the 57/58 samples from the
  1.1828 +   previous step.
  1.1829 +
  1.1830 +   in(0..(STATE_SHORT_LEN-1)) = time reversed samples from table
  1.1831 +                                look-up,
  1.1832 +                                idxVecDec((STATE_SHORT_LEN-1)..0)
  1.1833 +
  1.1834 +   in(STATE_SHORT_LEN..(2*STATE_SHORT_LEN-1)) = 0
  1.1835 +
  1.1836 +   Pk(z) = A~rk(z)/A~k(z), where
  1.1837 +                                  ___
  1.1838 +                                  \
  1.1839 +   A~rk(z)= z^(-LPC_FILTERORDER) + > a~ki*z^(i-(LPC_FILTERORDER-1))
  1.1840 +                                  /__
  1.1841 +                              i=0...(LPC_FILTERORDER-1)
  1.1842 +
  1.1843 +   and A~k(z) is taken from the block where the start state begins
  1.1844 +
  1.1845 +   in -> Pk(z) -> filtered
  1.1846 +
  1.1847 +   out(k) = filtered(STATE_SHORT_LEN-1-k) +
  1.1848 +                           filtered(2*STATE_SHORT_LEN-1-k),
  1.1849 +                                         k=0..(STATE_SHORT_LEN-1)
  1.1850 +
  1.1851 +
  1.1852 +
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  1.1856 +
  1.1857 +
  1.1858 +   The remaining 23/22 samples in the state are reconstructed by the
  1.1859 +   same adaptive codebook technique described in section 4.3.  The
  1.1860 +   location bit determines whether these are the first or the last 23/22
  1.1861 +   samples of the 80-sample state vector.  If the remaining 23/22
  1.1862 +   samples are the first samples, then the scalar encoded
  1.1863 +   STATE_SHORT_LEN state samples are time-reversed before initialization
  1.1864 +   of the adaptive codebook memory vector.
  1.1865 +
  1.1866 +   A reference implementation of the start state reconstruction is given
  1.1867 +   in Appendix A.44.
  1.1868 +
  1.1869 +4.3.  Excitation Decoding Loop
  1.1870 +
  1.1871 +   The decoding of the LPC excitation vector proceeds in the same order
  1.1872 +   in which the residual was encoded at the encoder.  That is, after the
  1.1873 +   decoding of the entire 80-sample state vector, the forward sub-blocks
  1.1874 +   (corresponding to samples occurring after the state vector samples)
  1.1875 +   are decoded, and then the backward sub-blocks (corresponding to
  1.1876 +   samples occurring before the state vector) are decoded, resulting in
  1.1877 +   a fully decoded block of excitation signal samples.
  1.1878 +
  1.1879 +   In particular, each sub-block is decoded by using the multistage
  1.1880 +   adaptive codebook decoding module described in section 4.4.  This
  1.1881 +   module relies upon an adaptive codebook memory constructed before
  1.1882 +   each run of the adaptive codebook decoding.  The construction of the
  1.1883 +   adaptive codebook memory in the decoder is identical to the method
  1.1884 +   outlined in section 3.6.3, except that it is done on the codebook
  1.1885 +   memory without perceptual weighting.
  1.1886 +
  1.1887 +   For the initial forward sub-block, the last STATE_LEN=80 samples of
  1.1888 +   the length CB_LMEM=147 adaptive codebook memory are filled with the
  1.1889 +   samples of the state vector.  For subsequent forward sub-blocks, the
  1.1890 +   first SUBL=40 samples of the adaptive codebook memory are discarded,
  1.1891 +   the remaining samples are shifted by SUBL samples toward the
  1.1892 +   beginning of the vector, and the newly decoded SUBL=40 samples are
  1.1893 +   placed at the end of the adaptive codebook memory.  For backward
  1.1894 +   sub-blocks, the construction is similar, except that every vector of
  1.1895 +   samples involved is first time reversed.
  1.1896 +
  1.1897 +   A reference implementation of the excitation decoding loop is found
  1.1898 +   in Appendix A.5.
  1.1899 +
  1.1900 +
  1.1901 +
  1.1902 +
  1.1903 +
  1.1904 +
  1.1905 +
  1.1906 +
  1.1907 +
  1.1908 +
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  1.1912 +
  1.1913 +
  1.1914 +4.4.  Multistage Adaptive Codebook Decoding
  1.1915 +
  1.1916 +   The Multistage Adaptive Codebook Decoding module is used at both the
  1.1917 +   sender (encoder) and the receiver (decoder) ends to produce a
  1.1918 +   synthetic signal in the residual domain that is eventually used to
  1.1919 +   produce synthetic speech.  The module takes the index values used to
  1.1920 +   construct vectors that are scaled and summed together to produce a
  1.1921 +   synthetic signal that is the output of the module.
  1.1922 +
  1.1923 +4.4.1.  Construction of the Decoded Excitation Signal
  1.1924 +
  1.1925 +   The unpacked index values provided at the input to the module are
  1.1926 +   references to extended codebooks, which are constructed as described
  1.1927 +   in section 3.6.3, except that they are based on the codebook memory
  1.1928 +   without the perceptual weighting.  The unpacked three indices are
  1.1929 +   used to look up three codebook vectors.  The unpacked three gain
  1.1930 +   indices are used to decode the corresponding 3 gains.  In this
  1.1931 +   decoding, the successive rescaling, as described in section 3.6.4.2,
  1.1932 +   is applied.
  1.1933 +
  1.1934 +   A reference implementation of the adaptive codebook decoding is
  1.1935 +   listed in Appendix A.32.
  1.1936 +
  1.1937 +4.5.  Packet Loss Concealment
  1.1938 +
  1.1939 +   If packet loss occurs, the decoder receives a signal saying that
  1.1940 +   information regarding a block is lost.  For such blocks it is
  1.1941 +   RECOMMENDED to use a Packet Loss Concealment (PLC) unit to create a
  1.1942 +   decoded signal that masks the effect of that packet loss.  In the
  1.1943 +   following we will describe an example of a PLC unit that can be used
  1.1944 +   with the iLBC codec.  As the PLC unit is used only at the decoder,
  1.1945 +   the PLC unit does not affect interoperability between
  1.1946 +   implementations.  Other PLC implementations MAY therefore be used.
  1.1947 +
  1.1948 +   The PLC described operates on the LP filters and the excitation
  1.1949 +   signals and is based on the following principles:
  1.1950 +
  1.1951 +4.5.1.  Block Received Correctly and Previous Block Also Received
  1.1952 +
  1.1953 +   If the block is received correctly, the PLC only records state
  1.1954 +   information of the current block that can be used in case the next
  1.1955 +   block is lost.  The LP filter coefficients for each sub-block and the
  1.1956 +   entire decoded excitation signal are all saved in the decoder state
  1.1957 +   structure.  All of this information will be needed if the following
  1.1958 +   block is lost.
  1.1959 +
  1.1960 +
  1.1961 +
  1.1962 +
  1.1963 +
  1.1964 +
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  1.1968 +
  1.1969 +
  1.1970 +4.5.2.  Block Not Received
  1.1971 +
  1.1972 +   If the block is not received, the block substitution is based on a
  1.1973 +   pitch-synchronous repetition of the excitation signal, which is
  1.1974 +   filtered by the last LP filter of the previous block.  The previous
  1.1975 +   block's information is stored in the decoder state structure.
  1.1976 +
  1.1977 +   A correlation analysis is performed on the previous block's
  1.1978 +   excitation signal in order to detect the amount of pitch periodicity
  1.1979 +   and a pitch value.  The correlation measure is also used to decide on
  1.1980 +   the voicing level (the degree to which the previous block's
  1.1981 +   excitation was a voiced or roughly periodic signal).  The excitation
  1.1982 +   in the previous block is used to create an excitation for the block
  1.1983 +   to be substituted, such that the pitch of the previous block is
  1.1984 +   maintained.  Therefore, the new excitation is constructed in a
  1.1985 +   pitch-synchronous manner.  In order to avoid a buzzy-sounding
  1.1986 +   substituted block, a random excitation is mixed with the new pitch
  1.1987 +   periodic excitation, and the relative use of the two components is
  1.1988 +   computed from the correlation measure (voicing level).
  1.1989 +
  1.1990 +   For the block to be substituted, the newly constructed excitation
  1.1991 +   signal is then passed through the LP filter to produce the speech
  1.1992 +   that will be substituted for the lost block.
  1.1993 +
  1.1994 +   For several consecutive lost blocks, the packet loss concealment
  1.1995 +   continues in a similar manner.  The correlation measure of the last
  1.1996 +   block received is still used along with the same pitch value.  The LP
  1.1997 +   filters of the last block received are also used again.  The energy
  1.1998 +   of the substituted excitation for consecutive lost blocks is
  1.1999 +   decreased, leading to a dampened excitation, and therefore to
  1.2000 +   dampened speech.
  1.2001 +
  1.2002 +4.5.3.  Block Received Correctly When Previous Block Not Received
  1.2003 +
  1.2004 +   For the case in which a block is received correctly when the previous
  1.2005 +   block was not, the correctly received block's directly decoded speech
  1.2006 +   (based solely on the received block) is not used as the actual
  1.2007 +   output.  The reason for this is that the directly decoded speech does
  1.2008 +   not necessarily smoothly merge into the synthetic speech generated
  1.2009 +   for the previous lost block.  If the two signals are not smoothly
  1.2010 +   merged, an audible discontinuity is accidentally produced.
  1.2011 +   Therefore, a correlation analysis between the two blocks of
  1.2012 +   excitation signal (the excitation of the previous concealed block and
  1.2013 +   that of the current received block) is performed to find the best
  1.2014 +   phase match.  Then a simple overlap-add procedure is performed to
  1.2015 +   merge the previous excitation smoothly into the current block's
  1.2016 +   excitation.
  1.2017 +
  1.2018 +
  1.2019 +
  1.2020 +
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  1.2024 +
  1.2025 +
  1.2026 +   The exact implementation of the packet loss concealment does not
  1.2027 +   influence interoperability of the codec.
  1.2028 +
  1.2029 +   A reference implementation of the packet loss concealment is
  1.2030 +   suggested in Appendix A.14.  Exact compliance with this suggested
  1.2031 +   algorithm is not needed for a reference implementation to be fully
  1.2032 +   compatible with the overall codec specification.
  1.2033 +
  1.2034 +4.6.  Enhancement
  1.2035 +
  1.2036 +   The decoder contains an enhancement unit that operates on the
  1.2037 +   reconstructed excitation signal.  The enhancement unit increases the
  1.2038 +   perceptual quality of the reconstructed signal by reducing the
  1.2039 +   speech-correlated noise in the voiced speech segments.  Compared to
  1.2040 +   traditional postfilters, the enhancer has an advantage in that it can
  1.2041 +   only modify the excitation signal slightly.  This means that there is
  1.2042 +   no risk of over enhancement.  The enhancer works very similarly for
  1.2043 +   both the 20 ms frame size mode and the 30 ms frame size mode.
  1.2044 +
  1.2045 +   For the mode with 20 ms frame size, the enhancer uses a memory of six
  1.2046 +   80-sample excitation blocks prior in time plus the two new 80-sample
  1.2047 +   excitation blocks.  For each block of 160 new unenhanced excitation
  1.2048 +   samples, 160 enhanced excitation samples are produced.  The enhanced
  1.2049 +   excitation is 40-sample delayed compared to the unenhanced
  1.2050 +   excitation, as the enhancer algorithm uses lookahead.
  1.2051 +
  1.2052 +   For the mode with 30 ms frame size, the enhancer uses a memory of
  1.2053 +   five 80-sample excitation blocks prior in time plus the three new
  1.2054 +   80-sample excitation blocks.  For each block of 240 new unenhanced
  1.2055 +   excitation samples, 240 enhanced excitation samples are produced.
  1.2056 +   The enhanced excitation is 80-sample delayed compared to the
  1.2057 +   unenhanced excitation, as the enhancer algorithm uses lookahead.
  1.2058 +
  1.2059 +   Outline of Enhancer
  1.2060 +
  1.2061 +   The speech enhancement unit operates on sub-blocks of 80 samples,
  1.2062 +   which means that there are two/three 80 sample sub-blocks per frame.
  1.2063 +   Each of these two/three sub-blocks is enhanced separately, but in an
  1.2064 +   analogous manner.
  1.2065 +
  1.2066 +
  1.2067 +
  1.2068 +
  1.2069 +
  1.2070 +
  1.2071 +
  1.2072 +
  1.2073 +
  1.2074 +
  1.2075 +
  1.2076 +
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  1.2080 +
  1.2081 +
  1.2082 +   unenhanced residual
  1.2083 +           |
  1.2084 +           |   +---------------+    +--------------+
  1.2085 +           +-> | 1. Pitch Est  | -> | 2. Find PSSQ | -------->
  1.2086 +               +---------------+  | +--------------+
  1.2087 +                                  +-----<-------<------<--+
  1.2088 +               +------------+         enh block 0..1/2    |
  1.2089 +            -> | 3. Smooth  |                             |
  1.2090 +               +------------+                             |
  1.2091 +                 \                                        |
  1.2092 +                 /\                                       |
  1.2093 +                /  \   Already                            |
  1.2094 +               / 4. \----------->----------->-----------+ |
  1.2095 +               \Crit/ Fulfilled                         | |
  1.2096 +                \? /                                    v |
  1.2097 +                 \/                                     | |
  1.2098 +                  \  +-----------------+    +---------+ | |
  1.2099 +              Not +->| 5. Use Constr.  | -> | 6. Mix  | ----->
  1.2100 +           Fulfilled +-----------------+    +---------+
  1.2101 +
  1.2102 +            ---------------> enhanced residual
  1.2103 +
  1.2104 +   Figure 4.2.  Flow chart of the enhancer.
  1.2105 +
  1.2106 +   1. Pitch estimation of each of the two/three new 80-sample blocks.
  1.2107 +
  1.2108 +   2. Find the pitch-period-synchronous sequence n (for block k) by a
  1.2109 +      search around the estimated pitch value.  Do this for n=1,2,3,
  1.2110 +      -1,-2,-3.
  1.2111 +
  1.2112 +   3. Calculate the smoothed residual generated by the six pitch-
  1.2113 +      period-synchronous sequences from prior step.
  1.2114 +
  1.2115 +   4. Check if the smoothed residual satisfies the criterion (section
  1.2116 +      4.6.4).
  1.2117 +
  1.2118 +   5. Use constraint to calculate mixing factor (section 4.6.5).
  1.2119 +
  1.2120 +   6. Mix smoothed signal with unenhanced residual (pssq(n) n=0).
  1.2121 +
  1.2122 +   The main idea of the enhancer is to find three 80 sample blocks
  1.2123 +   before and three 80-sample blocks after the analyzed unenhanced sub-
  1.2124 +   block and to use these to improve the quality of the excitation in
  1.2125 +   that sub-block.  The six blocks are chosen so that they have the
  1.2126 +   highest possible correlation with the unenhanced sub-block that is
  1.2127 +   being enhanced.  In other words, the six blocks are pitch-period-
  1.2128 +   synchronous sequences to the unenhanced sub-block.
  1.2129 +
  1.2130 +
  1.2131 +
  1.2132 +
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  1.2136 +
  1.2137 +
  1.2138 +   A linear combination of the six pitch-period-synchronous sequences is
  1.2139 +   calculated that approximates the sub-block.  If the squared error
  1.2140 +   between the approximation and the unenhanced sub-block is small
  1.2141 +   enough, the enhanced residual is set equal to this approximation.
  1.2142 +   For the cases when the squared error criterion is not fulfilled, a
  1.2143 +   linear combination of the approximation and the unenhanced residual
  1.2144 +   forms the enhanced residual.
  1.2145 +
  1.2146 +4.6.1.  Estimating the Pitch
  1.2147 +
  1.2148 +   Pitch estimates are needed to determine the locations of the pitch-
  1.2149 +   period-synchronous sequences in a complexity-efficient way.  For each
  1.2150 +   of the new two/three sub-blocks, a pitch estimate is calculated by
  1.2151 +   finding the maximum correlation in the range from lag 20 to lag 120.
  1.2152 +   These pitch estimates are used to narrow down the search for the best
  1.2153 +   possible pitch-period-synchronous sequences.
  1.2154 +
  1.2155 +4.6.2.  Determination of the Pitch-Synchronous Sequences
  1.2156 +
  1.2157 +   Upon receiving the pitch estimates from the prior step, the enhancer
  1.2158 +   analyzes and enhances one 80-sample sub-block at a time.  The pitch-
  1.2159 +   period-synchronous-sequences pssq(n) can be viewed as vectors of
  1.2160 +   length 80 samples each shifted n*lag samples from the current sub-
  1.2161 +   block.  The six pitch-period-synchronous-sequences, pssq(-3) to
  1.2162 +   pssq(-1) and pssq(1) to pssq(3), are found one at a time by the steps
  1.2163 +   below:
  1.2164 +
  1.2165 +   1) Calculate the estimate of the position of the pssq(n).  For
  1.2166 +      pssq(n) in front of pssq(0) (n > 0), the location of the pssq(n)
  1.2167 +      is estimated by moving one pitch estimate forward in time from the
  1.2168 +      exact location of pssq(n-1).  Similarly, pssq(n) behind pssq(0) (n
  1.2169 +      < 0) is estimated by moving one pitch estimate backward in time
  1.2170 +      from the exact location of pssq(n+1).  If the estimated pssq(n)
  1.2171 +      vector location is totally within the enhancer memory (Figure
  1.2172 +      4.3), steps 2, 3, and 4 are performed, otherwise the pssq(n) is
  1.2173 +      set to zeros.
  1.2174 +
  1.2175 +   2) Compute the correlation between the unenhanced excitation and
  1.2176 +      vectors around the estimated location interval of pssq(n).  The
  1.2177 +      correlation is calculated in the interval estimated location +/- 2
  1.2178 +      samples.  This results in five correlation values.
  1.2179 +
  1.2180 +   3) The five correlation values are upsampled by a factor of 4, by
  1.2181 +      using four simple upsampling filters (MA filters with coefficients
  1.2182 +      upsFilter1.. upsFilter4).  Within these the maximum value is
  1.2183 +      found, which specifies the best pitch-period with a resolution of
  1.2184 +      a quarter of a sample.
  1.2185 +
  1.2186 +
  1.2187 +
  1.2188 +
  1.2189 +Andersen, et al.              Experimental                     [Page 39]
  1.2190 +
  1.2191 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.2192 +
  1.2193 +
  1.2194 +      upsFilter1[7]={0.000000 0.000000 0.000000 1.000000
  1.2195 +             0.000000 0.000000 0.000000}
  1.2196 +      upsFilter2[7]={0.015625 -0.076904 0.288330 0.862061
  1.2197 +            -0.106445 0.018799 -0.015625}
  1.2198 +      upsFilter3[7]={0.023682 -0.124268 0.601563 0.601563
  1.2199 +            -0.124268 0.023682 -0.023682}
  1.2200 +      upsFilter4[7]={0.018799 -0.106445 0.862061 0.288330
  1.2201 +            -0.076904 0.015625 -0.018799}
  1.2202 +
  1.2203 +   4) Generate the pssq(n) vector by upsampling of the excitation memory
  1.2204 +      and extracting the sequence that corresponds to the lag delay that
  1.2205 +      was calculated in prior step.
  1.2206 +
  1.2207 +   With the steps above, all the pssq(n) can be found in an iterative
  1.2208 +   manner, first moving backward in time from pssq(0) and then forward
  1.2209 +   in time from pssq(0).
  1.2210 +
  1.2211 +
  1.2212 +   0              159             319             479             639
  1.2213 +   +---------------------------------------------------------------+
  1.2214 +   |  -5   |  -4   |  -3   |  -2   |  -1   |   0   |   1   |   2   |
  1.2215 +   +---------------------------------------------------------------+
  1.2216 +                                               |pssq 0 |
  1.2217 +                                          |pssq -1| |pssq 1 |
  1.2218 +                                       |pssq -2|       |pssq 2 |
  1.2219 +                                    |pssq -3|             |pssq 3 |
  1.2220 +
  1.2221 +   Figure 4.3.  Enhancement for 20 ms frame size.
  1.2222 +
  1.2223 +   Figure 4.3 depicts pitch-period-synchronous sequences in the
  1.2224 +   enhancement of the first 80 sample block in the 20 ms frame size
  1.2225 +   mode.  The unenhanced signal input is stored in the last two sub-
  1.2226 +   blocks (1 - 2), and the six other sub-blocks contain unenhanced
  1.2227 +   residual prior-in-time.  We perform the enhancement algorithm on two
  1.2228 +   blocks of 80 samples, where the first of the two blocks consists of
  1.2229 +   the last 40 samples of sub-block 0 and the first 40 samples of sub-
  1.2230 +   block 1.  The second 80-sample block consists of the last 40 samples
  1.2231 +   of sub-block 1 and the first 40 samples of sub-block 2.
  1.2232 +
  1.2233 +
  1.2234 +
  1.2235 +
  1.2236 +
  1.2237 +
  1.2238 +
  1.2239 +
  1.2240 +
  1.2241 +
  1.2242 +
  1.2243 +
  1.2244 +
  1.2245 +Andersen, et al.              Experimental                     [Page 40]
  1.2246 +
  1.2247 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.2248 +
  1.2249 +
  1.2250 +   0              159             319             479             639
  1.2251 +   +---------------------------------------------------------------+
  1.2252 +   |  -4   |  -3   |  -2   |  -1   |   0   |   1   |   2   |   3   |
  1.2253 +   +---------------------------------------------------------------+
  1.2254 +                                   |pssq 0 |
  1.2255 +                              |pssq -1| |pssq 1 |
  1.2256 +                           |pssq -2|       |pssq 2 |
  1.2257 +                        |pssq -3|             |pssq 3 |
  1.2258 +
  1.2259 +   Figure 4.4.  Enhancement for 30 ms frame size.
  1.2260 +
  1.2261 +   Figure 4.4 depicts pitch-period-synchronous sequences in the
  1.2262 +   enhancement of the first 80-sample block in the 30 ms frame size
  1.2263 +   mode.  The unenhanced signal input is stored in the last three sub-
  1.2264 +   blocks (1 - 3).  The five other sub-blocks contain unenhanced
  1.2265 +   residual prior-in-time.  The enhancement algorithm is performed on
  1.2266 +   the three 80 sample sub-blocks 0, 1, and 2.
  1.2267 +
  1.2268 +4.6.3.  Calculation of the Smoothed Excitation
  1.2269 +
  1.2270 +   A linear combination of the six pssq(n) (n!=0) form a smoothed
  1.2271 +   approximation, z, of pssq(0).  Most of the weight is put on the
  1.2272 +   sequences that are close to pssq(0), as these are likely to be most
  1.2273 +   similar to pssq(0).  The smoothed vector is also rescaled so that the
  1.2274 +   energy of z is the same as the energy of pssq(0).
  1.2275 +
  1.2276 +      ___
  1.2277 +      \
  1.2278 +   y = > pssq(i) * pssq_weight(i)
  1.2279 +      /__
  1.2280 +   i=-3,-2,-1,1,2,3
  1.2281 +
  1.2282 +   pssq_weight(i) = 0.5*(1-cos(2*pi*(i+4)/(2*3+2)))
  1.2283 +
  1.2284 +   z = C * y, where C = ||pssq(0)||/||y||
  1.2285 +
  1.2286 +4.6.4.  Enhancer Criterion
  1.2287 +
  1.2288 +   The criterion of the enhancer is that the enhanced excitation is not
  1.2289 +   allowed to differ much from the unenhanced excitation.  This
  1.2290 +   criterion is checked for each 80-sample sub-block.
  1.2291 +
  1.2292 +   e < (b * ||pssq(0)||^2), where b=0.05 and   (Constraint 1)
  1.2293 +
  1.2294 +   e = (pssq(0)-z)*(pssq(0)-z), and "*" means the dot product
  1.2295 +
  1.2296 +
  1.2297 +
  1.2298 +
  1.2299 +
  1.2300 +
  1.2301 +Andersen, et al.              Experimental                     [Page 41]
  1.2302 +
  1.2303 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.2304 +
  1.2305 +
  1.2306 +4.6.5.  Enhancing the excitation
  1.2307 +
  1.2308 +   From the criterion in the previous section, it is clear that the
  1.2309 +   excitation is not allowed to change much.  The purpose of this
  1.2310 +   constraint is to prevent the creation of an enhanced signal
  1.2311 +   significantly different from the original signal.  This also means
  1.2312 +   that the constraint limits the numerical size of the errors that the
  1.2313 +   enhancement procedure can make.  That is especially important in
  1.2314 +   unvoiced segments and background noise segments for which increased
  1.2315 +   periodicity could lead to lower perceived quality.
  1.2316 +
  1.2317 +   When the constraint in the prior section is not met, the enhanced
  1.2318 +   residual is instead calculated through a constrained optimization by
  1.2319 +   using the Lagrange multiplier technique.  The new constraint is that
  1.2320 +
  1.2321 +      e = (b * ||pssq(0)||^2)                     (Constraint 2)
  1.2322 +
  1.2323 +   We distinguish two solution regions for the optimization: 1) the
  1.2324 +   region where the first constraint is fulfilled and 2) the region
  1.2325 +   where the first constraint is not fulfilled and the second constraint
  1.2326 +   must be used.
  1.2327 +
  1.2328 +   In the first case, where the second constraint is not needed, the
  1.2329 +   optimized re-estimated vector is simply z, the energy-scaled version
  1.2330 +   of y.
  1.2331 +
  1.2332 +   In the second case, where the second constraint is activated and
  1.2333 +   becomes an equality constraint, we have
  1.2334 +
  1.2335 +      z= A*y + B*pssq(0)
  1.2336 +
  1.2337 +   where
  1.2338 +
  1.2339 +      A = sqrt((b-b^2/4)*(w00*w00)/ (w11*w00 + w10*w10)) and
  1.2340 +
  1.2341 +      w11 = pssq(0)*pssq(0)
  1.2342 +      w00 = y*y
  1.2343 +      w10 = y*pssq(0)    (* symbolizes the dot product)
  1.2344 +
  1.2345 +   and
  1.2346 +
  1.2347 +      B = 1 - b/2 - A * w10/w00
  1.2348 +
  1.2349 +   Appendix A.16 contains a listing of a reference implementation for
  1.2350 +   the enhancement method.
  1.2351 +
  1.2352 +
  1.2353 +
  1.2354 +
  1.2355 +
  1.2356 +
  1.2357 +Andersen, et al.              Experimental                     [Page 42]
  1.2358 +
  1.2359 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.2360 +
  1.2361 +
  1.2362 +4.7.  Synthesis Filtering
  1.2363 +
  1.2364 +   Upon decoding or PLC of the LP excitation block, the decoded speech
  1.2365 +   block is obtained by running the decoded LP synthesis filter,
  1.2366 +   1/A~k(z), over the block.  The synthesis filters have to be shifted
  1.2367 +   to compensate for the delay in the enhancer.  For 20 ms frame size
  1.2368 +   mode, they SHOULD be shifted one 40-sample sub-block, and for 30 ms
  1.2369 +   frame size mode, they SHOULD be shifted two 40-sample sub-blocks.
  1.2370 +   The LP coefficients SHOULD be changed at the first sample of every
  1.2371 +   sub-block while keeping the filter state.  For PLC blocks, one
  1.2372 +   solution is to apply the last LP coefficients of the last decoded
  1.2373 +   speech block for all sub-blocks.
  1.2374 +
  1.2375 +   The reference implementation for the synthesis filtering can be found
  1.2376 +   in Appendix A.48.
  1.2377 +
  1.2378 +4.8.  Post Filtering
  1.2379 +
  1.2380 +   If desired, the decoded block can be filtered by a high-pass filter.
  1.2381 +   This removes the low frequencies of the decoded signal.  A reference
  1.2382 +   implementation of this, with cutoff at 65 Hz, is shown in Appendix
  1.2383 +   A.30.
  1.2384 +
  1.2385 +5.  Security Considerations
  1.2386 +
  1.2387 +   This algorithm for the coding of speech signals is not subject to any
  1.2388 +   known security consideration; however, its RTP payload format [1] is
  1.2389 +   subject to several considerations, which are addressed there.
  1.2390 +   Confidentiality of the media streams is achieved by encryption;
  1.2391 +   therefore external mechanisms, such as SRTP [5], MAY be used for that
  1.2392 +   purpose.
  1.2393 +
  1.2394 +6.  Evaluation of the iLBC Implementations
  1.2395 +
  1.2396 +   It is possible and suggested to evaluate certain iLBC implementation
  1.2397 +   by utilizing methodology and tools available at
  1.2398 +   http://www.ilbcfreeware.org/evaluation.html
  1.2399 +
  1.2400 +7.  References
  1.2401 +
  1.2402 +7.1.  Normative References
  1.2403 +
  1.2404 +   [1] Duric, A. and S. Andersen, "Real-time Transport Protocol (RTP)
  1.2405 +       Payload Format for internet Low Bit Rate Codec (iLBC) Speech",
  1.2406 +       RFC 3952, December 2004.
  1.2407 +
  1.2408 +   [2] Bradner, S., "Key words for use in RFCs to Indicate Requirement
  1.2409 +       Levels", BCP 14, RFC 2119, March 1997.
  1.2410 +
  1.2411 +
  1.2412 +
  1.2413 +Andersen, et al.              Experimental                     [Page 43]
  1.2414 +
  1.2415 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.2416 +
  1.2417 +
  1.2418 +   [3] PacketCable(TM) Audio/Video Codecs Specification, Cable
  1.2419 +       Television Laboratories, Inc.
  1.2420 +
  1.2421 +7.2.  Informative References
  1.2422 +
  1.2423 +   [4] ITU-T Recommendation G.711, available online from the ITU
  1.2424 +       bookstore at http://www.itu.int.
  1.2425 +
  1.2426 +   [5] Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K. Norman,
  1.2427 +       "The Secure Real Time Transport Protocol (SRTP)", RFC 3711, March
  1.2428 +       2004.
  1.2429 +
  1.2430 +8.  Acknowledgements
  1.2431 +
  1.2432 +   This extensive work, besides listed authors, has the following
  1.2433 +   authors, who could not have been listed among "official" authors (due
  1.2434 +   to IESG restrictions in the number of authors who can be listed):
  1.2435 +
  1.2436 +      Manohar N. Murthi (Department of Electrical and Computer
  1.2437 +      Engineering, University of Miami), Fredrik Galschiodt, Julian
  1.2438 +      Spittka, and Jan Skoglund (Global IP Sound).
  1.2439 +
  1.2440 +   The authors are deeply indebted to the following people and thank
  1.2441 +   them sincerely:
  1.2442 +
  1.2443 +      Henry Sinnreich, Patrik Faltstrom, Alan Johnston, and Jean-
  1.2444 +      Francois Mule for great support of the iLBC initiative and for
  1.2445 +      valuable feedback and comments.
  1.2446 +
  1.2447 +      Peter Vary, Frank Mertz, and Christoph Erdmann (RWTH Aachen);
  1.2448 +      Vladimir Cuperman (Niftybox LLC); Thomas Eriksson (Chalmers Univ
  1.2449 +      of Tech), and Gernot Kubin (TU Graz), for thorough review of the
  1.2450 +      iLBC document and their valuable feedback and remarks.
  1.2451 +
  1.2452 +
  1.2453 +
  1.2454 +
  1.2455 +
  1.2456 +
  1.2457 +
  1.2458 +
  1.2459 +
  1.2460 +
  1.2461 +
  1.2462 +
  1.2463 +
  1.2464 +
  1.2465 +
  1.2466 +
  1.2467 +
  1.2468 +
  1.2469 +Andersen, et al.              Experimental                     [Page 44]
  1.2470 +
  1.2471 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.2472 +
  1.2473 +
  1.2474 +APPENDIX A.  Reference Implementation
  1.2475 +
  1.2476 +   This appendix contains the complete c-code for a reference
  1.2477 +   implementation of encoder and decoder for the specified codec.
  1.2478 +
  1.2479 +   The c-code consists of the following files with highest-level
  1.2480 +   functions:
  1.2481 +
  1.2482 +         iLBC_test.c: main function for evaluation purpose
  1.2483 +         iLBC_encode.h: encoder header
  1.2484 +         iLBC_encode.c: encoder function
  1.2485 +         iLBC_decode.h: decoder header
  1.2486 +         iLBC_decode.c: decoder function
  1.2487 +
  1.2488 +   The following files contain global defines and constants:
  1.2489 +
  1.2490 +         iLBC_define.h: global defines
  1.2491 +         constants.h: global constants header
  1.2492 +         constants.c: global constants memory allocations
  1.2493 +
  1.2494 +   The following files contain subroutines:
  1.2495 +
  1.2496 +         anaFilter.h: lpc analysis filter header
  1.2497 +         anaFilter.c: lpc analysis filter function
  1.2498 +         createCB.h: codebook construction header
  1.2499 +         createCB.c: codebook construction function
  1.2500 +         doCPLC.h: packet loss concealment header
  1.2501 +         doCPLC.c: packet loss concealment function
  1.2502 +         enhancer.h: signal enhancement header
  1.2503 +         enhancer.c: signal enhancement function
  1.2504 +         filter.h: general filter header
  1.2505 +         filter.c: general filter functions
  1.2506 +         FrameClassify.h: start state classification header
  1.2507 +         FrameClassify.c: start state classification function
  1.2508 +         gainquant.h: gain quantization header
  1.2509 +         gainquant.c: gain quantization function
  1.2510 +         getCBvec.h: codebook vector construction header
  1.2511 +         getCBvec.c: codebook vector construction function
  1.2512 +         helpfun.h: general purpose header
  1.2513 +         helpfun.c: general purpose functions
  1.2514 +         hpInput.h: input high pass filter header
  1.2515 +         hpInput.c: input high pass filter function
  1.2516 +         hpOutput.h: output high pass filter header
  1.2517 +         hpOutput.c: output high pass filter function
  1.2518 +         iCBConstruct.h: excitation decoding header
  1.2519 +         iCBConstruct.c: excitation decoding function
  1.2520 +         iCBSearch.h: excitation encoding header
  1.2521 +         iCBSearch.c: excitation encoding function
  1.2522 +
  1.2523 +
  1.2524 +
  1.2525 +Andersen, et al.              Experimental                     [Page 45]
  1.2526 +
  1.2527 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.2528 +
  1.2529 +
  1.2530 +         LPCdecode.h: lpc decoding header
  1.2531 +         LPCdecode.c: lpc decoding function
  1.2532 +         LPCencode.h: lpc encoding header
  1.2533 +         LPCencode.c: lpc encoding function
  1.2534 +         lsf.h: line spectral frequencies header
  1.2535 +         lsf.c: line spectral frequencies functions
  1.2536 +         packing.h: bitstream packetization header
  1.2537 +         packing.c: bitstream packetization functions
  1.2538 +         StateConstructW.h: state decoding header
  1.2539 +         StateConstructW.c: state decoding functions
  1.2540 +         StateSearchW.h: state encoding header
  1.2541 +         StateSearchW.c: state encoding function
  1.2542 +         syntFilter.h: lpc synthesis filter header
  1.2543 +         syntFilter.c: lpc synthesis filter function
  1.2544 +
  1.2545 +   The implementation is portable and should work on many different
  1.2546 +   platforms.  However, it is not difficult to optimize the
  1.2547 +   implementation on particular platforms, an exercise left to the
  1.2548 +   reader.
  1.2549 +
  1.2550 +A.1.  iLBC_test.c
  1.2551 +
  1.2552 +   /******************************************************************
  1.2553 +
  1.2554 +       iLBC Speech Coder ANSI-C Source Code
  1.2555 +
  1.2556 +       iLBC_test.c
  1.2557 +
  1.2558 +       Copyright (C) The Internet Society (2004).
  1.2559 +       All Rights Reserved.
  1.2560 +
  1.2561 +   ******************************************************************/
  1.2562 +
  1.2563 +   #include <math.h>
  1.2564 +   #include <stdlib.h>
  1.2565 +   #include <stdio.h>
  1.2566 +   #include <string.h>
  1.2567 +   #include "iLBC_define.h"
  1.2568 +   #include "iLBC_encode.h"
  1.2569 +   #include "iLBC_decode.h"
  1.2570 +
  1.2571 +   /* Runtime statistics */
  1.2572 +   #include <time.h>
  1.2573 +
  1.2574 +   #define ILBCNOOFWORDS_MAX   (NO_OF_BYTES_30MS/2)
  1.2575 +
  1.2576 +   /*----------------------------------------------------------------*
  1.2577 +    *  Encoder interface function
  1.2578 +
  1.2579 +
  1.2580 +
  1.2581 +Andersen, et al.              Experimental                     [Page 46]
  1.2582 +
  1.2583 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.2584 +
  1.2585 +
  1.2586 +    *---------------------------------------------------------------*/
  1.2587 +
  1.2588 +   short encode(   /* (o) Number of bytes encoded */
  1.2589 +       iLBC_Enc_Inst_t *iLBCenc_inst,
  1.2590 +                                   /* (i/o) Encoder instance */
  1.2591 +       short *encoded_data,    /* (o) The encoded bytes */
  1.2592 +       short *data                 /* (i) The signal block to encode*/
  1.2593 +   ){
  1.2594 +       float block[BLOCKL_MAX];
  1.2595 +       int k;
  1.2596 +
  1.2597 +       /* convert signal to float */
  1.2598 +
  1.2599 +       for (k=0; k<iLBCenc_inst->blockl; k++)
  1.2600 +           block[k] = (float)data[k];
  1.2601 +
  1.2602 +       /* do the actual encoding */
  1.2603 +
  1.2604 +       iLBC_encode((unsigned char *)encoded_data, block, iLBCenc_inst);
  1.2605 +
  1.2606 +
  1.2607 +       return (iLBCenc_inst->no_of_bytes);
  1.2608 +   }
  1.2609 +
  1.2610 +   /*----------------------------------------------------------------*
  1.2611 +    *  Decoder interface function
  1.2612 +    *---------------------------------------------------------------*/
  1.2613 +
  1.2614 +   short decode(       /* (o) Number of decoded samples */
  1.2615 +       iLBC_Dec_Inst_t *iLBCdec_inst,  /* (i/o) Decoder instance */
  1.2616 +       short *decoded_data,        /* (o) Decoded signal block*/
  1.2617 +       short *encoded_data,        /* (i) Encoded bytes */
  1.2618 +       short mode                       /* (i) 0=PL, 1=Normal */
  1.2619 +   ){
  1.2620 +       int k;
  1.2621 +       float decblock[BLOCKL_MAX], dtmp;
  1.2622 +
  1.2623 +       /* check if mode is valid */
  1.2624 +
  1.2625 +       if (mode<0 || mode>1) {
  1.2626 +           printf("\nERROR - Wrong mode - 0, 1 allowed\n"); exit(3);}
  1.2627 +
  1.2628 +       /* do actual decoding of block */
  1.2629 +
  1.2630 +       iLBC_decode(decblock, (unsigned char *)encoded_data,
  1.2631 +           iLBCdec_inst, mode);
  1.2632 +
  1.2633 +       /* convert to short */
  1.2634 +
  1.2635 +
  1.2636 +
  1.2637 +Andersen, et al.              Experimental                     [Page 47]
  1.2638 +
  1.2639 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.2640 +
  1.2641 +
  1.2642 +       for (k=0; k<iLBCdec_inst->blockl; k++){
  1.2643 +           dtmp=decblock[k];
  1.2644 +
  1.2645 +           if (dtmp<MIN_SAMPLE)
  1.2646 +               dtmp=MIN_SAMPLE;
  1.2647 +           else if (dtmp>MAX_SAMPLE)
  1.2648 +               dtmp=MAX_SAMPLE;
  1.2649 +           decoded_data[k] = (short) dtmp;
  1.2650 +       }
  1.2651 +
  1.2652 +       return (iLBCdec_inst->blockl);
  1.2653 +   }
  1.2654 +
  1.2655 +   /*---------------------------------------------------------------*
  1.2656 +    *  Main program to test iLBC encoding and decoding
  1.2657 +    *
  1.2658 +    *  Usage:
  1.2659 +    *    exefile_name.exe <infile> <bytefile> <outfile> <channel>
  1.2660 +    *
  1.2661 +    *    <infile>   : Input file, speech for encoder (16-bit pcm file)
  1.2662 +    *    <bytefile> : Bit stream output from the encoder
  1.2663 +    *    <outfile>  : Output file, decoded speech (16-bit pcm file)
  1.2664 +    *    <channel>  : Bit error file, optional (16-bit)
  1.2665 +    *                     1 - Packet received correctly
  1.2666 +    *                     0 - Packet Lost
  1.2667 +    *
  1.2668 +    *--------------------------------------------------------------*/
  1.2669 +
  1.2670 +   int main(int argc, char* argv[])
  1.2671 +   {
  1.2672 +
  1.2673 +       /* Runtime statistics */
  1.2674 +
  1.2675 +       float starttime;
  1.2676 +       float runtime;
  1.2677 +       float outtime;
  1.2678 +
  1.2679 +       FILE *ifileid,*efileid,*ofileid, *cfileid;
  1.2680 +       short data[BLOCKL_MAX];
  1.2681 +       short encoded_data[ILBCNOOFWORDS_MAX], decoded_data[BLOCKL_MAX];
  1.2682 +       int len;
  1.2683 +       short pli, mode;
  1.2684 +       int blockcount = 0;
  1.2685 +       int packetlosscount = 0;
  1.2686 +
  1.2687 +       /* Create structs */
  1.2688 +       iLBC_Enc_Inst_t Enc_Inst;
  1.2689 +       iLBC_Dec_Inst_t Dec_Inst;
  1.2690 +
  1.2691 +
  1.2692 +
  1.2693 +Andersen, et al.              Experimental                     [Page 48]
  1.2694 +
  1.2695 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.2696 +
  1.2697 +
  1.2698 +       /* get arguments and open files */
  1.2699 +
  1.2700 +       if ((argc!=5) && (argc!=6)) {
  1.2701 +           fprintf(stderr,
  1.2702 +           "\n*-----------------------------------------------*\n");
  1.2703 +           fprintf(stderr,
  1.2704 +           "   %s <20,30> input encoded decoded (channel)\n\n",
  1.2705 +               argv[0]);
  1.2706 +           fprintf(stderr,
  1.2707 +           "   mode    : Frame size for the encoding/decoding\n");
  1.2708 +           fprintf(stderr,
  1.2709 +           "                 20 - 20 ms\n");
  1.2710 +           fprintf(stderr,
  1.2711 +           "                 30 - 30 ms\n");
  1.2712 +           fprintf(stderr,
  1.2713 +           "   input   : Speech for encoder (16-bit pcm file)\n");
  1.2714 +           fprintf(stderr,
  1.2715 +           "   encoded : Encoded bit stream\n");
  1.2716 +           fprintf(stderr,
  1.2717 +           "   decoded : Decoded speech (16-bit pcm file)\n");
  1.2718 +           fprintf(stderr,
  1.2719 +           "   channel : Packet loss pattern, optional (16-bit)\n");
  1.2720 +           fprintf(stderr,
  1.2721 +           "                  1 - Packet received correctly\n");
  1.2722 +           fprintf(stderr,
  1.2723 +           "                  0 - Packet Lost\n");
  1.2724 +           fprintf(stderr,
  1.2725 +           "*-----------------------------------------------*\n\n");
  1.2726 +           exit(1);
  1.2727 +       }
  1.2728 +       mode=atoi(argv[1]);
  1.2729 +       if (mode != 20 && mode != 30) {
  1.2730 +           fprintf(stderr,"Wrong mode %s, must be 20, or 30\n",
  1.2731 +               argv[1]);
  1.2732 +           exit(2);
  1.2733 +       }
  1.2734 +       if ( (ifileid=fopen(argv[2],"rb")) == NULL) {
  1.2735 +           fprintf(stderr,"Cannot open input file %s\n", argv[2]);
  1.2736 +           exit(2);}
  1.2737 +       if ( (efileid=fopen(argv[3],"wb")) == NULL) {
  1.2738 +           fprintf(stderr, "Cannot open encoded file %s\n",
  1.2739 +               argv[3]); exit(1);}
  1.2740 +       if ( (ofileid=fopen(argv[4],"wb")) == NULL) {
  1.2741 +           fprintf(stderr, "Cannot open decoded file %s\n",
  1.2742 +               argv[4]); exit(1);}
  1.2743 +       if (argc==6) {
  1.2744 +           if( (cfileid=fopen(argv[5],"rb")) == NULL) {
  1.2745 +               fprintf(stderr, "Cannot open channel file %s\n",
  1.2746 +
  1.2747 +
  1.2748 +
  1.2749 +Andersen, et al.              Experimental                     [Page 49]
  1.2750 +
  1.2751 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.2752 +
  1.2753 +
  1.2754 +                   argv[5]);
  1.2755 +               exit(1);
  1.2756 +           }
  1.2757 +       } else {
  1.2758 +           cfileid=NULL;
  1.2759 +       }
  1.2760 +
  1.2761 +       /* print info */
  1.2762 +
  1.2763 +       fprintf(stderr, "\n");
  1.2764 +       fprintf(stderr,
  1.2765 +           "*---------------------------------------------------*\n");
  1.2766 +       fprintf(stderr,
  1.2767 +           "*                                                   *\n");
  1.2768 +       fprintf(stderr,
  1.2769 +           "*      iLBC test program                            *\n");
  1.2770 +       fprintf(stderr,
  1.2771 +           "*                                                   *\n");
  1.2772 +       fprintf(stderr,
  1.2773 +           "*                                                   *\n");
  1.2774 +       fprintf(stderr,
  1.2775 +           "*---------------------------------------------------*\n");
  1.2776 +       fprintf(stderr,"\nMode           : %2d ms\n", mode);
  1.2777 +       fprintf(stderr,"Input file     : %s\n", argv[2]);
  1.2778 +       fprintf(stderr,"Encoded file   : %s\n", argv[3]);
  1.2779 +       fprintf(stderr,"Output file    : %s\n", argv[4]);
  1.2780 +       if (argc==6) {
  1.2781 +           fprintf(stderr,"Channel file   : %s\n", argv[5]);
  1.2782 +       }
  1.2783 +       fprintf(stderr,"\n");
  1.2784 +
  1.2785 +       /* Initialization */
  1.2786 +
  1.2787 +       initEncode(&Enc_Inst, mode);
  1.2788 +       initDecode(&Dec_Inst, mode, 1);
  1.2789 +
  1.2790 +       /* Runtime statistics */
  1.2791 +
  1.2792 +       starttime=clock()/(float)CLOCKS_PER_SEC;
  1.2793 +
  1.2794 +       /* loop over input blocks */
  1.2795 +
  1.2796 +       while (fread(data,sizeof(short),Enc_Inst.blockl,ifileid)==
  1.2797 +               Enc_Inst.blockl) {
  1.2798 +
  1.2799 +           blockcount++;
  1.2800 +
  1.2801 +           /* encoding */
  1.2802 +
  1.2803 +
  1.2804 +
  1.2805 +Andersen, et al.              Experimental                     [Page 50]
  1.2806 +
  1.2807 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.2808 +
  1.2809 +
  1.2810 +           fprintf(stderr, "--- Encoding block %i --- ",blockcount);
  1.2811 +           len=encode(&Enc_Inst, encoded_data, data);
  1.2812 +           fprintf(stderr, "\r");
  1.2813 +
  1.2814 +           /* write byte file */
  1.2815 +
  1.2816 +           fwrite(encoded_data, sizeof(unsigned char), len, efileid);
  1.2817 +
  1.2818 +           /* get channel data if provided */
  1.2819 +           if (argc==6) {
  1.2820 +               if (fread(&pli, sizeof(short), 1, cfileid)) {
  1.2821 +                   if ((pli!=0)&&(pli!=1)) {
  1.2822 +                       fprintf(stderr, "Error in channel file\n");
  1.2823 +                       exit(0);
  1.2824 +                   }
  1.2825 +                   if (pli==0) {
  1.2826 +                       /* Packet loss -> remove info from frame */
  1.2827 +                       memset(encoded_data, 0,
  1.2828 +                           sizeof(short)*ILBCNOOFWORDS_MAX);
  1.2829 +                       packetlosscount++;
  1.2830 +                   }
  1.2831 +               } else {
  1.2832 +                   fprintf(stderr, "Error. Channel file too short\n");
  1.2833 +                   exit(0);
  1.2834 +               }
  1.2835 +           } else {
  1.2836 +               pli=1;
  1.2837 +           }
  1.2838 +
  1.2839 +           /* decoding */
  1.2840 +
  1.2841 +           fprintf(stderr, "--- Decoding block %i --- ",blockcount);
  1.2842 +
  1.2843 +           len=decode(&Dec_Inst, decoded_data, encoded_data, pli);
  1.2844 +           fprintf(stderr, "\r");
  1.2845 +
  1.2846 +           /* write output file */
  1.2847 +
  1.2848 +           fwrite(decoded_data,sizeof(short),len,ofileid);
  1.2849 +       }
  1.2850 +
  1.2851 +       /* Runtime statistics */
  1.2852 +
  1.2853 +       runtime = (float)(clock()/(float)CLOCKS_PER_SEC-starttime);
  1.2854 +       outtime = (float)((float)blockcount*(float)mode/1000.0);
  1.2855 +       printf("\n\nLength of speech file: %.1f s\n", outtime);
  1.2856 +       printf("Packet loss          : %.1f%%\n",
  1.2857 +           100.0*(float)packetlosscount/(float)blockcount);
  1.2858 +
  1.2859 +
  1.2860 +
  1.2861 +Andersen, et al.              Experimental                     [Page 51]
  1.2862 +
  1.2863 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.2864 +
  1.2865 +
  1.2866 +       printf("Time to run iLBC     :");
  1.2867 +       printf(" %.1f s (%.1f %% of realtime)\n\n", runtime,
  1.2868 +           (100*runtime/outtime));
  1.2869 +
  1.2870 +       /* close files */
  1.2871 +
  1.2872 +       fclose(ifileid);  fclose(efileid); fclose(ofileid);
  1.2873 +       if (argc==6) {
  1.2874 +           fclose(cfileid);
  1.2875 +       }
  1.2876 +       return(0);
  1.2877 +   }
  1.2878 +
  1.2879 +A.2.  iLBC_encode.h
  1.2880 +
  1.2881 +   /******************************************************************
  1.2882 +
  1.2883 +       iLBC Speech Coder ANSI-C Source Code
  1.2884 +
  1.2885 +       iLBC_encode.h
  1.2886 +
  1.2887 +       Copyright (C) The Internet Society (2004).
  1.2888 +       All Rights Reserved.
  1.2889 +
  1.2890 +   ******************************************************************/
  1.2891 +
  1.2892 +   #ifndef __iLBC_ILBCENCODE_H
  1.2893 +   #define __iLBC_ILBCENCODE_H
  1.2894 +
  1.2895 +   #include "iLBC_define.h"
  1.2896 +
  1.2897 +   short initEncode(                   /* (o) Number of bytes
  1.2898 +                                              encoded */
  1.2899 +       iLBC_Enc_Inst_t *iLBCenc_inst,  /* (i/o) Encoder instance */
  1.2900 +       int mode                    /* (i) frame size mode */
  1.2901 +   );
  1.2902 +
  1.2903 +   void iLBC_encode(
  1.2904 +
  1.2905 +       unsigned char *bytes,           /* (o) encoded data bits iLBC */
  1.2906 +       float *block,                   /* (o) speech vector to
  1.2907 +                                              encode */
  1.2908 +       iLBC_Enc_Inst_t *iLBCenc_inst   /* (i/o) the general encoder
  1.2909 +                                              state */
  1.2910 +   );
  1.2911 +
  1.2912 +   #endif
  1.2913 +
  1.2914 +
  1.2915 +
  1.2916 +
  1.2917 +Andersen, et al.              Experimental                     [Page 52]
  1.2918 +
  1.2919 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.2920 +
  1.2921 +
  1.2922 +A.3.  iLBC_encode.c
  1.2923 +
  1.2924 +   /******************************************************************
  1.2925 +
  1.2926 +       iLBC Speech Coder ANSI-C Source Code
  1.2927 +
  1.2928 +       iLBC_encode.c
  1.2929 +
  1.2930 +       Copyright (C) The Internet Society (2004).
  1.2931 +       All Rights Reserved.
  1.2932 +
  1.2933 +   ******************************************************************/
  1.2934 +
  1.2935 +   #include <math.h>
  1.2936 +   #include <stdlib.h>
  1.2937 +   #include <string.h>
  1.2938 +
  1.2939 +   #include "iLBC_define.h"
  1.2940 +   #include "LPCencode.h"
  1.2941 +   #include "FrameClassify.h"
  1.2942 +   #include "StateSearchW.h"
  1.2943 +   #include "StateConstructW.h"
  1.2944 +   #include "helpfun.h"
  1.2945 +   #include "constants.h"
  1.2946 +   #include "packing.h"
  1.2947 +   #include "iCBSearch.h"
  1.2948 +   #include "iCBConstruct.h"
  1.2949 +   #include "hpInput.h"
  1.2950 +   #include "anaFilter.h"
  1.2951 +   #include "syntFilter.h"
  1.2952 +
  1.2953 +   /*----------------------------------------------------------------*
  1.2954 +    *  Initiation of encoder instance.
  1.2955 +    *---------------------------------------------------------------*/
  1.2956 +
  1.2957 +   short initEncode(                   /* (o) Number of bytes
  1.2958 +                                              encoded */
  1.2959 +       iLBC_Enc_Inst_t *iLBCenc_inst,  /* (i/o) Encoder instance */
  1.2960 +       int mode                    /* (i) frame size mode */
  1.2961 +   ){
  1.2962 +       iLBCenc_inst->mode = mode;
  1.2963 +       if (mode==30) {
  1.2964 +           iLBCenc_inst->blockl = BLOCKL_30MS;
  1.2965 +           iLBCenc_inst->nsub = NSUB_30MS;
  1.2966 +           iLBCenc_inst->nasub = NASUB_30MS;
  1.2967 +           iLBCenc_inst->lpc_n = LPC_N_30MS;
  1.2968 +           iLBCenc_inst->no_of_bytes = NO_OF_BYTES_30MS;
  1.2969 +           iLBCenc_inst->no_of_words = NO_OF_WORDS_30MS;
  1.2970 +
  1.2971 +
  1.2972 +
  1.2973 +Andersen, et al.              Experimental                     [Page 53]
  1.2974 +
  1.2975 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.2976 +
  1.2977 +
  1.2978 +           iLBCenc_inst->state_short_len=STATE_SHORT_LEN_30MS;
  1.2979 +           /* ULP init */
  1.2980 +           iLBCenc_inst->ULP_inst=&ULP_30msTbl;
  1.2981 +       }
  1.2982 +       else if (mode==20) {
  1.2983 +           iLBCenc_inst->blockl = BLOCKL_20MS;
  1.2984 +           iLBCenc_inst->nsub = NSUB_20MS;
  1.2985 +           iLBCenc_inst->nasub = NASUB_20MS;
  1.2986 +           iLBCenc_inst->lpc_n = LPC_N_20MS;
  1.2987 +           iLBCenc_inst->no_of_bytes = NO_OF_BYTES_20MS;
  1.2988 +           iLBCenc_inst->no_of_words = NO_OF_WORDS_20MS;
  1.2989 +           iLBCenc_inst->state_short_len=STATE_SHORT_LEN_20MS;
  1.2990 +           /* ULP init */
  1.2991 +           iLBCenc_inst->ULP_inst=&ULP_20msTbl;
  1.2992 +       }
  1.2993 +       else {
  1.2994 +           exit(2);
  1.2995 +       }
  1.2996 +
  1.2997 +       memset((*iLBCenc_inst).anaMem, 0,
  1.2998 +           LPC_FILTERORDER*sizeof(float));
  1.2999 +       memcpy((*iLBCenc_inst).lsfold, lsfmeanTbl,
  1.3000 +           LPC_FILTERORDER*sizeof(float));
  1.3001 +       memcpy((*iLBCenc_inst).lsfdeqold, lsfmeanTbl,
  1.3002 +           LPC_FILTERORDER*sizeof(float));
  1.3003 +       memset((*iLBCenc_inst).lpc_buffer, 0,
  1.3004 +           (LPC_LOOKBACK+BLOCKL_MAX)*sizeof(float));
  1.3005 +       memset((*iLBCenc_inst).hpimem, 0, 4*sizeof(float));
  1.3006 +
  1.3007 +       return (iLBCenc_inst->no_of_bytes);
  1.3008 +   }
  1.3009 +
  1.3010 +   /*----------------------------------------------------------------*
  1.3011 +    *  main encoder function
  1.3012 +    *---------------------------------------------------------------*/
  1.3013 +
  1.3014 +   void iLBC_encode(
  1.3015 +       unsigned char *bytes,           /* (o) encoded data bits iLBC */
  1.3016 +       float *block,                   /* (o) speech vector to
  1.3017 +                                              encode */
  1.3018 +       iLBC_Enc_Inst_t *iLBCenc_inst   /* (i/o) the general encoder
  1.3019 +                                              state */
  1.3020 +   ){
  1.3021 +
  1.3022 +       float data[BLOCKL_MAX];
  1.3023 +       float residual[BLOCKL_MAX], reverseResidual[BLOCKL_MAX];
  1.3024 +
  1.3025 +       int start, idxForMax, idxVec[STATE_LEN];
  1.3026 +
  1.3027 +
  1.3028 +
  1.3029 +Andersen, et al.              Experimental                     [Page 54]
  1.3030 +
  1.3031 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.3032 +
  1.3033 +
  1.3034 +       float reverseDecresidual[BLOCKL_MAX], mem[CB_MEML];
  1.3035 +       int n, k, meml_gotten, Nfor, Nback, i, pos;
  1.3036 +       int gain_index[CB_NSTAGES*NASUB_MAX],
  1.3037 +           extra_gain_index[CB_NSTAGES];
  1.3038 +       int cb_index[CB_NSTAGES*NASUB_MAX],extra_cb_index[CB_NSTAGES];
  1.3039 +       int lsf_i[LSF_NSPLIT*LPC_N_MAX];
  1.3040 +       unsigned char *pbytes;
  1.3041 +       int diff, start_pos, state_first;
  1.3042 +       float en1, en2;
  1.3043 +       int index, ulp, firstpart;
  1.3044 +       int subcount, subframe;
  1.3045 +       float weightState[LPC_FILTERORDER];
  1.3046 +       float syntdenum[NSUB_MAX*(LPC_FILTERORDER+1)];
  1.3047 +       float weightdenum[NSUB_MAX*(LPC_FILTERORDER+1)];
  1.3048 +       float decresidual[BLOCKL_MAX];
  1.3049 +
  1.3050 +       /* high pass filtering of input signal if such is not done
  1.3051 +              prior to calling this function */
  1.3052 +
  1.3053 +       hpInput(block, iLBCenc_inst->blockl,
  1.3054 +                   data, (*iLBCenc_inst).hpimem);
  1.3055 +
  1.3056 +       /* otherwise simply copy */
  1.3057 +
  1.3058 +       /*memcpy(data,block,iLBCenc_inst->blockl*sizeof(float));*/
  1.3059 +
  1.3060 +       /* LPC of hp filtered input data */
  1.3061 +
  1.3062 +       LPCencode(syntdenum, weightdenum, lsf_i, data, iLBCenc_inst);
  1.3063 +
  1.3064 +
  1.3065 +       /* inverse filter to get residual */
  1.3066 +
  1.3067 +       for (n=0; n<iLBCenc_inst->nsub; n++) {
  1.3068 +           anaFilter(&data[n*SUBL], &syntdenum[n*(LPC_FILTERORDER+1)],
  1.3069 +               SUBL, &residual[n*SUBL], iLBCenc_inst->anaMem);
  1.3070 +       }
  1.3071 +
  1.3072 +       /* find state location */
  1.3073 +
  1.3074 +       start = FrameClassify(iLBCenc_inst, residual);
  1.3075 +
  1.3076 +       /* check if state should be in first or last part of the
  1.3077 +       two subframes */
  1.3078 +
  1.3079 +       diff = STATE_LEN - iLBCenc_inst->state_short_len;
  1.3080 +       en1 = 0;
  1.3081 +       index = (start-1)*SUBL;
  1.3082 +
  1.3083 +
  1.3084 +
  1.3085 +Andersen, et al.              Experimental                     [Page 55]
  1.3086 +
  1.3087 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.3088 +
  1.3089 +
  1.3090 +       for (i = 0; i < iLBCenc_inst->state_short_len; i++) {
  1.3091 +           en1 += residual[index+i]*residual[index+i];
  1.3092 +       }
  1.3093 +       en2 = 0;
  1.3094 +       index = (start-1)*SUBL+diff;
  1.3095 +       for (i = 0; i < iLBCenc_inst->state_short_len; i++) {
  1.3096 +           en2 += residual[index+i]*residual[index+i];
  1.3097 +       }
  1.3098 +
  1.3099 +
  1.3100 +       if (en1 > en2) {
  1.3101 +           state_first = 1;
  1.3102 +           start_pos = (start-1)*SUBL;
  1.3103 +       } else {
  1.3104 +           state_first = 0;
  1.3105 +           start_pos = (start-1)*SUBL + diff;
  1.3106 +       }
  1.3107 +
  1.3108 +       /* scalar quantization of state */
  1.3109 +
  1.3110 +       StateSearchW(iLBCenc_inst, &residual[start_pos],
  1.3111 +           &syntdenum[(start-1)*(LPC_FILTERORDER+1)],
  1.3112 +           &weightdenum[(start-1)*(LPC_FILTERORDER+1)], &idxForMax,
  1.3113 +           idxVec, iLBCenc_inst->state_short_len, state_first);
  1.3114 +
  1.3115 +       StateConstructW(idxForMax, idxVec,
  1.3116 +           &syntdenum[(start-1)*(LPC_FILTERORDER+1)],
  1.3117 +           &decresidual[start_pos], iLBCenc_inst->state_short_len);
  1.3118 +
  1.3119 +       /* predictive quantization in state */
  1.3120 +
  1.3121 +       if (state_first) { /* put adaptive part in the end */
  1.3122 +
  1.3123 +           /* setup memory */
  1.3124 +
  1.3125 +           memset(mem, 0,
  1.3126 +               (CB_MEML-iLBCenc_inst->state_short_len)*sizeof(float));
  1.3127 +           memcpy(mem+CB_MEML-iLBCenc_inst->state_short_len,
  1.3128 +               decresidual+start_pos,
  1.3129 +               iLBCenc_inst->state_short_len*sizeof(float));
  1.3130 +           memset(weightState, 0, LPC_FILTERORDER*sizeof(float));
  1.3131 +
  1.3132 +           /* encode sub-frames */
  1.3133 +
  1.3134 +           iCBSearch(iLBCenc_inst, extra_cb_index, extra_gain_index,
  1.3135 +               &residual[start_pos+iLBCenc_inst->state_short_len],
  1.3136 +               mem+CB_MEML-stMemLTbl,
  1.3137 +               stMemLTbl, diff, CB_NSTAGES,
  1.3138 +
  1.3139 +
  1.3140 +
  1.3141 +Andersen, et al.              Experimental                     [Page 56]
  1.3142 +
  1.3143 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.3144 +
  1.3145 +
  1.3146 +               &weightdenum[start*(LPC_FILTERORDER+1)],
  1.3147 +               weightState, 0);
  1.3148 +
  1.3149 +           /* construct decoded vector */
  1.3150 +
  1.3151 +           iCBConstruct(
  1.3152 +               &decresidual[start_pos+iLBCenc_inst->state_short_len],
  1.3153 +               extra_cb_index, extra_gain_index,
  1.3154 +               mem+CB_MEML-stMemLTbl,
  1.3155 +               stMemLTbl, diff, CB_NSTAGES);
  1.3156 +
  1.3157 +       }
  1.3158 +       else { /* put adaptive part in the beginning */
  1.3159 +
  1.3160 +           /* create reversed vectors for prediction */
  1.3161 +
  1.3162 +           for (k=0; k<diff; k++) {
  1.3163 +               reverseResidual[k] = residual[(start+1)*SUBL-1
  1.3164 +                   -(k+iLBCenc_inst->state_short_len)];
  1.3165 +           }
  1.3166 +
  1.3167 +           /* setup memory */
  1.3168 +
  1.3169 +           meml_gotten = iLBCenc_inst->state_short_len;
  1.3170 +           for (k=0; k<meml_gotten; k++) {
  1.3171 +               mem[CB_MEML-1-k] = decresidual[start_pos + k];
  1.3172 +           }
  1.3173 +           memset(mem, 0, (CB_MEML-k)*sizeof(float));
  1.3174 +           memset(weightState, 0, LPC_FILTERORDER*sizeof(float));
  1.3175 +
  1.3176 +           /* encode sub-frames */
  1.3177 +
  1.3178 +           iCBSearch(iLBCenc_inst, extra_cb_index, extra_gain_index,
  1.3179 +               reverseResidual, mem+CB_MEML-stMemLTbl, stMemLTbl,
  1.3180 +               diff, CB_NSTAGES,
  1.3181 +               &weightdenum[(start-1)*(LPC_FILTERORDER+1)],
  1.3182 +               weightState, 0);
  1.3183 +
  1.3184 +           /* construct decoded vector */
  1.3185 +
  1.3186 +           iCBConstruct(reverseDecresidual, extra_cb_index,
  1.3187 +               extra_gain_index, mem+CB_MEML-stMemLTbl, stMemLTbl,
  1.3188 +               diff, CB_NSTAGES);
  1.3189 +
  1.3190 +           /* get decoded residual from reversed vector */
  1.3191 +
  1.3192 +           for (k=0; k<diff; k++) {
  1.3193 +               decresidual[start_pos-1-k] = reverseDecresidual[k];
  1.3194 +
  1.3195 +
  1.3196 +
  1.3197 +Andersen, et al.              Experimental                     [Page 57]
  1.3198 +
  1.3199 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.3200 +
  1.3201 +
  1.3202 +           }
  1.3203 +       }
  1.3204 +
  1.3205 +       /* counter for predicted sub-frames */
  1.3206 +
  1.3207 +       subcount=0;
  1.3208 +
  1.3209 +       /* forward prediction of sub-frames */
  1.3210 +
  1.3211 +       Nfor = iLBCenc_inst->nsub-start-1;
  1.3212 +
  1.3213 +
  1.3214 +       if ( Nfor > 0 ) {
  1.3215 +
  1.3216 +           /* setup memory */
  1.3217 +
  1.3218 +           memset(mem, 0, (CB_MEML-STATE_LEN)*sizeof(float));
  1.3219 +           memcpy(mem+CB_MEML-STATE_LEN, decresidual+(start-1)*SUBL,
  1.3220 +               STATE_LEN*sizeof(float));
  1.3221 +           memset(weightState, 0, LPC_FILTERORDER*sizeof(float));
  1.3222 +
  1.3223 +           /* loop over sub-frames to encode */
  1.3224 +
  1.3225 +           for (subframe=0; subframe<Nfor; subframe++) {
  1.3226 +
  1.3227 +               /* encode sub-frame */
  1.3228 +
  1.3229 +               iCBSearch(iLBCenc_inst, cb_index+subcount*CB_NSTAGES,
  1.3230 +                   gain_index+subcount*CB_NSTAGES,
  1.3231 +                   &residual[(start+1+subframe)*SUBL],
  1.3232 +                   mem+CB_MEML-memLfTbl[subcount],
  1.3233 +                   memLfTbl[subcount], SUBL, CB_NSTAGES,
  1.3234 +                   &weightdenum[(start+1+subframe)*
  1.3235 +                               (LPC_FILTERORDER+1)],
  1.3236 +                   weightState, subcount+1);
  1.3237 +
  1.3238 +               /* construct decoded vector */
  1.3239 +
  1.3240 +               iCBConstruct(&decresidual[(start+1+subframe)*SUBL],
  1.3241 +                   cb_index+subcount*CB_NSTAGES,
  1.3242 +                   gain_index+subcount*CB_NSTAGES,
  1.3243 +                   mem+CB_MEML-memLfTbl[subcount],
  1.3244 +                   memLfTbl[subcount], SUBL, CB_NSTAGES);
  1.3245 +
  1.3246 +               /* update memory */
  1.3247 +
  1.3248 +               memcpy(mem, mem+SUBL, (CB_MEML-SUBL)*sizeof(float));
  1.3249 +               memcpy(mem+CB_MEML-SUBL,
  1.3250 +
  1.3251 +
  1.3252 +
  1.3253 +Andersen, et al.              Experimental                     [Page 58]
  1.3254 +
  1.3255 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.3256 +
  1.3257 +
  1.3258 +                   &decresidual[(start+1+subframe)*SUBL],
  1.3259 +                   SUBL*sizeof(float));
  1.3260 +               memset(weightState, 0, LPC_FILTERORDER*sizeof(float));
  1.3261 +
  1.3262 +               subcount++;
  1.3263 +           }
  1.3264 +       }
  1.3265 +
  1.3266 +
  1.3267 +       /* backward prediction of sub-frames */
  1.3268 +
  1.3269 +       Nback = start-1;
  1.3270 +
  1.3271 +
  1.3272 +       if ( Nback > 0 ) {
  1.3273 +
  1.3274 +           /* create reverse order vectors */
  1.3275 +
  1.3276 +           for (n=0; n<Nback; n++) {
  1.3277 +               for (k=0; k<SUBL; k++) {
  1.3278 +                   reverseResidual[n*SUBL+k] =
  1.3279 +                       residual[(start-1)*SUBL-1-n*SUBL-k];
  1.3280 +                   reverseDecresidual[n*SUBL+k] =
  1.3281 +                       decresidual[(start-1)*SUBL-1-n*SUBL-k];
  1.3282 +               }
  1.3283 +           }
  1.3284 +
  1.3285 +           /* setup memory */
  1.3286 +
  1.3287 +           meml_gotten = SUBL*(iLBCenc_inst->nsub+1-start);
  1.3288 +
  1.3289 +
  1.3290 +           if ( meml_gotten > CB_MEML ) {
  1.3291 +               meml_gotten=CB_MEML;
  1.3292 +           }
  1.3293 +           for (k=0; k<meml_gotten; k++) {
  1.3294 +               mem[CB_MEML-1-k] = decresidual[(start-1)*SUBL + k];
  1.3295 +           }
  1.3296 +           memset(mem, 0, (CB_MEML-k)*sizeof(float));
  1.3297 +           memset(weightState, 0, LPC_FILTERORDER*sizeof(float));
  1.3298 +
  1.3299 +           /* loop over sub-frames to encode */
  1.3300 +
  1.3301 +           for (subframe=0; subframe<Nback; subframe++) {
  1.3302 +
  1.3303 +               /* encode sub-frame */
  1.3304 +
  1.3305 +               iCBSearch(iLBCenc_inst, cb_index+subcount*CB_NSTAGES,
  1.3306 +
  1.3307 +
  1.3308 +
  1.3309 +Andersen, et al.              Experimental                     [Page 59]
  1.3310 +
  1.3311 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.3312 +
  1.3313 +
  1.3314 +                   gain_index+subcount*CB_NSTAGES,
  1.3315 +                   &reverseResidual[subframe*SUBL],
  1.3316 +                   mem+CB_MEML-memLfTbl[subcount],
  1.3317 +                   memLfTbl[subcount], SUBL, CB_NSTAGES,
  1.3318 +                   &weightdenum[(start-2-subframe)*
  1.3319 +                               (LPC_FILTERORDER+1)],
  1.3320 +                   weightState, subcount+1);
  1.3321 +
  1.3322 +               /* construct decoded vector */
  1.3323 +
  1.3324 +               iCBConstruct(&reverseDecresidual[subframe*SUBL],
  1.3325 +                   cb_index+subcount*CB_NSTAGES,
  1.3326 +                   gain_index+subcount*CB_NSTAGES,
  1.3327 +                   mem+CB_MEML-memLfTbl[subcount],
  1.3328 +                   memLfTbl[subcount], SUBL, CB_NSTAGES);
  1.3329 +
  1.3330 +               /* update memory */
  1.3331 +
  1.3332 +               memcpy(mem, mem+SUBL, (CB_MEML-SUBL)*sizeof(float));
  1.3333 +               memcpy(mem+CB_MEML-SUBL,
  1.3334 +                   &reverseDecresidual[subframe*SUBL],
  1.3335 +                   SUBL*sizeof(float));
  1.3336 +               memset(weightState, 0, LPC_FILTERORDER*sizeof(float));
  1.3337 +
  1.3338 +               subcount++;
  1.3339 +
  1.3340 +           }
  1.3341 +
  1.3342 +           /* get decoded residual from reversed vector */
  1.3343 +
  1.3344 +           for (i=0; i<SUBL*Nback; i++) {
  1.3345 +               decresidual[SUBL*Nback - i - 1] =
  1.3346 +                   reverseDecresidual[i];
  1.3347 +           }
  1.3348 +       }
  1.3349 +       /* end encoding part */
  1.3350 +
  1.3351 +       /* adjust index */
  1.3352 +       index_conv_enc(cb_index);
  1.3353 +
  1.3354 +       /* pack bytes */
  1.3355 +
  1.3356 +       pbytes=bytes;
  1.3357 +       pos=0;
  1.3358 +
  1.3359 +       /* loop over the 3 ULP classes */
  1.3360 +
  1.3361 +       for (ulp=0; ulp<3; ulp++) {
  1.3362 +
  1.3363 +
  1.3364 +
  1.3365 +Andersen, et al.              Experimental                     [Page 60]
  1.3366 +
  1.3367 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.3368 +
  1.3369 +
  1.3370 +
  1.3371 +           /* LSF */
  1.3372 +           for (k=0; k<LSF_NSPLIT*iLBCenc_inst->lpc_n; k++) {
  1.3373 +               packsplit(&lsf_i[k], &firstpart, &lsf_i[k],
  1.3374 +                   iLBCenc_inst->ULP_inst->lsf_bits[k][ulp],
  1.3375 +                   iLBCenc_inst->ULP_inst->lsf_bits[k][ulp]+
  1.3376 +                   iLBCenc_inst->ULP_inst->lsf_bits[k][ulp+1]+
  1.3377 +                   iLBCenc_inst->ULP_inst->lsf_bits[k][ulp+2]);
  1.3378 +               dopack( &pbytes, firstpart,
  1.3379 +                   iLBCenc_inst->ULP_inst->lsf_bits[k][ulp], &pos);
  1.3380 +           }
  1.3381 +
  1.3382 +           /* Start block info */
  1.3383 +
  1.3384 +           packsplit(&start, &firstpart, &start,
  1.3385 +               iLBCenc_inst->ULP_inst->start_bits[ulp],
  1.3386 +               iLBCenc_inst->ULP_inst->start_bits[ulp]+
  1.3387 +               iLBCenc_inst->ULP_inst->start_bits[ulp+1]+
  1.3388 +               iLBCenc_inst->ULP_inst->start_bits[ulp+2]);
  1.3389 +           dopack( &pbytes, firstpart,
  1.3390 +               iLBCenc_inst->ULP_inst->start_bits[ulp], &pos);
  1.3391 +
  1.3392 +           packsplit(&state_first, &firstpart, &state_first,
  1.3393 +               iLBCenc_inst->ULP_inst->startfirst_bits[ulp],
  1.3394 +               iLBCenc_inst->ULP_inst->startfirst_bits[ulp]+
  1.3395 +               iLBCenc_inst->ULP_inst->startfirst_bits[ulp+1]+
  1.3396 +               iLBCenc_inst->ULP_inst->startfirst_bits[ulp+2]);
  1.3397 +           dopack( &pbytes, firstpart,
  1.3398 +               iLBCenc_inst->ULP_inst->startfirst_bits[ulp], &pos);
  1.3399 +
  1.3400 +           packsplit(&idxForMax, &firstpart, &idxForMax,
  1.3401 +               iLBCenc_inst->ULP_inst->scale_bits[ulp],
  1.3402 +               iLBCenc_inst->ULP_inst->scale_bits[ulp]+
  1.3403 +               iLBCenc_inst->ULP_inst->scale_bits[ulp+1]+
  1.3404 +               iLBCenc_inst->ULP_inst->scale_bits[ulp+2]);
  1.3405 +           dopack( &pbytes, firstpart,
  1.3406 +               iLBCenc_inst->ULP_inst->scale_bits[ulp], &pos);
  1.3407 +
  1.3408 +           for (k=0; k<iLBCenc_inst->state_short_len; k++) {
  1.3409 +               packsplit(idxVec+k, &firstpart, idxVec+k,
  1.3410 +                   iLBCenc_inst->ULP_inst->state_bits[ulp],
  1.3411 +                   iLBCenc_inst->ULP_inst->state_bits[ulp]+
  1.3412 +                   iLBCenc_inst->ULP_inst->state_bits[ulp+1]+
  1.3413 +                   iLBCenc_inst->ULP_inst->state_bits[ulp+2]);
  1.3414 +               dopack( &pbytes, firstpart,
  1.3415 +                   iLBCenc_inst->ULP_inst->state_bits[ulp], &pos);
  1.3416 +           }
  1.3417 +
  1.3418 +
  1.3419 +
  1.3420 +
  1.3421 +Andersen, et al.              Experimental                     [Page 61]
  1.3422 +
  1.3423 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.3424 +
  1.3425 +
  1.3426 +           /* 23/22 (20ms/30ms) sample block */
  1.3427 +
  1.3428 +           for (k=0;k<CB_NSTAGES;k++) {
  1.3429 +               packsplit(extra_cb_index+k, &firstpart,
  1.3430 +                   extra_cb_index+k,
  1.3431 +                   iLBCenc_inst->ULP_inst->extra_cb_index[k][ulp],
  1.3432 +                   iLBCenc_inst->ULP_inst->extra_cb_index[k][ulp]+
  1.3433 +                   iLBCenc_inst->ULP_inst->extra_cb_index[k][ulp+1]+
  1.3434 +                   iLBCenc_inst->ULP_inst->extra_cb_index[k][ulp+2]);
  1.3435 +               dopack( &pbytes, firstpart,
  1.3436 +                   iLBCenc_inst->ULP_inst->extra_cb_index[k][ulp],
  1.3437 +                   &pos);
  1.3438 +           }
  1.3439 +
  1.3440 +           for (k=0;k<CB_NSTAGES;k++) {
  1.3441 +               packsplit(extra_gain_index+k, &firstpart,
  1.3442 +                   extra_gain_index+k,
  1.3443 +                   iLBCenc_inst->ULP_inst->extra_cb_gain[k][ulp],
  1.3444 +                   iLBCenc_inst->ULP_inst->extra_cb_gain[k][ulp]+
  1.3445 +                   iLBCenc_inst->ULP_inst->extra_cb_gain[k][ulp+1]+
  1.3446 +                   iLBCenc_inst->ULP_inst->extra_cb_gain[k][ulp+2]);
  1.3447 +               dopack( &pbytes, firstpart,
  1.3448 +                   iLBCenc_inst->ULP_inst->extra_cb_gain[k][ulp],
  1.3449 +                   &pos);
  1.3450 +           }
  1.3451 +
  1.3452 +           /* The two/four (20ms/30ms) 40 sample sub-blocks */
  1.3453 +
  1.3454 +           for (i=0; i<iLBCenc_inst->nasub; i++) {
  1.3455 +               for (k=0; k<CB_NSTAGES; k++) {
  1.3456 +                   packsplit(cb_index+i*CB_NSTAGES+k, &firstpart,
  1.3457 +                       cb_index+i*CB_NSTAGES+k,
  1.3458 +                       iLBCenc_inst->ULP_inst->cb_index[i][k][ulp],
  1.3459 +                       iLBCenc_inst->ULP_inst->cb_index[i][k][ulp]+
  1.3460 +                       iLBCenc_inst->ULP_inst->cb_index[i][k][ulp+1]+
  1.3461 +                       iLBCenc_inst->ULP_inst->cb_index[i][k][ulp+2]);
  1.3462 +                   dopack( &pbytes, firstpart,
  1.3463 +                       iLBCenc_inst->ULP_inst->cb_index[i][k][ulp],
  1.3464 +                       &pos);
  1.3465 +               }
  1.3466 +           }
  1.3467 +
  1.3468 +           for (i=0; i<iLBCenc_inst->nasub; i++) {
  1.3469 +               for (k=0; k<CB_NSTAGES; k++) {
  1.3470 +                   packsplit(gain_index+i*CB_NSTAGES+k, &firstpart,
  1.3471 +                       gain_index+i*CB_NSTAGES+k,
  1.3472 +                       iLBCenc_inst->ULP_inst->cb_gain[i][k][ulp],
  1.3473 +                       iLBCenc_inst->ULP_inst->cb_gain[i][k][ulp]+
  1.3474 +
  1.3475 +
  1.3476 +
  1.3477 +Andersen, et al.              Experimental                     [Page 62]
  1.3478 +
  1.3479 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.3480 +
  1.3481 +
  1.3482 +                       iLBCenc_inst->ULP_inst->cb_gain[i][k][ulp+1]+
  1.3483 +                       iLBCenc_inst->ULP_inst->cb_gain[i][k][ulp+2]);
  1.3484 +                   dopack( &pbytes, firstpart,
  1.3485 +                       iLBCenc_inst->ULP_inst->cb_gain[i][k][ulp],
  1.3486 +                       &pos);
  1.3487 +               }
  1.3488 +           }
  1.3489 +       }
  1.3490 +
  1.3491 +       /* set the last bit to zero (otherwise the decoder
  1.3492 +          will treat it as a lost frame) */
  1.3493 +       dopack( &pbytes, 0, 1, &pos);
  1.3494 +   }
  1.3495 +
  1.3496 +A.4.  iLBC_decode.h
  1.3497 +
  1.3498 +   /******************************************************************
  1.3499 +
  1.3500 +       iLBC Speech Coder ANSI-C Source Code
  1.3501 +
  1.3502 +       iLBC_decode.h
  1.3503 +
  1.3504 +       Copyright (C) The Internet Society (2004).
  1.3505 +       All Rights Reserved.
  1.3506 +
  1.3507 +   ******************************************************************/
  1.3508 +
  1.3509 +   #ifndef __iLBC_ILBCDECODE_H
  1.3510 +   #define __iLBC_ILBCDECODE_H
  1.3511 +
  1.3512 +   #include "iLBC_define.h"
  1.3513 +
  1.3514 +   short initDecode(                   /* (o) Number of decoded
  1.3515 +                                              samples */
  1.3516 +       iLBC_Dec_Inst_t *iLBCdec_inst,  /* (i/o) Decoder instance */
  1.3517 +       int mode,                       /* (i) frame size mode */
  1.3518 +       int use_enhancer                /* (i) 1 to use enhancer
  1.3519 +                                              0 to run without
  1.3520 +                                                enhancer */
  1.3521 +   );
  1.3522 +
  1.3523 +   void iLBC_decode(
  1.3524 +       float *decblock,            /* (o) decoded signal block */
  1.3525 +       unsigned char *bytes,           /* (i) encoded signal bits */
  1.3526 +       iLBC_Dec_Inst_t *iLBCdec_inst,  /* (i/o) the decoder state
  1.3527 +                                                structure */
  1.3528 +       int mode                    /* (i) 0: bad packet, PLC,
  1.3529 +                                              1: normal */
  1.3530 +
  1.3531 +
  1.3532 +
  1.3533 +Andersen, et al.              Experimental                     [Page 63]
  1.3534 +
  1.3535 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.3536 +
  1.3537 +
  1.3538 +   );
  1.3539 +
  1.3540 +   #endif
  1.3541 +
  1.3542 +A.5.  iLBC_decode.c
  1.3543 +
  1.3544 +   /******************************************************************
  1.3545 +
  1.3546 +       iLBC Speech Coder ANSI-C Source Code
  1.3547 +
  1.3548 +       iLBC_decode.c
  1.3549 +
  1.3550 +       Copyright (C) The Internet Society (2004).
  1.3551 +       All Rights Reserved.
  1.3552 +
  1.3553 +   ******************************************************************/
  1.3554 +
  1.3555 +   #include <math.h>
  1.3556 +   #include <stdlib.h>
  1.3557 +
  1.3558 +   #include "iLBC_define.h"
  1.3559 +   #include "StateConstructW.h"
  1.3560 +   #include "LPCdecode.h"
  1.3561 +   #include "iCBConstruct.h"
  1.3562 +   #include "doCPLC.h"
  1.3563 +   #include "helpfun.h"
  1.3564 +   #include "constants.h"
  1.3565 +   #include "packing.h"
  1.3566 +   #include "string.h"
  1.3567 +   #include "enhancer.h"
  1.3568 +   #include "hpOutput.h"
  1.3569 +   #include "syntFilter.h"
  1.3570 +
  1.3571 +   /*----------------------------------------------------------------*
  1.3572 +    *  Initiation of decoder instance.
  1.3573 +    *---------------------------------------------------------------*/
  1.3574 +
  1.3575 +   short initDecode(                   /* (o) Number of decoded
  1.3576 +                                              samples */
  1.3577 +       iLBC_Dec_Inst_t *iLBCdec_inst,  /* (i/o) Decoder instance */
  1.3578 +       int mode,                       /* (i) frame size mode */
  1.3579 +       int use_enhancer                /* (i) 1 to use enhancer
  1.3580 +                                              0 to run without
  1.3581 +                                                enhancer */
  1.3582 +   ){
  1.3583 +       int i;
  1.3584 +
  1.3585 +       iLBCdec_inst->mode = mode;
  1.3586 +
  1.3587 +
  1.3588 +
  1.3589 +Andersen, et al.              Experimental                     [Page 64]
  1.3590 +
  1.3591 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.3592 +
  1.3593 +
  1.3594 +       if (mode==30) {
  1.3595 +           iLBCdec_inst->blockl = BLOCKL_30MS;
  1.3596 +           iLBCdec_inst->nsub = NSUB_30MS;
  1.3597 +           iLBCdec_inst->nasub = NASUB_30MS;
  1.3598 +           iLBCdec_inst->lpc_n = LPC_N_30MS;
  1.3599 +           iLBCdec_inst->no_of_bytes = NO_OF_BYTES_30MS;
  1.3600 +           iLBCdec_inst->no_of_words = NO_OF_WORDS_30MS;
  1.3601 +           iLBCdec_inst->state_short_len=STATE_SHORT_LEN_30MS;
  1.3602 +           /* ULP init */
  1.3603 +           iLBCdec_inst->ULP_inst=&ULP_30msTbl;
  1.3604 +       }
  1.3605 +       else if (mode==20) {
  1.3606 +           iLBCdec_inst->blockl = BLOCKL_20MS;
  1.3607 +           iLBCdec_inst->nsub = NSUB_20MS;
  1.3608 +           iLBCdec_inst->nasub = NASUB_20MS;
  1.3609 +           iLBCdec_inst->lpc_n = LPC_N_20MS;
  1.3610 +           iLBCdec_inst->no_of_bytes = NO_OF_BYTES_20MS;
  1.3611 +           iLBCdec_inst->no_of_words = NO_OF_WORDS_20MS;
  1.3612 +           iLBCdec_inst->state_short_len=STATE_SHORT_LEN_20MS;
  1.3613 +           /* ULP init */
  1.3614 +           iLBCdec_inst->ULP_inst=&ULP_20msTbl;
  1.3615 +       }
  1.3616 +       else {
  1.3617 +           exit(2);
  1.3618 +       }
  1.3619 +
  1.3620 +       memset(iLBCdec_inst->syntMem, 0,
  1.3621 +           LPC_FILTERORDER*sizeof(float));
  1.3622 +       memcpy((*iLBCdec_inst).lsfdeqold, lsfmeanTbl,
  1.3623 +           LPC_FILTERORDER*sizeof(float));
  1.3624 +
  1.3625 +       memset(iLBCdec_inst->old_syntdenum, 0,
  1.3626 +           ((LPC_FILTERORDER + 1)*NSUB_MAX)*sizeof(float));
  1.3627 +       for (i=0; i<NSUB_MAX; i++)
  1.3628 +           iLBCdec_inst->old_syntdenum[i*(LPC_FILTERORDER+1)]=1.0;
  1.3629 +
  1.3630 +       iLBCdec_inst->last_lag = 20;
  1.3631 +
  1.3632 +       iLBCdec_inst->prevLag = 120;
  1.3633 +       iLBCdec_inst->per = 0.0;
  1.3634 +       iLBCdec_inst->consPLICount = 0;
  1.3635 +       iLBCdec_inst->prevPLI = 0;
  1.3636 +       iLBCdec_inst->prevLpc[0] = 1.0;
  1.3637 +       memset(iLBCdec_inst->prevLpc+1,0,
  1.3638 +           LPC_FILTERORDER*sizeof(float));
  1.3639 +       memset(iLBCdec_inst->prevResidual, 0, BLOCKL_MAX*sizeof(float));
  1.3640 +       iLBCdec_inst->seed=777;
  1.3641 +
  1.3642 +
  1.3643 +
  1.3644 +
  1.3645 +Andersen, et al.              Experimental                     [Page 65]
  1.3646 +
  1.3647 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.3648 +
  1.3649 +
  1.3650 +       memset(iLBCdec_inst->hpomem, 0, 4*sizeof(float));
  1.3651 +
  1.3652 +       iLBCdec_inst->use_enhancer = use_enhancer;
  1.3653 +       memset(iLBCdec_inst->enh_buf, 0, ENH_BUFL*sizeof(float));
  1.3654 +       for (i=0;i<ENH_NBLOCKS_TOT;i++)
  1.3655 +           iLBCdec_inst->enh_period[i]=(float)40.0;
  1.3656 +
  1.3657 +       iLBCdec_inst->prev_enh_pl = 0;
  1.3658 +
  1.3659 +       return (iLBCdec_inst->blockl);
  1.3660 +   }
  1.3661 +
  1.3662 +   /*----------------------------------------------------------------*
  1.3663 +    *  frame residual decoder function (subrutine to iLBC_decode)
  1.3664 +    *---------------------------------------------------------------*/
  1.3665 +
  1.3666 +   void Decode(
  1.3667 +       iLBC_Dec_Inst_t *iLBCdec_inst,  /* (i/o) the decoder state
  1.3668 +                                                structure */
  1.3669 +       float *decresidual,             /* (o) decoded residual frame */
  1.3670 +       int start,                      /* (i) location of start
  1.3671 +                                              state */
  1.3672 +       int idxForMax,                  /* (i) codebook index for the
  1.3673 +                                              maximum value */
  1.3674 +       int *idxVec,                /* (i) codebook indexes for the
  1.3675 +                                              samples  in the start
  1.3676 +                                              state */
  1.3677 +       float *syntdenum,               /* (i) the decoded synthesis
  1.3678 +                                              filter coefficients */
  1.3679 +       int *cb_index,                  /* (i) the indexes for the
  1.3680 +                                              adaptive codebook */
  1.3681 +       int *gain_index,            /* (i) the indexes for the
  1.3682 +                                              corresponding gains */
  1.3683 +       int *extra_cb_index,        /* (i) the indexes for the
  1.3684 +                                              adaptive codebook part
  1.3685 +                                              of start state */
  1.3686 +       int *extra_gain_index,          /* (i) the indexes for the
  1.3687 +                                              corresponding gains */
  1.3688 +       int state_first                 /* (i) 1 if non adaptive part
  1.3689 +                                              of start state comes
  1.3690 +                                              first 0 if that part
  1.3691 +                                              comes last */
  1.3692 +   ){
  1.3693 +       float reverseDecresidual[BLOCKL_MAX], mem[CB_MEML];
  1.3694 +       int k, meml_gotten, Nfor, Nback, i;
  1.3695 +       int diff, start_pos;
  1.3696 +       int subcount, subframe;
  1.3697 +
  1.3698 +
  1.3699 +
  1.3700 +
  1.3701 +Andersen, et al.              Experimental                     [Page 66]
  1.3702 +
  1.3703 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.3704 +
  1.3705 +
  1.3706 +       diff = STATE_LEN - iLBCdec_inst->state_short_len;
  1.3707 +
  1.3708 +       if (state_first == 1) {
  1.3709 +           start_pos = (start-1)*SUBL;
  1.3710 +       } else {
  1.3711 +           start_pos = (start-1)*SUBL + diff;
  1.3712 +       }
  1.3713 +
  1.3714 +       /* decode scalar part of start state */
  1.3715 +
  1.3716 +       StateConstructW(idxForMax, idxVec,
  1.3717 +           &syntdenum[(start-1)*(LPC_FILTERORDER+1)],
  1.3718 +           &decresidual[start_pos], iLBCdec_inst->state_short_len);
  1.3719 +
  1.3720 +
  1.3721 +       if (state_first) { /* put adaptive part in the end */
  1.3722 +
  1.3723 +           /* setup memory */
  1.3724 +
  1.3725 +           memset(mem, 0,
  1.3726 +               (CB_MEML-iLBCdec_inst->state_short_len)*sizeof(float));
  1.3727 +           memcpy(mem+CB_MEML-iLBCdec_inst->state_short_len,
  1.3728 +               decresidual+start_pos,
  1.3729 +               iLBCdec_inst->state_short_len*sizeof(float));
  1.3730 +
  1.3731 +           /* construct decoded vector */
  1.3732 +
  1.3733 +           iCBConstruct(
  1.3734 +               &decresidual[start_pos+iLBCdec_inst->state_short_len],
  1.3735 +               extra_cb_index, extra_gain_index, mem+CB_MEML-stMemLTbl,
  1.3736 +               stMemLTbl, diff, CB_NSTAGES);
  1.3737 +
  1.3738 +       }
  1.3739 +       else {/* put adaptive part in the beginning */
  1.3740 +
  1.3741 +           /* create reversed vectors for prediction */
  1.3742 +
  1.3743 +           for (k=0; k<diff; k++) {
  1.3744 +               reverseDecresidual[k] =
  1.3745 +                   decresidual[(start+1)*SUBL-1-
  1.3746 +                           (k+iLBCdec_inst->state_short_len)];
  1.3747 +           }
  1.3748 +
  1.3749 +           /* setup memory */
  1.3750 +
  1.3751 +           meml_gotten = iLBCdec_inst->state_short_len;
  1.3752 +           for (k=0; k<meml_gotten; k++){
  1.3753 +               mem[CB_MEML-1-k] = decresidual[start_pos + k];
  1.3754 +
  1.3755 +
  1.3756 +
  1.3757 +Andersen, et al.              Experimental                     [Page 67]
  1.3758 +
  1.3759 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.3760 +
  1.3761 +
  1.3762 +           }
  1.3763 +           memset(mem, 0, (CB_MEML-k)*sizeof(float));
  1.3764 +
  1.3765 +           /* construct decoded vector */
  1.3766 +
  1.3767 +           iCBConstruct(reverseDecresidual, extra_cb_index,
  1.3768 +               extra_gain_index, mem+CB_MEML-stMemLTbl, stMemLTbl,
  1.3769 +               diff, CB_NSTAGES);
  1.3770 +
  1.3771 +           /* get decoded residual from reversed vector */
  1.3772 +
  1.3773 +           for (k=0; k<diff; k++) {
  1.3774 +               decresidual[start_pos-1-k] = reverseDecresidual[k];
  1.3775 +           }
  1.3776 +       }
  1.3777 +
  1.3778 +       /* counter for predicted sub-frames */
  1.3779 +
  1.3780 +       subcount=0;
  1.3781 +
  1.3782 +       /* forward prediction of sub-frames */
  1.3783 +
  1.3784 +       Nfor = iLBCdec_inst->nsub-start-1;
  1.3785 +
  1.3786 +       if ( Nfor > 0 ){
  1.3787 +
  1.3788 +           /* setup memory */
  1.3789 +
  1.3790 +           memset(mem, 0, (CB_MEML-STATE_LEN)*sizeof(float));
  1.3791 +           memcpy(mem+CB_MEML-STATE_LEN, decresidual+(start-1)*SUBL,
  1.3792 +               STATE_LEN*sizeof(float));
  1.3793 +
  1.3794 +           /* loop over sub-frames to encode */
  1.3795 +
  1.3796 +           for (subframe=0; subframe<Nfor; subframe++) {
  1.3797 +
  1.3798 +               /* construct decoded vector */
  1.3799 +
  1.3800 +               iCBConstruct(&decresidual[(start+1+subframe)*SUBL],
  1.3801 +                   cb_index+subcount*CB_NSTAGES,
  1.3802 +                   gain_index+subcount*CB_NSTAGES,
  1.3803 +                   mem+CB_MEML-memLfTbl[subcount],
  1.3804 +                   memLfTbl[subcount], SUBL, CB_NSTAGES);
  1.3805 +
  1.3806 +               /* update memory */
  1.3807 +
  1.3808 +               memcpy(mem, mem+SUBL, (CB_MEML-SUBL)*sizeof(float));
  1.3809 +               memcpy(mem+CB_MEML-SUBL,
  1.3810 +
  1.3811 +
  1.3812 +
  1.3813 +Andersen, et al.              Experimental                     [Page 68]
  1.3814 +
  1.3815 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.3816 +
  1.3817 +
  1.3818 +                   &decresidual[(start+1+subframe)*SUBL],
  1.3819 +                   SUBL*sizeof(float));
  1.3820 +
  1.3821 +               subcount++;
  1.3822 +
  1.3823 +           }
  1.3824 +
  1.3825 +       }
  1.3826 +
  1.3827 +       /* backward prediction of sub-frames */
  1.3828 +
  1.3829 +       Nback = start-1;
  1.3830 +
  1.3831 +       if ( Nback > 0 ) {
  1.3832 +
  1.3833 +           /* setup memory */
  1.3834 +
  1.3835 +           meml_gotten = SUBL*(iLBCdec_inst->nsub+1-start);
  1.3836 +
  1.3837 +           if ( meml_gotten > CB_MEML ) {
  1.3838 +               meml_gotten=CB_MEML;
  1.3839 +           }
  1.3840 +           for (k=0; k<meml_gotten; k++) {
  1.3841 +               mem[CB_MEML-1-k] = decresidual[(start-1)*SUBL + k];
  1.3842 +           }
  1.3843 +           memset(mem, 0, (CB_MEML-k)*sizeof(float));
  1.3844 +
  1.3845 +           /* loop over subframes to decode */
  1.3846 +
  1.3847 +           for (subframe=0; subframe<Nback; subframe++) {
  1.3848 +
  1.3849 +               /* construct decoded vector */
  1.3850 +
  1.3851 +               iCBConstruct(&reverseDecresidual[subframe*SUBL],
  1.3852 +                   cb_index+subcount*CB_NSTAGES,
  1.3853 +                   gain_index+subcount*CB_NSTAGES,
  1.3854 +                   mem+CB_MEML-memLfTbl[subcount], memLfTbl[subcount],
  1.3855 +                   SUBL, CB_NSTAGES);
  1.3856 +
  1.3857 +               /* update memory */
  1.3858 +
  1.3859 +               memcpy(mem, mem+SUBL, (CB_MEML-SUBL)*sizeof(float));
  1.3860 +               memcpy(mem+CB_MEML-SUBL,
  1.3861 +                   &reverseDecresidual[subframe*SUBL],
  1.3862 +                   SUBL*sizeof(float));
  1.3863 +
  1.3864 +               subcount++;
  1.3865 +           }
  1.3866 +
  1.3867 +
  1.3868 +
  1.3869 +Andersen, et al.              Experimental                     [Page 69]
  1.3870 +
  1.3871 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.3872 +
  1.3873 +
  1.3874 +           /* get decoded residual from reversed vector */
  1.3875 +
  1.3876 +           for (i=0; i<SUBL*Nback; i++)
  1.3877 +               decresidual[SUBL*Nback - i - 1] =
  1.3878 +               reverseDecresidual[i];
  1.3879 +       }
  1.3880 +   }
  1.3881 +
  1.3882 +   /*----------------------------------------------------------------*
  1.3883 +    *  main decoder function
  1.3884 +    *---------------------------------------------------------------*/
  1.3885 +
  1.3886 +   void iLBC_decode(
  1.3887 +       float *decblock,            /* (o) decoded signal block */
  1.3888 +       unsigned char *bytes,           /* (i) encoded signal bits */
  1.3889 +       iLBC_Dec_Inst_t *iLBCdec_inst,  /* (i/o) the decoder state
  1.3890 +                                                structure */
  1.3891 +       int mode                    /* (i) 0: bad packet, PLC,
  1.3892 +                                              1: normal */
  1.3893 +   ){
  1.3894 +       float data[BLOCKL_MAX];
  1.3895 +       float lsfdeq[LPC_FILTERORDER*LPC_N_MAX];
  1.3896 +       float PLCresidual[BLOCKL_MAX], PLClpc[LPC_FILTERORDER + 1];
  1.3897 +       float zeros[BLOCKL_MAX], one[LPC_FILTERORDER + 1];
  1.3898 +       int k, i, start, idxForMax, pos, lastpart, ulp;
  1.3899 +       int lag, ilag;
  1.3900 +       float cc, maxcc;
  1.3901 +       int idxVec[STATE_LEN];
  1.3902 +       int check;
  1.3903 +       int gain_index[NASUB_MAX*CB_NSTAGES],
  1.3904 +           extra_gain_index[CB_NSTAGES];
  1.3905 +       int cb_index[CB_NSTAGES*NASUB_MAX], extra_cb_index[CB_NSTAGES];
  1.3906 +       int lsf_i[LSF_NSPLIT*LPC_N_MAX];
  1.3907 +       int state_first;
  1.3908 +       int last_bit;
  1.3909 +       unsigned char *pbytes;
  1.3910 +       float weightdenum[(LPC_FILTERORDER + 1)*NSUB_MAX];
  1.3911 +       int order_plus_one;
  1.3912 +       float syntdenum[NSUB_MAX*(LPC_FILTERORDER+1)];
  1.3913 +       float decresidual[BLOCKL_MAX];
  1.3914 +
  1.3915 +       if (mode>0) { /* the data are good */
  1.3916 +
  1.3917 +           /* decode data */
  1.3918 +
  1.3919 +           pbytes=bytes;
  1.3920 +           pos=0;
  1.3921 +
  1.3922 +
  1.3923 +
  1.3924 +
  1.3925 +Andersen, et al.              Experimental                     [Page 70]
  1.3926 +
  1.3927 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.3928 +
  1.3929 +
  1.3930 +           /* Set everything to zero before decoding */
  1.3931 +
  1.3932 +           for (k=0; k<LSF_NSPLIT*LPC_N_MAX; k++) {
  1.3933 +               lsf_i[k]=0;
  1.3934 +           }
  1.3935 +           start=0;
  1.3936 +           state_first=0;
  1.3937 +           idxForMax=0;
  1.3938 +           for (k=0; k<iLBCdec_inst->state_short_len; k++) {
  1.3939 +               idxVec[k]=0;
  1.3940 +           }
  1.3941 +           for (k=0; k<CB_NSTAGES; k++) {
  1.3942 +               extra_cb_index[k]=0;
  1.3943 +           }
  1.3944 +           for (k=0; k<CB_NSTAGES; k++) {
  1.3945 +               extra_gain_index[k]=0;
  1.3946 +           }
  1.3947 +           for (i=0; i<iLBCdec_inst->nasub; i++) {
  1.3948 +               for (k=0; k<CB_NSTAGES; k++) {
  1.3949 +                   cb_index[i*CB_NSTAGES+k]=0;
  1.3950 +               }
  1.3951 +           }
  1.3952 +           for (i=0; i<iLBCdec_inst->nasub; i++) {
  1.3953 +               for (k=0; k<CB_NSTAGES; k++) {
  1.3954 +                   gain_index[i*CB_NSTAGES+k]=0;
  1.3955 +               }
  1.3956 +           }
  1.3957 +
  1.3958 +           /* loop over ULP classes */
  1.3959 +
  1.3960 +           for (ulp=0; ulp<3; ulp++) {
  1.3961 +
  1.3962 +               /* LSF */
  1.3963 +               for (k=0; k<LSF_NSPLIT*iLBCdec_inst->lpc_n; k++){
  1.3964 +                   unpack( &pbytes, &lastpart,
  1.3965 +                       iLBCdec_inst->ULP_inst->lsf_bits[k][ulp], &pos);
  1.3966 +                   packcombine(&lsf_i[k], lastpart,
  1.3967 +                       iLBCdec_inst->ULP_inst->lsf_bits[k][ulp]);
  1.3968 +               }
  1.3969 +
  1.3970 +               /* Start block info */
  1.3971 +
  1.3972 +               unpack( &pbytes, &lastpart,
  1.3973 +                   iLBCdec_inst->ULP_inst->start_bits[ulp], &pos);
  1.3974 +               packcombine(&start, lastpart,
  1.3975 +                   iLBCdec_inst->ULP_inst->start_bits[ulp]);
  1.3976 +
  1.3977 +               unpack( &pbytes, &lastpart,
  1.3978 +
  1.3979 +
  1.3980 +
  1.3981 +Andersen, et al.              Experimental                     [Page 71]
  1.3982 +
  1.3983 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.3984 +
  1.3985 +
  1.3986 +                   iLBCdec_inst->ULP_inst->startfirst_bits[ulp], &pos);
  1.3987 +               packcombine(&state_first, lastpart,
  1.3988 +                   iLBCdec_inst->ULP_inst->startfirst_bits[ulp]);
  1.3989 +
  1.3990 +               unpack( &pbytes, &lastpart,
  1.3991 +                   iLBCdec_inst->ULP_inst->scale_bits[ulp], &pos);
  1.3992 +               packcombine(&idxForMax, lastpart,
  1.3993 +                   iLBCdec_inst->ULP_inst->scale_bits[ulp]);
  1.3994 +
  1.3995 +               for (k=0; k<iLBCdec_inst->state_short_len; k++) {
  1.3996 +                   unpack( &pbytes, &lastpart,
  1.3997 +                       iLBCdec_inst->ULP_inst->state_bits[ulp], &pos);
  1.3998 +                   packcombine(idxVec+k, lastpart,
  1.3999 +                       iLBCdec_inst->ULP_inst->state_bits[ulp]);
  1.4000 +               }
  1.4001 +
  1.4002 +               /* 23/22 (20ms/30ms) sample block */
  1.4003 +
  1.4004 +               for (k=0; k<CB_NSTAGES; k++) {
  1.4005 +                   unpack( &pbytes, &lastpart,
  1.4006 +                       iLBCdec_inst->ULP_inst->extra_cb_index[k][ulp],
  1.4007 +                       &pos);
  1.4008 +                   packcombine(extra_cb_index+k, lastpart,
  1.4009 +                       iLBCdec_inst->ULP_inst->extra_cb_index[k][ulp]);
  1.4010 +               }
  1.4011 +               for (k=0; k<CB_NSTAGES; k++) {
  1.4012 +                   unpack( &pbytes, &lastpart,
  1.4013 +                       iLBCdec_inst->ULP_inst->extra_cb_gain[k][ulp],
  1.4014 +                       &pos);
  1.4015 +                   packcombine(extra_gain_index+k, lastpart,
  1.4016 +                       iLBCdec_inst->ULP_inst->extra_cb_gain[k][ulp]);
  1.4017 +               }
  1.4018 +
  1.4019 +               /* The two/four (20ms/30ms) 40 sample sub-blocks */
  1.4020 +
  1.4021 +               for (i=0; i<iLBCdec_inst->nasub; i++) {
  1.4022 +                   for (k=0; k<CB_NSTAGES; k++) {
  1.4023 +                       unpack( &pbytes, &lastpart,
  1.4024 +                       iLBCdec_inst->ULP_inst->cb_index[i][k][ulp],
  1.4025 +                           &pos);
  1.4026 +                       packcombine(cb_index+i*CB_NSTAGES+k, lastpart,
  1.4027 +                       iLBCdec_inst->ULP_inst->cb_index[i][k][ulp]);
  1.4028 +                   }
  1.4029 +               }
  1.4030 +
  1.4031 +               for (i=0; i<iLBCdec_inst->nasub; i++) {
  1.4032 +                   for (k=0; k<CB_NSTAGES; k++) {
  1.4033 +                       unpack( &pbytes, &lastpart,
  1.4034 +
  1.4035 +
  1.4036 +
  1.4037 +Andersen, et al.              Experimental                     [Page 72]
  1.4038 +
  1.4039 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.4040 +
  1.4041 +
  1.4042 +                       iLBCdec_inst->ULP_inst->cb_gain[i][k][ulp],
  1.4043 +                           &pos);
  1.4044 +                       packcombine(gain_index+i*CB_NSTAGES+k, lastpart,
  1.4045 +                           iLBCdec_inst->ULP_inst->cb_gain[i][k][ulp]);
  1.4046 +                   }
  1.4047 +               }
  1.4048 +           }
  1.4049 +           /* Extract last bit. If it is 1 this indicates an
  1.4050 +              empty/lost frame */
  1.4051 +           unpack( &pbytes, &last_bit, 1, &pos);
  1.4052 +
  1.4053 +           /* Check for bit errors or empty/lost frames */
  1.4054 +           if (start<1)
  1.4055 +               mode = 0;
  1.4056 +           if (iLBCdec_inst->mode==20 && start>3)
  1.4057 +               mode = 0;
  1.4058 +           if (iLBCdec_inst->mode==30 && start>5)
  1.4059 +               mode = 0;
  1.4060 +           if (last_bit==1)
  1.4061 +               mode = 0;
  1.4062 +
  1.4063 +           if (mode==1) { /* No bit errors was detected,
  1.4064 +                             continue decoding */
  1.4065 +
  1.4066 +               /* adjust index */
  1.4067 +               index_conv_dec(cb_index);
  1.4068 +
  1.4069 +               /* decode the lsf */
  1.4070 +
  1.4071 +               SimplelsfDEQ(lsfdeq, lsf_i, iLBCdec_inst->lpc_n);
  1.4072 +               check=LSF_check(lsfdeq, LPC_FILTERORDER,
  1.4073 +                   iLBCdec_inst->lpc_n);
  1.4074 +               DecoderInterpolateLSF(syntdenum, weightdenum,
  1.4075 +                   lsfdeq, LPC_FILTERORDER, iLBCdec_inst);
  1.4076 +
  1.4077 +               Decode(iLBCdec_inst, decresidual, start, idxForMax,
  1.4078 +                   idxVec, syntdenum, cb_index, gain_index,
  1.4079 +                   extra_cb_index, extra_gain_index,
  1.4080 +                   state_first);
  1.4081 +
  1.4082 +               /* preparing the plc for a future loss! */
  1.4083 +
  1.4084 +               doThePLC(PLCresidual, PLClpc, 0, decresidual,
  1.4085 +                   syntdenum +
  1.4086 +                   (LPC_FILTERORDER + 1)*(iLBCdec_inst->nsub - 1),
  1.4087 +                   (*iLBCdec_inst).last_lag, iLBCdec_inst);
  1.4088 +
  1.4089 +
  1.4090 +
  1.4091 +
  1.4092 +
  1.4093 +Andersen, et al.              Experimental                     [Page 73]
  1.4094 +
  1.4095 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.4096 +
  1.4097 +
  1.4098 +               memcpy(decresidual, PLCresidual,
  1.4099 +                   iLBCdec_inst->blockl*sizeof(float));
  1.4100 +           }
  1.4101 +
  1.4102 +       }
  1.4103 +
  1.4104 +       if (mode == 0) {
  1.4105 +           /* the data is bad (either a PLC call
  1.4106 +            * was made or a severe bit error was detected)
  1.4107 +            */
  1.4108 +
  1.4109 +           /* packet loss conceal */
  1.4110 +
  1.4111 +           memset(zeros, 0, BLOCKL_MAX*sizeof(float));
  1.4112 +
  1.4113 +           one[0] = 1;
  1.4114 +           memset(one+1, 0, LPC_FILTERORDER*sizeof(float));
  1.4115 +
  1.4116 +           start=0;
  1.4117 +
  1.4118 +           doThePLC(PLCresidual, PLClpc, 1, zeros, one,
  1.4119 +               (*iLBCdec_inst).last_lag, iLBCdec_inst);
  1.4120 +           memcpy(decresidual, PLCresidual,
  1.4121 +               iLBCdec_inst->blockl*sizeof(float));
  1.4122 +
  1.4123 +           order_plus_one = LPC_FILTERORDER + 1;
  1.4124 +           for (i = 0; i < iLBCdec_inst->nsub; i++) {
  1.4125 +               memcpy(syntdenum+(i*order_plus_one), PLClpc,
  1.4126 +                   order_plus_one*sizeof(float));
  1.4127 +           }
  1.4128 +       }
  1.4129 +
  1.4130 +       if (iLBCdec_inst->use_enhancer == 1) {
  1.4131 +
  1.4132 +           /* post filtering */
  1.4133 +
  1.4134 +           iLBCdec_inst->last_lag =
  1.4135 +               enhancerInterface(data, decresidual, iLBCdec_inst);
  1.4136 +
  1.4137 +           /* synthesis filtering */
  1.4138 +
  1.4139 +           if (iLBCdec_inst->mode==20) {
  1.4140 +               /* Enhancer has 40 samples delay */
  1.4141 +               i=0;
  1.4142 +               syntFilter(data + i*SUBL,
  1.4143 +                   iLBCdec_inst->old_syntdenum +
  1.4144 +                   (i+iLBCdec_inst->nsub-1)*(LPC_FILTERORDER+1),
  1.4145 +                   SUBL, iLBCdec_inst->syntMem);
  1.4146 +
  1.4147 +
  1.4148 +
  1.4149 +Andersen, et al.              Experimental                     [Page 74]
  1.4150 +
  1.4151 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.4152 +
  1.4153 +
  1.4154 +               for (i=1; i < iLBCdec_inst->nsub; i++) {
  1.4155 +                   syntFilter(data + i*SUBL,
  1.4156 +                       syntdenum + (i-1)*(LPC_FILTERORDER+1),
  1.4157 +                       SUBL, iLBCdec_inst->syntMem);
  1.4158 +               }
  1.4159 +           } else if (iLBCdec_inst->mode==30) {
  1.4160 +               /* Enhancer has 80 samples delay */
  1.4161 +               for (i=0; i < 2; i++) {
  1.4162 +                   syntFilter(data + i*SUBL,
  1.4163 +                       iLBCdec_inst->old_syntdenum +
  1.4164 +                       (i+iLBCdec_inst->nsub-2)*(LPC_FILTERORDER+1),
  1.4165 +                       SUBL, iLBCdec_inst->syntMem);
  1.4166 +               }
  1.4167 +               for (i=2; i < iLBCdec_inst->nsub; i++) {
  1.4168 +                   syntFilter(data + i*SUBL,
  1.4169 +                       syntdenum + (i-2)*(LPC_FILTERORDER+1), SUBL,
  1.4170 +                       iLBCdec_inst->syntMem);
  1.4171 +               }
  1.4172 +           }
  1.4173 +
  1.4174 +       } else {
  1.4175 +
  1.4176 +           /* Find last lag */
  1.4177 +           lag = 20;
  1.4178 +           maxcc = xCorrCoef(&decresidual[BLOCKL_MAX-ENH_BLOCKL],
  1.4179 +               &decresidual[BLOCKL_MAX-ENH_BLOCKL-lag], ENH_BLOCKL);
  1.4180 +
  1.4181 +           for (ilag=21; ilag<120; ilag++) {
  1.4182 +               cc = xCorrCoef(&decresidual[BLOCKL_MAX-ENH_BLOCKL],
  1.4183 +                   &decresidual[BLOCKL_MAX-ENH_BLOCKL-ilag],
  1.4184 +                   ENH_BLOCKL);
  1.4185 +
  1.4186 +               if (cc > maxcc) {
  1.4187 +                   maxcc = cc;
  1.4188 +                   lag = ilag;
  1.4189 +               }
  1.4190 +           }
  1.4191 +           iLBCdec_inst->last_lag = lag;
  1.4192 +
  1.4193 +           /* copy data and run synthesis filter */
  1.4194 +
  1.4195 +           memcpy(data, decresidual,
  1.4196 +               iLBCdec_inst->blockl*sizeof(float));
  1.4197 +           for (i=0; i < iLBCdec_inst->nsub; i++) {
  1.4198 +               syntFilter(data + i*SUBL,
  1.4199 +                   syntdenum + i*(LPC_FILTERORDER+1), SUBL,
  1.4200 +                   iLBCdec_inst->syntMem);
  1.4201 +           }
  1.4202 +
  1.4203 +
  1.4204 +
  1.4205 +Andersen, et al.              Experimental                     [Page 75]
  1.4206 +
  1.4207 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.4208 +
  1.4209 +
  1.4210 +       }
  1.4211 +
  1.4212 +       /* high pass filtering on output if desired, otherwise
  1.4213 +          copy to out */
  1.4214 +
  1.4215 +       hpOutput(data, iLBCdec_inst->blockl,
  1.4216 +                   decblock,iLBCdec_inst->hpomem);
  1.4217 +
  1.4218 +       /* memcpy(decblock,data,iLBCdec_inst->blockl*sizeof(float));*/
  1.4219 +
  1.4220 +       memcpy(iLBCdec_inst->old_syntdenum, syntdenum,
  1.4221 +
  1.4222 +           iLBCdec_inst->nsub*(LPC_FILTERORDER+1)*sizeof(float));
  1.4223 +
  1.4224 +       iLBCdec_inst->prev_enh_pl=0;
  1.4225 +
  1.4226 +       if (mode==0) { /* PLC was used */
  1.4227 +           iLBCdec_inst->prev_enh_pl=1;
  1.4228 +       }
  1.4229 +   }
  1.4230 +
  1.4231 +A.6.  iLBC_define.h
  1.4232 +
  1.4233 +   /******************************************************************
  1.4234 +
  1.4235 +       iLBC Speech Coder ANSI-C Source Code
  1.4236 +
  1.4237 +       iLBC_define.h
  1.4238 +
  1.4239 +       Copyright (C) The Internet Society (2004).
  1.4240 +       All Rights Reserved.
  1.4241 +
  1.4242 +   ******************************************************************/
  1.4243 +   #include <string.h>
  1.4244 +
  1.4245 +   #ifndef __iLBC_ILBCDEFINE_H
  1.4246 +   #define __iLBC_ILBCDEFINE_H
  1.4247 +
  1.4248 +   /* general codec settings */
  1.4249 +
  1.4250 +   #define FS                      (float)8000.0
  1.4251 +   #define BLOCKL_20MS             160
  1.4252 +   #define BLOCKL_30MS             240
  1.4253 +   #define BLOCKL_MAX              240
  1.4254 +   #define NSUB_20MS               4
  1.4255 +   #define NSUB_30MS               6
  1.4256 +   #define NSUB_MAX            6
  1.4257 +   #define NASUB_20MS              2
  1.4258 +
  1.4259 +
  1.4260 +
  1.4261 +Andersen, et al.              Experimental                     [Page 76]
  1.4262 +
  1.4263 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.4264 +
  1.4265 +
  1.4266 +   #define NASUB_30MS              4
  1.4267 +   #define NASUB_MAX               4
  1.4268 +   #define SUBL                40
  1.4269 +   #define STATE_LEN               80
  1.4270 +   #define STATE_SHORT_LEN_30MS    58
  1.4271 +   #define STATE_SHORT_LEN_20MS    57
  1.4272 +
  1.4273 +   /* LPC settings */
  1.4274 +
  1.4275 +   #define LPC_FILTERORDER         10
  1.4276 +   #define LPC_CHIRP_SYNTDENUM     (float)0.9025
  1.4277 +   #define LPC_CHIRP_WEIGHTDENUM   (float)0.4222
  1.4278 +   #define LPC_LOOKBACK        60
  1.4279 +   #define LPC_N_20MS              1
  1.4280 +   #define LPC_N_30MS              2
  1.4281 +   #define LPC_N_MAX               2
  1.4282 +   #define LPC_ASYMDIFF        20
  1.4283 +   #define LPC_BW                  (float)60.0
  1.4284 +   #define LPC_WN                  (float)1.0001
  1.4285 +   #define LSF_NSPLIT              3
  1.4286 +   #define LSF_NUMBER_OF_STEPS     4
  1.4287 +   #define LPC_HALFORDER           (LPC_FILTERORDER/2)
  1.4288 +
  1.4289 +   /* cb settings */
  1.4290 +
  1.4291 +   #define CB_NSTAGES              3
  1.4292 +   #define CB_EXPAND               2
  1.4293 +   #define CB_MEML                 147
  1.4294 +   #define CB_FILTERLEN        2*4
  1.4295 +   #define CB_HALFFILTERLEN    4
  1.4296 +   #define CB_RESRANGE             34
  1.4297 +   #define CB_MAXGAIN              (float)1.3
  1.4298 +
  1.4299 +   /* enhancer */
  1.4300 +
  1.4301 +   #define ENH_BLOCKL              80  /* block length */
  1.4302 +   #define ENH_BLOCKL_HALF         (ENH_BLOCKL/2)
  1.4303 +   #define ENH_HL                  3   /* 2*ENH_HL+1 is number blocks
  1.4304 +                                          in said second sequence */
  1.4305 +   #define ENH_SLOP            2   /* max difference estimated and
  1.4306 +                                          correct pitch period */
  1.4307 +   #define ENH_PLOCSL              20  /* pitch-estimates and pitch-
  1.4308 +                                          locations buffer length */
  1.4309 +   #define ENH_OVERHANG        2
  1.4310 +   #define ENH_UPS0            4   /* upsampling rate */
  1.4311 +   #define ENH_FL0                 3   /* 2*FLO+1 is the length of
  1.4312 +                                          each filter */
  1.4313 +   #define ENH_VECTL               (ENH_BLOCKL+2*ENH_FL0)
  1.4314 +
  1.4315 +
  1.4316 +
  1.4317 +Andersen, et al.              Experimental                     [Page 77]
  1.4318 +
  1.4319 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.4320 +
  1.4321 +
  1.4322 +   #define ENH_CORRDIM             (2*ENH_SLOP+1)
  1.4323 +   #define ENH_NBLOCKS             (BLOCKL_MAX/ENH_BLOCKL)
  1.4324 +   #define ENH_NBLOCKS_EXTRA       5
  1.4325 +   #define ENH_NBLOCKS_TOT         8   /* ENH_NBLOCKS +
  1.4326 +                                          ENH_NBLOCKS_EXTRA */
  1.4327 +   #define ENH_BUFL            (ENH_NBLOCKS_TOT)*ENH_BLOCKL
  1.4328 +   #define ENH_ALPHA0              (float)0.05
  1.4329 +
  1.4330 +   /* Down sampling */
  1.4331 +
  1.4332 +   #define FILTERORDER_DS          7
  1.4333 +   #define DELAY_DS            3
  1.4334 +   #define FACTOR_DS               2
  1.4335 +
  1.4336 +   /* bit stream defs */
  1.4337 +
  1.4338 +   #define NO_OF_BYTES_20MS    38
  1.4339 +   #define NO_OF_BYTES_30MS    50
  1.4340 +   #define NO_OF_WORDS_20MS    19
  1.4341 +   #define NO_OF_WORDS_30MS    25
  1.4342 +   #define STATE_BITS              3
  1.4343 +   #define BYTE_LEN            8
  1.4344 +   #define ULP_CLASSES             3
  1.4345 +
  1.4346 +   /* help parameters */
  1.4347 +
  1.4348 +   #define FLOAT_MAX               (float)1.0e37
  1.4349 +   #define EPS                     (float)2.220446049250313e-016
  1.4350 +   #define PI                      (float)3.14159265358979323846
  1.4351 +   #define MIN_SAMPLE              -32768
  1.4352 +   #define MAX_SAMPLE              32767
  1.4353 +   #define TWO_PI                  (float)6.283185307
  1.4354 +   #define PI2                     (float)0.159154943
  1.4355 +
  1.4356 +   /* type definition encoder instance */
  1.4357 +   typedef struct iLBC_ULP_Inst_t_ {
  1.4358 +       int lsf_bits[6][ULP_CLASSES+2];
  1.4359 +       int start_bits[ULP_CLASSES+2];
  1.4360 +       int startfirst_bits[ULP_CLASSES+2];
  1.4361 +       int scale_bits[ULP_CLASSES+2];
  1.4362 +       int state_bits[ULP_CLASSES+2];
  1.4363 +       int extra_cb_index[CB_NSTAGES][ULP_CLASSES+2];
  1.4364 +       int extra_cb_gain[CB_NSTAGES][ULP_CLASSES+2];
  1.4365 +       int cb_index[NSUB_MAX][CB_NSTAGES][ULP_CLASSES+2];
  1.4366 +       int cb_gain[NSUB_MAX][CB_NSTAGES][ULP_CLASSES+2];
  1.4367 +   } iLBC_ULP_Inst_t;
  1.4368 +
  1.4369 +   /* type definition encoder instance */
  1.4370 +
  1.4371 +
  1.4372 +
  1.4373 +Andersen, et al.              Experimental                     [Page 78]
  1.4374 +
  1.4375 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.4376 +
  1.4377 +
  1.4378 +   typedef struct iLBC_Enc_Inst_t_ {
  1.4379 +
  1.4380 +       /* flag for frame size mode */
  1.4381 +       int mode;
  1.4382 +
  1.4383 +       /* basic parameters for different frame sizes */
  1.4384 +       int blockl;
  1.4385 +       int nsub;
  1.4386 +       int nasub;
  1.4387 +       int no_of_bytes, no_of_words;
  1.4388 +       int lpc_n;
  1.4389 +       int state_short_len;
  1.4390 +       const iLBC_ULP_Inst_t *ULP_inst;
  1.4391 +
  1.4392 +       /* analysis filter state */
  1.4393 +       float anaMem[LPC_FILTERORDER];
  1.4394 +
  1.4395 +       /* old lsf parameters for interpolation */
  1.4396 +       float lsfold[LPC_FILTERORDER];
  1.4397 +       float lsfdeqold[LPC_FILTERORDER];
  1.4398 +
  1.4399 +       /* signal buffer for LP analysis */
  1.4400 +       float lpc_buffer[LPC_LOOKBACK + BLOCKL_MAX];
  1.4401 +
  1.4402 +       /* state of input HP filter */
  1.4403 +       float hpimem[4];
  1.4404 +
  1.4405 +   } iLBC_Enc_Inst_t;
  1.4406 +
  1.4407 +   /* type definition decoder instance */
  1.4408 +   typedef struct iLBC_Dec_Inst_t_ {
  1.4409 +
  1.4410 +       /* flag for frame size mode */
  1.4411 +       int mode;
  1.4412 +
  1.4413 +       /* basic parameters for different frame sizes */
  1.4414 +       int blockl;
  1.4415 +       int nsub;
  1.4416 +       int nasub;
  1.4417 +       int no_of_bytes, no_of_words;
  1.4418 +       int lpc_n;
  1.4419 +       int state_short_len;
  1.4420 +       const iLBC_ULP_Inst_t *ULP_inst;
  1.4421 +
  1.4422 +       /* synthesis filter state */
  1.4423 +       float syntMem[LPC_FILTERORDER];
  1.4424 +
  1.4425 +       /* old LSF for interpolation */
  1.4426 +
  1.4427 +
  1.4428 +
  1.4429 +Andersen, et al.              Experimental                     [Page 79]
  1.4430 +
  1.4431 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.4432 +
  1.4433 +
  1.4434 +       float lsfdeqold[LPC_FILTERORDER];
  1.4435 +
  1.4436 +       /* pitch lag estimated in enhancer and used in PLC */
  1.4437 +       int last_lag;
  1.4438 +
  1.4439 +       /* PLC state information */
  1.4440 +       int prevLag, consPLICount, prevPLI, prev_enh_pl;
  1.4441 +       float prevLpc[LPC_FILTERORDER+1];
  1.4442 +       float prevResidual[NSUB_MAX*SUBL];
  1.4443 +       float per;
  1.4444 +       unsigned long seed;
  1.4445 +
  1.4446 +       /* previous synthesis filter parameters */
  1.4447 +       float old_syntdenum[(LPC_FILTERORDER + 1)*NSUB_MAX];
  1.4448 +
  1.4449 +       /* state of output HP filter */
  1.4450 +       float hpomem[4];
  1.4451 +
  1.4452 +       /* enhancer state information */
  1.4453 +       int use_enhancer;
  1.4454 +       float enh_buf[ENH_BUFL];
  1.4455 +       float enh_period[ENH_NBLOCKS_TOT];
  1.4456 +
  1.4457 +   } iLBC_Dec_Inst_t;
  1.4458 +
  1.4459 +   #endif
  1.4460 +
  1.4461 +A.7.  constants.h
  1.4462 +
  1.4463 +   /******************************************************************
  1.4464 +
  1.4465 +       iLBC Speech Coder ANSI-C Source Code
  1.4466 +
  1.4467 +       constants.h
  1.4468 +
  1.4469 +       Copyright (C) The Internet Society (2004).
  1.4470 +       All Rights Reserved.
  1.4471 +
  1.4472 +   ******************************************************************/
  1.4473 +
  1.4474 +   #ifndef __iLBC_CONSTANTS_H
  1.4475 +   #define __iLBC_CONSTANTS_H
  1.4476 +
  1.4477 +   #include "iLBC_define.h"
  1.4478 +
  1.4479 +
  1.4480 +   /* ULP bit allocation */
  1.4481 +
  1.4482 +
  1.4483 +
  1.4484 +
  1.4485 +Andersen, et al.              Experimental                     [Page 80]
  1.4486 +
  1.4487 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.4488 +
  1.4489 +
  1.4490 +   extern const iLBC_ULP_Inst_t ULP_20msTbl;
  1.4491 +   extern const iLBC_ULP_Inst_t ULP_30msTbl;
  1.4492 +
  1.4493 +   /* high pass filters */
  1.4494 +
  1.4495 +   extern float hpi_zero_coefsTbl[];
  1.4496 +   extern float hpi_pole_coefsTbl[];
  1.4497 +   extern float hpo_zero_coefsTbl[];
  1.4498 +   extern float hpo_pole_coefsTbl[];
  1.4499 +
  1.4500 +   /* low pass filters */
  1.4501 +   extern float lpFilt_coefsTbl[];
  1.4502 +
  1.4503 +   /* LPC analysis and quantization */
  1.4504 +
  1.4505 +   extern float lpc_winTbl[];
  1.4506 +   extern float lpc_asymwinTbl[];
  1.4507 +   extern float lpc_lagwinTbl[];
  1.4508 +   extern float lsfCbTbl[];
  1.4509 +   extern float lsfmeanTbl[];
  1.4510 +   extern int   dim_lsfCbTbl[];
  1.4511 +   extern int   size_lsfCbTbl[];
  1.4512 +   extern float lsf_weightTbl_30ms[];
  1.4513 +   extern float lsf_weightTbl_20ms[];
  1.4514 +
  1.4515 +   /* state quantization tables */
  1.4516 +
  1.4517 +   extern float state_sq3Tbl[];
  1.4518 +   extern float state_frgqTbl[];
  1.4519 +
  1.4520 +   /* gain quantization tables */
  1.4521 +
  1.4522 +   extern float gain_sq3Tbl[];
  1.4523 +   extern float gain_sq4Tbl[];
  1.4524 +   extern float gain_sq5Tbl[];
  1.4525 +
  1.4526 +   /* adaptive codebook definitions */
  1.4527 +
  1.4528 +   extern int search_rangeTbl[5][CB_NSTAGES];
  1.4529 +   extern int memLfTbl[];
  1.4530 +   extern int stMemLTbl;
  1.4531 +   extern float cbfiltersTbl[CB_FILTERLEN];
  1.4532 +
  1.4533 +   /* enhancer definitions */
  1.4534 +
  1.4535 +   extern float polyphaserTbl[];
  1.4536 +   extern float enh_plocsTbl[];
  1.4537 +
  1.4538 +
  1.4539 +
  1.4540 +
  1.4541 +Andersen, et al.              Experimental                     [Page 81]
  1.4542 +
  1.4543 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.4544 +
  1.4545 +
  1.4546 +   #endif
  1.4547 +
  1.4548 +A.8.  constants.c
  1.4549 +
  1.4550 +   /******************************************************************
  1.4551 +
  1.4552 +       iLBC Speech Coder ANSI-C Source Code
  1.4553 +
  1.4554 +       constants.c
  1.4555 +
  1.4556 +       Copyright (C) The Internet Society (2004).
  1.4557 +       All Rights Reserved.
  1.4558 +
  1.4559 +   ******************************************************************/
  1.4560 +
  1.4561 +   #include "iLBC_define.h"
  1.4562 +
  1.4563 +   /* ULP bit allocation */
  1.4564 +
  1.4565 +       /* 20 ms frame */
  1.4566 +
  1.4567 +   const iLBC_ULP_Inst_t ULP_20msTbl = {
  1.4568 +       /* LSF */
  1.4569 +       {   {6,0,0,0,0}, {7,0,0,0,0}, {7,0,0,0,0},
  1.4570 +           {0,0,0,0,0}, {0,0,0,0,0}, {0,0,0,0,0}},
  1.4571 +       /* Start state location, gain and samples */
  1.4572 +       {2,0,0,0,0},
  1.4573 +       {1,0,0,0,0},
  1.4574 +       {6,0,0,0,0},
  1.4575 +       {0,1,2,0,0},
  1.4576 +       /* extra CB index and extra CB gain */
  1.4577 +       {{6,0,1,0,0}, {0,0,7,0,0}, {0,0,7,0,0}},
  1.4578 +       {{2,0,3,0,0}, {1,1,2,0,0}, {0,0,3,0,0}},
  1.4579 +       /* CB index and CB gain */
  1.4580 +       {   {{7,0,1,0,0}, {0,0,7,0,0}, {0,0,7,0,0}},
  1.4581 +           {{0,0,8,0,0}, {0,0,8,0,0}, {0,0,8,0,0}},
  1.4582 +           {{0,0,0,0,0}, {0,0,0,0,0}, {0,0,0,0,0}},
  1.4583 +           {{0,0,0,0,0}, {0,0,0,0,0}, {0,0,0,0,0}}},
  1.4584 +       {   {{1,2,2,0,0}, {1,1,2,0,0}, {0,0,3,0,0}},
  1.4585 +           {{1,1,3,0,0}, {0,2,2,0,0}, {0,0,3,0,0}},
  1.4586 +           {{0,0,0,0,0}, {0,0,0,0,0}, {0,0,0,0,0}},
  1.4587 +           {{0,0,0,0,0}, {0,0,0,0,0}, {0,0,0,0,0}}}
  1.4588 +   };
  1.4589 +
  1.4590 +       /* 30 ms frame */
  1.4591 +
  1.4592 +   const iLBC_ULP_Inst_t ULP_30msTbl = {
  1.4593 +       /* LSF */
  1.4594 +
  1.4595 +
  1.4596 +
  1.4597 +Andersen, et al.              Experimental                     [Page 82]
  1.4598 +
  1.4599 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.4600 +
  1.4601 +
  1.4602 +       {   {6,0,0,0,0}, {7,0,0,0,0}, {7,0,0,0,0},
  1.4603 +           {6,0,0,0,0}, {7,0,0,0,0}, {7,0,0,0,0}},
  1.4604 +       /* Start state location, gain and samples */
  1.4605 +       {3,0,0,0,0},
  1.4606 +       {1,0,0,0,0},
  1.4607 +       {6,0,0,0,0},
  1.4608 +       {0,1,2,0,0},
  1.4609 +       /* extra CB index and extra CB gain */
  1.4610 +       {{4,2,1,0,0}, {0,0,7,0,0}, {0,0,7,0,0}},
  1.4611 +       {{1,1,3,0,0}, {1,1,2,0,0}, {0,0,3,0,0}},
  1.4612 +       /* CB index and CB gain */
  1.4613 +       {   {{6,1,1,0,0}, {0,0,7,0,0}, {0,0,7,0,0}},
  1.4614 +           {{0,7,1,0,0}, {0,0,8,0,0}, {0,0,8,0,0}},
  1.4615 +           {{0,7,1,0,0}, {0,0,8,0,0}, {0,0,8,0,0}},
  1.4616 +           {{0,7,1,0,0}, {0,0,8,0,0}, {0,0,8,0,0}}},
  1.4617 +       {   {{1,2,2,0,0}, {1,2,1,0,0}, {0,0,3,0,0}},
  1.4618 +           {{0,2,3,0,0}, {0,2,2,0,0}, {0,0,3,0,0}},
  1.4619 +           {{0,1,4,0,0}, {0,1,3,0,0}, {0,0,3,0,0}},
  1.4620 +           {{0,1,4,0,0}, {0,1,3,0,0}, {0,0,3,0,0}}}
  1.4621 +   };
  1.4622 +
  1.4623 +   /* HP Filters */
  1.4624 +
  1.4625 +   float hpi_zero_coefsTbl[3] = {
  1.4626 +       (float)0.92727436, (float)-1.8544941, (float)0.92727436
  1.4627 +   };
  1.4628 +   float hpi_pole_coefsTbl[3] = {
  1.4629 +       (float)1.0, (float)-1.9059465, (float)0.9114024
  1.4630 +   };
  1.4631 +   float hpo_zero_coefsTbl[3] = {
  1.4632 +       (float)0.93980581, (float)-1.8795834, (float)0.93980581
  1.4633 +   };
  1.4634 +   float hpo_pole_coefsTbl[3] = {
  1.4635 +       (float)1.0, (float)-1.9330735, (float)0.93589199
  1.4636 +   };
  1.4637 +
  1.4638 +   /* LP Filter */
  1.4639 +
  1.4640 +   float lpFilt_coefsTbl[FILTERORDER_DS]={
  1.4641 +       (float)-0.066650, (float)0.125000, (float)0.316650,
  1.4642 +       (float)0.414063, (float)0.316650,
  1.4643 +       (float)0.125000, (float)-0.066650
  1.4644 +   };
  1.4645 +
  1.4646 +   /* State quantization tables */
  1.4647 +
  1.4648 +   float state_sq3Tbl[8] = {
  1.4649 +       (float)-3.719849, (float)-2.177490, (float)-1.130005,
  1.4650 +
  1.4651 +
  1.4652 +
  1.4653 +Andersen, et al.              Experimental                     [Page 83]
  1.4654 +
  1.4655 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.4656 +
  1.4657 +
  1.4658 +       (float)-0.309692, (float)0.444214, (float)1.329712,
  1.4659 +       (float)2.436279, (float)3.983887
  1.4660 +   };
  1.4661 +
  1.4662 +   float state_frgqTbl[64] = {
  1.4663 +       (float)1.000085, (float)1.071695, (float)1.140395,
  1.4664 +       (float)1.206868, (float)1.277188, (float)1.351503,
  1.4665 +       (float)1.429380, (float)1.500727, (float)1.569049,
  1.4666 +       (float)1.639599, (float)1.707071, (float)1.781531,
  1.4667 +       (float)1.840799, (float)1.901550, (float)1.956695,
  1.4668 +       (float)2.006750, (float)2.055474, (float)2.102787,
  1.4669 +       (float)2.142819, (float)2.183592, (float)2.217962,
  1.4670 +       (float)2.257177, (float)2.295739, (float)2.332967,
  1.4671 +       (float)2.369248, (float)2.402792, (float)2.435080,
  1.4672 +       (float)2.468598, (float)2.503394, (float)2.539284,
  1.4673 +       (float)2.572944, (float)2.605036, (float)2.636331,
  1.4674 +       (float)2.668939, (float)2.698780, (float)2.729101,
  1.4675 +       (float)2.759786, (float)2.789834, (float)2.818679,
  1.4676 +       (float)2.848074, (float)2.877470, (float)2.906899,
  1.4677 +       (float)2.936655, (float)2.967804, (float)3.000115,
  1.4678 +       (float)3.033367, (float)3.066355, (float)3.104231,
  1.4679 +       (float)3.141499, (float)3.183012, (float)3.222952,
  1.4680 +       (float)3.265433, (float)3.308441, (float)3.350823,
  1.4681 +       (float)3.395275, (float)3.442793, (float)3.490801,
  1.4682 +       (float)3.542514, (float)3.604064, (float)3.666050,
  1.4683 +       (float)3.740994, (float)3.830749, (float)3.938770,
  1.4684 +       (float)4.101764
  1.4685 +   };
  1.4686 +
  1.4687 +   /* CB tables */
  1.4688 +
  1.4689 +   int search_rangeTbl[5][CB_NSTAGES]={{58,58,58}, {108,44,44},
  1.4690 +               {108,108,108}, {108,108,108}, {108,108,108}};
  1.4691 +   int stMemLTbl=85;
  1.4692 +   int memLfTbl[NASUB_MAX]={147,147,147,147};
  1.4693 +
  1.4694 +   /* expansion filter(s) */
  1.4695 +
  1.4696 +   float cbfiltersTbl[CB_FILTERLEN]={
  1.4697 +       (float)-0.034180, (float)0.108887, (float)-0.184326,
  1.4698 +       (float)0.806152,  (float)0.713379, (float)-0.144043,
  1.4699 +       (float)0.083740,  (float)-0.033691
  1.4700 +   };
  1.4701 +
  1.4702 +   /* Gain Quantization */
  1.4703 +
  1.4704 +   float gain_sq3Tbl[8]={
  1.4705 +       (float)-1.000000,  (float)-0.659973,  (float)-0.330017,
  1.4706 +
  1.4707 +
  1.4708 +
  1.4709 +Andersen, et al.              Experimental                     [Page 84]
  1.4710 +
  1.4711 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.4712 +
  1.4713 +
  1.4714 +       (float)0.000000, (float)0.250000, (float)0.500000,
  1.4715 +       (float)0.750000, (float)1.00000};
  1.4716 +
  1.4717 +   float gain_sq4Tbl[16]={
  1.4718 +       (float)-1.049988, (float)-0.900024, (float)-0.750000,
  1.4719 +       (float)-0.599976, (float)-0.450012, (float)-0.299988,
  1.4720 +       (float)-0.150024, (float)0.000000, (float)0.150024,
  1.4721 +       (float)0.299988, (float)0.450012, (float)0.599976,
  1.4722 +       (float)0.750000, (float)0.900024, (float)1.049988,
  1.4723 +       (float)1.200012};
  1.4724 +
  1.4725 +   float gain_sq5Tbl[32]={
  1.4726 +       (float)0.037476, (float)0.075012, (float)0.112488,
  1.4727 +       (float)0.150024, (float)0.187500, (float)0.224976,
  1.4728 +       (float)0.262512, (float)0.299988, (float)0.337524,
  1.4729 +       (float)0.375000, (float)0.412476, (float)0.450012,
  1.4730 +       (float)0.487488, (float)0.525024, (float)0.562500,
  1.4731 +       (float)0.599976, (float)0.637512, (float)0.674988,
  1.4732 +       (float)0.712524, (float)0.750000, (float)0.787476,
  1.4733 +       (float)0.825012, (float)0.862488, (float)0.900024,
  1.4734 +       (float)0.937500, (float)0.974976, (float)1.012512,
  1.4735 +       (float)1.049988, (float)1.087524, (float)1.125000,
  1.4736 +       (float)1.162476, (float)1.200012};
  1.4737 +
  1.4738 +   /* Enhancer - Upsamling a factor 4 (ENH_UPS0 = 4) */
  1.4739 +   float polyphaserTbl[ENH_UPS0*(2*ENH_FL0+1)]={
  1.4740 +       (float)0.000000, (float)0.000000, (float)0.000000,
  1.4741 +   (float)1.000000,
  1.4742 +           (float)0.000000, (float)0.000000, (float)0.000000,
  1.4743 +       (float)0.015625, (float)-0.076904, (float)0.288330,
  1.4744 +   (float)0.862061,
  1.4745 +           (float)-0.106445, (float)0.018799, (float)-0.015625,
  1.4746 +       (float)0.023682, (float)-0.124268, (float)0.601563,
  1.4747 +   (float)0.601563,
  1.4748 +           (float)-0.124268, (float)0.023682, (float)-0.023682,
  1.4749 +       (float)0.018799, (float)-0.106445, (float)0.862061,
  1.4750 +   (float)0.288330,
  1.4751 +           (float)-0.076904, (float)0.015625, (float)-0.018799};
  1.4752 +
  1.4753 +   float enh_plocsTbl[ENH_NBLOCKS_TOT] = {(float)40.0, (float)120.0,
  1.4754 +               (float)200.0, (float)280.0, (float)360.0,
  1.4755 +               (float)440.0, (float)520.0, (float)600.0};
  1.4756 +
  1.4757 +   /* LPC analysis and quantization */
  1.4758 +
  1.4759 +   int dim_lsfCbTbl[LSF_NSPLIT] = {3, 3, 4};
  1.4760 +   int size_lsfCbTbl[LSF_NSPLIT] = {64,128,128};
  1.4761 +
  1.4762 +
  1.4763 +
  1.4764 +
  1.4765 +Andersen, et al.              Experimental                     [Page 85]
  1.4766 +
  1.4767 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.4768 +
  1.4769 +
  1.4770 +   float lsfmeanTbl[LPC_FILTERORDER] = {
  1.4771 +       (float)0.281738, (float)0.445801, (float)0.663330,
  1.4772 +       (float)0.962524, (float)1.251831, (float)1.533081,
  1.4773 +       (float)1.850586, (float)2.137817, (float)2.481445,
  1.4774 +       (float)2.777344};
  1.4775 +
  1.4776 +   float lsf_weightTbl_30ms[6] = {(float)(1.0/2.0), (float)1.0,
  1.4777 +   (float)(2.0/3.0),
  1.4778 +       (float)(1.0/3.0), (float)0.0, (float)0.0};
  1.4779 +
  1.4780 +   float lsf_weightTbl_20ms[4] = {(float)(3.0/4.0), (float)(2.0/4.0),
  1.4781 +       (float)(1.0/4.0), (float)(0.0)};
  1.4782 +
  1.4783 +   /* Hanning LPC window */
  1.4784 +   float lpc_winTbl[BLOCKL_MAX]={
  1.4785 +       (float)0.000183, (float)0.000671, (float)0.001526,
  1.4786 +       (float)0.002716, (float)0.004242, (float)0.006104,
  1.4787 +       (float)0.008301, (float)0.010834, (float)0.013702,
  1.4788 +       (float)0.016907, (float)0.020416, (float)0.024261,
  1.4789 +       (float)0.028442, (float)0.032928, (float)0.037750,
  1.4790 +       (float)0.042877, (float)0.048309, (float)0.054047,
  1.4791 +       (float)0.060089, (float)0.066437, (float)0.073090,
  1.4792 +       (float)0.080017, (float)0.087219, (float)0.094727,
  1.4793 +       (float)0.102509, (float)0.110535, (float)0.118835,
  1.4794 +       (float)0.127411, (float)0.136230, (float)0.145294,
  1.4795 +       (float)0.154602, (float)0.164154, (float)0.173920,
  1.4796 +       (float)0.183899, (float)0.194122, (float)0.204529,
  1.4797 +       (float)0.215149, (float)0.225952, (float)0.236938,
  1.4798 +       (float)0.248108, (float)0.259460, (float)0.270966,
  1.4799 +       (float)0.282654, (float)0.294464, (float)0.306396,
  1.4800 +       (float)0.318481, (float)0.330688, (float)0.343018,
  1.4801 +       (float)0.355438, (float)0.367981, (float)0.380585,
  1.4802 +       (float)0.393280, (float)0.406067, (float)0.418884,
  1.4803 +       (float)0.431763, (float)0.444702, (float)0.457672,
  1.4804 +       (float)0.470673, (float)0.483704, (float)0.496735,
  1.4805 +       (float)0.509766, (float)0.522797, (float)0.535828,
  1.4806 +       (float)0.548798, (float)0.561768, (float)0.574677,
  1.4807 +       (float)0.587524, (float)0.600342, (float)0.613068,
  1.4808 +       (float)0.625732, (float)0.638306, (float)0.650787,
  1.4809 +       (float)0.663147, (float)0.675415, (float)0.687561,
  1.4810 +       (float)0.699585, (float)0.711487, (float)0.723206,
  1.4811 +       (float)0.734802, (float)0.746216, (float)0.757477,
  1.4812 +       (float)0.768585, (float)0.779480, (float)0.790192,
  1.4813 +       (float)0.800720, (float)0.811005, (float)0.821106,
  1.4814 +       (float)0.830994, (float)0.840668, (float)0.850067,
  1.4815 +       (float)0.859253, (float)0.868225, (float)0.876892,
  1.4816 +       (float)0.885345, (float)0.893524, (float)0.901428,
  1.4817 +       (float)0.909058, (float)0.916412, (float)0.923492,
  1.4818 +
  1.4819 +
  1.4820 +
  1.4821 +Andersen, et al.              Experimental                     [Page 86]
  1.4822 +
  1.4823 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.4824 +
  1.4825 +
  1.4826 +       (float)0.930267, (float)0.936768, (float)0.942963,
  1.4827 +       (float)0.948853, (float)0.954437, (float)0.959717,
  1.4828 +       (float)0.964691, (float)0.969360, (float)0.973694,
  1.4829 +       (float)0.977692, (float)0.981384, (float)0.984741,
  1.4830 +       (float)0.987762, (float)0.990479, (float)0.992828,
  1.4831 +       (float)0.994873, (float)0.996552, (float)0.997925,
  1.4832 +       (float)0.998932, (float)0.999603, (float)0.999969,
  1.4833 +       (float)0.999969, (float)0.999603, (float)0.998932,
  1.4834 +       (float)0.997925, (float)0.996552, (float)0.994873,
  1.4835 +       (float)0.992828, (float)0.990479, (float)0.987762,
  1.4836 +       (float)0.984741, (float)0.981384, (float)0.977692,
  1.4837 +       (float)0.973694, (float)0.969360, (float)0.964691,
  1.4838 +       (float)0.959717, (float)0.954437, (float)0.948853,
  1.4839 +       (float)0.942963, (float)0.936768, (float)0.930267,
  1.4840 +       (float)0.923492, (float)0.916412, (float)0.909058,
  1.4841 +       (float)0.901428, (float)0.893524, (float)0.885345,
  1.4842 +       (float)0.876892, (float)0.868225, (float)0.859253,
  1.4843 +       (float)0.850067, (float)0.840668, (float)0.830994,
  1.4844 +       (float)0.821106, (float)0.811005, (float)0.800720,
  1.4845 +       (float)0.790192, (float)0.779480, (float)0.768585,
  1.4846 +       (float)0.757477, (float)0.746216, (float)0.734802,
  1.4847 +       (float)0.723206, (float)0.711487, (float)0.699585,
  1.4848 +       (float)0.687561, (float)0.675415, (float)0.663147,
  1.4849 +       (float)0.650787, (float)0.638306, (float)0.625732,
  1.4850 +       (float)0.613068, (float)0.600342, (float)0.587524,
  1.4851 +       (float)0.574677, (float)0.561768, (float)0.548798,
  1.4852 +       (float)0.535828, (float)0.522797, (float)0.509766,
  1.4853 +       (float)0.496735, (float)0.483704, (float)0.470673,
  1.4854 +       (float)0.457672, (float)0.444702, (float)0.431763,
  1.4855 +       (float)0.418884, (float)0.406067, (float)0.393280,
  1.4856 +       (float)0.380585, (float)0.367981, (float)0.355438,
  1.4857 +       (float)0.343018, (float)0.330688, (float)0.318481,
  1.4858 +       (float)0.306396, (float)0.294464, (float)0.282654,
  1.4859 +       (float)0.270966, (float)0.259460, (float)0.248108,
  1.4860 +       (float)0.236938, (float)0.225952, (float)0.215149,
  1.4861 +       (float)0.204529, (float)0.194122, (float)0.183899,
  1.4862 +       (float)0.173920, (float)0.164154, (float)0.154602,
  1.4863 +       (float)0.145294, (float)0.136230, (float)0.127411,
  1.4864 +       (float)0.118835, (float)0.110535, (float)0.102509,
  1.4865 +       (float)0.094727, (float)0.087219, (float)0.080017,
  1.4866 +       (float)0.073090, (float)0.066437, (float)0.060089,
  1.4867 +       (float)0.054047, (float)0.048309, (float)0.042877,
  1.4868 +       (float)0.037750, (float)0.032928, (float)0.028442,
  1.4869 +       (float)0.024261, (float)0.020416, (float)0.016907,
  1.4870 +       (float)0.013702, (float)0.010834, (float)0.008301,
  1.4871 +       (float)0.006104, (float)0.004242, (float)0.002716,
  1.4872 +       (float)0.001526, (float)0.000671, (float)0.000183
  1.4873 +   };
  1.4874 +
  1.4875 +
  1.4876 +
  1.4877 +Andersen, et al.              Experimental                     [Page 87]
  1.4878 +
  1.4879 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.4880 +
  1.4881 +
  1.4882 +   /* Asymmetric LPC window */
  1.4883 +   float lpc_asymwinTbl[BLOCKL_MAX]={
  1.4884 +       (float)0.000061, (float)0.000214, (float)0.000458,
  1.4885 +       (float)0.000824, (float)0.001282, (float)0.001831,
  1.4886 +       (float)0.002472, (float)0.003235, (float)0.004120,
  1.4887 +       (float)0.005066, (float)0.006134, (float)0.007294,
  1.4888 +       (float)0.008545, (float)0.009918, (float)0.011383,
  1.4889 +       (float)0.012939, (float)0.014587, (float)0.016357,
  1.4890 +       (float)0.018219, (float)0.020172, (float)0.022217,
  1.4891 +       (float)0.024353, (float)0.026611, (float)0.028961,
  1.4892 +       (float)0.031372, (float)0.033905, (float)0.036530,
  1.4893 +       (float)0.039276, (float)0.042084, (float)0.044983,
  1.4894 +       (float)0.047974, (float)0.051086, (float)0.054260,
  1.4895 +       (float)0.057526, (float)0.060883, (float)0.064331,
  1.4896 +       (float)0.067871, (float)0.071503, (float)0.075226,
  1.4897 +       (float)0.079010, (float)0.082916, (float)0.086884,
  1.4898 +       (float)0.090942, (float)0.095062, (float)0.099304,
  1.4899 +       (float)0.103607, (float)0.107971, (float)0.112427,
  1.4900 +       (float)0.116974, (float)0.121582, (float)0.126282,
  1.4901 +       (float)0.131073, (float)0.135895, (float)0.140839,
  1.4902 +       (float)0.145813, (float)0.150879, (float)0.156006,
  1.4903 +       (float)0.161224, (float)0.166504, (float)0.171844,
  1.4904 +       (float)0.177246, (float)0.182709, (float)0.188263,
  1.4905 +       (float)0.193848, (float)0.199524, (float)0.205231,
  1.4906 +       (float)0.211029, (float)0.216858, (float)0.222778,
  1.4907 +       (float)0.228729, (float)0.234741, (float)0.240814,
  1.4908 +       (float)0.246918, (float)0.253082, (float)0.259308,
  1.4909 +       (float)0.265564, (float)0.271881, (float)0.278259,
  1.4910 +       (float)0.284668, (float)0.291107, (float)0.297607,
  1.4911 +       (float)0.304138, (float)0.310730, (float)0.317322,
  1.4912 +       (float)0.323975, (float)0.330658, (float)0.337372,
  1.4913 +       (float)0.344147, (float)0.350922, (float)0.357727,
  1.4914 +       (float)0.364594, (float)0.371460, (float)0.378357,
  1.4915 +       (float)0.385284, (float)0.392212, (float)0.399170,
  1.4916 +       (float)0.406158, (float)0.413177, (float)0.420197,
  1.4917 +       (float)0.427246, (float)0.434296, (float)0.441376,
  1.4918 +       (float)0.448456, (float)0.455536, (float)0.462646,
  1.4919 +       (float)0.469757, (float)0.476868, (float)0.483978,
  1.4920 +       (float)0.491089, (float)0.498230, (float)0.505341,
  1.4921 +       (float)0.512451, (float)0.519592, (float)0.526703,
  1.4922 +       (float)0.533813, (float)0.540924, (float)0.548004,
  1.4923 +       (float)0.555084, (float)0.562164, (float)0.569244,
  1.4924 +       (float)0.576294, (float)0.583313, (float)0.590332,
  1.4925 +       (float)0.597321, (float)0.604309, (float)0.611267,
  1.4926 +       (float)0.618195, (float)0.625092, (float)0.631989,
  1.4927 +       (float)0.638855, (float)0.645660, (float)0.652466,
  1.4928 +       (float)0.659241, (float)0.665985, (float)0.672668,
  1.4929 +       (float)0.679352, (float)0.685974, (float)0.692566,
  1.4930 +
  1.4931 +
  1.4932 +
  1.4933 +Andersen, et al.              Experimental                     [Page 88]
  1.4934 +
  1.4935 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.4936 +
  1.4937 +
  1.4938 +       (float)0.699127, (float)0.705658, (float)0.712128,
  1.4939 +       (float)0.718536, (float)0.724945, (float)0.731262,
  1.4940 +       (float)0.737549, (float)0.743805, (float)0.750000,
  1.4941 +       (float)0.756134, (float)0.762238, (float)0.768280,
  1.4942 +       (float)0.774261, (float)0.780182, (float)0.786072,
  1.4943 +       (float)0.791870, (float)0.797638, (float)0.803314,
  1.4944 +       (float)0.808960, (float)0.814514, (float)0.820038,
  1.4945 +       (float)0.825470, (float)0.830841, (float)0.836151,
  1.4946 +       (float)0.841400, (float)0.846558, (float)0.851654,
  1.4947 +       (float)0.856689, (float)0.861633, (float)0.866516,
  1.4948 +       (float)0.871338, (float)0.876068, (float)0.880737,
  1.4949 +       (float)0.885315, (float)0.889801, (float)0.894226,
  1.4950 +       (float)0.898560, (float)0.902832, (float)0.907013,
  1.4951 +       (float)0.911102, (float)0.915100, (float)0.919037,
  1.4952 +       (float)0.922882, (float)0.926636, (float)0.930328,
  1.4953 +       (float)0.933899, (float)0.937408, (float)0.940796,
  1.4954 +       (float)0.944122, (float)0.947357, (float)0.950470,
  1.4955 +       (float)0.953522, (float)0.956482, (float)0.959351,
  1.4956 +       (float)0.962097, (float)0.964783, (float)0.967377,
  1.4957 +       (float)0.969849, (float)0.972229, (float)0.974518,
  1.4958 +       (float)0.976715, (float)0.978821, (float)0.980835,
  1.4959 +       (float)0.982727, (float)0.984528, (float)0.986237,
  1.4960 +       (float)0.987854, (float)0.989380, (float)0.990784,
  1.4961 +       (float)0.992096, (float)0.993317, (float)0.994415,
  1.4962 +       (float)0.995422, (float)0.996338, (float)0.997162,
  1.4963 +       (float)0.997864, (float)0.998474, (float)0.998962,
  1.4964 +       (float)0.999390, (float)0.999695, (float)0.999878,
  1.4965 +       (float)0.999969, (float)0.999969, (float)0.996918,
  1.4966 +       (float)0.987701, (float)0.972382, (float)0.951050,
  1.4967 +       (float)0.923889, (float)0.891022, (float)0.852631,
  1.4968 +       (float)0.809021, (float)0.760406, (float)0.707092,
  1.4969 +       (float)0.649445, (float)0.587799, (float)0.522491,
  1.4970 +       (float)0.453979, (float)0.382690, (float)0.309021,
  1.4971 +       (float)0.233459, (float)0.156433, (float)0.078461
  1.4972 +   };
  1.4973 +
  1.4974 +   /* Lag window for LPC */
  1.4975 +   float lpc_lagwinTbl[LPC_FILTERORDER + 1]={
  1.4976 +       (float)1.000100, (float)0.998890, (float)0.995569,
  1.4977 +           (float)0.990057, (float)0.982392,
  1.4978 +       (float)0.972623, (float)0.960816, (float)0.947047,
  1.4979 +           (float)0.931405, (float)0.913989, (float)0.894909};
  1.4980 +
  1.4981 +   /* LSF quantization*/
  1.4982 +   float lsfCbTbl[64 * 3 + 128 * 3 + 128 * 4] = {
  1.4983 +   (float)0.155396, (float)0.273193, (float)0.451172,
  1.4984 +   (float)0.390503, (float)0.648071, (float)1.002075,
  1.4985 +   (float)0.440186, (float)0.692261, (float)0.955688,
  1.4986 +
  1.4987 +
  1.4988 +
  1.4989 +Andersen, et al.              Experimental                     [Page 89]
  1.4990 +
  1.4991 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.4992 +
  1.4993 +
  1.4994 +   (float)0.343628, (float)0.642334, (float)1.071533,
  1.4995 +   (float)0.318359, (float)0.491577, (float)0.670532,
  1.4996 +   (float)0.193115, (float)0.375488, (float)0.725708,
  1.4997 +   (float)0.364136, (float)0.510376, (float)0.658691,
  1.4998 +   (float)0.297485, (float)0.527588, (float)0.842529,
  1.4999 +   (float)0.227173, (float)0.365967, (float)0.563110,
  1.5000 +   (float)0.244995, (float)0.396729, (float)0.636475,
  1.5001 +   (float)0.169434, (float)0.300171, (float)0.520264,
  1.5002 +   (float)0.312866, (float)0.464478, (float)0.643188,
  1.5003 +   (float)0.248535, (float)0.429932, (float)0.626099,
  1.5004 +   (float)0.236206, (float)0.491333, (float)0.817139,
  1.5005 +   (float)0.334961, (float)0.625122, (float)0.895752,
  1.5006 +   (float)0.343018, (float)0.518555, (float)0.698608,
  1.5007 +   (float)0.372803, (float)0.659790, (float)0.945435,
  1.5008 +   (float)0.176880, (float)0.316528, (float)0.581421,
  1.5009 +   (float)0.416382, (float)0.625977, (float)0.805176,
  1.5010 +   (float)0.303223, (float)0.568726, (float)0.915039,
  1.5011 +   (float)0.203613, (float)0.351440, (float)0.588135,
  1.5012 +   (float)0.221191, (float)0.375000, (float)0.614746,
  1.5013 +   (float)0.199951, (float)0.323364, (float)0.476074,
  1.5014 +   (float)0.300781, (float)0.433350, (float)0.566895,
  1.5015 +   (float)0.226196, (float)0.354004, (float)0.507568,
  1.5016 +   (float)0.300049, (float)0.508179, (float)0.711670,
  1.5017 +   (float)0.312012, (float)0.492676, (float)0.763428,
  1.5018 +   (float)0.329956, (float)0.541016, (float)0.795776,
  1.5019 +   (float)0.373779, (float)0.604614, (float)0.928833,
  1.5020 +   (float)0.210571, (float)0.452026, (float)0.755249,
  1.5021 +   (float)0.271118, (float)0.473267, (float)0.662476,
  1.5022 +   (float)0.285522, (float)0.436890, (float)0.634399,
  1.5023 +   (float)0.246704, (float)0.565552, (float)0.859009,
  1.5024 +   (float)0.270508, (float)0.406250, (float)0.553589,
  1.5025 +   (float)0.361450, (float)0.578491, (float)0.813843,
  1.5026 +   (float)0.342651, (float)0.482788, (float)0.622437,
  1.5027 +   (float)0.340332, (float)0.549438, (float)0.743164,
  1.5028 +   (float)0.200439, (float)0.336304, (float)0.540894,
  1.5029 +   (float)0.407837, (float)0.644775, (float)0.895142,
  1.5030 +   (float)0.294678, (float)0.454834, (float)0.699097,
  1.5031 +   (float)0.193115, (float)0.344482, (float)0.643188,
  1.5032 +   (float)0.275757, (float)0.420776, (float)0.598755,
  1.5033 +   (float)0.380493, (float)0.608643, (float)0.861084,
  1.5034 +   (float)0.222778, (float)0.426147, (float)0.676514,
  1.5035 +   (float)0.407471, (float)0.700195, (float)1.053101,
  1.5036 +   (float)0.218384, (float)0.377197, (float)0.669922,
  1.5037 +   (float)0.313232, (float)0.454102, (float)0.600952,
  1.5038 +   (float)0.347412, (float)0.571533, (float)0.874146,
  1.5039 +   (float)0.238037, (float)0.405396, (float)0.729492,
  1.5040 +   (float)0.223877, (float)0.412964, (float)0.822021,
  1.5041 +   (float)0.395264, (float)0.582153, (float)0.743896,
  1.5042 +
  1.5043 +
  1.5044 +
  1.5045 +Andersen, et al.              Experimental                     [Page 90]
  1.5046 +
  1.5047 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.5048 +
  1.5049 +
  1.5050 +   (float)0.247925, (float)0.485596, (float)0.720581,
  1.5051 +   (float)0.229126, (float)0.496582, (float)0.907715,
  1.5052 +   (float)0.260132, (float)0.566895, (float)1.012695,
  1.5053 +   (float)0.337402, (float)0.611572, (float)0.978149,
  1.5054 +   (float)0.267822, (float)0.447632, (float)0.769287,
  1.5055 +   (float)0.250610, (float)0.381714, (float)0.530029,
  1.5056 +   (float)0.430054, (float)0.805054, (float)1.221924,
  1.5057 +   (float)0.382568, (float)0.544067, (float)0.701660,
  1.5058 +   (float)0.383545, (float)0.710327, (float)1.149170,
  1.5059 +   (float)0.271362, (float)0.529053, (float)0.775513,
  1.5060 +   (float)0.246826, (float)0.393555, (float)0.588623,
  1.5061 +   (float)0.266846, (float)0.422119, (float)0.676758,
  1.5062 +   (float)0.311523, (float)0.580688, (float)0.838623,
  1.5063 +   (float)1.331177, (float)1.576782, (float)1.779541,
  1.5064 +   (float)1.160034, (float)1.401978, (float)1.768188,
  1.5065 +   (float)1.161865, (float)1.525146, (float)1.715332,
  1.5066 +   (float)0.759521, (float)0.913940, (float)1.119873,
  1.5067 +   (float)0.947144, (float)1.121338, (float)1.282471,
  1.5068 +   (float)1.015015, (float)1.557007, (float)1.804932,
  1.5069 +   (float)1.172974, (float)1.402100, (float)1.692627,
  1.5070 +   (float)1.087524, (float)1.474243, (float)1.665405,
  1.5071 +   (float)0.899536, (float)1.105225, (float)1.406250,
  1.5072 +   (float)1.148438, (float)1.484741, (float)1.796265,
  1.5073 +   (float)0.785645, (float)1.209839, (float)1.567749,
  1.5074 +   (float)0.867798, (float)1.166504, (float)1.450684,
  1.5075 +   (float)0.922485, (float)1.229858, (float)1.420898,
  1.5076 +   (float)0.791260, (float)1.123291, (float)1.409546,
  1.5077 +   (float)0.788940, (float)0.966064, (float)1.340332,
  1.5078 +   (float)1.051147, (float)1.272827, (float)1.556641,
  1.5079 +   (float)0.866821, (float)1.181152, (float)1.538818,
  1.5080 +   (float)0.906738, (float)1.373535, (float)1.607910,
  1.5081 +   (float)1.244751, (float)1.581421, (float)1.933838,
  1.5082 +   (float)0.913940, (float)1.337280, (float)1.539673,
  1.5083 +   (float)0.680542, (float)0.959229, (float)1.662720,
  1.5084 +   (float)0.887207, (float)1.430542, (float)1.800781,
  1.5085 +   (float)0.912598, (float)1.433594, (float)1.683960,
  1.5086 +   (float)0.860474, (float)1.060303, (float)1.455322,
  1.5087 +   (float)1.005127, (float)1.381104, (float)1.706909,
  1.5088 +   (float)0.800781, (float)1.363892, (float)1.829102,
  1.5089 +   (float)0.781860, (float)1.124390, (float)1.505981,
  1.5090 +   (float)1.003662, (float)1.471436, (float)1.684692,
  1.5091 +   (float)0.981323, (float)1.309570, (float)1.618042,
  1.5092 +   (float)1.228760, (float)1.554321, (float)1.756470,
  1.5093 +   (float)0.734375, (float)0.895752, (float)1.225586,
  1.5094 +   (float)0.841797, (float)1.055664, (float)1.249268,
  1.5095 +   (float)0.920166, (float)1.119385, (float)1.486206,
  1.5096 +   (float)0.894409, (float)1.539063, (float)1.828979,
  1.5097 +   (float)1.283691, (float)1.543335, (float)1.858276,
  1.5098 +
  1.5099 +
  1.5100 +
  1.5101 +Andersen, et al.              Experimental                     [Page 91]
  1.5102 +
  1.5103 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.5104 +
  1.5105 +
  1.5106 +   (float)0.676025, (float)0.933105, (float)1.490845,
  1.5107 +   (float)0.821289, (float)1.491821, (float)1.739868,
  1.5108 +   (float)0.923218, (float)1.144653, (float)1.580566,
  1.5109 +   (float)1.057251, (float)1.345581, (float)1.635864,
  1.5110 +   (float)0.888672, (float)1.074951, (float)1.353149,
  1.5111 +   (float)0.942749, (float)1.195435, (float)1.505493,
  1.5112 +   (float)1.492310, (float)1.788086, (float)2.039673,
  1.5113 +   (float)1.070313, (float)1.634399, (float)1.860962,
  1.5114 +   (float)1.253296, (float)1.488892, (float)1.686035,
  1.5115 +   (float)0.647095, (float)0.864014, (float)1.401855,
  1.5116 +   (float)0.866699, (float)1.254883, (float)1.453369,
  1.5117 +   (float)1.063965, (float)1.532593, (float)1.731323,
  1.5118 +   (float)1.167847, (float)1.521484, (float)1.884033,
  1.5119 +   (float)0.956055, (float)1.502075, (float)1.745605,
  1.5120 +   (float)0.928711, (float)1.288574, (float)1.479614,
  1.5121 +   (float)1.088013, (float)1.380737, (float)1.570801,
  1.5122 +   (float)0.905029, (float)1.186768, (float)1.371948,
  1.5123 +   (float)1.057861, (float)1.421021, (float)1.617432,
  1.5124 +   (float)1.108276, (float)1.312500, (float)1.501465,
  1.5125 +   (float)0.979492, (float)1.416992, (float)1.624268,
  1.5126 +   (float)1.276001, (float)1.661011, (float)2.007935,
  1.5127 +   (float)0.993042, (float)1.168579, (float)1.331665,
  1.5128 +   (float)0.778198, (float)0.944946, (float)1.235962,
  1.5129 +   (float)1.223755, (float)1.491333, (float)1.815674,
  1.5130 +   (float)0.852661, (float)1.350464, (float)1.722290,
  1.5131 +   (float)1.134766, (float)1.593140, (float)1.787354,
  1.5132 +   (float)1.051392, (float)1.339722, (float)1.531006,
  1.5133 +   (float)0.803589, (float)1.271240, (float)1.652100,
  1.5134 +   (float)0.755737, (float)1.143555, (float)1.639404,
  1.5135 +   (float)0.700928, (float)0.837280, (float)1.130371,
  1.5136 +   (float)0.942749, (float)1.197876, (float)1.669800,
  1.5137 +   (float)0.993286, (float)1.378296, (float)1.566528,
  1.5138 +   (float)0.801025, (float)1.095337, (float)1.298950,
  1.5139 +   (float)0.739990, (float)1.032959, (float)1.383667,
  1.5140 +   (float)0.845703, (float)1.072266, (float)1.543823,
  1.5141 +   (float)0.915649, (float)1.072266, (float)1.224487,
  1.5142 +   (float)1.021973, (float)1.226196, (float)1.481323,
  1.5143 +   (float)0.999878, (float)1.204102, (float)1.555908,
  1.5144 +   (float)0.722290, (float)0.913940, (float)1.340210,
  1.5145 +   (float)0.673340, (float)0.835938, (float)1.259521,
  1.5146 +   (float)0.832397, (float)1.208374, (float)1.394165,
  1.5147 +   (float)0.962158, (float)1.576172, (float)1.912842,
  1.5148 +   (float)1.166748, (float)1.370850, (float)1.556763,
  1.5149 +   (float)0.946289, (float)1.138550, (float)1.400391,
  1.5150 +   (float)1.035034, (float)1.218262, (float)1.386475,
  1.5151 +   (float)1.393799, (float)1.717773, (float)2.000244,
  1.5152 +   (float)0.972656, (float)1.260986, (float)1.760620,
  1.5153 +   (float)1.028198, (float)1.288452, (float)1.484619,
  1.5154 +
  1.5155 +
  1.5156 +
  1.5157 +Andersen, et al.              Experimental                     [Page 92]
  1.5158 +
  1.5159 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.5160 +
  1.5161 +
  1.5162 +   (float)0.773560, (float)1.258057, (float)1.756714,
  1.5163 +   (float)1.080322, (float)1.328003, (float)1.742676,
  1.5164 +   (float)0.823975, (float)1.450806, (float)1.917725,
  1.5165 +   (float)0.859009, (float)1.016602, (float)1.191895,
  1.5166 +   (float)0.843994, (float)1.131104, (float)1.645020,
  1.5167 +   (float)1.189697, (float)1.702759, (float)1.894409,
  1.5168 +   (float)1.346680, (float)1.763184, (float)2.066040,
  1.5169 +   (float)0.980469, (float)1.253784, (float)1.441650,
  1.5170 +   (float)1.338135, (float)1.641968, (float)1.932739,
  1.5171 +   (float)1.223267, (float)1.424194, (float)1.626465,
  1.5172 +   (float)0.765747, (float)1.004150, (float)1.579102,
  1.5173 +   (float)1.042847, (float)1.269165, (float)1.647461,
  1.5174 +   (float)0.968750, (float)1.257568, (float)1.555786,
  1.5175 +   (float)0.826294, (float)0.993408, (float)1.275146,
  1.5176 +   (float)0.742310, (float)0.950439, (float)1.430542,
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  1.5178 +   (float)1.072998, (float)1.261719, (float)1.441895,
  1.5179 +   (float)0.859375, (float)1.036377, (float)1.314819,
  1.5180 +   (float)0.895752, (float)1.267212, (float)1.605591,
  1.5181 +   (float)0.805420, (float)0.962891, (float)1.142334,
  1.5182 +   (float)0.795654, (float)1.005493, (float)1.468506,
  1.5183 +   (float)1.105347, (float)1.313843, (float)1.584839,
  1.5184 +   (float)0.792236, (float)1.221802, (float)1.465698,
  1.5185 +   (float)1.170532, (float)1.467651, (float)1.664063,
  1.5186 +   (float)0.838257, (float)1.153198, (float)1.342163,
  1.5187 +   (float)0.968018, (float)1.198242, (float)1.391235,
  1.5188 +   (float)1.250122, (float)1.623535, (float)1.823608,
  1.5189 +   (float)0.711670, (float)1.058350, (float)1.512085,
  1.5190 +   (float)1.204834, (float)1.454468, (float)1.739136,
  1.5191 +   (float)1.137451, (float)1.421753, (float)1.620117,
  1.5192 +   (float)0.820435, (float)1.322754, (float)1.578247,
  1.5193 +   (float)0.798706, (float)1.005005, (float)1.213867,
  1.5194 +   (float)0.980713, (float)1.324951, (float)1.512939,
  1.5195 +   (float)1.112305, (float)1.438843, (float)1.735596,
  1.5196 +   (float)1.135498, (float)1.356689, (float)1.635742,
  1.5197 +   (float)1.101318, (float)1.387451, (float)1.686523,
  1.5198 +   (float)0.849854, (float)1.276978, (float)1.523438,
  1.5199 +   (float)1.377930, (float)1.627563, (float)1.858154,
  1.5200 +   (float)0.884888, (float)1.095459, (float)1.287476,
  1.5201 +   (float)1.289795, (float)1.505859, (float)1.756592,
  1.5202 +   (float)0.817505, (float)1.384155, (float)1.650513,
  1.5203 +   (float)1.446655, (float)1.702148, (float)1.931885,
  1.5204 +   (float)0.835815, (float)1.023071, (float)1.385376,
  1.5205 +   (float)0.916626, (float)1.139038, (float)1.335327,
  1.5206 +   (float)0.980103, (float)1.174072, (float)1.453735,
  1.5207 +   (float)1.705688, (float)2.153809, (float)2.398315, (float)2.743408,
  1.5208 +   (float)1.797119, (float)2.016846, (float)2.445679, (float)2.701904,
  1.5209 +   (float)1.990356, (float)2.219116, (float)2.576416, (float)2.813477,
  1.5210 +
  1.5211 +
  1.5212 +
  1.5213 +Andersen, et al.              Experimental                     [Page 93]
  1.5214 +
  1.5215 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.5216 +
  1.5217 +
  1.5218 +   (float)1.849365, (float)2.190918, (float)2.611572, (float)2.835083,
  1.5219 +   (float)1.657959, (float)1.854370, (float)2.159058, (float)2.726196,
  1.5220 +   (float)1.437744, (float)1.897705, (float)2.253174, (float)2.655396,
  1.5221 +   (float)2.028687, (float)2.247314, (float)2.542358, (float)2.875854,
  1.5222 +   (float)1.736938, (float)1.922119, (float)2.185913, (float)2.743408,
  1.5223 +   (float)1.521606, (float)1.870972, (float)2.526855, (float)2.786987,
  1.5224 +   (float)1.841431, (float)2.050659, (float)2.463623, (float)2.857666,
  1.5225 +   (float)1.590088, (float)2.067261, (float)2.427979, (float)2.794434,
  1.5226 +   (float)1.746826, (float)2.057373, (float)2.320190, (float)2.800781,
  1.5227 +   (float)1.734619, (float)1.940552, (float)2.306030, (float)2.826416,
  1.5228 +   (float)1.786255, (float)2.204468, (float)2.457520, (float)2.795288,
  1.5229 +   (float)1.861084, (float)2.170532, (float)2.414551, (float)2.763672,
  1.5230 +   (float)2.001465, (float)2.307617, (float)2.552734, (float)2.811890,
  1.5231 +   (float)1.784424, (float)2.124146, (float)2.381592, (float)2.645508,
  1.5232 +   (float)1.888794, (float)2.135864, (float)2.418579, (float)2.861206,
  1.5233 +   (float)2.301147, (float)2.531250, (float)2.724976, (float)2.913086,
  1.5234 +   (float)1.837769, (float)2.051270, (float)2.261963, (float)2.553223,
  1.5235 +   (float)2.012939, (float)2.221191, (float)2.440186, (float)2.678101,
  1.5236 +   (float)1.429565, (float)1.858276, (float)2.582275, (float)2.845703,
  1.5237 +   (float)1.622803, (float)1.897705, (float)2.367310, (float)2.621094,
  1.5238 +   (float)1.581543, (float)1.960449, (float)2.515869, (float)2.736450,
  1.5239 +   (float)1.419434, (float)1.933960, (float)2.394653, (float)2.746704,
  1.5240 +   (float)1.721924, (float)2.059570, (float)2.421753, (float)2.769653,
  1.5241 +   (float)1.911011, (float)2.220703, (float)2.461060, (float)2.740723,
  1.5242 +   (float)1.581177, (float)1.860840, (float)2.516968, (float)2.874634,
  1.5243 +   (float)1.870361, (float)2.098755, (float)2.432373, (float)2.656494,
  1.5244 +   (float)2.059692, (float)2.279785, (float)2.495605, (float)2.729370,
  1.5245 +   (float)1.815674, (float)2.181519, (float)2.451538, (float)2.680542,
  1.5246 +   (float)1.407959, (float)1.768311, (float)2.343018, (float)2.668091,
  1.5247 +   (float)2.168701, (float)2.394653, (float)2.604736, (float)2.829346,
  1.5248 +   (float)1.636230, (float)1.865723, (float)2.329102, (float)2.824219,
  1.5249 +   (float)1.878906, (float)2.139526, (float)2.376709, (float)2.679810,
  1.5250 +   (float)1.765381, (float)1.971802, (float)2.195435, (float)2.586914,
  1.5251 +   (float)2.164795, (float)2.410889, (float)2.673706, (float)2.903198,
  1.5252 +   (float)2.071899, (float)2.331055, (float)2.645874, (float)2.907104,
  1.5253 +   (float)2.026001, (float)2.311523, (float)2.594849, (float)2.863892,
  1.5254 +   (float)1.948975, (float)2.180786, (float)2.514893, (float)2.797852,
  1.5255 +   (float)1.881836, (float)2.130859, (float)2.478149, (float)2.804199,
  1.5256 +   (float)2.238159, (float)2.452759, (float)2.652832, (float)2.868286,
  1.5257 +   (float)1.897949, (float)2.101685, (float)2.524292, (float)2.880127,
  1.5258 +   (float)1.856445, (float)2.074585, (float)2.541016, (float)2.791748,
  1.5259 +   (float)1.695557, (float)2.199097, (float)2.506226, (float)2.742676,
  1.5260 +   (float)1.612671, (float)1.877075, (float)2.435425, (float)2.732910,
  1.5261 +   (float)1.568848, (float)1.786499, (float)2.194580, (float)2.768555,
  1.5262 +   (float)1.953369, (float)2.164551, (float)2.486938, (float)2.874023,
  1.5263 +   (float)1.388306, (float)1.725342, (float)2.384521, (float)2.771851,
  1.5264 +   (float)2.115356, (float)2.337769, (float)2.592896, (float)2.864014,
  1.5265 +   (float)1.905762, (float)2.111328, (float)2.363525, (float)2.789307,
  1.5266 +
  1.5267 +
  1.5268 +
  1.5269 +Andersen, et al.              Experimental                     [Page 94]
  1.5270 +
  1.5271 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.5272 +
  1.5273 +
  1.5274 +   (float)1.882568, (float)2.332031, (float)2.598267, (float)2.827637,
  1.5275 +   (float)1.683594, (float)2.088745, (float)2.361938, (float)2.608643,
  1.5276 +   (float)1.874023, (float)2.182129, (float)2.536133, (float)2.766968,
  1.5277 +   (float)1.861938, (float)2.070435, (float)2.309692, (float)2.700562,
  1.5278 +   (float)1.722168, (float)2.107422, (float)2.477295, (float)2.837646,
  1.5279 +   (float)1.926880, (float)2.184692, (float)2.442627, (float)2.663818,
  1.5280 +   (float)2.123901, (float)2.337280, (float)2.553101, (float)2.777466,
  1.5281 +   (float)1.588135, (float)1.911499, (float)2.212769, (float)2.543945,
  1.5282 +   (float)2.053955, (float)2.370850, (float)2.712158, (float)2.939941,
  1.5283 +   (float)2.210449, (float)2.519653, (float)2.770386, (float)2.958618,
  1.5284 +   (float)2.199463, (float)2.474731, (float)2.718262, (float)2.919922,
  1.5285 +   (float)1.960083, (float)2.175415, (float)2.608032, (float)2.888794,
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  1.5289 +   (float)1.824951, (float)2.267456, (float)2.514526, (float)2.747925,
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  1.5294 +   (float)1.758057, (float)2.131470, (float)2.636597, (float)2.891602,
  1.5295 +   (float)2.071289, (float)2.299072, (float)2.550781, (float)2.814331,
  1.5296 +   (float)1.839600, (float)2.094360, (float)2.496460, (float)2.723999,
  1.5297 +   (float)1.882202, (float)2.088257, (float)2.636841, (float)2.923096,
  1.5298 +   (float)1.957886, (float)2.153198, (float)2.384399, (float)2.615234,
  1.5299 +   (float)1.992920, (float)2.351196, (float)2.654419, (float)2.889771,
  1.5300 +   (float)2.012817, (float)2.262451, (float)2.643799, (float)2.903076,
  1.5301 +   (float)2.025635, (float)2.254761, (float)2.508423, (float)2.784058,
  1.5302 +   (float)2.316040, (float)2.589355, (float)2.794189, (float)2.963623,
  1.5303 +   (float)1.741211, (float)2.279541, (float)2.578491, (float)2.816284,
  1.5304 +   (float)1.845337, (float)2.055786, (float)2.348511, (float)2.822021,
  1.5305 +   (float)1.679932, (float)1.926514, (float)2.499756, (float)2.835693,
  1.5306 +   (float)1.722534, (float)1.946899, (float)2.448486, (float)2.728760,
  1.5307 +   (float)1.829834, (float)2.043213, (float)2.580444, (float)2.867676,
  1.5308 +   (float)1.676636, (float)2.071655, (float)2.322510, (float)2.704834,
  1.5309 +   (float)1.791504, (float)2.113525, (float)2.469727, (float)2.784058,
  1.5310 +   (float)1.977051, (float)2.215088, (float)2.497437, (float)2.726929,
  1.5311 +   (float)1.800171, (float)2.106689, (float)2.357788, (float)2.738892,
  1.5312 +   (float)1.827759, (float)2.170166, (float)2.525879, (float)2.852417,
  1.5313 +   (float)1.918335, (float)2.132813, (float)2.488403, (float)2.728149,
  1.5314 +   (float)1.916748, (float)2.225098, (float)2.542603, (float)2.857666,
  1.5315 +   (float)1.761230, (float)1.976074, (float)2.507446, (float)2.884521,
  1.5316 +   (float)2.053711, (float)2.367432, (float)2.608032, (float)2.837646,
  1.5317 +   (float)1.595337, (float)2.000977, (float)2.307129, (float)2.578247,
  1.5318 +   (float)1.470581, (float)2.031250, (float)2.375854, (float)2.647583,
  1.5319 +   (float)1.801392, (float)2.128052, (float)2.399780, (float)2.822876,
  1.5320 +   (float)1.853638, (float)2.066650, (float)2.429199, (float)2.751465,
  1.5321 +   (float)1.956299, (float)2.163696, (float)2.394775, (float)2.734253,
  1.5322 +
  1.5323 +
  1.5324 +
  1.5325 +Andersen, et al.              Experimental                     [Page 95]
  1.5326 +
  1.5327 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.5328 +
  1.5329 +
  1.5330 +   (float)1.963623, (float)2.275757, (float)2.585327, (float)2.865234,
  1.5331 +   (float)1.887451, (float)2.105469, (float)2.331787, (float)2.587402,
  1.5332 +   (float)2.120117, (float)2.443359, (float)2.733887, (float)2.941406,
  1.5333 +   (float)1.506348, (float)1.766968, (float)2.400513, (float)2.851807,
  1.5334 +   (float)1.664551, (float)1.981079, (float)2.375732, (float)2.774414,
  1.5335 +   (float)1.720703, (float)1.978882, (float)2.391479, (float)2.640991,
  1.5336 +   (float)1.483398, (float)1.814819, (float)2.434448, (float)2.722290,
  1.5337 +   (float)1.769043, (float)2.136597, (float)2.563721, (float)2.774414,
  1.5338 +   (float)1.810791, (float)2.049316, (float)2.373901, (float)2.613647,
  1.5339 +   (float)1.788330, (float)2.005981, (float)2.359131, (float)2.723145,
  1.5340 +   (float)1.785156, (float)1.993164, (float)2.399780, (float)2.832520,
  1.5341 +   (float)1.695313, (float)2.022949, (float)2.522583, (float)2.745117,
  1.5342 +   (float)1.584106, (float)1.965576, (float)2.299927, (float)2.715576,
  1.5343 +   (float)1.894897, (float)2.249878, (float)2.655884, (float)2.897705,
  1.5344 +   (float)1.720581, (float)1.995728, (float)2.299438, (float)2.557007,
  1.5345 +   (float)1.619385, (float)2.173950, (float)2.574219, (float)2.787964,
  1.5346 +   (float)1.883179, (float)2.220459, (float)2.474365, (float)2.825073,
  1.5347 +   (float)1.447632, (float)2.045044, (float)2.555542, (float)2.744873,
  1.5348 +   (float)1.502686, (float)2.156616, (float)2.653320, (float)2.846558,
  1.5349 +   (float)1.711548, (float)1.944092, (float)2.282959, (float)2.685791,
  1.5350 +   (float)1.499756, (float)1.867554, (float)2.341064, (float)2.578857,
  1.5351 +   (float)1.916870, (float)2.135132, (float)2.568237, (float)2.826050,
  1.5352 +   (float)1.498047, (float)1.711182, (float)2.223267, (float)2.755127,
  1.5353 +   (float)1.808716, (float)1.997559, (float)2.256470, (float)2.758545,
  1.5354 +   (float)2.088501, (float)2.402710, (float)2.667358, (float)2.890259,
  1.5355 +   (float)1.545044, (float)1.819214, (float)2.324097, (float)2.692993,
  1.5356 +   (float)1.796021, (float)2.012573, (float)2.505737, (float)2.784912,
  1.5357 +   (float)1.786499, (float)2.041748, (float)2.290405, (float)2.650757,
  1.5358 +   (float)1.938232, (float)2.264404, (float)2.529053, (float)2.796143
  1.5359 +   };
  1.5360 +
  1.5361 +A.9.  anaFilter.h
  1.5362 +
  1.5363 +   /******************************************************************
  1.5364 +
  1.5365 +       iLBC Speech Coder ANSI-C Source Code
  1.5366 +
  1.5367 +       anaFilter.h
  1.5368 +
  1.5369 +       Copyright (C) The Internet Society (2004).
  1.5370 +       All Rights Reserved.
  1.5371 +
  1.5372 +   ******************************************************************/
  1.5373 +
  1.5374 +   #ifndef __iLBC_ANAFILTER_H
  1.5375 +   #define __iLBC_ANAFILTER_H
  1.5376 +
  1.5377 +   void anaFilter(
  1.5378 +
  1.5379 +
  1.5380 +
  1.5381 +Andersen, et al.              Experimental                     [Page 96]
  1.5382 +
  1.5383 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.5384 +
  1.5385 +
  1.5386 +       float *In,  /* (i) Signal to be filtered */
  1.5387 +       float *a,   /* (i) LP parameters */
  1.5388 +       int len,/* (i) Length of signal */
  1.5389 +       float *Out, /* (o) Filtered signal */
  1.5390 +       float *mem  /* (i/o) Filter state */
  1.5391 +   );
  1.5392 +
  1.5393 +   #endif
  1.5394 +
  1.5395 +A.10.  anaFilter.c
  1.5396 +
  1.5397 +   /******************************************************************
  1.5398 +
  1.5399 +       iLBC Speech Coder ANSI-C Source Code
  1.5400 +
  1.5401 +       anaFilter.c
  1.5402 +
  1.5403 +       Copyright (C) The Internet Society (2004).
  1.5404 +       All Rights Reserved.
  1.5405 +
  1.5406 +   ******************************************************************/
  1.5407 +
  1.5408 +   #include <string.h>
  1.5409 +   #include "iLBC_define.h"
  1.5410 +
  1.5411 +   /*----------------------------------------------------------------*
  1.5412 +    *  LP analysis filter.
  1.5413 +    *---------------------------------------------------------------*/
  1.5414 +
  1.5415 +   void anaFilter(
  1.5416 +       float *In,  /* (i) Signal to be filtered */
  1.5417 +       float *a,   /* (i) LP parameters */
  1.5418 +       int len,/* (i) Length of signal */
  1.5419 +       float *Out, /* (o) Filtered signal */
  1.5420 +       float *mem  /* (i/o) Filter state */
  1.5421 +   ){
  1.5422 +       int i, j;
  1.5423 +       float *po, *pi, *pm, *pa;
  1.5424 +
  1.5425 +       po = Out;
  1.5426 +
  1.5427 +       /* Filter first part using memory from past */
  1.5428 +
  1.5429 +       for (i=0; i<LPC_FILTERORDER; i++) {
  1.5430 +           pi = &In[i];
  1.5431 +           pm = &mem[LPC_FILTERORDER-1];
  1.5432 +           pa = a;
  1.5433 +           *po=0.0;
  1.5434 +
  1.5435 +
  1.5436 +
  1.5437 +Andersen, et al.              Experimental                     [Page 97]
  1.5438 +
  1.5439 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.5440 +
  1.5441 +
  1.5442 +           for (j=0; j<=i; j++) {
  1.5443 +               *po+=(*pa++)*(*pi--);
  1.5444 +           }
  1.5445 +           for (j=i+1; j<LPC_FILTERORDER+1; j++) {
  1.5446 +
  1.5447 +               *po+=(*pa++)*(*pm--);
  1.5448 +           }
  1.5449 +           po++;
  1.5450 +       }
  1.5451 +
  1.5452 +       /* Filter last part where the state is entirely
  1.5453 +          in the input vector */
  1.5454 +
  1.5455 +       for (i=LPC_FILTERORDER; i<len; i++) {
  1.5456 +           pi = &In[i];
  1.5457 +           pa = a;
  1.5458 +           *po=0.0;
  1.5459 +           for (j=0; j<LPC_FILTERORDER+1; j++) {
  1.5460 +               *po+=(*pa++)*(*pi--);
  1.5461 +           }
  1.5462 +           po++;
  1.5463 +       }
  1.5464 +
  1.5465 +       /* Update state vector */
  1.5466 +
  1.5467 +       memcpy(mem, &In[len-LPC_FILTERORDER],
  1.5468 +           LPC_FILTERORDER*sizeof(float));
  1.5469 +   }
  1.5470 +
  1.5471 +A.11.  createCB.h
  1.5472 +
  1.5473 +   /******************************************************************
  1.5474 +
  1.5475 +       iLBC Speech Coder ANSI-C Source Code
  1.5476 +
  1.5477 +       createCB.h
  1.5478 +
  1.5479 +       Copyright (C) The Internet Society (2004).
  1.5480 +       All Rights Reserved.
  1.5481 +
  1.5482 +   ******************************************************************/
  1.5483 +
  1.5484 +   #ifndef __iLBC_CREATECB_H
  1.5485 +   #define __iLBC_CREATECB_H
  1.5486 +
  1.5487 +   void filteredCBvecs(
  1.5488 +       float *cbvectors,   /* (o) Codebook vector for the
  1.5489 +                                  higher section */
  1.5490 +
  1.5491 +
  1.5492 +
  1.5493 +Andersen, et al.              Experimental                     [Page 98]
  1.5494 +
  1.5495 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.5496 +
  1.5497 +
  1.5498 +       float *mem,         /* (i) Buffer to create codebook
  1.5499 +                                  vectors from */
  1.5500 +       int lMem        /* (i) Length of buffer */
  1.5501 +   );
  1.5502 +
  1.5503 +   void searchAugmentedCB(
  1.5504 +       int low,        /* (i) Start index for the search */
  1.5505 +       int high,           /* (i) End index for the search */
  1.5506 +       int stage,          /* (i) Current stage */
  1.5507 +       int startIndex,     /* (i) CB index for the first
  1.5508 +                                  augmented vector */
  1.5509 +       float *target,      /* (i) Target vector for encoding */
  1.5510 +       float *buffer,      /* (i) Pointer to the end of the
  1.5511 +                                  buffer for augmented codebook
  1.5512 +                                  construction */
  1.5513 +       float *max_measure, /* (i/o) Currently maximum measure */
  1.5514 +       int *best_index,/* (o) Currently the best index */
  1.5515 +       float *gain,    /* (o) Currently the best gain */
  1.5516 +       float *energy,      /* (o) Energy of augmented
  1.5517 +                                  codebook vectors */
  1.5518 +       float *invenergy/* (o) Inv energy of aug codebook
  1.5519 +                                  vectors */
  1.5520 +   );
  1.5521 +
  1.5522 +   void createAugmentedVec(
  1.5523 +       int index,          /* (i) Index for the aug vector
  1.5524 +                                  to be created */
  1.5525 +       float *buffer,      /* (i) Pointer to the end of the
  1.5526 +                                  buffer for augmented codebook
  1.5527 +                                  construction */
  1.5528 +       float *cbVec    /* (o) The construced codebook vector */
  1.5529 +   );
  1.5530 +
  1.5531 +   #endif
  1.5532 +
  1.5533 +A.12.  createCB.c
  1.5534 +
  1.5535 +
  1.5536 +   /******************************************************************
  1.5537 +
  1.5538 +       iLBC Speech Coder ANSI-C Source Code
  1.5539 +
  1.5540 +       createCB.c
  1.5541 +
  1.5542 +       Copyright (C) The Internet Society (2004).
  1.5543 +       All Rights Reserved.
  1.5544 +
  1.5545 +   ******************************************************************/
  1.5546 +
  1.5547 +
  1.5548 +
  1.5549 +Andersen, et al.              Experimental                     [Page 99]
  1.5550 +
  1.5551 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.5552 +
  1.5553 +
  1.5554 +   #include "iLBC_define.h"
  1.5555 +   #include "constants.h"
  1.5556 +   #include <string.h>
  1.5557 +   #include <math.h>
  1.5558 +
  1.5559 +   /*----------------------------------------------------------------*
  1.5560 +    *  Construct an additional codebook vector by filtering the
  1.5561 +    *  initial codebook buffer. This vector is then used to expand
  1.5562 +    *  the codebook with an additional section.
  1.5563 +    *---------------------------------------------------------------*/
  1.5564 +
  1.5565 +   void filteredCBvecs(
  1.5566 +       float *cbvectors,   /* (o) Codebook vectors for the
  1.5567 +                                  higher section */
  1.5568 +       float *mem,         /* (i) Buffer to create codebook
  1.5569 +                                  vector from */
  1.5570 +       int lMem        /* (i) Length of buffer */
  1.5571 +   ){
  1.5572 +       int j, k;
  1.5573 +       float *pp, *pp1;
  1.5574 +       float tempbuff2[CB_MEML+CB_FILTERLEN];
  1.5575 +       float *pos;
  1.5576 +
  1.5577 +       memset(tempbuff2, 0, (CB_HALFFILTERLEN-1)*sizeof(float));
  1.5578 +       memcpy(&tempbuff2[CB_HALFFILTERLEN-1], mem, lMem*sizeof(float));
  1.5579 +       memset(&tempbuff2[lMem+CB_HALFFILTERLEN-1], 0,
  1.5580 +           (CB_HALFFILTERLEN+1)*sizeof(float));
  1.5581 +
  1.5582 +       /* Create codebook vector for higher section by filtering */
  1.5583 +
  1.5584 +       /* do filtering */
  1.5585 +       pos=cbvectors;
  1.5586 +       memset(pos, 0, lMem*sizeof(float));
  1.5587 +       for (k=0; k<lMem; k++) {
  1.5588 +           pp=&tempbuff2[k];
  1.5589 +           pp1=&cbfiltersTbl[CB_FILTERLEN-1];
  1.5590 +           for (j=0;j<CB_FILTERLEN;j++) {
  1.5591 +               (*pos)+=(*pp++)*(*pp1--);
  1.5592 +           }
  1.5593 +           pos++;
  1.5594 +       }
  1.5595 +   }
  1.5596 +
  1.5597 +   /*----------------------------------------------------------------*
  1.5598 +    *  Search the augmented part of the codebook to find the best
  1.5599 +    *  measure.
  1.5600 +    *----------------------------------------------------------------*/
  1.5601 +
  1.5602 +
  1.5603 +
  1.5604 +
  1.5605 +Andersen, et al.              Experimental                    [Page 100]
  1.5606 +
  1.5607 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.5608 +
  1.5609 +
  1.5610 +   void searchAugmentedCB(
  1.5611 +       int low,        /* (i) Start index for the search */
  1.5612 +       int high,           /* (i) End index for the search */
  1.5613 +       int stage,          /* (i) Current stage */
  1.5614 +       int startIndex,     /* (i) Codebook index for the first
  1.5615 +                                  aug vector */
  1.5616 +       float *target,      /* (i) Target vector for encoding */
  1.5617 +       float *buffer,      /* (i) Pointer to the end of the buffer for
  1.5618 +                                  augmented codebook construction */
  1.5619 +       float *max_measure, /* (i/o) Currently maximum measure */
  1.5620 +       int *best_index,/* (o) Currently the best index */
  1.5621 +       float *gain,    /* (o) Currently the best gain */
  1.5622 +       float *energy,      /* (o) Energy of augmented codebook
  1.5623 +                                  vectors */
  1.5624 +       float *invenergy/* (o) Inv energy of augmented codebook
  1.5625 +                                  vectors */
  1.5626 +   ) {
  1.5627 +       int icount, ilow, j, tmpIndex;
  1.5628 +       float *pp, *ppo, *ppi, *ppe, crossDot, alfa;
  1.5629 +       float weighted, measure, nrjRecursive;
  1.5630 +       float ftmp;
  1.5631 +
  1.5632 +       /* Compute the energy for the first (low-5)
  1.5633 +          noninterpolated samples */
  1.5634 +       nrjRecursive = (float) 0.0;
  1.5635 +       pp = buffer - low + 1;
  1.5636 +       for (j=0; j<(low-5); j++) {
  1.5637 +           nrjRecursive += ( (*pp)*(*pp) );
  1.5638 +           pp++;
  1.5639 +       }
  1.5640 +       ppe = buffer - low;
  1.5641 +
  1.5642 +
  1.5643 +       for (icount=low; icount<=high; icount++) {
  1.5644 +
  1.5645 +           /* Index of the codebook vector used for retrieving
  1.5646 +              energy values */
  1.5647 +           tmpIndex = startIndex+icount-20;
  1.5648 +
  1.5649 +           ilow = icount-4;
  1.5650 +
  1.5651 +           /* Update the energy recursively to save complexity */
  1.5652 +           nrjRecursive = nrjRecursive + (*ppe)*(*ppe);
  1.5653 +           ppe--;
  1.5654 +           energy[tmpIndex] = nrjRecursive;
  1.5655 +
  1.5656 +           /* Compute cross dot product for the first (low-5)
  1.5657 +              samples */
  1.5658 +
  1.5659 +
  1.5660 +
  1.5661 +Andersen, et al.              Experimental                    [Page 101]
  1.5662 +
  1.5663 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.5664 +
  1.5665 +
  1.5666 +           crossDot = (float) 0.0;
  1.5667 +           pp = buffer-icount;
  1.5668 +           for (j=0; j<ilow; j++) {
  1.5669 +               crossDot += target[j]*(*pp++);
  1.5670 +           }
  1.5671 +
  1.5672 +           /* interpolation */
  1.5673 +           alfa = (float) 0.2;
  1.5674 +           ppo = buffer-4;
  1.5675 +           ppi = buffer-icount-4;
  1.5676 +           for (j=ilow; j<icount; j++) {
  1.5677 +               weighted = ((float)1.0-alfa)*(*ppo)+alfa*(*ppi);
  1.5678 +               ppo++;
  1.5679 +               ppi++;
  1.5680 +               energy[tmpIndex] += weighted*weighted;
  1.5681 +               crossDot += target[j]*weighted;
  1.5682 +               alfa += (float)0.2;
  1.5683 +           }
  1.5684 +
  1.5685 +           /* Compute energy and cross dot product for the
  1.5686 +              remaining samples */
  1.5687 +           pp = buffer - icount;
  1.5688 +           for (j=icount; j<SUBL; j++) {
  1.5689 +               energy[tmpIndex] += (*pp)*(*pp);
  1.5690 +               crossDot += target[j]*(*pp++);
  1.5691 +           }
  1.5692 +
  1.5693 +           if (energy[tmpIndex]>0.0) {
  1.5694 +               invenergy[tmpIndex]=(float)1.0/(energy[tmpIndex]+EPS);
  1.5695 +           } else {
  1.5696 +               invenergy[tmpIndex] = (float) 0.0;
  1.5697 +           }
  1.5698 +
  1.5699 +           if (stage==0) {
  1.5700 +               measure = (float)-10000000.0;
  1.5701 +
  1.5702 +               if (crossDot > 0.0) {
  1.5703 +                   measure = crossDot*crossDot*invenergy[tmpIndex];
  1.5704 +               }
  1.5705 +           }
  1.5706 +           else {
  1.5707 +               measure = crossDot*crossDot*invenergy[tmpIndex];
  1.5708 +           }
  1.5709 +
  1.5710 +           /* check if measure is better */
  1.5711 +           ftmp = crossDot*invenergy[tmpIndex];
  1.5712 +
  1.5713 +           if ((measure>*max_measure) && (fabs(ftmp)<CB_MAXGAIN)) {
  1.5714 +
  1.5715 +
  1.5716 +
  1.5717 +Andersen, et al.              Experimental                    [Page 102]
  1.5718 +
  1.5719 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.5720 +
  1.5721 +
  1.5722 +               *best_index = tmpIndex;
  1.5723 +               *max_measure = measure;
  1.5724 +               *gain = ftmp;
  1.5725 +           }
  1.5726 +       }
  1.5727 +   }
  1.5728 +
  1.5729 +
  1.5730 +   /*----------------------------------------------------------------*
  1.5731 +    *  Recreate a specific codebook vector from the augmented part.
  1.5732 +    *
  1.5733 +    *----------------------------------------------------------------*/
  1.5734 +
  1.5735 +   void createAugmentedVec(
  1.5736 +       int index,      /* (i) Index for the augmented vector
  1.5737 +                              to be created */
  1.5738 +       float *buffer,  /* (i) Pointer to the end of the buffer for
  1.5739 +                              augmented codebook construction */
  1.5740 +       float *cbVec/* (o) The construced codebook vector */
  1.5741 +   ) {
  1.5742 +       int ilow, j;
  1.5743 +       float *pp, *ppo, *ppi, alfa, alfa1, weighted;
  1.5744 +
  1.5745 +       ilow = index-5;
  1.5746 +
  1.5747 +       /* copy the first noninterpolated part */
  1.5748 +
  1.5749 +       pp = buffer-index;
  1.5750 +       memcpy(cbVec,pp,sizeof(float)*index);
  1.5751 +
  1.5752 +       /* interpolation */
  1.5753 +
  1.5754 +       alfa1 = (float)0.2;
  1.5755 +       alfa = 0.0;
  1.5756 +       ppo = buffer-5;
  1.5757 +       ppi = buffer-index-5;
  1.5758 +       for (j=ilow; j<index; j++) {
  1.5759 +           weighted = ((float)1.0-alfa)*(*ppo)+alfa*(*ppi);
  1.5760 +           ppo++;
  1.5761 +           ppi++;
  1.5762 +           cbVec[j] = weighted;
  1.5763 +           alfa += alfa1;
  1.5764 +       }
  1.5765 +
  1.5766 +       /* copy the second noninterpolated part */
  1.5767 +
  1.5768 +       pp = buffer - index;
  1.5769 +       memcpy(cbVec+index,pp,sizeof(float)*(SUBL-index));
  1.5770 +
  1.5771 +
  1.5772 +
  1.5773 +Andersen, et al.              Experimental                    [Page 103]
  1.5774 +
  1.5775 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.5776 +
  1.5777 +
  1.5778 +   }
  1.5779 +
  1.5780 +A.13.  doCPLC.h
  1.5781 +
  1.5782 +   /******************************************************************
  1.5783 +
  1.5784 +       iLBC Speech Coder ANSI-C Source Code
  1.5785 +
  1.5786 +       doCPLC.h
  1.5787 +
  1.5788 +       Copyright (C) The Internet Society (2004).
  1.5789 +       All Rights Reserved.
  1.5790 +
  1.5791 +   ******************************************************************/
  1.5792 +
  1.5793 +   #ifndef __iLBC_DOLPC_H
  1.5794 +   #define __iLBC_DOLPC_H
  1.5795 +
  1.5796 +   void doThePLC(
  1.5797 +       float *PLCresidual, /* (o) concealed residual */
  1.5798 +       float *PLClpc,      /* (o) concealed LP parameters */
  1.5799 +       int PLI,        /* (i) packet loss indicator
  1.5800 +                                  0 - no PL, 1 = PL */
  1.5801 +       float *decresidual, /* (i) decoded residual */
  1.5802 +       float *lpc,         /* (i) decoded LPC (only used for no PL) */
  1.5803 +       int inlag,          /* (i) pitch lag */
  1.5804 +       iLBC_Dec_Inst_t *iLBCdec_inst
  1.5805 +                           /* (i/o) decoder instance */
  1.5806 +   );
  1.5807 +
  1.5808 +   #endif
  1.5809 +
  1.5810 +A.14.  doCPLC.c
  1.5811 +
  1.5812 +   /******************************************************************
  1.5813 +
  1.5814 +       iLBC Speech Coder ANSI-C Source Code
  1.5815 +
  1.5816 +       doCPLC.c
  1.5817 +
  1.5818 +       Copyright (C) The Internet Society (2004).
  1.5819 +       All Rights Reserved.
  1.5820 +
  1.5821 +   ******************************************************************/
  1.5822 +
  1.5823 +   #include <math.h>
  1.5824 +   #include <string.h>
  1.5825 +   #include <stdio.h>
  1.5826 +
  1.5827 +
  1.5828 +
  1.5829 +Andersen, et al.              Experimental                    [Page 104]
  1.5830 +
  1.5831 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.5832 +
  1.5833 +
  1.5834 +   #include "iLBC_define.h"
  1.5835 +
  1.5836 +   /*----------------------------------------------------------------*
  1.5837 +    *  Compute cross correlation and pitch gain for pitch prediction
  1.5838 +    *  of last subframe at given lag.
  1.5839 +    *---------------------------------------------------------------*/
  1.5840 +
  1.5841 +   void compCorr(
  1.5842 +       float *cc,      /* (o) cross correlation coefficient */
  1.5843 +       float *gc,      /* (o) gain */
  1.5844 +       float *pm,
  1.5845 +       float *buffer,  /* (i) signal buffer */
  1.5846 +       int lag,    /* (i) pitch lag */
  1.5847 +       int bLen,       /* (i) length of buffer */
  1.5848 +       int sRange      /* (i) correlation search length */
  1.5849 +   ){
  1.5850 +       int i;
  1.5851 +       float ftmp1, ftmp2, ftmp3;
  1.5852 +
  1.5853 +       /* Guard against getting outside buffer */
  1.5854 +       if ((bLen-sRange-lag)<0) {
  1.5855 +           sRange=bLen-lag;
  1.5856 +       }
  1.5857 +
  1.5858 +       ftmp1 = 0.0;
  1.5859 +       ftmp2 = 0.0;
  1.5860 +       ftmp3 = 0.0;
  1.5861 +       for (i=0; i<sRange; i++) {
  1.5862 +           ftmp1 += buffer[bLen-sRange+i] *
  1.5863 +               buffer[bLen-sRange+i-lag];
  1.5864 +           ftmp2 += buffer[bLen-sRange+i-lag] *
  1.5865 +                   buffer[bLen-sRange+i-lag];
  1.5866 +           ftmp3 += buffer[bLen-sRange+i] *
  1.5867 +                   buffer[bLen-sRange+i];
  1.5868 +       }
  1.5869 +
  1.5870 +       if (ftmp2 > 0.0) {
  1.5871 +           *cc = ftmp1*ftmp1/ftmp2;
  1.5872 +           *gc = (float)fabs(ftmp1/ftmp2);
  1.5873 +           *pm=(float)fabs(ftmp1)/
  1.5874 +               ((float)sqrt(ftmp2)*(float)sqrt(ftmp3));
  1.5875 +       }
  1.5876 +       else {
  1.5877 +           *cc = 0.0;
  1.5878 +           *gc = 0.0;
  1.5879 +           *pm=0.0;
  1.5880 +       }
  1.5881 +   }
  1.5882 +
  1.5883 +
  1.5884 +
  1.5885 +Andersen, et al.              Experimental                    [Page 105]
  1.5886 +
  1.5887 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.5888 +
  1.5889 +
  1.5890 +   /*----------------------------------------------------------------*
  1.5891 +    *  Packet loss concealment routine. Conceals a residual signal
  1.5892 +    *  and LP parameters. If no packet loss, update state.
  1.5893 +    *---------------------------------------------------------------*/
  1.5894 +
  1.5895 +   void doThePLC(
  1.5896 +       float *PLCresidual, /* (o) concealed residual */
  1.5897 +       float *PLClpc,      /* (o) concealed LP parameters */
  1.5898 +       int PLI,        /* (i) packet loss indicator
  1.5899 +                                  0 - no PL, 1 = PL */
  1.5900 +       float *decresidual, /* (i) decoded residual */
  1.5901 +       float *lpc,         /* (i) decoded LPC (only used for no PL) */
  1.5902 +       int inlag,          /* (i) pitch lag */
  1.5903 +       iLBC_Dec_Inst_t *iLBCdec_inst
  1.5904 +                           /* (i/o) decoder instance */
  1.5905 +   ){
  1.5906 +       int lag=20, randlag;
  1.5907 +       float gain, maxcc;
  1.5908 +       float use_gain;
  1.5909 +       float gain_comp, maxcc_comp, per, max_per;
  1.5910 +       int i, pick, use_lag;
  1.5911 +       float ftmp, randvec[BLOCKL_MAX], pitchfact, energy;
  1.5912 +
  1.5913 +       /* Packet Loss */
  1.5914 +
  1.5915 +       if (PLI == 1) {
  1.5916 +
  1.5917 +           iLBCdec_inst->consPLICount += 1;
  1.5918 +
  1.5919 +           /* if previous frame not lost,
  1.5920 +              determine pitch pred. gain */
  1.5921 +
  1.5922 +           if (iLBCdec_inst->prevPLI != 1) {
  1.5923 +
  1.5924 +               /* Search around the previous lag to find the
  1.5925 +                  best pitch period */
  1.5926 +
  1.5927 +               lag=inlag-3;
  1.5928 +               compCorr(&maxcc, &gain, &max_per,
  1.5929 +                   iLBCdec_inst->prevResidual,
  1.5930 +                   lag, iLBCdec_inst->blockl, 60);
  1.5931 +               for (i=inlag-2;i<=inlag+3;i++) {
  1.5932 +                   compCorr(&maxcc_comp, &gain_comp, &per,
  1.5933 +                       iLBCdec_inst->prevResidual,
  1.5934 +                       i, iLBCdec_inst->blockl, 60);
  1.5935 +
  1.5936 +                   if (maxcc_comp>maxcc) {
  1.5937 +                       maxcc=maxcc_comp;
  1.5938 +
  1.5939 +
  1.5940 +
  1.5941 +Andersen, et al.              Experimental                    [Page 106]
  1.5942 +
  1.5943 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.5944 +
  1.5945 +
  1.5946 +                       gain=gain_comp;
  1.5947 +                       lag=i;
  1.5948 +                       max_per=per;
  1.5949 +                   }
  1.5950 +               }
  1.5951 +
  1.5952 +           }
  1.5953 +
  1.5954 +           /* previous frame lost, use recorded lag and periodicity */
  1.5955 +
  1.5956 +           else {
  1.5957 +               lag=iLBCdec_inst->prevLag;
  1.5958 +               max_per=iLBCdec_inst->per;
  1.5959 +           }
  1.5960 +
  1.5961 +           /* downscaling */
  1.5962 +
  1.5963 +           use_gain=1.0;
  1.5964 +           if (iLBCdec_inst->consPLICount*iLBCdec_inst->blockl>320)
  1.5965 +               use_gain=(float)0.9;
  1.5966 +           else if (iLBCdec_inst->consPLICount*
  1.5967 +                           iLBCdec_inst->blockl>2*320)
  1.5968 +               use_gain=(float)0.7;
  1.5969 +           else if (iLBCdec_inst->consPLICount*
  1.5970 +                           iLBCdec_inst->blockl>3*320)
  1.5971 +               use_gain=(float)0.5;
  1.5972 +           else if (iLBCdec_inst->consPLICount*
  1.5973 +                           iLBCdec_inst->blockl>4*320)
  1.5974 +               use_gain=(float)0.0;
  1.5975 +
  1.5976 +           /* mix noise and pitch repeatition */
  1.5977 +           ftmp=(float)sqrt(max_per);
  1.5978 +           if (ftmp>(float)0.7)
  1.5979 +               pitchfact=(float)1.0;
  1.5980 +           else if (ftmp>(float)0.4)
  1.5981 +               pitchfact=(ftmp-(float)0.4)/((float)0.7-(float)0.4);
  1.5982 +           else
  1.5983 +               pitchfact=0.0;
  1.5984 +
  1.5985 +
  1.5986 +           /* avoid repetition of same pitch cycle */
  1.5987 +           use_lag=lag;
  1.5988 +           if (lag<80) {
  1.5989 +               use_lag=2*lag;
  1.5990 +           }
  1.5991 +
  1.5992 +           /* compute concealed residual */
  1.5993 +
  1.5994 +
  1.5995 +
  1.5996 +
  1.5997 +Andersen, et al.              Experimental                    [Page 107]
  1.5998 +
  1.5999 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.6000 +
  1.6001 +
  1.6002 +           energy = 0.0;
  1.6003 +           for (i=0; i<iLBCdec_inst->blockl; i++) {
  1.6004 +
  1.6005 +               /* noise component */
  1.6006 +
  1.6007 +               iLBCdec_inst->seed=(iLBCdec_inst->seed*69069L+1) &
  1.6008 +                   (0x80000000L-1);
  1.6009 +               randlag = 50 + ((signed long) iLBCdec_inst->seed)%70;
  1.6010 +               pick = i - randlag;
  1.6011 +
  1.6012 +               if (pick < 0) {
  1.6013 +                   randvec[i] =
  1.6014 +                       iLBCdec_inst->prevResidual[
  1.6015 +                                   iLBCdec_inst->blockl+pick];
  1.6016 +               } else {
  1.6017 +                   randvec[i] =  randvec[pick];
  1.6018 +               }
  1.6019 +
  1.6020 +               /* pitch repeatition component */
  1.6021 +               pick = i - use_lag;
  1.6022 +
  1.6023 +               if (pick < 0) {
  1.6024 +                   PLCresidual[i] =
  1.6025 +                       iLBCdec_inst->prevResidual[
  1.6026 +                                   iLBCdec_inst->blockl+pick];
  1.6027 +               } else {
  1.6028 +                   PLCresidual[i] = PLCresidual[pick];
  1.6029 +               }
  1.6030 +
  1.6031 +               /* mix random and periodicity component */
  1.6032 +
  1.6033 +               if (i<80)
  1.6034 +                   PLCresidual[i] = use_gain*(pitchfact *
  1.6035 +                               PLCresidual[i] +
  1.6036 +                               ((float)1.0 - pitchfact) * randvec[i]);
  1.6037 +               else if (i<160)
  1.6038 +                   PLCresidual[i] = (float)0.95*use_gain*(pitchfact *
  1.6039 +                               PLCresidual[i] +
  1.6040 +                               ((float)1.0 - pitchfact) * randvec[i]);
  1.6041 +               else
  1.6042 +                   PLCresidual[i] = (float)0.9*use_gain*(pitchfact *
  1.6043 +                               PLCresidual[i] +
  1.6044 +                               ((float)1.0 - pitchfact) * randvec[i]);
  1.6045 +
  1.6046 +               energy += PLCresidual[i] * PLCresidual[i];
  1.6047 +           }
  1.6048 +
  1.6049 +           /* less than 30 dB, use only noise */
  1.6050 +
  1.6051 +
  1.6052 +
  1.6053 +Andersen, et al.              Experimental                    [Page 108]
  1.6054 +
  1.6055 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.6056 +
  1.6057 +
  1.6058 +
  1.6059 +           if (sqrt(energy/(float)iLBCdec_inst->blockl) < 30.0) {
  1.6060 +               gain=0.0;
  1.6061 +               for (i=0; i<iLBCdec_inst->blockl; i++) {
  1.6062 +                   PLCresidual[i] = randvec[i];
  1.6063 +               }
  1.6064 +           }
  1.6065 +
  1.6066 +           /* use old LPC */
  1.6067 +
  1.6068 +           memcpy(PLClpc,iLBCdec_inst->prevLpc,
  1.6069 +               (LPC_FILTERORDER+1)*sizeof(float));
  1.6070 +
  1.6071 +       }
  1.6072 +
  1.6073 +       /* no packet loss, copy input */
  1.6074 +
  1.6075 +       else {
  1.6076 +           memcpy(PLCresidual, decresidual,
  1.6077 +               iLBCdec_inst->blockl*sizeof(float));
  1.6078 +           memcpy(PLClpc, lpc, (LPC_FILTERORDER+1)*sizeof(float));
  1.6079 +           iLBCdec_inst->consPLICount = 0;
  1.6080 +       }
  1.6081 +
  1.6082 +       /* update state */
  1.6083 +
  1.6084 +       if (PLI) {
  1.6085 +           iLBCdec_inst->prevLag = lag;
  1.6086 +           iLBCdec_inst->per=max_per;
  1.6087 +       }
  1.6088 +
  1.6089 +       iLBCdec_inst->prevPLI = PLI;
  1.6090 +       memcpy(iLBCdec_inst->prevLpc, PLClpc,
  1.6091 +           (LPC_FILTERORDER+1)*sizeof(float));
  1.6092 +       memcpy(iLBCdec_inst->prevResidual, PLCresidual,
  1.6093 +           iLBCdec_inst->blockl*sizeof(float));
  1.6094 +   }
  1.6095 +
  1.6096 +A.15.  enhancer.h
  1.6097 +
  1.6098 +   /******************************************************************
  1.6099 +
  1.6100 +       iLBC Speech Coder ANSI-C Source Code
  1.6101 +
  1.6102 +       enhancer.h
  1.6103 +
  1.6104 +       Copyright (C) The Internet Society (2004).
  1.6105 +       All Rights Reserved.
  1.6106 +
  1.6107 +
  1.6108 +
  1.6109 +Andersen, et al.              Experimental                    [Page 109]
  1.6110 +
  1.6111 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.6112 +
  1.6113 +
  1.6114 +   ******************************************************************/
  1.6115 +
  1.6116 +   #ifndef __ENHANCER_H
  1.6117 +   #define __ENHANCER_H
  1.6118 +
  1.6119 +   #include "iLBC_define.h"
  1.6120 +
  1.6121 +   float xCorrCoef(
  1.6122 +       float *target,      /* (i) first array */
  1.6123 +       float *regressor,   /* (i) second array */
  1.6124 +       int subl        /* (i) dimension arrays */
  1.6125 +   );
  1.6126 +
  1.6127 +   int enhancerInterface(
  1.6128 +       float *out,         /* (o) the enhanced recidual signal */
  1.6129 +       float *in,          /* (i) the recidual signal to enhance */
  1.6130 +       iLBC_Dec_Inst_t *iLBCdec_inst
  1.6131 +                           /* (i/o) the decoder state structure */
  1.6132 +   );
  1.6133 +
  1.6134 +   #endif
  1.6135 +
  1.6136 +A.16.  enhancer.c
  1.6137 +
  1.6138 +   /******************************************************************
  1.6139 +
  1.6140 +       iLBC Speech Coder ANSI-C Source Code
  1.6141 +
  1.6142 +       enhancer.c
  1.6143 +
  1.6144 +       Copyright (C) The Internet Society (2004).
  1.6145 +       All Rights Reserved.
  1.6146 +
  1.6147 +   ******************************************************************/
  1.6148 +
  1.6149 +   #include <math.h>
  1.6150 +   #include <string.h>
  1.6151 +   #include "iLBC_define.h"
  1.6152 +   #include "constants.h"
  1.6153 +   #include "filter.h"
  1.6154 +
  1.6155 +   /*----------------------------------------------------------------*
  1.6156 +    * Find index in array such that the array element with said
  1.6157 +    * index is the element of said array closest to "value"
  1.6158 +    * according to the squared-error criterion
  1.6159 +    *---------------------------------------------------------------*/
  1.6160 +
  1.6161 +   void NearestNeighbor(
  1.6162 +
  1.6163 +
  1.6164 +
  1.6165 +Andersen, et al.              Experimental                    [Page 110]
  1.6166 +
  1.6167 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.6168 +
  1.6169 +
  1.6170 +       int   *index,   /* (o) index of array element closest
  1.6171 +                              to value */
  1.6172 +       float *array,   /* (i) data array */
  1.6173 +       float value,/* (i) value */
  1.6174 +       int arlength/* (i) dimension of data array */
  1.6175 +   ){
  1.6176 +       int i;
  1.6177 +       float bestcrit,crit;
  1.6178 +
  1.6179 +       crit=array[0]-value;
  1.6180 +       bestcrit=crit*crit;
  1.6181 +       *index=0;
  1.6182 +       for (i=1; i<arlength; i++) {
  1.6183 +           crit=array[i]-value;
  1.6184 +           crit=crit*crit;
  1.6185 +
  1.6186 +           if (crit<bestcrit) {
  1.6187 +               bestcrit=crit;
  1.6188 +               *index=i;
  1.6189 +           }
  1.6190 +       }
  1.6191 +   }
  1.6192 +
  1.6193 +   /*----------------------------------------------------------------*
  1.6194 +    * compute cross correlation between sequences
  1.6195 +    *---------------------------------------------------------------*/
  1.6196 +
  1.6197 +   void mycorr1(
  1.6198 +       float* corr,    /* (o) correlation of seq1 and seq2 */
  1.6199 +       float* seq1,    /* (i) first sequence */
  1.6200 +       int dim1,           /* (i) dimension first seq1 */
  1.6201 +       const float *seq2,  /* (i) second sequence */
  1.6202 +       int dim2        /* (i) dimension seq2 */
  1.6203 +   ){
  1.6204 +       int i,j;
  1.6205 +
  1.6206 +       for (i=0; i<=dim1-dim2; i++) {
  1.6207 +           corr[i]=0.0;
  1.6208 +           for (j=0; j<dim2; j++) {
  1.6209 +               corr[i] += seq1[i+j] * seq2[j];
  1.6210 +           }
  1.6211 +       }
  1.6212 +   }
  1.6213 +
  1.6214 +   /*----------------------------------------------------------------*
  1.6215 +    * upsample finite array assuming zeros outside bounds
  1.6216 +    *---------------------------------------------------------------*/
  1.6217 +
  1.6218 +
  1.6219 +
  1.6220 +
  1.6221 +Andersen, et al.              Experimental                    [Page 111]
  1.6222 +
  1.6223 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.6224 +
  1.6225 +
  1.6226 +   void enh_upsample(
  1.6227 +       float* useq1,   /* (o) upsampled output sequence */
  1.6228 +       float* seq1,/* (i) unupsampled sequence */
  1.6229 +       int dim1,       /* (i) dimension seq1 */
  1.6230 +       int hfl         /* (i) polyphase filter length=2*hfl+1 */
  1.6231 +   ){
  1.6232 +       float *pu,*ps;
  1.6233 +       int i,j,k,q,filterlength,hfl2;
  1.6234 +       const float *polyp[ENH_UPS0]; /* pointers to
  1.6235 +                                        polyphase columns */
  1.6236 +       const float *pp;
  1.6237 +
  1.6238 +       /* define pointers for filter */
  1.6239 +
  1.6240 +       filterlength=2*hfl+1;
  1.6241 +
  1.6242 +       if ( filterlength > dim1 ) {
  1.6243 +           hfl2=(int) (dim1/2);
  1.6244 +           for (j=0; j<ENH_UPS0; j++) {
  1.6245 +               polyp[j]=polyphaserTbl+j*filterlength+hfl-hfl2;
  1.6246 +           }
  1.6247 +           hfl=hfl2;
  1.6248 +           filterlength=2*hfl+1;
  1.6249 +       }
  1.6250 +       else {
  1.6251 +           for (j=0; j<ENH_UPS0; j++) {
  1.6252 +               polyp[j]=polyphaserTbl+j*filterlength;
  1.6253 +           }
  1.6254 +       }
  1.6255 +
  1.6256 +       /* filtering: filter overhangs left side of sequence */
  1.6257 +
  1.6258 +       pu=useq1;
  1.6259 +       for (i=hfl; i<filterlength; i++) {
  1.6260 +           for (j=0; j<ENH_UPS0; j++) {
  1.6261 +               *pu=0.0;
  1.6262 +               pp = polyp[j];
  1.6263 +               ps = seq1+i;
  1.6264 +               for (k=0; k<=i; k++) {
  1.6265 +                   *pu += *ps-- * *pp++;
  1.6266 +               }
  1.6267 +               pu++;
  1.6268 +           }
  1.6269 +       }
  1.6270 +
  1.6271 +       /* filtering: simple convolution=inner products */
  1.6272 +
  1.6273 +       for (i=filterlength; i<dim1; i++) {
  1.6274 +
  1.6275 +
  1.6276 +
  1.6277 +Andersen, et al.              Experimental                    [Page 112]
  1.6278 +
  1.6279 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.6280 +
  1.6281 +
  1.6282 +           for (j=0;j<ENH_UPS0; j++){
  1.6283 +               *pu=0.0;
  1.6284 +               pp = polyp[j];
  1.6285 +               ps = seq1+i;
  1.6286 +               for (k=0; k<filterlength; k++) {
  1.6287 +                   *pu += *ps-- * *pp++;
  1.6288 +               }
  1.6289 +               pu++;
  1.6290 +           }
  1.6291 +       }
  1.6292 +
  1.6293 +       /* filtering: filter overhangs right side of sequence */
  1.6294 +
  1.6295 +       for (q=1; q<=hfl; q++) {
  1.6296 +           for (j=0; j<ENH_UPS0; j++) {
  1.6297 +               *pu=0.0;
  1.6298 +               pp = polyp[j]+q;
  1.6299 +               ps = seq1+dim1-1;
  1.6300 +               for (k=0; k<filterlength-q; k++) {
  1.6301 +                   *pu += *ps-- * *pp++;
  1.6302 +               }
  1.6303 +               pu++;
  1.6304 +           }
  1.6305 +       }
  1.6306 +   }
  1.6307 +
  1.6308 +
  1.6309 +   /*----------------------------------------------------------------*
  1.6310 +    * find segment starting near idata+estSegPos that has highest
  1.6311 +    * correlation with idata+centerStartPos through
  1.6312 +    * idata+centerStartPos+ENH_BLOCKL-1 segment is found at a
  1.6313 +    * resolution of ENH_UPSO times the original of the original
  1.6314 +    * sampling rate
  1.6315 +    *---------------------------------------------------------------*/
  1.6316 +
  1.6317 +   void refiner(
  1.6318 +       float *seg,         /* (o) segment array */
  1.6319 +       float *updStartPos, /* (o) updated start point */
  1.6320 +       float* idata,       /* (i) original data buffer */
  1.6321 +       int idatal,         /* (i) dimension of idata */
  1.6322 +       int centerStartPos, /* (i) beginning center segment */
  1.6323 +       float estSegPos,/* (i) estimated beginning other segment */
  1.6324 +       float period    /* (i) estimated pitch period */
  1.6325 +   ){
  1.6326 +       int estSegPosRounded,searchSegStartPos,searchSegEndPos,corrdim;
  1.6327 +       int tloc,tloc2,i,st,en,fraction;
  1.6328 +       float vect[ENH_VECTL],corrVec[ENH_CORRDIM],maxv;
  1.6329 +       float corrVecUps[ENH_CORRDIM*ENH_UPS0];
  1.6330 +
  1.6331 +
  1.6332 +
  1.6333 +Andersen, et al.              Experimental                    [Page 113]
  1.6334 +
  1.6335 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.6336 +
  1.6337 +
  1.6338 +       /* defining array bounds */
  1.6339 +
  1.6340 +       estSegPosRounded=(int)(estSegPos - 0.5);
  1.6341 +
  1.6342 +       searchSegStartPos=estSegPosRounded-ENH_SLOP;
  1.6343 +
  1.6344 +       if (searchSegStartPos<0) {
  1.6345 +           searchSegStartPos=0;
  1.6346 +       }
  1.6347 +       searchSegEndPos=estSegPosRounded+ENH_SLOP;
  1.6348 +
  1.6349 +       if (searchSegEndPos+ENH_BLOCKL >= idatal) {
  1.6350 +           searchSegEndPos=idatal-ENH_BLOCKL-1;
  1.6351 +       }
  1.6352 +       corrdim=searchSegEndPos-searchSegStartPos+1;
  1.6353 +
  1.6354 +       /* compute upsampled correlation (corr33) and find
  1.6355 +          location of max */
  1.6356 +
  1.6357 +       mycorr1(corrVec,idata+searchSegStartPos,
  1.6358 +           corrdim+ENH_BLOCKL-1,idata+centerStartPos,ENH_BLOCKL);
  1.6359 +       enh_upsample(corrVecUps,corrVec,corrdim,ENH_FL0);
  1.6360 +       tloc=0; maxv=corrVecUps[0];
  1.6361 +       for (i=1; i<ENH_UPS0*corrdim; i++) {
  1.6362 +
  1.6363 +           if (corrVecUps[i]>maxv) {
  1.6364 +               tloc=i;
  1.6365 +               maxv=corrVecUps[i];
  1.6366 +           }
  1.6367 +       }
  1.6368 +
  1.6369 +       /* make vector can be upsampled without ever running outside
  1.6370 +          bounds */
  1.6371 +
  1.6372 +       *updStartPos= (float)searchSegStartPos +
  1.6373 +           (float)tloc/(float)ENH_UPS0+(float)1.0;
  1.6374 +       tloc2=(int)(tloc/ENH_UPS0);
  1.6375 +
  1.6376 +       if (tloc>tloc2*ENH_UPS0) {
  1.6377 +           tloc2++;
  1.6378 +       }
  1.6379 +       st=searchSegStartPos+tloc2-ENH_FL0;
  1.6380 +
  1.6381 +       if (st<0) {
  1.6382 +           memset(vect,0,-st*sizeof(float));
  1.6383 +           memcpy(&vect[-st],idata, (ENH_VECTL+st)*sizeof(float));
  1.6384 +       }
  1.6385 +       else {
  1.6386 +
  1.6387 +
  1.6388 +
  1.6389 +Andersen, et al.              Experimental                    [Page 114]
  1.6390 +
  1.6391 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.6392 +
  1.6393 +
  1.6394 +           en=st+ENH_VECTL;
  1.6395 +
  1.6396 +           if (en>idatal) {
  1.6397 +               memcpy(vect, &idata[st],
  1.6398 +                   (ENH_VECTL-(en-idatal))*sizeof(float));
  1.6399 +               memset(&vect[ENH_VECTL-(en-idatal)], 0,
  1.6400 +                   (en-idatal)*sizeof(float));
  1.6401 +           }
  1.6402 +           else {
  1.6403 +               memcpy(vect, &idata[st], ENH_VECTL*sizeof(float));
  1.6404 +           }
  1.6405 +       }
  1.6406 +       fraction=tloc2*ENH_UPS0-tloc;
  1.6407 +
  1.6408 +       /* compute the segment (this is actually a convolution) */
  1.6409 +
  1.6410 +       mycorr1(seg,vect,ENH_VECTL,polyphaserTbl+(2*ENH_FL0+1)*fraction,
  1.6411 +           2*ENH_FL0+1);
  1.6412 +   }
  1.6413 +
  1.6414 +   /*----------------------------------------------------------------*
  1.6415 +    * find the smoothed output data
  1.6416 +    *---------------------------------------------------------------*/
  1.6417 +
  1.6418 +   void smath(
  1.6419 +       float *odata,   /* (o) smoothed output */
  1.6420 +       float *sseq,/* (i) said second sequence of waveforms */
  1.6421 +       int hl,         /* (i) 2*hl+1 is sseq dimension */
  1.6422 +       float alpha0/* (i) max smoothing energy fraction */
  1.6423 +   ){
  1.6424 +       int i,k;
  1.6425 +       float w00,w10,w11,A,B,C,*psseq,err,errs;
  1.6426 +       float surround[BLOCKL_MAX]; /* shape contributed by other than
  1.6427 +                                      current */
  1.6428 +       float wt[2*ENH_HL+1];       /* waveform weighting to get
  1.6429 +                                      surround shape */
  1.6430 +       float denom;
  1.6431 +
  1.6432 +       /* create shape of contribution from all waveforms except the
  1.6433 +          current one */
  1.6434 +
  1.6435 +       for (i=1; i<=2*hl+1; i++) {
  1.6436 +           wt[i-1] = (float)0.5*(1 - (float)cos(2*PI*i/(2*hl+2)));
  1.6437 +       }
  1.6438 +       wt[hl]=0.0; /* for clarity, not used */
  1.6439 +       for (i=0; i<ENH_BLOCKL; i++) {
  1.6440 +           surround[i]=sseq[i]*wt[0];
  1.6441 +       }
  1.6442 +
  1.6443 +
  1.6444 +
  1.6445 +Andersen, et al.              Experimental                    [Page 115]
  1.6446 +
  1.6447 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.6448 +
  1.6449 +
  1.6450 +       for (k=1; k<hl; k++) {
  1.6451 +           psseq=sseq+k*ENH_BLOCKL;
  1.6452 +           for(i=0;i<ENH_BLOCKL; i++) {
  1.6453 +               surround[i]+=psseq[i]*wt[k];
  1.6454 +           }
  1.6455 +       }
  1.6456 +       for (k=hl+1; k<=2*hl; k++) {
  1.6457 +           psseq=sseq+k*ENH_BLOCKL;
  1.6458 +           for(i=0;i<ENH_BLOCKL; i++) {
  1.6459 +               surround[i]+=psseq[i]*wt[k];
  1.6460 +           }
  1.6461 +       }
  1.6462 +
  1.6463 +       /* compute some inner products */
  1.6464 +
  1.6465 +       w00 = w10 = w11 = 0.0;
  1.6466 +       psseq=sseq+hl*ENH_BLOCKL; /* current block  */
  1.6467 +       for (i=0; i<ENH_BLOCKL;i++) {
  1.6468 +           w00+=psseq[i]*psseq[i];
  1.6469 +           w11+=surround[i]*surround[i];
  1.6470 +           w10+=surround[i]*psseq[i];
  1.6471 +       }
  1.6472 +
  1.6473 +       if (fabs(w11) < 1.0) {
  1.6474 +           w11=1.0;
  1.6475 +       }
  1.6476 +       C = (float)sqrt( w00/w11);
  1.6477 +
  1.6478 +       /* first try enhancement without power-constraint */
  1.6479 +
  1.6480 +       errs=0.0;
  1.6481 +       psseq=sseq+hl*ENH_BLOCKL;
  1.6482 +       for (i=0; i<ENH_BLOCKL; i++) {
  1.6483 +           odata[i]=C*surround[i];
  1.6484 +           err=psseq[i]-odata[i];
  1.6485 +           errs+=err*err;
  1.6486 +       }
  1.6487 +
  1.6488 +       /* if constraint violated by first try, add constraint */
  1.6489 +
  1.6490 +       if (errs > alpha0 * w00) {
  1.6491 +           if ( w00 < 1) {
  1.6492 +               w00=1;
  1.6493 +           }
  1.6494 +           denom = (w11*w00-w10*w10)/(w00*w00);
  1.6495 +
  1.6496 +           if (denom > 0.0001) { /* eliminates numerical problems
  1.6497 +                                    for if smooth */
  1.6498 +
  1.6499 +
  1.6500 +
  1.6501 +Andersen, et al.              Experimental                    [Page 116]
  1.6502 +
  1.6503 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.6504 +
  1.6505 +
  1.6506 +               A = (float)sqrt( (alpha0- alpha0*alpha0/4)/denom);
  1.6507 +               B = -alpha0/2 - A * w10/w00;
  1.6508 +               B = B+1;
  1.6509 +           }
  1.6510 +           else { /* essentially no difference between cycles;
  1.6511 +                     smoothing not needed */
  1.6512 +               A= 0.0;
  1.6513 +               B= 1.0;
  1.6514 +           }
  1.6515 +
  1.6516 +           /* create smoothed sequence */
  1.6517 +
  1.6518 +           psseq=sseq+hl*ENH_BLOCKL;
  1.6519 +           for (i=0; i<ENH_BLOCKL; i++) {
  1.6520 +               odata[i]=A*surround[i]+B*psseq[i];
  1.6521 +           }
  1.6522 +       }
  1.6523 +   }
  1.6524 +
  1.6525 +   /*----------------------------------------------------------------*
  1.6526 +    * get the pitch-synchronous sample sequence
  1.6527 +    *---------------------------------------------------------------*/
  1.6528 +
  1.6529 +   void getsseq(
  1.6530 +       float *sseq,    /* (o) the pitch-synchronous sequence */
  1.6531 +       float *idata,       /* (i) original data */
  1.6532 +       int idatal,         /* (i) dimension of data */
  1.6533 +       int centerStartPos, /* (i) where current block starts */
  1.6534 +       float *period,      /* (i) rough-pitch-period array */
  1.6535 +       float *plocs,       /* (i) where periods of period array
  1.6536 +                                  are taken */
  1.6537 +       int periodl,    /* (i) dimension period array */
  1.6538 +       int hl              /* (i) 2*hl+1 is the number of sequences */
  1.6539 +   ){
  1.6540 +       int i,centerEndPos,q;
  1.6541 +       float blockStartPos[2*ENH_HL+1];
  1.6542 +       int lagBlock[2*ENH_HL+1];
  1.6543 +       float plocs2[ENH_PLOCSL];
  1.6544 +       float *psseq;
  1.6545 +
  1.6546 +       centerEndPos=centerStartPos+ENH_BLOCKL-1;
  1.6547 +
  1.6548 +       /* present */
  1.6549 +
  1.6550 +       NearestNeighbor(lagBlock+hl,plocs,
  1.6551 +           (float)0.5*(centerStartPos+centerEndPos),periodl);
  1.6552 +
  1.6553 +       blockStartPos[hl]=(float)centerStartPos;
  1.6554 +
  1.6555 +
  1.6556 +
  1.6557 +Andersen, et al.              Experimental                    [Page 117]
  1.6558 +
  1.6559 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.6560 +
  1.6561 +
  1.6562 +       psseq=sseq+ENH_BLOCKL*hl;
  1.6563 +       memcpy(psseq, idata+centerStartPos, ENH_BLOCKL*sizeof(float));
  1.6564 +
  1.6565 +       /* past */
  1.6566 +
  1.6567 +       for (q=hl-1; q>=0; q--) {
  1.6568 +           blockStartPos[q]=blockStartPos[q+1]-period[lagBlock[q+1]];
  1.6569 +           NearestNeighbor(lagBlock+q,plocs,
  1.6570 +               blockStartPos[q]+
  1.6571 +               ENH_BLOCKL_HALF-period[lagBlock[q+1]], periodl);
  1.6572 +
  1.6573 +
  1.6574 +           if (blockStartPos[q]-ENH_OVERHANG>=0) {
  1.6575 +               refiner(sseq+q*ENH_BLOCKL, blockStartPos+q, idata,
  1.6576 +                   idatal, centerStartPos, blockStartPos[q],
  1.6577 +                   period[lagBlock[q+1]]);
  1.6578 +           } else {
  1.6579 +               psseq=sseq+q*ENH_BLOCKL;
  1.6580 +               memset(psseq, 0, ENH_BLOCKL*sizeof(float));
  1.6581 +           }
  1.6582 +       }
  1.6583 +
  1.6584 +       /* future */
  1.6585 +
  1.6586 +       for (i=0; i<periodl; i++) {
  1.6587 +           plocs2[i]=plocs[i]-period[i];
  1.6588 +       }
  1.6589 +       for (q=hl+1; q<=2*hl; q++) {
  1.6590 +           NearestNeighbor(lagBlock+q,plocs2,
  1.6591 +               blockStartPos[q-1]+ENH_BLOCKL_HALF,periodl);
  1.6592 +
  1.6593 +           blockStartPos[q]=blockStartPos[q-1]+period[lagBlock[q]];
  1.6594 +           if (blockStartPos[q]+ENH_BLOCKL+ENH_OVERHANG<idatal) {
  1.6595 +               refiner(sseq+ENH_BLOCKL*q, blockStartPos+q, idata,
  1.6596 +                   idatal, centerStartPos, blockStartPos[q],
  1.6597 +                   period[lagBlock[q]]);
  1.6598 +           }
  1.6599 +           else {
  1.6600 +               psseq=sseq+q*ENH_BLOCKL;
  1.6601 +               memset(psseq, 0, ENH_BLOCKL*sizeof(float));
  1.6602 +           }
  1.6603 +       }
  1.6604 +   }
  1.6605 +
  1.6606 +   /*----------------------------------------------------------------*
  1.6607 +    * perform enhancement on idata+centerStartPos through
  1.6608 +    * idata+centerStartPos+ENH_BLOCKL-1
  1.6609 +    *---------------------------------------------------------------*/
  1.6610 +
  1.6611 +
  1.6612 +
  1.6613 +Andersen, et al.              Experimental                    [Page 118]
  1.6614 +
  1.6615 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.6616 +
  1.6617 +
  1.6618 +   void enhancer(
  1.6619 +       float *odata,       /* (o) smoothed block, dimension blockl */
  1.6620 +       float *idata,       /* (i) data buffer used for enhancing */
  1.6621 +       int idatal,         /* (i) dimension idata */
  1.6622 +       int centerStartPos, /* (i) first sample current block
  1.6623 +                                  within idata */
  1.6624 +       float alpha0,       /* (i) max correction-energy-fraction
  1.6625 +                                 (in [0,1]) */
  1.6626 +       float *period,      /* (i) pitch period array */
  1.6627 +       float *plocs,       /* (i) locations where period array
  1.6628 +                                  values valid */
  1.6629 +       int periodl         /* (i) dimension of period and plocs */
  1.6630 +   ){
  1.6631 +       float sseq[(2*ENH_HL+1)*ENH_BLOCKL];
  1.6632 +
  1.6633 +       /* get said second sequence of segments */
  1.6634 +
  1.6635 +       getsseq(sseq,idata,idatal,centerStartPos,period,
  1.6636 +           plocs,periodl,ENH_HL);
  1.6637 +
  1.6638 +       /* compute the smoothed output from said second sequence */
  1.6639 +
  1.6640 +       smath(odata,sseq,ENH_HL,alpha0);
  1.6641 +
  1.6642 +   }
  1.6643 +
  1.6644 +   /*----------------------------------------------------------------*
  1.6645 +    * cross correlation
  1.6646 +    *---------------------------------------------------------------*/
  1.6647 +
  1.6648 +   float xCorrCoef(
  1.6649 +       float *target,      /* (i) first array */
  1.6650 +       float *regressor,   /* (i) second array */
  1.6651 +       int subl        /* (i) dimension arrays */
  1.6652 +   ){
  1.6653 +       int i;
  1.6654 +       float ftmp1, ftmp2;
  1.6655 +
  1.6656 +       ftmp1 = 0.0;
  1.6657 +       ftmp2 = 0.0;
  1.6658 +       for (i=0; i<subl; i++) {
  1.6659 +           ftmp1 += target[i]*regressor[i];
  1.6660 +           ftmp2 += regressor[i]*regressor[i];
  1.6661 +       }
  1.6662 +
  1.6663 +       if (ftmp1 > 0.0) {
  1.6664 +           return (float)(ftmp1*ftmp1/ftmp2);
  1.6665 +       }
  1.6666 +
  1.6667 +
  1.6668 +
  1.6669 +Andersen, et al.              Experimental                    [Page 119]
  1.6670 +
  1.6671 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.6672 +
  1.6673 +
  1.6674 +       else {
  1.6675 +           return (float)0.0;
  1.6676 +       }
  1.6677 +   }
  1.6678 +
  1.6679 +   /*----------------------------------------------------------------*
  1.6680 +    * interface for enhancer
  1.6681 +    *---------------------------------------------------------------*/
  1.6682 +
  1.6683 +   int enhancerInterface(
  1.6684 +       float *out,                     /* (o) enhanced signal */
  1.6685 +       float *in,                      /* (i) unenhanced signal */
  1.6686 +       iLBC_Dec_Inst_t *iLBCdec_inst   /* (i) buffers etc */
  1.6687 +   ){
  1.6688 +       float *enh_buf, *enh_period;
  1.6689 +       int iblock, isample;
  1.6690 +       int lag=0, ilag, i, ioffset;
  1.6691 +       float cc, maxcc;
  1.6692 +       float ftmp1, ftmp2;
  1.6693 +       float *inPtr, *enh_bufPtr1, *enh_bufPtr2;
  1.6694 +       float plc_pred[ENH_BLOCKL];
  1.6695 +
  1.6696 +       float lpState[6], downsampled[(ENH_NBLOCKS*ENH_BLOCKL+120)/2];
  1.6697 +       int inLen=ENH_NBLOCKS*ENH_BLOCKL+120;
  1.6698 +       int start, plc_blockl, inlag;
  1.6699 +
  1.6700 +       enh_buf=iLBCdec_inst->enh_buf;
  1.6701 +       enh_period=iLBCdec_inst->enh_period;
  1.6702 +
  1.6703 +       memmove(enh_buf, &enh_buf[iLBCdec_inst->blockl],
  1.6704 +           (ENH_BUFL-iLBCdec_inst->blockl)*sizeof(float));
  1.6705 +
  1.6706 +       memcpy(&enh_buf[ENH_BUFL-iLBCdec_inst->blockl], in,
  1.6707 +           iLBCdec_inst->blockl*sizeof(float));
  1.6708 +
  1.6709 +       if (iLBCdec_inst->mode==30)
  1.6710 +           plc_blockl=ENH_BLOCKL;
  1.6711 +       else
  1.6712 +           plc_blockl=40;
  1.6713 +
  1.6714 +       /* when 20 ms frame, move processing one block */
  1.6715 +       ioffset=0;
  1.6716 +       if (iLBCdec_inst->mode==20) ioffset=1;
  1.6717 +
  1.6718 +       i=3-ioffset;
  1.6719 +       memmove(enh_period, &enh_period[i],
  1.6720 +           (ENH_NBLOCKS_TOT-i)*sizeof(float));
  1.6721 +
  1.6722 +
  1.6723 +
  1.6724 +
  1.6725 +Andersen, et al.              Experimental                    [Page 120]
  1.6726 +
  1.6727 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.6728 +
  1.6729 +
  1.6730 +       /* Set state information to the 6 samples right before
  1.6731 +          the samples to be downsampled. */
  1.6732 +
  1.6733 +       memcpy(lpState,
  1.6734 +           enh_buf+(ENH_NBLOCKS_EXTRA+ioffset)*ENH_BLOCKL-126,
  1.6735 +           6*sizeof(float));
  1.6736 +
  1.6737 +       /* Down sample a factor 2 to save computations */
  1.6738 +
  1.6739 +       DownSample(enh_buf+(ENH_NBLOCKS_EXTRA+ioffset)*ENH_BLOCKL-120,
  1.6740 +                   lpFilt_coefsTbl, inLen-ioffset*ENH_BLOCKL,
  1.6741 +                   lpState, downsampled);
  1.6742 +
  1.6743 +       /* Estimate the pitch in the down sampled domain. */
  1.6744 +       for (iblock = 0; iblock<ENH_NBLOCKS-ioffset; iblock++) {
  1.6745 +
  1.6746 +           lag = 10;
  1.6747 +           maxcc = xCorrCoef(downsampled+60+iblock*
  1.6748 +               ENH_BLOCKL_HALF, downsampled+60+iblock*
  1.6749 +               ENH_BLOCKL_HALF-lag, ENH_BLOCKL_HALF);
  1.6750 +           for (ilag=11; ilag<60; ilag++) {
  1.6751 +               cc = xCorrCoef(downsampled+60+iblock*
  1.6752 +                   ENH_BLOCKL_HALF, downsampled+60+iblock*
  1.6753 +                   ENH_BLOCKL_HALF-ilag, ENH_BLOCKL_HALF);
  1.6754 +
  1.6755 +               if (cc > maxcc) {
  1.6756 +                   maxcc = cc;
  1.6757 +                   lag = ilag;
  1.6758 +               }
  1.6759 +           }
  1.6760 +
  1.6761 +           /* Store the estimated lag in the non-downsampled domain */
  1.6762 +           enh_period[iblock+ENH_NBLOCKS_EXTRA+ioffset] = (float)lag*2;
  1.6763 +
  1.6764 +
  1.6765 +       }
  1.6766 +
  1.6767 +
  1.6768 +       /* PLC was performed on the previous packet */
  1.6769 +       if (iLBCdec_inst->prev_enh_pl==1) {
  1.6770 +
  1.6771 +           inlag=(int)enh_period[ENH_NBLOCKS_EXTRA+ioffset];
  1.6772 +
  1.6773 +           lag = inlag-1;
  1.6774 +           maxcc = xCorrCoef(in, in+lag, plc_blockl);
  1.6775 +           for (ilag=inlag; ilag<=inlag+1; ilag++) {
  1.6776 +               cc = xCorrCoef(in, in+ilag, plc_blockl);
  1.6777 +
  1.6778 +
  1.6779 +
  1.6780 +
  1.6781 +Andersen, et al.              Experimental                    [Page 121]
  1.6782 +
  1.6783 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.6784 +
  1.6785 +
  1.6786 +               if (cc > maxcc) {
  1.6787 +                   maxcc = cc;
  1.6788 +                   lag = ilag;
  1.6789 +               }
  1.6790 +           }
  1.6791 +
  1.6792 +           enh_period[ENH_NBLOCKS_EXTRA+ioffset-1]=(float)lag;
  1.6793 +
  1.6794 +           /* compute new concealed residual for the old lookahead,
  1.6795 +              mix the forward PLC with a backward PLC from
  1.6796 +              the new frame */
  1.6797 +
  1.6798 +           inPtr=&in[lag-1];
  1.6799 +
  1.6800 +           enh_bufPtr1=&plc_pred[plc_blockl-1];
  1.6801 +
  1.6802 +           if (lag>plc_blockl) {
  1.6803 +               start=plc_blockl;
  1.6804 +           } else {
  1.6805 +               start=lag;
  1.6806 +           }
  1.6807 +
  1.6808 +           for (isample = start; isample>0; isample--) {
  1.6809 +               *enh_bufPtr1-- = *inPtr--;
  1.6810 +           }
  1.6811 +
  1.6812 +           enh_bufPtr2=&enh_buf[ENH_BUFL-1-iLBCdec_inst->blockl];
  1.6813 +           for (isample = (plc_blockl-1-lag); isample>=0; isample--) {
  1.6814 +               *enh_bufPtr1-- = *enh_bufPtr2--;
  1.6815 +           }
  1.6816 +
  1.6817 +           /* limit energy change */
  1.6818 +           ftmp2=0.0;
  1.6819 +           ftmp1=0.0;
  1.6820 +           for (i=0;i<plc_blockl;i++) {
  1.6821 +               ftmp2+=enh_buf[ENH_BUFL-1-iLBCdec_inst->blockl-i]*
  1.6822 +                   enh_buf[ENH_BUFL-1-iLBCdec_inst->blockl-i];
  1.6823 +               ftmp1+=plc_pred[i]*plc_pred[i];
  1.6824 +           }
  1.6825 +           ftmp1=(float)sqrt(ftmp1/(float)plc_blockl);
  1.6826 +           ftmp2=(float)sqrt(ftmp2/(float)plc_blockl);
  1.6827 +           if (ftmp1>(float)2.0*ftmp2 && ftmp1>0.0) {
  1.6828 +               for (i=0;i<plc_blockl-10;i++) {
  1.6829 +                   plc_pred[i]*=(float)2.0*ftmp2/ftmp1;
  1.6830 +               }
  1.6831 +               for (i=plc_blockl-10;i<plc_blockl;i++) {
  1.6832 +                   plc_pred[i]*=(float)(i-plc_blockl+10)*
  1.6833 +                       ((float)1.0-(float)2.0*ftmp2/ftmp1)/(float)(10)+
  1.6834 +
  1.6835 +
  1.6836 +
  1.6837 +Andersen, et al.              Experimental                    [Page 122]
  1.6838 +
  1.6839 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.6840 +
  1.6841 +
  1.6842 +                       (float)2.0*ftmp2/ftmp1;
  1.6843 +               }
  1.6844 +           }
  1.6845 +
  1.6846 +           enh_bufPtr1=&enh_buf[ENH_BUFL-1-iLBCdec_inst->blockl];
  1.6847 +           for (i=0; i<plc_blockl; i++) {
  1.6848 +               ftmp1 = (float) (i+1) / (float) (plc_blockl+1);
  1.6849 +               *enh_bufPtr1 *= ftmp1;
  1.6850 +               *enh_bufPtr1 += ((float)1.0-ftmp1)*
  1.6851 +                                   plc_pred[plc_blockl-1-i];
  1.6852 +               enh_bufPtr1--;
  1.6853 +           }
  1.6854 +       }
  1.6855 +
  1.6856 +       if (iLBCdec_inst->mode==20) {
  1.6857 +           /* Enhancer with 40 samples delay */
  1.6858 +           for (iblock = 0; iblock<2; iblock++) {
  1.6859 +               enhancer(out+iblock*ENH_BLOCKL, enh_buf,
  1.6860 +                   ENH_BUFL, (5+iblock)*ENH_BLOCKL+40,
  1.6861 +                   ENH_ALPHA0, enh_period, enh_plocsTbl,
  1.6862 +                       ENH_NBLOCKS_TOT);
  1.6863 +           }
  1.6864 +       } else if (iLBCdec_inst->mode==30) {
  1.6865 +           /* Enhancer with 80 samples delay */
  1.6866 +           for (iblock = 0; iblock<3; iblock++) {
  1.6867 +               enhancer(out+iblock*ENH_BLOCKL, enh_buf,
  1.6868 +                   ENH_BUFL, (4+iblock)*ENH_BLOCKL,
  1.6869 +                   ENH_ALPHA0, enh_period, enh_plocsTbl,
  1.6870 +                       ENH_NBLOCKS_TOT);
  1.6871 +           }
  1.6872 +       }
  1.6873 +
  1.6874 +       return (lag*2);
  1.6875 +   }
  1.6876 +
  1.6877 +A.17.  filter.h
  1.6878 +
  1.6879 +   /******************************************************************
  1.6880 +
  1.6881 +       iLBC Speech Coder ANSI-C Source Code
  1.6882 +
  1.6883 +       filter.h
  1.6884 +
  1.6885 +       Copyright (C) The Internet Society (2004).
  1.6886 +       All Rights Reserved.
  1.6887 +
  1.6888 +   ******************************************************************/
  1.6889 +
  1.6890 +
  1.6891 +
  1.6892 +
  1.6893 +Andersen, et al.              Experimental                    [Page 123]
  1.6894 +
  1.6895 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.6896 +
  1.6897 +
  1.6898 +   #ifndef __iLBC_FILTER_H
  1.6899 +   #define __iLBC_FILTER_H
  1.6900 +
  1.6901 +   void AllPoleFilter(
  1.6902 +       float *InOut,   /* (i/o) on entrance InOut[-orderCoef] to
  1.6903 +                              InOut[-1] contain the state of the
  1.6904 +                              filter (delayed samples). InOut[0] to
  1.6905 +                              InOut[lengthInOut-1] contain the filter
  1.6906 +                              input, on en exit InOut[-orderCoef] to
  1.6907 +                              InOut[-1] is unchanged and InOut[0] to
  1.6908 +                              InOut[lengthInOut-1] contain filtered
  1.6909 +                              samples */
  1.6910 +       float *Coef,/* (i) filter coefficients, Coef[0] is assumed
  1.6911 +                              to be 1.0 */
  1.6912 +       int lengthInOut,/* (i) number of input/output samples */
  1.6913 +       int orderCoef   /* (i) number of filter coefficients */
  1.6914 +   );
  1.6915 +
  1.6916 +   void AllZeroFilter(
  1.6917 +       float *In,      /* (i) In[0] to In[lengthInOut-1] contain
  1.6918 +                              filter input samples */
  1.6919 +       float *Coef,/* (i) filter coefficients (Coef[0] is assumed
  1.6920 +                              to be 1.0) */
  1.6921 +       int lengthInOut,/* (i) number of input/output samples */
  1.6922 +       int orderCoef,  /* (i) number of filter coefficients */
  1.6923 +       float *Out      /* (i/o) on entrance Out[-orderCoef] to Out[-1]
  1.6924 +                              contain the filter state, on exit Out[0]
  1.6925 +                              to Out[lengthInOut-1] contain filtered
  1.6926 +                              samples */
  1.6927 +   );
  1.6928 +
  1.6929 +   void ZeroPoleFilter(
  1.6930 +       float *In,      /* (i) In[0] to In[lengthInOut-1] contain filter
  1.6931 +                              input samples In[-orderCoef] to In[-1]
  1.6932 +                              contain state of all-zero section */
  1.6933 +       float *ZeroCoef,/* (i) filter coefficients for all-zero
  1.6934 +                              section (ZeroCoef[0] is assumed to
  1.6935 +                              be 1.0) */
  1.6936 +       float *PoleCoef,/* (i) filter coefficients for all-pole section
  1.6937 +                              (ZeroCoef[0] is assumed to be 1.0) */
  1.6938 +       int lengthInOut,/* (i) number of input/output samples */
  1.6939 +       int orderCoef,  /* (i) number of filter coefficients */
  1.6940 +       float *Out      /* (i/o) on entrance Out[-orderCoef] to Out[-1]
  1.6941 +                              contain state of all-pole section. On
  1.6942 +                              exit Out[0] to Out[lengthInOut-1]
  1.6943 +                              contain filtered samples */
  1.6944 +   );
  1.6945 +
  1.6946 +
  1.6947 +
  1.6948 +
  1.6949 +Andersen, et al.              Experimental                    [Page 124]
  1.6950 +
  1.6951 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.6952 +
  1.6953 +
  1.6954 +   void DownSample (
  1.6955 +       float  *In,     /* (i) input samples */
  1.6956 +       float  *Coef,   /* (i) filter coefficients */
  1.6957 +       int lengthIn,   /* (i) number of input samples */
  1.6958 +       float  *state,  /* (i) filter state */
  1.6959 +       float  *Out     /* (o) downsampled output */
  1.6960 +   );
  1.6961 +
  1.6962 +   #endif
  1.6963 +
  1.6964 +A.18.  filter.c
  1.6965 +
  1.6966 +   /******************************************************************
  1.6967 +
  1.6968 +       iLBC Speech Coder ANSI-C Source Code
  1.6969 +
  1.6970 +       filter.c
  1.6971 +
  1.6972 +       Copyright (C) The Internet Society (2004).
  1.6973 +       All Rights Reserved.
  1.6974 +
  1.6975 +   ******************************************************************/
  1.6976 +
  1.6977 +   #include "iLBC_define.h"
  1.6978 +
  1.6979 +   /*----------------------------------------------------------------*
  1.6980 +    *  all-pole filter
  1.6981 +    *---------------------------------------------------------------*/
  1.6982 +
  1.6983 +   void AllPoleFilter(
  1.6984 +       float *InOut,   /* (i/o) on entrance InOut[-orderCoef] to
  1.6985 +                              InOut[-1] contain the state of the
  1.6986 +                              filter (delayed samples). InOut[0] to
  1.6987 +                              InOut[lengthInOut-1] contain the filter
  1.6988 +                              input, on en exit InOut[-orderCoef] to
  1.6989 +                              InOut[-1] is unchanged and InOut[0] to
  1.6990 +                              InOut[lengthInOut-1] contain filtered
  1.6991 +                              samples */
  1.6992 +       float *Coef,/* (i) filter coefficients, Coef[0] is assumed
  1.6993 +                              to be 1.0 */
  1.6994 +       int lengthInOut,/* (i) number of input/output samples */
  1.6995 +       int orderCoef   /* (i) number of filter coefficients */
  1.6996 +   ){
  1.6997 +       int n,k;
  1.6998 +
  1.6999 +       for(n=0;n<lengthInOut;n++){
  1.7000 +           for(k=1;k<=orderCoef;k++){
  1.7001 +               *InOut -= Coef[k]*InOut[-k];
  1.7002 +
  1.7003 +
  1.7004 +
  1.7005 +Andersen, et al.              Experimental                    [Page 125]
  1.7006 +
  1.7007 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.7008 +
  1.7009 +
  1.7010 +           }
  1.7011 +           InOut++;
  1.7012 +       }
  1.7013 +   }
  1.7014 +
  1.7015 +   /*----------------------------------------------------------------*
  1.7016 +    *  all-zero filter
  1.7017 +    *---------------------------------------------------------------*/
  1.7018 +
  1.7019 +   void AllZeroFilter(
  1.7020 +       float *In,      /* (i) In[0] to In[lengthInOut-1] contain
  1.7021 +                              filter input samples */
  1.7022 +       float *Coef,/* (i) filter coefficients (Coef[0] is assumed
  1.7023 +                              to be 1.0) */
  1.7024 +       int lengthInOut,/* (i) number of input/output samples */
  1.7025 +       int orderCoef,  /* (i) number of filter coefficients */
  1.7026 +       float *Out      /* (i/o) on entrance Out[-orderCoef] to Out[-1]
  1.7027 +                              contain the filter state, on exit Out[0]
  1.7028 +                              to Out[lengthInOut-1] contain filtered
  1.7029 +                              samples */
  1.7030 +   ){
  1.7031 +       int n,k;
  1.7032 +
  1.7033 +       for(n=0;n<lengthInOut;n++){
  1.7034 +           *Out = Coef[0]*In[0];
  1.7035 +           for(k=1;k<=orderCoef;k++){
  1.7036 +               *Out += Coef[k]*In[-k];
  1.7037 +           }
  1.7038 +           Out++;
  1.7039 +           In++;
  1.7040 +       }
  1.7041 +   }
  1.7042 +
  1.7043 +   /*----------------------------------------------------------------*
  1.7044 +    *  pole-zero filter
  1.7045 +    *---------------------------------------------------------------*/
  1.7046 +
  1.7047 +   void ZeroPoleFilter(
  1.7048 +       float *In,      /* (i) In[0] to In[lengthInOut-1] contain
  1.7049 +                              filter input samples In[-orderCoef] to
  1.7050 +                              In[-1] contain state of all-zero
  1.7051 +                              section */
  1.7052 +       float *ZeroCoef,/* (i) filter coefficients for all-zero
  1.7053 +                              section (ZeroCoef[0] is assumed to
  1.7054 +                              be 1.0) */
  1.7055 +       float *PoleCoef,/* (i) filter coefficients for all-pole section
  1.7056 +                              (ZeroCoef[0] is assumed to be 1.0) */
  1.7057 +       int lengthInOut,/* (i) number of input/output samples */
  1.7058 +
  1.7059 +
  1.7060 +
  1.7061 +Andersen, et al.              Experimental                    [Page 126]
  1.7062 +
  1.7063 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.7064 +
  1.7065 +
  1.7066 +       int orderCoef,  /* (i) number of filter coefficients */
  1.7067 +       float *Out      /* (i/o) on entrance Out[-orderCoef] to Out[-1]
  1.7068 +                              contain state of all-pole section. On
  1.7069 +                              exit Out[0] to Out[lengthInOut-1]
  1.7070 +                              contain filtered samples */
  1.7071 +   ){
  1.7072 +       AllZeroFilter(In,ZeroCoef,lengthInOut,orderCoef,Out);
  1.7073 +       AllPoleFilter(Out,PoleCoef,lengthInOut,orderCoef);
  1.7074 +   }
  1.7075 +
  1.7076 +   /*----------------------------------------------------------------*
  1.7077 +    * downsample (LP filter and decimation)
  1.7078 +    *---------------------------------------------------------------*/
  1.7079 +
  1.7080 +   void DownSample (
  1.7081 +       float  *In,     /* (i) input samples */
  1.7082 +       float  *Coef,   /* (i) filter coefficients */
  1.7083 +       int lengthIn,   /* (i) number of input samples */
  1.7084 +       float  *state,  /* (i) filter state */
  1.7085 +       float  *Out     /* (o) downsampled output */
  1.7086 +   ){
  1.7087 +       float   o;
  1.7088 +       float *Out_ptr = Out;
  1.7089 +       float *Coef_ptr, *In_ptr;
  1.7090 +       float *state_ptr;
  1.7091 +       int i, j, stop;
  1.7092 +
  1.7093 +       /* LP filter and decimate at the same time */
  1.7094 +
  1.7095 +       for (i = DELAY_DS; i < lengthIn; i+=FACTOR_DS)
  1.7096 +       {
  1.7097 +           Coef_ptr = &Coef[0];
  1.7098 +           In_ptr = &In[i];
  1.7099 +           state_ptr = &state[FILTERORDER_DS-2];
  1.7100 +
  1.7101 +           o = (float)0.0;
  1.7102 +
  1.7103 +           stop = (i < FILTERORDER_DS) ? i + 1 : FILTERORDER_DS;
  1.7104 +
  1.7105 +           for (j = 0; j < stop; j++)
  1.7106 +           {
  1.7107 +               o += *Coef_ptr++ * (*In_ptr--);
  1.7108 +           }
  1.7109 +           for (j = i + 1; j < FILTERORDER_DS; j++)
  1.7110 +           {
  1.7111 +               o += *Coef_ptr++ * (*state_ptr--);
  1.7112 +           }
  1.7113 +
  1.7114 +
  1.7115 +
  1.7116 +
  1.7117 +Andersen, et al.              Experimental                    [Page 127]
  1.7118 +
  1.7119 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.7120 +
  1.7121 +
  1.7122 +           *Out_ptr++ = o;
  1.7123 +       }
  1.7124 +
  1.7125 +       /* Get the last part (use zeros as input for the future) */
  1.7126 +
  1.7127 +       for (i=(lengthIn+FACTOR_DS); i<(lengthIn+DELAY_DS);
  1.7128 +               i+=FACTOR_DS) {
  1.7129 +
  1.7130 +           o=(float)0.0;
  1.7131 +
  1.7132 +           if (i<lengthIn) {
  1.7133 +               Coef_ptr = &Coef[0];
  1.7134 +               In_ptr = &In[i];
  1.7135 +               for (j=0; j<FILTERORDER_DS; j++) {
  1.7136 +                       o += *Coef_ptr++ * (*Out_ptr--);
  1.7137 +               }
  1.7138 +           } else {
  1.7139 +               Coef_ptr = &Coef[i-lengthIn];
  1.7140 +               In_ptr = &In[lengthIn-1];
  1.7141 +               for (j=0; j<FILTERORDER_DS-(i-lengthIn); j++) {
  1.7142 +                       o += *Coef_ptr++ * (*In_ptr--);
  1.7143 +               }
  1.7144 +           }
  1.7145 +           *Out_ptr++ = o;
  1.7146 +       }
  1.7147 +   }
  1.7148 +
  1.7149 +A.19.  FrameClassify.h
  1.7150 +
  1.7151 +   /******************************************************************
  1.7152 +
  1.7153 +       iLBC Speech Coder ANSI-C Source Code
  1.7154 +
  1.7155 +       FrameClassify.h
  1.7156 +
  1.7157 +       Copyright (C) The Internet Society (2004).
  1.7158 +       All Rights Reserved.
  1.7159 +
  1.7160 +   ******************************************************************/
  1.7161 +
  1.7162 +   #ifndef __iLBC_FRAMECLASSIFY_H
  1.7163 +   #define __iLBC_FRAMECLASSIFY_H
  1.7164 +
  1.7165 +   int FrameClassify(      /* index to the max-energy sub-frame */
  1.7166 +       iLBC_Enc_Inst_t *iLBCenc_inst,
  1.7167 +                           /* (i/o) the encoder state structure */
  1.7168 +       float *residual     /* (i) lpc residual signal */
  1.7169 +   );
  1.7170 +
  1.7171 +
  1.7172 +
  1.7173 +Andersen, et al.              Experimental                    [Page 128]
  1.7174 +
  1.7175 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.7176 +
  1.7177 +
  1.7178 +   #endif
  1.7179 +
  1.7180 +A.20.  FrameClassify.c
  1.7181 +
  1.7182 +   /******************************************************************
  1.7183 +
  1.7184 +       iLBC Speech Coder ANSI-C Source Code
  1.7185 +
  1.7186 +       FrameClassify.c
  1.7187 +
  1.7188 +       Copyright (C) The Internet Society (2004).
  1.7189 +       All Rights Reserved.
  1.7190 +
  1.7191 +   ******************************************************************/
  1.7192 +
  1.7193 +   #include "iLBC_define.h"
  1.7194 +
  1.7195 +   /*---------------------------------------------------------------*
  1.7196 +    *  Classification of subframes to localize start state
  1.7197 +    *--------------------------------------------------------------*/
  1.7198 +
  1.7199 +   int FrameClassify(      /* index to the max-energy sub-frame */
  1.7200 +       iLBC_Enc_Inst_t *iLBCenc_inst,
  1.7201 +                           /* (i/o) the encoder state structure */
  1.7202 +       float *residual     /* (i) lpc residual signal */
  1.7203 +   ) {
  1.7204 +       float max_ssqEn, fssqEn[NSUB_MAX], bssqEn[NSUB_MAX], *pp;
  1.7205 +       int n, l, max_ssqEn_n;
  1.7206 +       const float ssqEn_win[NSUB_MAX-1]={(float)0.8,(float)0.9,
  1.7207 +           (float)1.0,(float)0.9,(float)0.8};
  1.7208 +       const float sampEn_win[5]={(float)1.0/(float)6.0,
  1.7209 +           (float)2.0/(float)6.0, (float)3.0/(float)6.0,
  1.7210 +           (float)4.0/(float)6.0, (float)5.0/(float)6.0};
  1.7211 +
  1.7212 +       /* init the front and back energies to zero */
  1.7213 +
  1.7214 +       memset(fssqEn, 0, NSUB_MAX*sizeof(float));
  1.7215 +       memset(bssqEn, 0, NSUB_MAX*sizeof(float));
  1.7216 +
  1.7217 +       /* Calculate front of first seqence */
  1.7218 +
  1.7219 +       n=0;
  1.7220 +       pp=residual;
  1.7221 +       for (l=0; l<5; l++) {
  1.7222 +           fssqEn[n] += sampEn_win[l] * (*pp) * (*pp);
  1.7223 +           pp++;
  1.7224 +       }
  1.7225 +       for (l=5; l<SUBL; l++) {
  1.7226 +
  1.7227 +
  1.7228 +
  1.7229 +Andersen, et al.              Experimental                    [Page 129]
  1.7230 +
  1.7231 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.7232 +
  1.7233 +
  1.7234 +           fssqEn[n] += (*pp) * (*pp);
  1.7235 +           pp++;
  1.7236 +       }
  1.7237 +
  1.7238 +       /* Calculate front and back of all middle sequences */
  1.7239 +
  1.7240 +       for (n=1; n<iLBCenc_inst->nsub-1; n++) {
  1.7241 +           pp=residual+n*SUBL;
  1.7242 +           for (l=0; l<5; l++) {
  1.7243 +               fssqEn[n] += sampEn_win[l] * (*pp) * (*pp);
  1.7244 +               bssqEn[n] += (*pp) * (*pp);
  1.7245 +               pp++;
  1.7246 +           }
  1.7247 +           for (l=5; l<SUBL-5; l++) {
  1.7248 +               fssqEn[n] += (*pp) * (*pp);
  1.7249 +               bssqEn[n] += (*pp) * (*pp);
  1.7250 +               pp++;
  1.7251 +           }
  1.7252 +           for (l=SUBL-5; l<SUBL; l++) {
  1.7253 +               fssqEn[n] += (*pp) * (*pp);
  1.7254 +               bssqEn[n] += sampEn_win[SUBL-l-1] * (*pp) * (*pp);
  1.7255 +               pp++;
  1.7256 +           }
  1.7257 +       }
  1.7258 +
  1.7259 +       /* Calculate back of last seqence */
  1.7260 +
  1.7261 +       n=iLBCenc_inst->nsub-1;
  1.7262 +       pp=residual+n*SUBL;
  1.7263 +       for (l=0; l<SUBL-5; l++) {
  1.7264 +           bssqEn[n] += (*pp) * (*pp);
  1.7265 +           pp++;
  1.7266 +       }
  1.7267 +       for (l=SUBL-5; l<SUBL; l++) {
  1.7268 +           bssqEn[n] += sampEn_win[SUBL-l-1] * (*pp) * (*pp);
  1.7269 +           pp++;
  1.7270 +       }
  1.7271 +
  1.7272 +       /* find the index to the weighted 80 sample with
  1.7273 +          most energy */
  1.7274 +
  1.7275 +       if (iLBCenc_inst->mode==20) l=1;
  1.7276 +       else                        l=0;
  1.7277 +
  1.7278 +       max_ssqEn=(fssqEn[0]+bssqEn[1])*ssqEn_win[l];
  1.7279 +       max_ssqEn_n=1;
  1.7280 +       for (n=2; n<iLBCenc_inst->nsub; n++) {
  1.7281 +
  1.7282 +
  1.7283 +
  1.7284 +
  1.7285 +Andersen, et al.              Experimental                    [Page 130]
  1.7286 +
  1.7287 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.7288 +
  1.7289 +
  1.7290 +           l++;
  1.7291 +           if ((fssqEn[n-1]+bssqEn[n])*ssqEn_win[l] > max_ssqEn) {
  1.7292 +               max_ssqEn=(fssqEn[n-1]+bssqEn[n]) *
  1.7293 +                               ssqEn_win[l];
  1.7294 +               max_ssqEn_n=n;
  1.7295 +           }
  1.7296 +       }
  1.7297 +
  1.7298 +       return max_ssqEn_n;
  1.7299 +   }
  1.7300 +
  1.7301 +A.21.  gainquant.h
  1.7302 +
  1.7303 +   /******************************************************************
  1.7304 +
  1.7305 +       iLBC Speech Coder ANSI-C Source Code
  1.7306 +
  1.7307 +       gainquant.h
  1.7308 +
  1.7309 +       Copyright (C) The Internet Society (2004).
  1.7310 +       All Rights Reserved.
  1.7311 +
  1.7312 +   ******************************************************************/
  1.7313 +
  1.7314 +   #ifndef __iLBC_GAINQUANT_H
  1.7315 +   #define __iLBC_GAINQUANT_H
  1.7316 +
  1.7317 +   float gainquant(/* (o) quantized gain value */
  1.7318 +       float in,       /* (i) gain value */
  1.7319 +       float maxIn,/* (i) maximum of gain value */
  1.7320 +       int cblen,      /* (i) number of quantization indices */
  1.7321 +       int *index      /* (o) quantization index */
  1.7322 +   );
  1.7323 +
  1.7324 +   float gaindequant(  /* (o) quantized gain value */
  1.7325 +       int index,      /* (i) quantization index */
  1.7326 +       float maxIn,/* (i) maximum of unquantized gain */
  1.7327 +       int cblen       /* (i) number of quantization indices */
  1.7328 +   );
  1.7329 +
  1.7330 +   #endif
  1.7331 +
  1.7332 +A.22.  gainquant.c
  1.7333 +
  1.7334 +   /******************************************************************
  1.7335 +
  1.7336 +       iLBC Speech Coder ANSI-C Source Code
  1.7337 +
  1.7338 +
  1.7339 +
  1.7340 +
  1.7341 +Andersen, et al.              Experimental                    [Page 131]
  1.7342 +
  1.7343 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.7344 +
  1.7345 +
  1.7346 +       gainquant.c
  1.7347 +
  1.7348 +       Copyright (C) The Internet Society (2004).
  1.7349 +       All Rights Reserved.
  1.7350 +
  1.7351 +   ******************************************************************/
  1.7352 +
  1.7353 +   #include <string.h>
  1.7354 +   #include <math.h>
  1.7355 +   #include "constants.h"
  1.7356 +   #include "filter.h"
  1.7357 +
  1.7358 +   /*----------------------------------------------------------------*
  1.7359 +    *  quantizer for the gain in the gain-shape coding of residual
  1.7360 +    *---------------------------------------------------------------*/
  1.7361 +
  1.7362 +   float gainquant(/* (o) quantized gain value */
  1.7363 +       float in,       /* (i) gain value */
  1.7364 +       float maxIn,/* (i) maximum of gain value */
  1.7365 +       int cblen,      /* (i) number of quantization indices */
  1.7366 +       int *index      /* (o) quantization index */
  1.7367 +   ){
  1.7368 +       int i, tindex;
  1.7369 +       float minmeasure,measure, *cb, scale;
  1.7370 +
  1.7371 +       /* ensure a lower bound on the scaling factor */
  1.7372 +
  1.7373 +       scale=maxIn;
  1.7374 +
  1.7375 +       if (scale<0.1) {
  1.7376 +           scale=(float)0.1;
  1.7377 +       }
  1.7378 +
  1.7379 +       /* select the quantization table */
  1.7380 +
  1.7381 +       if (cblen == 8) {
  1.7382 +           cb = gain_sq3Tbl;
  1.7383 +       } else if (cblen == 16) {
  1.7384 +           cb = gain_sq4Tbl;
  1.7385 +       } else  {
  1.7386 +           cb = gain_sq5Tbl;
  1.7387 +       }
  1.7388 +
  1.7389 +       /* select the best index in the quantization table */
  1.7390 +
  1.7391 +       minmeasure=10000000.0;
  1.7392 +       tindex=0;
  1.7393 +       for (i=0; i<cblen; i++) {
  1.7394 +
  1.7395 +
  1.7396 +
  1.7397 +Andersen, et al.              Experimental                    [Page 132]
  1.7398 +
  1.7399 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.7400 +
  1.7401 +
  1.7402 +           measure=(in-scale*cb[i])*(in-scale*cb[i]);
  1.7403 +
  1.7404 +           if (measure<minmeasure) {
  1.7405 +               tindex=i;
  1.7406 +               minmeasure=measure;
  1.7407 +           }
  1.7408 +       }
  1.7409 +       *index=tindex;
  1.7410 +
  1.7411 +       /* return the quantized value */
  1.7412 +
  1.7413 +       return scale*cb[tindex];
  1.7414 +   }
  1.7415 +
  1.7416 +   /*----------------------------------------------------------------*
  1.7417 +    *  decoder for quantized gains in the gain-shape coding of
  1.7418 +    *  residual
  1.7419 +    *---------------------------------------------------------------*/
  1.7420 +
  1.7421 +   float gaindequant(  /* (o) quantized gain value */
  1.7422 +       int index,      /* (i) quantization index */
  1.7423 +       float maxIn,/* (i) maximum of unquantized gain */
  1.7424 +       int cblen       /* (i) number of quantization indices */
  1.7425 +   ){
  1.7426 +       float scale;
  1.7427 +
  1.7428 +       /* obtain correct scale factor */
  1.7429 +
  1.7430 +       scale=(float)fabs(maxIn);
  1.7431 +
  1.7432 +       if (scale<0.1) {
  1.7433 +           scale=(float)0.1;
  1.7434 +       }
  1.7435 +
  1.7436 +       /* select the quantization table and return the decoded value */
  1.7437 +
  1.7438 +       if (cblen==8) {
  1.7439 +           return scale*gain_sq3Tbl[index];
  1.7440 +       } else if (cblen==16) {
  1.7441 +           return scale*gain_sq4Tbl[index];
  1.7442 +       }
  1.7443 +       else if (cblen==32) {
  1.7444 +           return scale*gain_sq5Tbl[index];
  1.7445 +       }
  1.7446 +
  1.7447 +       return 0.0;
  1.7448 +   }
  1.7449 +
  1.7450 +
  1.7451 +
  1.7452 +
  1.7453 +Andersen, et al.              Experimental                    [Page 133]
  1.7454 +
  1.7455 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.7456 +
  1.7457 +
  1.7458 +A.23.  getCBvec.h
  1.7459 +
  1.7460 +   /******************************************************************
  1.7461 +
  1.7462 +       iLBC Speech Coder ANSI-C Source Code
  1.7463 +
  1.7464 +       getCBvec.h
  1.7465 +
  1.7466 +       Copyright (C) The Internet Society (2004).
  1.7467 +       All Rights Reserved.
  1.7468 +
  1.7469 +   ******************************************************************/
  1.7470 +
  1.7471 +   #ifndef __iLBC_GETCBVEC_H
  1.7472 +   #define __iLBC_GETCBVEC_H
  1.7473 +
  1.7474 +   void getCBvec(
  1.7475 +       float *cbvec,   /* (o) Constructed codebook vector */
  1.7476 +       float *mem,     /* (i) Codebook buffer */
  1.7477 +       int index,      /* (i) Codebook index */
  1.7478 +       int lMem,       /* (i) Length of codebook buffer */
  1.7479 +       int cbveclen/* (i) Codebook vector length */
  1.7480 +   );
  1.7481 +
  1.7482 +   #endif
  1.7483 +
  1.7484 +A.24.  getCBvec.c
  1.7485 +
  1.7486 +   /******************************************************************
  1.7487 +
  1.7488 +       iLBC Speech Coder ANSI-C Source Code
  1.7489 +
  1.7490 +       getCBvec.c
  1.7491 +
  1.7492 +       Copyright (C) The Internet Society (2004).
  1.7493 +       All Rights Reserved.
  1.7494 +
  1.7495 +   ******************************************************************/
  1.7496 +
  1.7497 +   #include "iLBC_define.h"
  1.7498 +   #include "constants.h"
  1.7499 +   #include <string.h>
  1.7500 +
  1.7501 +   /*----------------------------------------------------------------*
  1.7502 +    *  Construct codebook vector for given index.
  1.7503 +    *---------------------------------------------------------------*/
  1.7504 +
  1.7505 +   void getCBvec(
  1.7506 +
  1.7507 +
  1.7508 +
  1.7509 +Andersen, et al.              Experimental                    [Page 134]
  1.7510 +
  1.7511 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.7512 +
  1.7513 +
  1.7514 +       float *cbvec,   /* (o) Constructed codebook vector */
  1.7515 +       float *mem,     /* (i) Codebook buffer */
  1.7516 +       int index,      /* (i) Codebook index */
  1.7517 +       int lMem,       /* (i) Length of codebook buffer */
  1.7518 +       int cbveclen/* (i) Codebook vector length */
  1.7519 +   ){
  1.7520 +       int j, k, n, memInd, sFilt;
  1.7521 +       float tmpbuf[CB_MEML];
  1.7522 +       int base_size;
  1.7523 +       int ilow, ihigh;
  1.7524 +       float alfa, alfa1;
  1.7525 +
  1.7526 +       /* Determine size of codebook sections */
  1.7527 +
  1.7528 +       base_size=lMem-cbveclen+1;
  1.7529 +
  1.7530 +       if (cbveclen==SUBL) {
  1.7531 +           base_size+=cbveclen/2;
  1.7532 +       }
  1.7533 +
  1.7534 +       /* No filter -> First codebook section */
  1.7535 +
  1.7536 +       if (index<lMem-cbveclen+1) {
  1.7537 +
  1.7538 +           /* first non-interpolated vectors */
  1.7539 +
  1.7540 +           k=index+cbveclen;
  1.7541 +           /* get vector */
  1.7542 +           memcpy(cbvec, mem+lMem-k, cbveclen*sizeof(float));
  1.7543 +
  1.7544 +       } else if (index < base_size) {
  1.7545 +
  1.7546 +           k=2*(index-(lMem-cbveclen+1))+cbveclen;
  1.7547 +
  1.7548 +           ihigh=k/2;
  1.7549 +           ilow=ihigh-5;
  1.7550 +
  1.7551 +           /* Copy first noninterpolated part */
  1.7552 +
  1.7553 +           memcpy(cbvec, mem+lMem-k/2, ilow*sizeof(float));
  1.7554 +
  1.7555 +           /* interpolation */
  1.7556 +
  1.7557 +           alfa1=(float)0.2;
  1.7558 +           alfa=0.0;
  1.7559 +           for (j=ilow; j<ihigh; j++) {
  1.7560 +               cbvec[j]=((float)1.0-alfa)*mem[lMem-k/2+j]+
  1.7561 +                   alfa*mem[lMem-k+j];
  1.7562 +
  1.7563 +
  1.7564 +
  1.7565 +Andersen, et al.              Experimental                    [Page 135]
  1.7566 +
  1.7567 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.7568 +
  1.7569 +
  1.7570 +               alfa+=alfa1;
  1.7571 +           }
  1.7572 +
  1.7573 +           /* Copy second noninterpolated part */
  1.7574 +
  1.7575 +           memcpy(cbvec+ihigh, mem+lMem-k+ihigh,
  1.7576 +               (cbveclen-ihigh)*sizeof(float));
  1.7577 +
  1.7578 +       }
  1.7579 +
  1.7580 +       /* Higher codebook section based on filtering */
  1.7581 +
  1.7582 +       else {
  1.7583 +
  1.7584 +           /* first non-interpolated vectors */
  1.7585 +
  1.7586 +           if (index-base_size<lMem-cbveclen+1) {
  1.7587 +               float tempbuff2[CB_MEML+CB_FILTERLEN+1];
  1.7588 +               float *pos;
  1.7589 +               float *pp, *pp1;
  1.7590 +
  1.7591 +               memset(tempbuff2, 0,
  1.7592 +                   CB_HALFFILTERLEN*sizeof(float));
  1.7593 +               memcpy(&tempbuff2[CB_HALFFILTERLEN], mem,
  1.7594 +                   lMem*sizeof(float));
  1.7595 +               memset(&tempbuff2[lMem+CB_HALFFILTERLEN], 0,
  1.7596 +                   (CB_HALFFILTERLEN+1)*sizeof(float));
  1.7597 +
  1.7598 +               k=index-base_size+cbveclen;
  1.7599 +               sFilt=lMem-k;
  1.7600 +               memInd=sFilt+1-CB_HALFFILTERLEN;
  1.7601 +
  1.7602 +               /* do filtering */
  1.7603 +               pos=cbvec;
  1.7604 +               memset(pos, 0, cbveclen*sizeof(float));
  1.7605 +               for (n=0; n<cbveclen; n++) {
  1.7606 +                   pp=&tempbuff2[memInd+n+CB_HALFFILTERLEN];
  1.7607 +                   pp1=&cbfiltersTbl[CB_FILTERLEN-1];
  1.7608 +                   for (j=0; j<CB_FILTERLEN; j++) {
  1.7609 +                       (*pos)+=(*pp++)*(*pp1--);
  1.7610 +                   }
  1.7611 +                   pos++;
  1.7612 +               }
  1.7613 +           }
  1.7614 +
  1.7615 +           /* interpolated vectors */
  1.7616 +
  1.7617 +           else {
  1.7618 +
  1.7619 +
  1.7620 +
  1.7621 +Andersen, et al.              Experimental                    [Page 136]
  1.7622 +
  1.7623 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.7624 +
  1.7625 +
  1.7626 +               float tempbuff2[CB_MEML+CB_FILTERLEN+1];
  1.7627 +
  1.7628 +               float *pos;
  1.7629 +               float *pp, *pp1;
  1.7630 +               int i;
  1.7631 +
  1.7632 +               memset(tempbuff2, 0,
  1.7633 +                   CB_HALFFILTERLEN*sizeof(float));
  1.7634 +               memcpy(&tempbuff2[CB_HALFFILTERLEN], mem,
  1.7635 +                   lMem*sizeof(float));
  1.7636 +               memset(&tempbuff2[lMem+CB_HALFFILTERLEN], 0,
  1.7637 +                   (CB_HALFFILTERLEN+1)*sizeof(float));
  1.7638 +
  1.7639 +               k=2*(index-base_size-
  1.7640 +                   (lMem-cbveclen+1))+cbveclen;
  1.7641 +               sFilt=lMem-k;
  1.7642 +               memInd=sFilt+1-CB_HALFFILTERLEN;
  1.7643 +
  1.7644 +               /* do filtering */
  1.7645 +               pos=&tmpbuf[sFilt];
  1.7646 +               memset(pos, 0, k*sizeof(float));
  1.7647 +               for (i=0; i<k; i++) {
  1.7648 +                   pp=&tempbuff2[memInd+i+CB_HALFFILTERLEN];
  1.7649 +                   pp1=&cbfiltersTbl[CB_FILTERLEN-1];
  1.7650 +                   for (j=0; j<CB_FILTERLEN; j++) {
  1.7651 +                       (*pos)+=(*pp++)*(*pp1--);
  1.7652 +                   }
  1.7653 +                   pos++;
  1.7654 +               }
  1.7655 +
  1.7656 +               ihigh=k/2;
  1.7657 +               ilow=ihigh-5;
  1.7658 +
  1.7659 +               /* Copy first noninterpolated part */
  1.7660 +
  1.7661 +               memcpy(cbvec, tmpbuf+lMem-k/2,
  1.7662 +                   ilow*sizeof(float));
  1.7663 +
  1.7664 +               /* interpolation */
  1.7665 +
  1.7666 +               alfa1=(float)0.2;
  1.7667 +               alfa=0.0;
  1.7668 +               for (j=ilow; j<ihigh; j++) {
  1.7669 +                   cbvec[j]=((float)1.0-alfa)*
  1.7670 +                       tmpbuf[lMem-k/2+j]+alfa*tmpbuf[lMem-k+j];
  1.7671 +                   alfa+=alfa1;
  1.7672 +               }
  1.7673 +
  1.7674 +
  1.7675 +
  1.7676 +
  1.7677 +Andersen, et al.              Experimental                    [Page 137]
  1.7678 +
  1.7679 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.7680 +
  1.7681 +
  1.7682 +               /* Copy second noninterpolated part */
  1.7683 +
  1.7684 +               memcpy(cbvec+ihigh, tmpbuf+lMem-k+ihigh,
  1.7685 +                   (cbveclen-ihigh)*sizeof(float));
  1.7686 +           }
  1.7687 +       }
  1.7688 +   }
  1.7689 +
  1.7690 +A.25.  helpfun.h
  1.7691 +
  1.7692 +   /******************************************************************
  1.7693 +
  1.7694 +       iLBC Speech Coder ANSI-C Source Code
  1.7695 +
  1.7696 +       helpfun.h
  1.7697 +
  1.7698 +       Copyright (C) The Internet Society (2004).
  1.7699 +       All Rights Reserved.
  1.7700 +
  1.7701 +   ******************************************************************/
  1.7702 +
  1.7703 +   #ifndef __iLBC_HELPFUN_H
  1.7704 +   #define __iLBC_HELPFUN_H
  1.7705 +
  1.7706 +   void autocorr(
  1.7707 +       float *r,       /* (o) autocorrelation vector */
  1.7708 +       const float *x, /* (i) data vector */
  1.7709 +       int N,          /* (i) length of data vector */
  1.7710 +       int order       /* largest lag for calculated
  1.7711 +                          autocorrelations */
  1.7712 +   );
  1.7713 +
  1.7714 +   void window(
  1.7715 +       float *z,       /* (o) the windowed data */
  1.7716 +       const float *x, /* (i) the original data vector */
  1.7717 +       const float *y, /* (i) the window */
  1.7718 +       int N           /* (i) length of all vectors */
  1.7719 +   );
  1.7720 +
  1.7721 +   void levdurb(
  1.7722 +       float *a,       /* (o) lpc coefficient vector starting
  1.7723 +                              with 1.0 */
  1.7724 +       float *k,       /* (o) reflection coefficients */
  1.7725 +       float *r,       /* (i) autocorrelation vector */
  1.7726 +       int order       /* (i) order of lpc filter */
  1.7727 +   );
  1.7728 +
  1.7729 +   void interpolate(
  1.7730 +
  1.7731 +
  1.7732 +
  1.7733 +Andersen, et al.              Experimental                    [Page 138]
  1.7734 +
  1.7735 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.7736 +
  1.7737 +
  1.7738 +       float *out,     /* (o) the interpolated vector */
  1.7739 +       float *in1,     /* (i) the first vector for the
  1.7740 +                              interpolation */
  1.7741 +       float *in2,     /* (i) the second vector for the
  1.7742 +                              interpolation */
  1.7743 +       float coef,     /* (i) interpolation weights */
  1.7744 +       int length      /* (i) length of all vectors */
  1.7745 +   );
  1.7746 +
  1.7747 +   void bwexpand(
  1.7748 +       float *out,     /* (o) the bandwidth expanded lpc
  1.7749 +                              coefficients */
  1.7750 +       float *in,      /* (i) the lpc coefficients before bandwidth
  1.7751 +                              expansion */
  1.7752 +       float coef,     /* (i) the bandwidth expansion factor */
  1.7753 +       int length      /* (i) the length of lpc coefficient vectors */
  1.7754 +   );
  1.7755 +
  1.7756 +   void vq(
  1.7757 +       float *Xq,      /* (o) the quantized vector */
  1.7758 +       int *index,     /* (o) the quantization index */
  1.7759 +       const float *CB,/* (i) the vector quantization codebook */
  1.7760 +       float *X,       /* (i) the vector to quantize */
  1.7761 +       int n_cb,       /* (i) the number of vectors in the codebook */
  1.7762 +       int dim         /* (i) the dimension of all vectors */
  1.7763 +   );
  1.7764 +
  1.7765 +   void SplitVQ(
  1.7766 +       float *qX,      /* (o) the quantized vector */
  1.7767 +       int *index,     /* (o) a vector of indexes for all vector
  1.7768 +                              codebooks in the split */
  1.7769 +       float *X,       /* (i) the vector to quantize */
  1.7770 +       const float *CB,/* (i) the quantizer codebook */
  1.7771 +       int nsplit,     /* the number of vector splits */
  1.7772 +       const int *dim, /* the dimension of X and qX */
  1.7773 +       const int *cbsize /* the number of vectors in the codebook */
  1.7774 +   );
  1.7775 +
  1.7776 +
  1.7777 +   void sort_sq(
  1.7778 +       float *xq,      /* (o) the quantized value */
  1.7779 +       int *index,     /* (o) the quantization index */
  1.7780 +       float x,    /* (i) the value to quantize */
  1.7781 +       const float *cb,/* (i) the quantization codebook */
  1.7782 +       int cb_size     /* (i) the size of the quantization codebook */
  1.7783 +   );
  1.7784 +
  1.7785 +   int LSF_check(      /* (o) 1 for stable lsf vectors and 0 for
  1.7786 +
  1.7787 +
  1.7788 +
  1.7789 +Andersen, et al.              Experimental                    [Page 139]
  1.7790 +
  1.7791 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.7792 +
  1.7793 +
  1.7794 +                              nonstable ones */
  1.7795 +       float *lsf,     /* (i) a table of lsf vectors */
  1.7796 +       int dim,    /* (i) the dimension of each lsf vector */
  1.7797 +       int NoAn    /* (i) the number of lsf vectors in the
  1.7798 +                              table */
  1.7799 +   );
  1.7800 +
  1.7801 +   #endif
  1.7802 +
  1.7803 +A.26.  helpfun.c
  1.7804 +
  1.7805 +   /******************************************************************
  1.7806 +
  1.7807 +       iLBC Speech Coder ANSI-C Source Code
  1.7808 +
  1.7809 +       helpfun.c
  1.7810 +
  1.7811 +       Copyright (C) The Internet Society (2004).
  1.7812 +       All Rights Reserved.
  1.7813 +
  1.7814 +   ******************************************************************/
  1.7815 +
  1.7816 +   #include <math.h>
  1.7817 +
  1.7818 +   #include "iLBC_define.h"
  1.7819 +   #include "constants.h"
  1.7820 +
  1.7821 +   /*----------------------------------------------------------------*
  1.7822 +    *  calculation of auto correlation
  1.7823 +    *---------------------------------------------------------------*/
  1.7824 +
  1.7825 +   void autocorr(
  1.7826 +       float *r,       /* (o) autocorrelation vector */
  1.7827 +       const float *x, /* (i) data vector */
  1.7828 +       int N,          /* (i) length of data vector */
  1.7829 +       int order       /* largest lag for calculated
  1.7830 +                          autocorrelations */
  1.7831 +   ){
  1.7832 +       int     lag, n;
  1.7833 +       float   sum;
  1.7834 +
  1.7835 +       for (lag = 0; lag <= order; lag++) {
  1.7836 +           sum = 0;
  1.7837 +           for (n = 0; n < N - lag; n++) {
  1.7838 +               sum += x[n] * x[n+lag];
  1.7839 +           }
  1.7840 +           r[lag] = sum;
  1.7841 +       }
  1.7842 +
  1.7843 +
  1.7844 +
  1.7845 +Andersen, et al.              Experimental                    [Page 140]
  1.7846 +
  1.7847 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.7848 +
  1.7849 +
  1.7850 +   }
  1.7851 +
  1.7852 +   /*----------------------------------------------------------------*
  1.7853 +    *  window multiplication
  1.7854 +    *---------------------------------------------------------------*/
  1.7855 +
  1.7856 +   void window(
  1.7857 +       float *z,       /* (o) the windowed data */
  1.7858 +       const float *x, /* (i) the original data vector */
  1.7859 +       const float *y, /* (i) the window */
  1.7860 +       int N           /* (i) length of all vectors */
  1.7861 +   ){
  1.7862 +       int     i;
  1.7863 +
  1.7864 +       for (i = 0; i < N; i++) {
  1.7865 +           z[i] = x[i] * y[i];
  1.7866 +       }
  1.7867 +   }
  1.7868 +
  1.7869 +   /*----------------------------------------------------------------*
  1.7870 +    *  levinson-durbin solution for lpc coefficients
  1.7871 +    *---------------------------------------------------------------*/
  1.7872 +
  1.7873 +   void levdurb(
  1.7874 +       float *a,       /* (o) lpc coefficient vector starting
  1.7875 +                              with 1.0 */
  1.7876 +       float *k,       /* (o) reflection coefficients */
  1.7877 +       float *r,       /* (i) autocorrelation vector */
  1.7878 +       int order       /* (i) order of lpc filter */
  1.7879 +   ){
  1.7880 +       float  sum, alpha;
  1.7881 +       int     m, m_h, i;
  1.7882 +
  1.7883 +       a[0] = 1.0;
  1.7884 +
  1.7885 +       if (r[0] < EPS) { /* if r[0] <= 0, set LPC coeff. to zero */
  1.7886 +           for (i = 0; i < order; i++) {
  1.7887 +               k[i] = 0;
  1.7888 +               a[i+1] = 0;
  1.7889 +           }
  1.7890 +       } else {
  1.7891 +           a[1] = k[0] = -r[1]/r[0];
  1.7892 +           alpha = r[0] + r[1] * k[0];
  1.7893 +           for (m = 1; m < order; m++){
  1.7894 +               sum = r[m + 1];
  1.7895 +               for (i = 0; i < m; i++){
  1.7896 +                   sum += a[i+1] * r[m - i];
  1.7897 +               }
  1.7898 +
  1.7899 +
  1.7900 +
  1.7901 +Andersen, et al.              Experimental                    [Page 141]
  1.7902 +
  1.7903 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.7904 +
  1.7905 +
  1.7906 +               k[m] = -sum / alpha;
  1.7907 +               alpha += k[m] * sum;
  1.7908 +               m_h = (m + 1) >> 1;
  1.7909 +               for (i = 0; i < m_h; i++){
  1.7910 +                   sum = a[i+1] + k[m] * a[m - i];
  1.7911 +                   a[m - i] += k[m] * a[i+1];
  1.7912 +                   a[i+1] = sum;
  1.7913 +               }
  1.7914 +               a[m+1] = k[m];
  1.7915 +           }
  1.7916 +       }
  1.7917 +   }
  1.7918 +
  1.7919 +   /*----------------------------------------------------------------*
  1.7920 +    *  interpolation between vectors
  1.7921 +    *---------------------------------------------------------------*/
  1.7922 +
  1.7923 +   void interpolate(
  1.7924 +       float *out,      /* (o) the interpolated vector */
  1.7925 +       float *in1,     /* (i) the first vector for the
  1.7926 +                              interpolation */
  1.7927 +       float *in2,     /* (i) the second vector for the
  1.7928 +                              interpolation */
  1.7929 +       float coef,      /* (i) interpolation weights */
  1.7930 +       int length      /* (i) length of all vectors */
  1.7931 +   ){
  1.7932 +       int i;
  1.7933 +       float invcoef;
  1.7934 +
  1.7935 +       invcoef = (float)1.0 - coef;
  1.7936 +       for (i = 0; i < length; i++) {
  1.7937 +           out[i] = coef * in1[i] + invcoef * in2[i];
  1.7938 +       }
  1.7939 +   }
  1.7940 +
  1.7941 +   /*----------------------------------------------------------------*
  1.7942 +    *  lpc bandwidth expansion
  1.7943 +    *---------------------------------------------------------------*/
  1.7944 +
  1.7945 +   void bwexpand(
  1.7946 +       float *out,      /* (o) the bandwidth expanded lpc
  1.7947 +                              coefficients */
  1.7948 +       float *in,      /* (i) the lpc coefficients before bandwidth
  1.7949 +                              expansion */
  1.7950 +       float coef,     /* (i) the bandwidth expansion factor */
  1.7951 +       int length      /* (i) the length of lpc coefficient vectors */
  1.7952 +   ){
  1.7953 +       int i;
  1.7954 +
  1.7955 +
  1.7956 +
  1.7957 +Andersen, et al.              Experimental                    [Page 142]
  1.7958 +
  1.7959 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.7960 +
  1.7961 +
  1.7962 +       float  chirp;
  1.7963 +
  1.7964 +       chirp = coef;
  1.7965 +
  1.7966 +       out[0] = in[0];
  1.7967 +       for (i = 1; i < length; i++) {
  1.7968 +           out[i] = chirp * in[i];
  1.7969 +           chirp *= coef;
  1.7970 +       }
  1.7971 +   }
  1.7972 +
  1.7973 +   /*----------------------------------------------------------------*
  1.7974 +    *  vector quantization
  1.7975 +    *---------------------------------------------------------------*/
  1.7976 +
  1.7977 +   void vq(
  1.7978 +       float *Xq,      /* (o) the quantized vector */
  1.7979 +       int *index,     /* (o) the quantization index */
  1.7980 +       const float *CB,/* (i) the vector quantization codebook */
  1.7981 +       float *X,       /* (i) the vector to quantize */
  1.7982 +       int n_cb,       /* (i) the number of vectors in the codebook */
  1.7983 +       int dim         /* (i) the dimension of all vectors */
  1.7984 +   ){
  1.7985 +       int     i, j;
  1.7986 +       int     pos, minindex;
  1.7987 +       float   dist, tmp, mindist;
  1.7988 +
  1.7989 +       pos = 0;
  1.7990 +       mindist = FLOAT_MAX;
  1.7991 +       minindex = 0;
  1.7992 +       for (j = 0; j < n_cb; j++) {
  1.7993 +           dist = X[0] - CB[pos];
  1.7994 +           dist *= dist;
  1.7995 +           for (i = 1; i < dim; i++) {
  1.7996 +               tmp = X[i] - CB[pos + i];
  1.7997 +               dist += tmp*tmp;
  1.7998 +           }
  1.7999 +
  1.8000 +           if (dist < mindist) {
  1.8001 +               mindist = dist;
  1.8002 +               minindex = j;
  1.8003 +           }
  1.8004 +           pos += dim;
  1.8005 +       }
  1.8006 +       for (i = 0; i < dim; i++) {
  1.8007 +           Xq[i] = CB[minindex*dim + i];
  1.8008 +       }
  1.8009 +       *index = minindex;
  1.8010 +
  1.8011 +
  1.8012 +
  1.8013 +Andersen, et al.              Experimental                    [Page 143]
  1.8014 +
  1.8015 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.8016 +
  1.8017 +
  1.8018 +   }
  1.8019 +
  1.8020 +   /*----------------------------------------------------------------*
  1.8021 +    *  split vector quantization
  1.8022 +    *---------------------------------------------------------------*/
  1.8023 +
  1.8024 +   void SplitVQ(
  1.8025 +       float *qX,      /* (o) the quantized vector */
  1.8026 +       int *index,     /* (o) a vector of indexes for all vector
  1.8027 +                              codebooks in the split */
  1.8028 +       float *X,       /* (i) the vector to quantize */
  1.8029 +       const float *CB,/* (i) the quantizer codebook */
  1.8030 +       int nsplit,     /* the number of vector splits */
  1.8031 +       const int *dim, /* the dimension of X and qX */
  1.8032 +       const int *cbsize /* the number of vectors in the codebook */
  1.8033 +   ){
  1.8034 +       int    cb_pos, X_pos, i;
  1.8035 +
  1.8036 +       cb_pos = 0;
  1.8037 +       X_pos= 0;
  1.8038 +       for (i = 0; i < nsplit; i++) {
  1.8039 +           vq(qX + X_pos, index + i, CB + cb_pos, X + X_pos,
  1.8040 +               cbsize[i], dim[i]);
  1.8041 +           X_pos += dim[i];
  1.8042 +           cb_pos += dim[i] * cbsize[i];
  1.8043 +       }
  1.8044 +   }
  1.8045 +
  1.8046 +   /*----------------------------------------------------------------*
  1.8047 +    *  scalar quantization
  1.8048 +    *---------------------------------------------------------------*/
  1.8049 +
  1.8050 +   void sort_sq(
  1.8051 +       float *xq,      /* (o) the quantized value */
  1.8052 +       int *index,     /* (o) the quantization index */
  1.8053 +       float x,    /* (i) the value to quantize */
  1.8054 +       const float *cb,/* (i) the quantization codebook */
  1.8055 +       int cb_size      /* (i) the size of the quantization codebook */
  1.8056 +   ){
  1.8057 +       int i;
  1.8058 +
  1.8059 +       if (x <= cb[0]) {
  1.8060 +           *index = 0;
  1.8061 +           *xq = cb[0];
  1.8062 +       } else {
  1.8063 +           i = 0;
  1.8064 +           while ((x > cb[i]) && i < cb_size - 1) {
  1.8065 +               i++;
  1.8066 +
  1.8067 +
  1.8068 +
  1.8069 +Andersen, et al.              Experimental                    [Page 144]
  1.8070 +
  1.8071 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.8072 +
  1.8073 +
  1.8074 +           }
  1.8075 +
  1.8076 +           if (x > ((cb[i] + cb[i - 1])/2)) {
  1.8077 +               *index = i;
  1.8078 +               *xq = cb[i];
  1.8079 +           } else {
  1.8080 +               *index = i - 1;
  1.8081 +               *xq = cb[i - 1];
  1.8082 +           }
  1.8083 +       }
  1.8084 +   }
  1.8085 +
  1.8086 +   /*----------------------------------------------------------------*
  1.8087 +    *  check for stability of lsf coefficients
  1.8088 +    *---------------------------------------------------------------*/
  1.8089 +
  1.8090 +   int LSF_check(    /* (o) 1 for stable lsf vectors and 0 for
  1.8091 +                              nonstable ones */
  1.8092 +       float *lsf,     /* (i) a table of lsf vectors */
  1.8093 +       int dim,    /* (i) the dimension of each lsf vector */
  1.8094 +       int NoAn    /* (i) the number of lsf vectors in the
  1.8095 +                              table */
  1.8096 +   ){
  1.8097 +       int k,n,m, Nit=2, change=0,pos;
  1.8098 +       float tmp;
  1.8099 +       static float eps=(float)0.039; /* 50 Hz */
  1.8100 +       static float eps2=(float)0.0195;
  1.8101 +       static float maxlsf=(float)3.14; /* 4000 Hz */
  1.8102 +       static float minlsf=(float)0.01; /* 0 Hz */
  1.8103 +
  1.8104 +       /* LSF separation check*/
  1.8105 +
  1.8106 +       for (n=0; n<Nit; n++) { /* Run through a couple of times */
  1.8107 +           for (m=0; m<NoAn; m++) { /* Number of analyses per frame */
  1.8108 +               for (k=0; k<(dim-1); k++) {
  1.8109 +                   pos=m*dim+k;
  1.8110 +
  1.8111 +                   if ((lsf[pos+1]-lsf[pos])<eps) {
  1.8112 +
  1.8113 +                       if (lsf[pos+1]<lsf[pos]) {
  1.8114 +                           tmp=lsf[pos+1];
  1.8115 +                           lsf[pos+1]= lsf[pos]+eps2;
  1.8116 +                           lsf[pos]= lsf[pos+1]-eps2;
  1.8117 +                       } else {
  1.8118 +                           lsf[pos]-=eps2;
  1.8119 +                           lsf[pos+1]+=eps2;
  1.8120 +                       }
  1.8121 +                       change=1;
  1.8122 +
  1.8123 +
  1.8124 +
  1.8125 +Andersen, et al.              Experimental                    [Page 145]
  1.8126 +
  1.8127 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.8128 +
  1.8129 +
  1.8130 +                   }
  1.8131 +
  1.8132 +                   if (lsf[pos]<minlsf) {
  1.8133 +                       lsf[pos]=minlsf;
  1.8134 +                       change=1;
  1.8135 +                   }
  1.8136 +
  1.8137 +                   if (lsf[pos]>maxlsf) {
  1.8138 +                       lsf[pos]=maxlsf;
  1.8139 +                       change=1;
  1.8140 +                   }
  1.8141 +               }
  1.8142 +           }
  1.8143 +       }
  1.8144 +
  1.8145 +       return change;
  1.8146 +   }
  1.8147 +
  1.8148 +A.27.  hpInput.h
  1.8149 +
  1.8150 +   /******************************************************************
  1.8151 +
  1.8152 +       iLBC Speech Coder ANSI-C Source Code
  1.8153 +
  1.8154 +       hpInput.h
  1.8155 +
  1.8156 +       Copyright (C) The Internet Society (2004).
  1.8157 +       All Rights Reserved.
  1.8158 +
  1.8159 +   ******************************************************************/
  1.8160 +
  1.8161 +   #ifndef __iLBC_HPINPUT_H
  1.8162 +   #define __iLBC_HPINPUT_H
  1.8163 +
  1.8164 +   void hpInput(
  1.8165 +       float *In,  /* (i) vector to filter */
  1.8166 +       int len,    /* (i) length of vector to filter */
  1.8167 +       float *Out, /* (o) the resulting filtered vector */
  1.8168 +       float *mem  /* (i/o) the filter state */
  1.8169 +   );
  1.8170 +
  1.8171 +   #endif
  1.8172 +
  1.8173 +A.28.  hpInput.c
  1.8174 +
  1.8175 +   /******************************************************************
  1.8176 +
  1.8177 +       iLBC Speech Coder ANSI-C Source Code
  1.8178 +
  1.8179 +
  1.8180 +
  1.8181 +Andersen, et al.              Experimental                    [Page 146]
  1.8182 +
  1.8183 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.8184 +
  1.8185 +
  1.8186 +       hpInput.c
  1.8187 +
  1.8188 +       Copyright (C) The Internet Society (2004).
  1.8189 +       All Rights Reserved.
  1.8190 +
  1.8191 +   ******************************************************************/
  1.8192 +
  1.8193 +   #include "constants.h"
  1.8194 +
  1.8195 +   /*----------------------------------------------------------------*
  1.8196 +    *  Input high-pass filter
  1.8197 +    *---------------------------------------------------------------*/
  1.8198 +
  1.8199 +   void hpInput(
  1.8200 +       float *In,  /* (i) vector to filter */
  1.8201 +       int len,    /* (i) length of vector to filter */
  1.8202 +       float *Out, /* (o) the resulting filtered vector */
  1.8203 +       float *mem  /* (i/o) the filter state */
  1.8204 +   ){
  1.8205 +       int i;
  1.8206 +       float *pi, *po;
  1.8207 +
  1.8208 +       /* all-zero section*/
  1.8209 +
  1.8210 +       pi = &In[0];
  1.8211 +       po = &Out[0];
  1.8212 +       for (i=0; i<len; i++) {
  1.8213 +           *po = hpi_zero_coefsTbl[0] * (*pi);
  1.8214 +           *po += hpi_zero_coefsTbl[1] * mem[0];
  1.8215 +           *po += hpi_zero_coefsTbl[2] * mem[1];
  1.8216 +
  1.8217 +           mem[1] = mem[0];
  1.8218 +           mem[0] = *pi;
  1.8219 +           po++;
  1.8220 +           pi++;
  1.8221 +
  1.8222 +       }
  1.8223 +
  1.8224 +       /* all-pole section*/
  1.8225 +
  1.8226 +       po = &Out[0];
  1.8227 +       for (i=0; i<len; i++) {
  1.8228 +           *po -= hpi_pole_coefsTbl[1] * mem[2];
  1.8229 +           *po -= hpi_pole_coefsTbl[2] * mem[3];
  1.8230 +
  1.8231 +           mem[3] = mem[2];
  1.8232 +           mem[2] = *po;
  1.8233 +           po++;
  1.8234 +
  1.8235 +
  1.8236 +
  1.8237 +Andersen, et al.              Experimental                    [Page 147]
  1.8238 +
  1.8239 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.8240 +
  1.8241 +
  1.8242 +       }
  1.8243 +   }
  1.8244 +
  1.8245 +A.29.  hpOutput.h
  1.8246 +
  1.8247 +   /******************************************************************
  1.8248 +
  1.8249 +       iLBC Speech Coder ANSI-C Source Code
  1.8250 +
  1.8251 +       hpOutput.h
  1.8252 +
  1.8253 +       Copyright (C) The Internet Society (2004).
  1.8254 +       All Rights Reserved.
  1.8255 +
  1.8256 +   ******************************************************************/
  1.8257 +
  1.8258 +   #ifndef __iLBC_HPOUTPUT_H
  1.8259 +   #define __iLBC_HPOUTPUT_H
  1.8260 +
  1.8261 +   void hpOutput(
  1.8262 +       float *In,  /* (i) vector to filter */
  1.8263 +       int len,/* (i) length of vector to filter */
  1.8264 +       float *Out, /* (o) the resulting filtered vector */
  1.8265 +       float *mem  /* (i/o) the filter state */
  1.8266 +   );
  1.8267 +
  1.8268 +   #endif
  1.8269 +
  1.8270 +A.30.  hpOutput.c
  1.8271 +
  1.8272 +   /******************************************************************
  1.8273 +
  1.8274 +       iLBC Speech Coder ANSI-C Source Code
  1.8275 +
  1.8276 +       hpOutput.c
  1.8277 +
  1.8278 +       Copyright (C) The Internet Society (2004).
  1.8279 +       All Rights Reserved.
  1.8280 +
  1.8281 +   ******************************************************************/
  1.8282 +
  1.8283 +   #include "constants.h"
  1.8284 +
  1.8285 +   /*----------------------------------------------------------------*
  1.8286 +    *  Output high-pass filter
  1.8287 +    *---------------------------------------------------------------*/
  1.8288 +
  1.8289 +   void hpOutput(
  1.8290 +
  1.8291 +
  1.8292 +
  1.8293 +Andersen, et al.              Experimental                    [Page 148]
  1.8294 +
  1.8295 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.8296 +
  1.8297 +
  1.8298 +       float *In,  /* (i) vector to filter */
  1.8299 +       int len,/* (i) length of vector to filter */
  1.8300 +       float *Out, /* (o) the resulting filtered vector */
  1.8301 +       float *mem  /* (i/o) the filter state */
  1.8302 +   ){
  1.8303 +       int i;
  1.8304 +       float *pi, *po;
  1.8305 +
  1.8306 +       /* all-zero section*/
  1.8307 +
  1.8308 +       pi = &In[0];
  1.8309 +       po = &Out[0];
  1.8310 +       for (i=0; i<len; i++) {
  1.8311 +           *po = hpo_zero_coefsTbl[0] * (*pi);
  1.8312 +           *po += hpo_zero_coefsTbl[1] * mem[0];
  1.8313 +           *po += hpo_zero_coefsTbl[2] * mem[1];
  1.8314 +
  1.8315 +           mem[1] = mem[0];
  1.8316 +           mem[0] = *pi;
  1.8317 +           po++;
  1.8318 +           pi++;
  1.8319 +
  1.8320 +       }
  1.8321 +
  1.8322 +       /* all-pole section*/
  1.8323 +
  1.8324 +       po = &Out[0];
  1.8325 +       for (i=0; i<len; i++) {
  1.8326 +           *po -= hpo_pole_coefsTbl[1] * mem[2];
  1.8327 +           *po -= hpo_pole_coefsTbl[2] * mem[3];
  1.8328 +
  1.8329 +           mem[3] = mem[2];
  1.8330 +           mem[2] = *po;
  1.8331 +           po++;
  1.8332 +       }
  1.8333 +   }
  1.8334 +
  1.8335 +A.31.  iCBConstruct.h
  1.8336 +
  1.8337 +   /******************************************************************
  1.8338 +
  1.8339 +       iLBC Speech Coder ANSI-C Source Code
  1.8340 +
  1.8341 +       iCBConstruct.h
  1.8342 +
  1.8343 +       Copyright (C) The Internet Society (2004).
  1.8344 +       All Rights Reserved.
  1.8345 +
  1.8346 +
  1.8347 +
  1.8348 +
  1.8349 +Andersen, et al.              Experimental                    [Page 149]
  1.8350 +
  1.8351 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.8352 +
  1.8353 +
  1.8354 +   ******************************************************************/
  1.8355 +
  1.8356 +   #ifndef __iLBC_ICBCONSTRUCT_H
  1.8357 +   #define __iLBC_ICBCONSTRUCT_H
  1.8358 +
  1.8359 +   void index_conv_enc(
  1.8360 +       int *index          /* (i/o) Codebook indexes */
  1.8361 +   );
  1.8362 +
  1.8363 +   void index_conv_dec(
  1.8364 +       int *index          /* (i/o) Codebook indexes */
  1.8365 +   );
  1.8366 +
  1.8367 +   void iCBConstruct(
  1.8368 +       float *decvector,   /* (o) Decoded vector */
  1.8369 +       int *index,         /* (i) Codebook indices */
  1.8370 +       int *gain_index,/* (i) Gain quantization indices */
  1.8371 +       float *mem,         /* (i) Buffer for codevector construction */
  1.8372 +       int lMem,           /* (i) Length of buffer */
  1.8373 +       int veclen,         /* (i) Length of vector */
  1.8374 +       int nStages         /* (i) Number of codebook stages */
  1.8375 +   );
  1.8376 +
  1.8377 +   #endif
  1.8378 +
  1.8379 +A.32.  iCBConstruct.c
  1.8380 +
  1.8381 +   /******************************************************************
  1.8382 +
  1.8383 +       iLBC Speech Coder ANSI-C Source Code
  1.8384 +
  1.8385 +       iCBConstruct.c
  1.8386 +
  1.8387 +       Copyright (C) The Internet Society (2004).
  1.8388 +       All Rights Reserved.
  1.8389 +
  1.8390 +   ******************************************************************/
  1.8391 +
  1.8392 +   #include <math.h>
  1.8393 +
  1.8394 +   #include "iLBC_define.h"
  1.8395 +   #include "gainquant.h"
  1.8396 +   #include "getCBvec.h"
  1.8397 +
  1.8398 +   /*----------------------------------------------------------------*
  1.8399 +    *  Convert the codebook indexes to make the search easier
  1.8400 +    *---------------------------------------------------------------*/
  1.8401 +
  1.8402 +
  1.8403 +
  1.8404 +
  1.8405 +Andersen, et al.              Experimental                    [Page 150]
  1.8406 +
  1.8407 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.8408 +
  1.8409 +
  1.8410 +   void index_conv_enc(
  1.8411 +       int *index          /* (i/o) Codebook indexes */
  1.8412 +   ){
  1.8413 +       int k;
  1.8414 +
  1.8415 +       for (k=1; k<CB_NSTAGES; k++) {
  1.8416 +
  1.8417 +           if ((index[k]>=108)&&(index[k]<172)) {
  1.8418 +               index[k]-=64;
  1.8419 +           } else if (index[k]>=236) {
  1.8420 +               index[k]-=128;
  1.8421 +           } else {
  1.8422 +               /* ERROR */
  1.8423 +           }
  1.8424 +       }
  1.8425 +   }
  1.8426 +
  1.8427 +   void index_conv_dec(
  1.8428 +       int *index          /* (i/o) Codebook indexes */
  1.8429 +   ){
  1.8430 +       int k;
  1.8431 +
  1.8432 +       for (k=1; k<CB_NSTAGES; k++) {
  1.8433 +
  1.8434 +           if ((index[k]>=44)&&(index[k]<108)) {
  1.8435 +               index[k]+=64;
  1.8436 +           } else if ((index[k]>=108)&&(index[k]<128)) {
  1.8437 +               index[k]+=128;
  1.8438 +           } else {
  1.8439 +               /* ERROR */
  1.8440 +           }
  1.8441 +       }
  1.8442 +   }
  1.8443 +
  1.8444 +   /*----------------------------------------------------------------*
  1.8445 +    *  Construct decoded vector from codebook and gains.
  1.8446 +    *---------------------------------------------------------------*/
  1.8447 +
  1.8448 +   void iCBConstruct(
  1.8449 +       float *decvector,   /* (o) Decoded vector */
  1.8450 +       int *index,         /* (i) Codebook indices */
  1.8451 +       int *gain_index,/* (i) Gain quantization indices */
  1.8452 +       float *mem,         /* (i) Buffer for codevector construction */
  1.8453 +       int lMem,           /* (i) Length of buffer */
  1.8454 +       int veclen,         /* (i) Length of vector */
  1.8455 +       int nStages         /* (i) Number of codebook stages */
  1.8456 +   ){
  1.8457 +       int j,k;
  1.8458 +
  1.8459 +
  1.8460 +
  1.8461 +Andersen, et al.              Experimental                    [Page 151]
  1.8462 +
  1.8463 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.8464 +
  1.8465 +
  1.8466 +       float gain[CB_NSTAGES];
  1.8467 +       float cbvec[SUBL];
  1.8468 +
  1.8469 +       /* gain de-quantization */
  1.8470 +
  1.8471 +       gain[0] = gaindequant(gain_index[0], 1.0, 32);
  1.8472 +       if (nStages > 1) {
  1.8473 +           gain[1] = gaindequant(gain_index[1],
  1.8474 +               (float)fabs(gain[0]), 16);
  1.8475 +       }
  1.8476 +       if (nStages > 2) {
  1.8477 +           gain[2] = gaindequant(gain_index[2],
  1.8478 +               (float)fabs(gain[1]), 8);
  1.8479 +       }
  1.8480 +
  1.8481 +       /* codebook vector construction and construction of
  1.8482 +       total vector */
  1.8483 +
  1.8484 +       getCBvec(cbvec, mem, index[0], lMem, veclen);
  1.8485 +       for (j=0;j<veclen;j++){
  1.8486 +           decvector[j] = gain[0]*cbvec[j];
  1.8487 +       }
  1.8488 +       if (nStages > 1) {
  1.8489 +           for (k=1; k<nStages; k++) {
  1.8490 +               getCBvec(cbvec, mem, index[k], lMem, veclen);
  1.8491 +               for (j=0;j<veclen;j++) {
  1.8492 +                   decvector[j] += gain[k]*cbvec[j];
  1.8493 +               }
  1.8494 +           }
  1.8495 +       }
  1.8496 +   }
  1.8497 +
  1.8498 +A.33.  iCBSearch.h
  1.8499 +
  1.8500 +   /******************************************************************
  1.8501 +
  1.8502 +       iLBC Speech Coder ANSI-C Source Code
  1.8503 +
  1.8504 +       iCBSearch.h
  1.8505 +
  1.8506 +       Copyright (C) The Internet Society (2004).
  1.8507 +       All Rights Reserved.
  1.8508 +
  1.8509 +   ******************************************************************/
  1.8510 +
  1.8511 +   #ifndef __iLBC_ICBSEARCH_H
  1.8512 +   #define __iLBC_ICBSEARCH_H
  1.8513 +
  1.8514 +
  1.8515 +
  1.8516 +
  1.8517 +Andersen, et al.              Experimental                    [Page 152]
  1.8518 +
  1.8519 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.8520 +
  1.8521 +
  1.8522 +   void iCBSearch(
  1.8523 +       iLBC_Enc_Inst_t *iLBCenc_inst,
  1.8524 +                           /* (i) the encoder state structure */
  1.8525 +       int *index,         /* (o) Codebook indices */
  1.8526 +       int *gain_index,/* (o) Gain quantization indices */
  1.8527 +       float *intarget,/* (i) Target vector for encoding */
  1.8528 +       float *mem,         /* (i) Buffer for codebook construction */
  1.8529 +       int lMem,           /* (i) Length of buffer */
  1.8530 +       int lTarget,    /* (i) Length of vector */
  1.8531 +       int nStages,    /* (i) Number of codebook stages */
  1.8532 +       float *weightDenum, /* (i) weighting filter coefficients */
  1.8533 +       float *weightState, /* (i) weighting filter state */
  1.8534 +       int block           /* (i) the sub-block number */
  1.8535 +   );
  1.8536 +
  1.8537 +   #endif
  1.8538 +
  1.8539 +A.34.  iCBSearch.c
  1.8540 +
  1.8541 +   /******************************************************************
  1.8542 +
  1.8543 +       iLBC Speech Coder ANSI-C Source Code
  1.8544 +
  1.8545 +       iCBSearch.c
  1.8546 +
  1.8547 +       Copyright (C) The Internet Society (2004).
  1.8548 +       All Rights Reserved.
  1.8549 +
  1.8550 +   ******************************************************************/
  1.8551 +
  1.8552 +   #include <math.h>
  1.8553 +   #include <string.h>
  1.8554 +
  1.8555 +   #include "iLBC_define.h"
  1.8556 +   #include "gainquant.h"
  1.8557 +   #include "createCB.h"
  1.8558 +   #include "filter.h"
  1.8559 +   #include "constants.h"
  1.8560 +
  1.8561 +   /*----------------------------------------------------------------*
  1.8562 +    *  Search routine for codebook encoding and gain quantization.
  1.8563 +    *---------------------------------------------------------------*/
  1.8564 +
  1.8565 +   void iCBSearch(
  1.8566 +       iLBC_Enc_Inst_t *iLBCenc_inst,
  1.8567 +                           /* (i) the encoder state structure */
  1.8568 +       int *index,         /* (o) Codebook indices */
  1.8569 +       int *gain_index,/* (o) Gain quantization indices */
  1.8570 +
  1.8571 +
  1.8572 +
  1.8573 +Andersen, et al.              Experimental                    [Page 153]
  1.8574 +
  1.8575 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.8576 +
  1.8577 +
  1.8578 +       float *intarget,/* (i) Target vector for encoding */
  1.8579 +       float *mem,         /* (i) Buffer for codebook construction */
  1.8580 +       int lMem,           /* (i) Length of buffer */
  1.8581 +       int lTarget,    /* (i) Length of vector */
  1.8582 +       int nStages,    /* (i) Number of codebook stages */
  1.8583 +       float *weightDenum, /* (i) weighting filter coefficients */
  1.8584 +       float *weightState, /* (i) weighting filter state */
  1.8585 +       int block           /* (i) the sub-block number */
  1.8586 +   ){
  1.8587 +       int i, j, icount, stage, best_index, range, counter;
  1.8588 +       float max_measure, gain, measure, crossDot, ftmp;
  1.8589 +       float gains[CB_NSTAGES];
  1.8590 +       float target[SUBL];
  1.8591 +       int base_index, sInd, eInd, base_size;
  1.8592 +       int sIndAug=0, eIndAug=0;
  1.8593 +       float buf[CB_MEML+SUBL+2*LPC_FILTERORDER];
  1.8594 +       float invenergy[CB_EXPAND*128], energy[CB_EXPAND*128];
  1.8595 +       float *pp, *ppi=0, *ppo=0, *ppe=0;
  1.8596 +       float cbvectors[CB_MEML];
  1.8597 +       float tene, cene, cvec[SUBL];
  1.8598 +       float aug_vec[SUBL];
  1.8599 +
  1.8600 +       memset(cvec,0,SUBL*sizeof(float));
  1.8601 +
  1.8602 +       /* Determine size of codebook sections */
  1.8603 +
  1.8604 +       base_size=lMem-lTarget+1;
  1.8605 +
  1.8606 +       if (lTarget==SUBL) {
  1.8607 +           base_size=lMem-lTarget+1+lTarget/2;
  1.8608 +       }
  1.8609 +
  1.8610 +       /* setup buffer for weighting */
  1.8611 +
  1.8612 +       memcpy(buf,weightState,sizeof(float)*LPC_FILTERORDER);
  1.8613 +       memcpy(buf+LPC_FILTERORDER,mem,lMem*sizeof(float));
  1.8614 +       memcpy(buf+LPC_FILTERORDER+lMem,intarget,lTarget*sizeof(float));
  1.8615 +
  1.8616 +       /* weighting */
  1.8617 +
  1.8618 +       AllPoleFilter(buf+LPC_FILTERORDER, weightDenum,
  1.8619 +           lMem+lTarget, LPC_FILTERORDER);
  1.8620 +
  1.8621 +       /* Construct the codebook and target needed */
  1.8622 +
  1.8623 +       memcpy(target, buf+LPC_FILTERORDER+lMem, lTarget*sizeof(float));
  1.8624 +
  1.8625 +       tene=0.0;
  1.8626 +
  1.8627 +
  1.8628 +
  1.8629 +Andersen, et al.              Experimental                    [Page 154]
  1.8630 +
  1.8631 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.8632 +
  1.8633 +
  1.8634 +       for (i=0; i<lTarget; i++) {
  1.8635 +           tene+=target[i]*target[i];
  1.8636 +       }
  1.8637 +
  1.8638 +       /* Prepare search over one more codebook section. This section
  1.8639 +          is created by filtering the original buffer with a filter. */
  1.8640 +
  1.8641 +       filteredCBvecs(cbvectors, buf+LPC_FILTERORDER, lMem);
  1.8642 +
  1.8643 +       /* The Main Loop over stages */
  1.8644 +
  1.8645 +       for (stage=0; stage<nStages; stage++) {
  1.8646 +
  1.8647 +           range = search_rangeTbl[block][stage];
  1.8648 +
  1.8649 +           /* initialize search measure */
  1.8650 +
  1.8651 +           max_measure = (float)-10000000.0;
  1.8652 +           gain = (float)0.0;
  1.8653 +           best_index = 0;
  1.8654 +
  1.8655 +           /* Compute cross dot product between the target
  1.8656 +              and the CB memory */
  1.8657 +
  1.8658 +           crossDot=0.0;
  1.8659 +           pp=buf+LPC_FILTERORDER+lMem-lTarget;
  1.8660 +           for (j=0; j<lTarget; j++) {
  1.8661 +               crossDot += target[j]*(*pp++);
  1.8662 +           }
  1.8663 +
  1.8664 +           if (stage==0) {
  1.8665 +
  1.8666 +               /* Calculate energy in the first block of
  1.8667 +                 'lTarget' samples. */
  1.8668 +               ppe = energy;
  1.8669 +               ppi = buf+LPC_FILTERORDER+lMem-lTarget-1;
  1.8670 +               ppo = buf+LPC_FILTERORDER+lMem-1;
  1.8671 +
  1.8672 +               *ppe=0.0;
  1.8673 +               pp=buf+LPC_FILTERORDER+lMem-lTarget;
  1.8674 +               for (j=0; j<lTarget; j++) {
  1.8675 +                   *ppe+=(*pp)*(*pp++);
  1.8676 +               }
  1.8677 +
  1.8678 +               if (*ppe>0.0) {
  1.8679 +                   invenergy[0] = (float) 1.0 / (*ppe + EPS);
  1.8680 +               } else {
  1.8681 +                   invenergy[0] = (float) 0.0;
  1.8682 +
  1.8683 +
  1.8684 +
  1.8685 +Andersen, et al.              Experimental                    [Page 155]
  1.8686 +
  1.8687 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.8688 +
  1.8689 +
  1.8690 +               }
  1.8691 +               ppe++;
  1.8692 +
  1.8693 +               measure=(float)-10000000.0;
  1.8694 +
  1.8695 +               if (crossDot > 0.0) {
  1.8696 +                      measure = crossDot*crossDot*invenergy[0];
  1.8697 +               }
  1.8698 +           }
  1.8699 +           else {
  1.8700 +               measure = crossDot*crossDot*invenergy[0];
  1.8701 +           }
  1.8702 +
  1.8703 +           /* check if measure is better */
  1.8704 +           ftmp = crossDot*invenergy[0];
  1.8705 +
  1.8706 +           if ((measure>max_measure) && (fabs(ftmp)<CB_MAXGAIN)) {
  1.8707 +               best_index = 0;
  1.8708 +               max_measure = measure;
  1.8709 +               gain = ftmp;
  1.8710 +           }
  1.8711 +
  1.8712 +           /* loop over the main first codebook section,
  1.8713 +              full search */
  1.8714 +
  1.8715 +           for (icount=1; icount<range; icount++) {
  1.8716 +
  1.8717 +               /* calculate measure */
  1.8718 +
  1.8719 +               crossDot=0.0;
  1.8720 +               pp = buf+LPC_FILTERORDER+lMem-lTarget-icount;
  1.8721 +
  1.8722 +               for (j=0; j<lTarget; j++) {
  1.8723 +                   crossDot += target[j]*(*pp++);
  1.8724 +               }
  1.8725 +
  1.8726 +               if (stage==0) {
  1.8727 +                   *ppe++ = energy[icount-1] + (*ppi)*(*ppi) -
  1.8728 +                       (*ppo)*(*ppo);
  1.8729 +                   ppo--;
  1.8730 +                   ppi--;
  1.8731 +
  1.8732 +                   if (energy[icount]>0.0) {
  1.8733 +                       invenergy[icount] =
  1.8734 +                           (float)1.0/(energy[icount]+EPS);
  1.8735 +                   } else {
  1.8736 +                       invenergy[icount] = (float) 0.0;
  1.8737 +                   }
  1.8738 +
  1.8739 +
  1.8740 +
  1.8741 +Andersen, et al.              Experimental                    [Page 156]
  1.8742 +
  1.8743 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.8744 +
  1.8745 +
  1.8746 +                   measure=(float)-10000000.0;
  1.8747 +
  1.8748 +                   if (crossDot > 0.0) {
  1.8749 +                       measure = crossDot*crossDot*invenergy[icount];
  1.8750 +                   }
  1.8751 +               }
  1.8752 +               else {
  1.8753 +                   measure = crossDot*crossDot*invenergy[icount];
  1.8754 +               }
  1.8755 +
  1.8756 +               /* check if measure is better */
  1.8757 +               ftmp = crossDot*invenergy[icount];
  1.8758 +
  1.8759 +               if ((measure>max_measure) && (fabs(ftmp)<CB_MAXGAIN)) {
  1.8760 +                   best_index = icount;
  1.8761 +                   max_measure = measure;
  1.8762 +                   gain = ftmp;
  1.8763 +               }
  1.8764 +           }
  1.8765 +
  1.8766 +           /* Loop over augmented part in the first codebook
  1.8767 +            * section, full search.
  1.8768 +            * The vectors are interpolated.
  1.8769 +            */
  1.8770 +
  1.8771 +           if (lTarget==SUBL) {
  1.8772 +
  1.8773 +               /* Search for best possible cb vector and
  1.8774 +                  compute the CB-vectors' energy. */
  1.8775 +               searchAugmentedCB(20, 39, stage, base_size-lTarget/2,
  1.8776 +                   target, buf+LPC_FILTERORDER+lMem,
  1.8777 +                   &max_measure, &best_index, &gain, energy,
  1.8778 +                   invenergy);
  1.8779 +           }
  1.8780 +
  1.8781 +           /* set search range for following codebook sections */
  1.8782 +
  1.8783 +           base_index=best_index;
  1.8784 +
  1.8785 +           /* unrestricted search */
  1.8786 +
  1.8787 +           if (CB_RESRANGE == -1) {
  1.8788 +               sInd=0;
  1.8789 +               eInd=range-1;
  1.8790 +               sIndAug=20;
  1.8791 +               eIndAug=39;
  1.8792 +           }
  1.8793 +
  1.8794 +
  1.8795 +
  1.8796 +
  1.8797 +Andersen, et al.              Experimental                    [Page 157]
  1.8798 +
  1.8799 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.8800 +
  1.8801 +
  1.8802 +           /* restricted search around best index from first
  1.8803 +           codebook section */
  1.8804 +
  1.8805 +           else {
  1.8806 +               /* Initialize search indices */
  1.8807 +               sIndAug=0;
  1.8808 +               eIndAug=0;
  1.8809 +               sInd=base_index-CB_RESRANGE/2;
  1.8810 +               eInd=sInd+CB_RESRANGE;
  1.8811 +
  1.8812 +               if (lTarget==SUBL) {
  1.8813 +
  1.8814 +                   if (sInd<0) {
  1.8815 +
  1.8816 +                       sIndAug = 40 + sInd;
  1.8817 +                       eIndAug = 39;
  1.8818 +                       sInd=0;
  1.8819 +
  1.8820 +                   } else if ( base_index < (base_size-20) ) {
  1.8821 +
  1.8822 +                       if (eInd > range) {
  1.8823 +                           sInd -= (eInd-range);
  1.8824 +                           eInd = range;
  1.8825 +                       }
  1.8826 +                   } else { /* base_index >= (base_size-20) */
  1.8827 +
  1.8828 +                       if (sInd < (base_size-20)) {
  1.8829 +                           sIndAug = 20;
  1.8830 +                           sInd = 0;
  1.8831 +                           eInd = 0;
  1.8832 +                           eIndAug = 19 + CB_RESRANGE;
  1.8833 +
  1.8834 +                           if(eIndAug > 39) {
  1.8835 +                               eInd = eIndAug-39;
  1.8836 +                               eIndAug = 39;
  1.8837 +                           }
  1.8838 +                       } else {
  1.8839 +                           sIndAug = 20 + sInd - (base_size-20);
  1.8840 +                           eIndAug = 39;
  1.8841 +                           sInd = 0;
  1.8842 +                           eInd = CB_RESRANGE - (eIndAug-sIndAug+1);
  1.8843 +                       }
  1.8844 +                   }
  1.8845 +
  1.8846 +               } else { /* lTarget = 22 or 23 */
  1.8847 +
  1.8848 +                   if (sInd < 0) {
  1.8849 +                       eInd -= sInd;
  1.8850 +
  1.8851 +
  1.8852 +
  1.8853 +Andersen, et al.              Experimental                    [Page 158]
  1.8854 +
  1.8855 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.8856 +
  1.8857 +
  1.8858 +                       sInd = 0;
  1.8859 +                   }
  1.8860 +
  1.8861 +                   if(eInd > range) {
  1.8862 +                       sInd -= (eInd - range);
  1.8863 +                       eInd = range;
  1.8864 +                   }
  1.8865 +               }
  1.8866 +           }
  1.8867 +
  1.8868 +           /* search of higher codebook section */
  1.8869 +
  1.8870 +           /* index search range */
  1.8871 +           counter = sInd;
  1.8872 +           sInd += base_size;
  1.8873 +           eInd += base_size;
  1.8874 +
  1.8875 +
  1.8876 +           if (stage==0) {
  1.8877 +               ppe = energy+base_size;
  1.8878 +               *ppe=0.0;
  1.8879 +
  1.8880 +               pp=cbvectors+lMem-lTarget;
  1.8881 +               for (j=0; j<lTarget; j++) {
  1.8882 +                   *ppe+=(*pp)*(*pp++);
  1.8883 +               }
  1.8884 +
  1.8885 +               ppi = cbvectors + lMem - 1 - lTarget;
  1.8886 +               ppo = cbvectors + lMem - 1;
  1.8887 +
  1.8888 +               for (j=0; j<(range-1); j++) {
  1.8889 +                   *(ppe+1) = *ppe + (*ppi)*(*ppi) - (*ppo)*(*ppo);
  1.8890 +                   ppo--;
  1.8891 +                   ppi--;
  1.8892 +                   ppe++;
  1.8893 +               }
  1.8894 +           }
  1.8895 +
  1.8896 +           /* loop over search range */
  1.8897 +
  1.8898 +           for (icount=sInd; icount<eInd; icount++) {
  1.8899 +
  1.8900 +               /* calculate measure */
  1.8901 +
  1.8902 +               crossDot=0.0;
  1.8903 +               pp=cbvectors + lMem - (counter++) - lTarget;
  1.8904 +
  1.8905 +               for (j=0;j<lTarget;j++) {
  1.8906 +
  1.8907 +
  1.8908 +
  1.8909 +Andersen, et al.              Experimental                    [Page 159]
  1.8910 +
  1.8911 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.8912 +
  1.8913 +
  1.8914 +                   crossDot += target[j]*(*pp++);
  1.8915 +               }
  1.8916 +
  1.8917 +               if (energy[icount]>0.0) {
  1.8918 +                   invenergy[icount] =(float)1.0/(energy[icount]+EPS);
  1.8919 +               } else {
  1.8920 +                   invenergy[icount] =(float)0.0;
  1.8921 +               }
  1.8922 +
  1.8923 +               if (stage==0) {
  1.8924 +
  1.8925 +                   measure=(float)-10000000.0;
  1.8926 +
  1.8927 +                   if (crossDot > 0.0) {
  1.8928 +                       measure = crossDot*crossDot*
  1.8929 +                           invenergy[icount];
  1.8930 +                   }
  1.8931 +               }
  1.8932 +               else {
  1.8933 +                   measure = crossDot*crossDot*invenergy[icount];
  1.8934 +               }
  1.8935 +
  1.8936 +               /* check if measure is better */
  1.8937 +               ftmp = crossDot*invenergy[icount];
  1.8938 +
  1.8939 +               if ((measure>max_measure) && (fabs(ftmp)<CB_MAXGAIN)) {
  1.8940 +                   best_index = icount;
  1.8941 +                   max_measure = measure;
  1.8942 +                   gain = ftmp;
  1.8943 +               }
  1.8944 +           }
  1.8945 +
  1.8946 +           /* Search the augmented CB inside the limited range. */
  1.8947 +
  1.8948 +           if ((lTarget==SUBL)&&(sIndAug!=0)) {
  1.8949 +               searchAugmentedCB(sIndAug, eIndAug, stage,
  1.8950 +                   2*base_size-20, target, cbvectors+lMem,
  1.8951 +                   &max_measure, &best_index, &gain, energy,
  1.8952 +                   invenergy);
  1.8953 +           }
  1.8954 +
  1.8955 +           /* record best index */
  1.8956 +
  1.8957 +           index[stage] = best_index;
  1.8958 +
  1.8959 +           /* gain quantization */
  1.8960 +
  1.8961 +           if (stage==0){
  1.8962 +
  1.8963 +
  1.8964 +
  1.8965 +Andersen, et al.              Experimental                    [Page 160]
  1.8966 +
  1.8967 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.8968 +
  1.8969 +
  1.8970 +
  1.8971 +               if (gain<0.0){
  1.8972 +                   gain = 0.0;
  1.8973 +               }
  1.8974 +
  1.8975 +               if (gain>CB_MAXGAIN) {
  1.8976 +                   gain = (float)CB_MAXGAIN;
  1.8977 +               }
  1.8978 +               gain = gainquant(gain, 1.0, 32, &gain_index[stage]);
  1.8979 +           }
  1.8980 +           else {
  1.8981 +               if (stage==1) {
  1.8982 +                   gain = gainquant(gain, (float)fabs(gains[stage-1]),
  1.8983 +                       16, &gain_index[stage]);
  1.8984 +               } else {
  1.8985 +                   gain = gainquant(gain, (float)fabs(gains[stage-1]),
  1.8986 +                       8, &gain_index[stage]);
  1.8987 +               }
  1.8988 +           }
  1.8989 +
  1.8990 +           /* Extract the best (according to measure)
  1.8991 +              codebook vector */
  1.8992 +
  1.8993 +           if (lTarget==(STATE_LEN-iLBCenc_inst->state_short_len)) {
  1.8994 +
  1.8995 +               if (index[stage]<base_size) {
  1.8996 +                   pp=buf+LPC_FILTERORDER+lMem-lTarget-index[stage];
  1.8997 +               } else {
  1.8998 +                   pp=cbvectors+lMem-lTarget-
  1.8999 +                       index[stage]+base_size;
  1.9000 +               }
  1.9001 +           } else {
  1.9002 +
  1.9003 +               if (index[stage]<base_size) {
  1.9004 +                   if (index[stage]<(base_size-20)) {
  1.9005 +                       pp=buf+LPC_FILTERORDER+lMem-
  1.9006 +                           lTarget-index[stage];
  1.9007 +                   } else {
  1.9008 +                       createAugmentedVec(index[stage]-base_size+40,
  1.9009 +                               buf+LPC_FILTERORDER+lMem,aug_vec);
  1.9010 +                       pp=aug_vec;
  1.9011 +                   }
  1.9012 +               } else {
  1.9013 +                   int filterno, position;
  1.9014 +
  1.9015 +                   filterno=index[stage]/base_size;
  1.9016 +                   position=index[stage]-filterno*base_size;
  1.9017 +
  1.9018 +
  1.9019 +
  1.9020 +
  1.9021 +Andersen, et al.              Experimental                    [Page 161]
  1.9022 +
  1.9023 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.9024 +
  1.9025 +
  1.9026 +
  1.9027 +                   if (position<(base_size-20)) {
  1.9028 +                       pp=cbvectors+filterno*lMem-lTarget-
  1.9029 +                           index[stage]+filterno*base_size;
  1.9030 +                   } else {
  1.9031 +                       createAugmentedVec(
  1.9032 +                           index[stage]-(filterno+1)*base_size+40,
  1.9033 +                           cbvectors+filterno*lMem,aug_vec);
  1.9034 +                       pp=aug_vec;
  1.9035 +                   }
  1.9036 +               }
  1.9037 +           }
  1.9038 +
  1.9039 +           /* Subtract the best codebook vector, according
  1.9040 +              to measure, from the target vector */
  1.9041 +
  1.9042 +           for (j=0;j<lTarget;j++) {
  1.9043 +               cvec[j] += gain*(*pp);
  1.9044 +               target[j] -= gain*(*pp++);
  1.9045 +           }
  1.9046 +
  1.9047 +           /* record quantized gain */
  1.9048 +
  1.9049 +           gains[stage]=gain;
  1.9050 +
  1.9051 +       }/* end of Main Loop. for (stage=0;... */
  1.9052 +
  1.9053 +       /* Gain adjustment for energy matching */
  1.9054 +       cene=0.0;
  1.9055 +       for (i=0; i<lTarget; i++) {
  1.9056 +           cene+=cvec[i]*cvec[i];
  1.9057 +       }
  1.9058 +       j=gain_index[0];
  1.9059 +
  1.9060 +       for (i=gain_index[0]; i<32; i++) {
  1.9061 +           ftmp=cene*gain_sq5Tbl[i]*gain_sq5Tbl[i];
  1.9062 +
  1.9063 +           if ((ftmp<(tene*gains[0]*gains[0])) &&
  1.9064 +               (gain_sq5Tbl[j]<(2.0*gains[0]))) {
  1.9065 +               j=i;
  1.9066 +           }
  1.9067 +       }
  1.9068 +       gain_index[0]=j;
  1.9069 +   }
  1.9070 +
  1.9071 +
  1.9072 +
  1.9073 +
  1.9074 +
  1.9075 +
  1.9076 +
  1.9077 +Andersen, et al.              Experimental                    [Page 162]
  1.9078 +
  1.9079 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.9080 +
  1.9081 +
  1.9082 +A.35.  LPCdecode.h
  1.9083 +
  1.9084 +   /******************************************************************
  1.9085 +
  1.9086 +       iLBC Speech Coder ANSI-C Source Code
  1.9087 +
  1.9088 +       LPC_decode.h
  1.9089 +
  1.9090 +       Copyright (C) The Internet Society (2004).
  1.9091 +       All Rights Reserved.
  1.9092 +
  1.9093 +   ******************************************************************/
  1.9094 +
  1.9095 +   #ifndef __iLBC_LPC_DECODE_H
  1.9096 +   #define __iLBC_LPC_DECODE_H
  1.9097 +
  1.9098 +   void LSFinterpolate2a_dec(
  1.9099 +       float *a,           /* (o) lpc coefficients for a sub-frame */
  1.9100 +       float *lsf1,    /* (i) first lsf coefficient vector */
  1.9101 +       float *lsf2,    /* (i) second lsf coefficient vector */
  1.9102 +       float coef,         /* (i) interpolation weight */
  1.9103 +       int length          /* (i) length of lsf vectors */
  1.9104 +   );
  1.9105 +
  1.9106 +   void SimplelsfDEQ(
  1.9107 +       float *lsfdeq,      /* (o) dequantized lsf coefficients */
  1.9108 +       int *index,         /* (i) quantization index */
  1.9109 +       int lpc_n           /* (i) number of LPCs */
  1.9110 +   );
  1.9111 +
  1.9112 +   void DecoderInterpolateLSF(
  1.9113 +       float *syntdenum,   /* (o) synthesis filter coefficients */
  1.9114 +       float *weightdenum, /* (o) weighting denumerator
  1.9115 +                                  coefficients */
  1.9116 +       float *lsfdeq,      /* (i) dequantized lsf coefficients */
  1.9117 +       int length,         /* (i) length of lsf coefficient vector */
  1.9118 +       iLBC_Dec_Inst_t *iLBCdec_inst
  1.9119 +                           /* (i) the decoder state structure */
  1.9120 +   );
  1.9121 +
  1.9122 +   #endif
  1.9123 +
  1.9124 +
  1.9125 +
  1.9126 +
  1.9127 +
  1.9128 +
  1.9129 +
  1.9130 +
  1.9131 +
  1.9132 +
  1.9133 +Andersen, et al.              Experimental                    [Page 163]
  1.9134 +
  1.9135 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.9136 +
  1.9137 +
  1.9138 +A.36.  LPCdecode.c
  1.9139 +
  1.9140 +   /******************************************************************
  1.9141 +
  1.9142 +       iLBC Speech Coder ANSI-C Source Code
  1.9143 +
  1.9144 +       LPC_decode.c
  1.9145 +
  1.9146 +       Copyright (C) The Internet Society (2004).
  1.9147 +       All Rights Reserved.
  1.9148 +
  1.9149 +   ******************************************************************/
  1.9150 +
  1.9151 +   #include <math.h>
  1.9152 +   #include <string.h>
  1.9153 +
  1.9154 +   #include "helpfun.h"
  1.9155 +   #include "lsf.h"
  1.9156 +   #include "iLBC_define.h"
  1.9157 +   #include "constants.h"
  1.9158 +
  1.9159 +   /*---------------------------------------------------------------*
  1.9160 +    *  interpolation of lsf coefficients for the decoder
  1.9161 +    *--------------------------------------------------------------*/
  1.9162 +
  1.9163 +   void LSFinterpolate2a_dec(
  1.9164 +       float *a,           /* (o) lpc coefficients for a sub-frame */
  1.9165 +       float *lsf1,    /* (i) first lsf coefficient vector */
  1.9166 +       float *lsf2,    /* (i) second lsf coefficient vector */
  1.9167 +       float coef,         /* (i) interpolation weight */
  1.9168 +       int length          /* (i) length of lsf vectors */
  1.9169 +   ){
  1.9170 +       float  lsftmp[LPC_FILTERORDER];
  1.9171 +
  1.9172 +       interpolate(lsftmp, lsf1, lsf2, coef, length);
  1.9173 +       lsf2a(a, lsftmp);
  1.9174 +   }
  1.9175 +
  1.9176 +   /*---------------------------------------------------------------*
  1.9177 +    *  obtain dequantized lsf coefficients from quantization index
  1.9178 +    *--------------------------------------------------------------*/
  1.9179 +
  1.9180 +   void SimplelsfDEQ(
  1.9181 +       float *lsfdeq,    /* (o) dequantized lsf coefficients */
  1.9182 +       int *index,         /* (i) quantization index */
  1.9183 +       int lpc_n           /* (i) number of LPCs */
  1.9184 +   ){
  1.9185 +       int i, j, pos, cb_pos;
  1.9186 +
  1.9187 +
  1.9188 +
  1.9189 +Andersen, et al.              Experimental                    [Page 164]
  1.9190 +
  1.9191 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.9192 +
  1.9193 +
  1.9194 +       /* decode first LSF */
  1.9195 +
  1.9196 +       pos = 0;
  1.9197 +       cb_pos = 0;
  1.9198 +       for (i = 0; i < LSF_NSPLIT; i++) {
  1.9199 +           for (j = 0; j < dim_lsfCbTbl[i]; j++) {
  1.9200 +               lsfdeq[pos + j] = lsfCbTbl[cb_pos +
  1.9201 +                   (long)(index[i])*dim_lsfCbTbl[i] + j];
  1.9202 +           }
  1.9203 +           pos += dim_lsfCbTbl[i];
  1.9204 +           cb_pos += size_lsfCbTbl[i]*dim_lsfCbTbl[i];
  1.9205 +       }
  1.9206 +
  1.9207 +       if (lpc_n>1) {
  1.9208 +
  1.9209 +           /* decode last LSF */
  1.9210 +
  1.9211 +           pos = 0;
  1.9212 +           cb_pos = 0;
  1.9213 +           for (i = 0; i < LSF_NSPLIT; i++) {
  1.9214 +               for (j = 0; j < dim_lsfCbTbl[i]; j++) {
  1.9215 +                   lsfdeq[LPC_FILTERORDER + pos + j] =
  1.9216 +                       lsfCbTbl[cb_pos +
  1.9217 +                       (long)(index[LSF_NSPLIT + i])*
  1.9218 +                       dim_lsfCbTbl[i] + j];
  1.9219 +               }
  1.9220 +               pos += dim_lsfCbTbl[i];
  1.9221 +               cb_pos += size_lsfCbTbl[i]*dim_lsfCbTbl[i];
  1.9222 +           }
  1.9223 +       }
  1.9224 +   }
  1.9225 +
  1.9226 +   /*----------------------------------------------------------------*
  1.9227 +    *  obtain synthesis and weighting filters form lsf coefficients
  1.9228 +    *---------------------------------------------------------------*/
  1.9229 +
  1.9230 +   void DecoderInterpolateLSF(
  1.9231 +       float *syntdenum, /* (o) synthesis filter coefficients */
  1.9232 +       float *weightdenum, /* (o) weighting denumerator
  1.9233 +                                  coefficients */
  1.9234 +       float *lsfdeq,       /* (i) dequantized lsf coefficients */
  1.9235 +       int length,         /* (i) length of lsf coefficient vector */
  1.9236 +       iLBC_Dec_Inst_t *iLBCdec_inst
  1.9237 +                           /* (i) the decoder state structure */
  1.9238 +   ){
  1.9239 +       int    i, pos, lp_length;
  1.9240 +       float  lp[LPC_FILTERORDER + 1], *lsfdeq2;
  1.9241 +
  1.9242 +
  1.9243 +
  1.9244 +
  1.9245 +Andersen, et al.              Experimental                    [Page 165]
  1.9246 +
  1.9247 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.9248 +
  1.9249 +
  1.9250 +       lsfdeq2 = lsfdeq + length;
  1.9251 +       lp_length = length + 1;
  1.9252 +
  1.9253 +       if (iLBCdec_inst->mode==30) {
  1.9254 +           /* sub-frame 1: Interpolation between old and first */
  1.9255 +
  1.9256 +           LSFinterpolate2a_dec(lp, iLBCdec_inst->lsfdeqold, lsfdeq,
  1.9257 +               lsf_weightTbl_30ms[0], length);
  1.9258 +           memcpy(syntdenum,lp,lp_length*sizeof(float));
  1.9259 +           bwexpand(weightdenum, lp, LPC_CHIRP_WEIGHTDENUM,
  1.9260 +               lp_length);
  1.9261 +
  1.9262 +           /* sub-frames 2 to 6: interpolation between first
  1.9263 +              and last LSF */
  1.9264 +
  1.9265 +           pos = lp_length;
  1.9266 +           for (i = 1; i < 6; i++) {
  1.9267 +               LSFinterpolate2a_dec(lp, lsfdeq, lsfdeq2,
  1.9268 +                   lsf_weightTbl_30ms[i], length);
  1.9269 +               memcpy(syntdenum + pos,lp,lp_length*sizeof(float));
  1.9270 +               bwexpand(weightdenum + pos, lp,
  1.9271 +                   LPC_CHIRP_WEIGHTDENUM, lp_length);
  1.9272 +               pos += lp_length;
  1.9273 +           }
  1.9274 +       }
  1.9275 +       else {
  1.9276 +           pos = 0;
  1.9277 +           for (i = 0; i < iLBCdec_inst->nsub; i++) {
  1.9278 +               LSFinterpolate2a_dec(lp, iLBCdec_inst->lsfdeqold,
  1.9279 +                   lsfdeq, lsf_weightTbl_20ms[i], length);
  1.9280 +               memcpy(syntdenum+pos,lp,lp_length*sizeof(float));
  1.9281 +               bwexpand(weightdenum+pos, lp, LPC_CHIRP_WEIGHTDENUM,
  1.9282 +                   lp_length);
  1.9283 +               pos += lp_length;
  1.9284 +           }
  1.9285 +       }
  1.9286 +
  1.9287 +       /* update memory */
  1.9288 +
  1.9289 +       if (iLBCdec_inst->mode==30)
  1.9290 +           memcpy(iLBCdec_inst->lsfdeqold, lsfdeq2,
  1.9291 +                       length*sizeof(float));
  1.9292 +       else
  1.9293 +           memcpy(iLBCdec_inst->lsfdeqold, lsfdeq,
  1.9294 +                       length*sizeof(float));
  1.9295 +
  1.9296 +   }
  1.9297 +
  1.9298 +
  1.9299 +
  1.9300 +
  1.9301 +Andersen, et al.              Experimental                    [Page 166]
  1.9302 +
  1.9303 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.9304 +
  1.9305 +
  1.9306 +A.37.  LPCencode.h
  1.9307 +
  1.9308 +   /******************************************************************
  1.9309 +
  1.9310 +       iLBC Speech Coder ANSI-C Source Code
  1.9311 +
  1.9312 +       LPCencode.h
  1.9313 +
  1.9314 +       Copyright (C) The Internet Society (2004).
  1.9315 +       All Rights Reserved.
  1.9316 +
  1.9317 +   ******************************************************************/
  1.9318 +
  1.9319 +   #ifndef __iLBC_LPCENCOD_H
  1.9320 +   #define __iLBC_LPCENCOD_H
  1.9321 +
  1.9322 +   void LPCencode(
  1.9323 +       float *syntdenum,   /* (i/o) synthesis filter coefficients
  1.9324 +                                  before/after encoding */
  1.9325 +       float *weightdenum, /* (i/o) weighting denumerator coefficients
  1.9326 +                                  before/after encoding */
  1.9327 +       int *lsf_index,     /* (o) lsf quantization index */
  1.9328 +       float *data,    /* (i) lsf coefficients to quantize */
  1.9329 +       iLBC_Enc_Inst_t *iLBCenc_inst
  1.9330 +                           /* (i/o) the encoder state structure */
  1.9331 +   );
  1.9332 +
  1.9333 +   #endif
  1.9334 +
  1.9335 +A.38.  LPCencode.c
  1.9336 +
  1.9337 +   /******************************************************************
  1.9338 +
  1.9339 +       iLBC Speech Coder ANSI-C Source Code
  1.9340 +
  1.9341 +       LPCencode.c
  1.9342 +
  1.9343 +       Copyright (C) The Internet Society (2004).
  1.9344 +       All Rights Reserved.
  1.9345 +
  1.9346 +   ******************************************************************/
  1.9347 +
  1.9348 +   #include <string.h>
  1.9349 +
  1.9350 +   #include "iLBC_define.h"
  1.9351 +   #include "helpfun.h"
  1.9352 +   #include "lsf.h"
  1.9353 +   #include "constants.h"
  1.9354 +
  1.9355 +
  1.9356 +
  1.9357 +Andersen, et al.              Experimental                    [Page 167]
  1.9358 +
  1.9359 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.9360 +
  1.9361 +
  1.9362 +   /*----------------------------------------------------------------*
  1.9363 +    *  lpc analysis (subrutine to LPCencode)
  1.9364 +    *---------------------------------------------------------------*/
  1.9365 +
  1.9366 +   void SimpleAnalysis(
  1.9367 +       float *lsf,         /* (o) lsf coefficients */
  1.9368 +       float *data,    /* (i) new data vector */
  1.9369 +       iLBC_Enc_Inst_t *iLBCenc_inst
  1.9370 +                           /* (i/o) the encoder state structure */
  1.9371 +   ){
  1.9372 +       int k, is;
  1.9373 +       float temp[BLOCKL_MAX], lp[LPC_FILTERORDER + 1];
  1.9374 +       float lp2[LPC_FILTERORDER + 1];
  1.9375 +       float r[LPC_FILTERORDER + 1];
  1.9376 +
  1.9377 +       is=LPC_LOOKBACK+BLOCKL_MAX-iLBCenc_inst->blockl;
  1.9378 +       memcpy(iLBCenc_inst->lpc_buffer+is,data,
  1.9379 +           iLBCenc_inst->blockl*sizeof(float));
  1.9380 +
  1.9381 +       /* No lookahead, last window is asymmetric */
  1.9382 +
  1.9383 +       for (k = 0; k < iLBCenc_inst->lpc_n; k++) {
  1.9384 +
  1.9385 +           is = LPC_LOOKBACK;
  1.9386 +
  1.9387 +           if (k < (iLBCenc_inst->lpc_n - 1)) {
  1.9388 +               window(temp, lpc_winTbl,
  1.9389 +                   iLBCenc_inst->lpc_buffer, BLOCKL_MAX);
  1.9390 +           } else {
  1.9391 +               window(temp, lpc_asymwinTbl,
  1.9392 +                   iLBCenc_inst->lpc_buffer + is, BLOCKL_MAX);
  1.9393 +           }
  1.9394 +
  1.9395 +           autocorr(r, temp, BLOCKL_MAX, LPC_FILTERORDER);
  1.9396 +           window(r, r, lpc_lagwinTbl, LPC_FILTERORDER + 1);
  1.9397 +
  1.9398 +           levdurb(lp, temp, r, LPC_FILTERORDER);
  1.9399 +           bwexpand(lp2, lp, LPC_CHIRP_SYNTDENUM, LPC_FILTERORDER+1);
  1.9400 +
  1.9401 +           a2lsf(lsf + k*LPC_FILTERORDER, lp2);
  1.9402 +       }
  1.9403 +       is=LPC_LOOKBACK+BLOCKL_MAX-iLBCenc_inst->blockl;
  1.9404 +       memmove(iLBCenc_inst->lpc_buffer,
  1.9405 +           iLBCenc_inst->lpc_buffer+LPC_LOOKBACK+BLOCKL_MAX-is,
  1.9406 +           is*sizeof(float));
  1.9407 +   }
  1.9408 +
  1.9409 +   /*----------------------------------------------------------------*
  1.9410 +
  1.9411 +
  1.9412 +
  1.9413 +Andersen, et al.              Experimental                    [Page 168]
  1.9414 +
  1.9415 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.9416 +
  1.9417 +
  1.9418 +    *  lsf interpolator and conversion from lsf to a coefficients
  1.9419 +    *  (subrutine to SimpleInterpolateLSF)
  1.9420 +    *---------------------------------------------------------------*/
  1.9421 +
  1.9422 +   void LSFinterpolate2a_enc(
  1.9423 +       float *a,       /* (o) lpc coefficients */
  1.9424 +       float *lsf1,/* (i) first set of lsf coefficients */
  1.9425 +       float *lsf2,/* (i) second set of lsf coefficients */
  1.9426 +       float coef,     /* (i) weighting coefficient to use between
  1.9427 +                              lsf1 and lsf2 */
  1.9428 +       long length      /* (i) length of coefficient vectors */
  1.9429 +   ){
  1.9430 +       float  lsftmp[LPC_FILTERORDER];
  1.9431 +
  1.9432 +       interpolate(lsftmp, lsf1, lsf2, coef, length);
  1.9433 +       lsf2a(a, lsftmp);
  1.9434 +   }
  1.9435 +
  1.9436 +   /*----------------------------------------------------------------*
  1.9437 +    *  lsf interpolator (subrutine to LPCencode)
  1.9438 +    *---------------------------------------------------------------*/
  1.9439 +
  1.9440 +   void SimpleInterpolateLSF(
  1.9441 +       float *syntdenum,   /* (o) the synthesis filter denominator
  1.9442 +                                  resulting from the quantized
  1.9443 +                                  interpolated lsf */
  1.9444 +       float *weightdenum, /* (o) the weighting filter denominator
  1.9445 +                                  resulting from the unquantized
  1.9446 +                                  interpolated lsf */
  1.9447 +       float *lsf,         /* (i) the unquantized lsf coefficients */
  1.9448 +       float *lsfdeq,      /* (i) the dequantized lsf coefficients */
  1.9449 +       float *lsfold,      /* (i) the unquantized lsf coefficients of
  1.9450 +                                  the previous signal frame */
  1.9451 +       float *lsfdeqold, /* (i) the dequantized lsf coefficients of
  1.9452 +                                  the previous signal frame */
  1.9453 +       int length,         /* (i) should equate LPC_FILTERORDER */
  1.9454 +       iLBC_Enc_Inst_t *iLBCenc_inst
  1.9455 +                           /* (i/o) the encoder state structure */
  1.9456 +   ){
  1.9457 +       int    i, pos, lp_length;
  1.9458 +       float  lp[LPC_FILTERORDER + 1], *lsf2, *lsfdeq2;
  1.9459 +
  1.9460 +       lsf2 = lsf + length;
  1.9461 +       lsfdeq2 = lsfdeq + length;
  1.9462 +       lp_length = length + 1;
  1.9463 +
  1.9464 +       if (iLBCenc_inst->mode==30) {
  1.9465 +           /* sub-frame 1: Interpolation between old and first
  1.9466 +
  1.9467 +
  1.9468 +
  1.9469 +Andersen, et al.              Experimental                    [Page 169]
  1.9470 +
  1.9471 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.9472 +
  1.9473 +
  1.9474 +              set of lsf coefficients */
  1.9475 +
  1.9476 +           LSFinterpolate2a_enc(lp, lsfdeqold, lsfdeq,
  1.9477 +               lsf_weightTbl_30ms[0], length);
  1.9478 +           memcpy(syntdenum,lp,lp_length*sizeof(float));
  1.9479 +           LSFinterpolate2a_enc(lp, lsfold, lsf,
  1.9480 +               lsf_weightTbl_30ms[0], length);
  1.9481 +           bwexpand(weightdenum, lp, LPC_CHIRP_WEIGHTDENUM, lp_length);
  1.9482 +
  1.9483 +           /* sub-frame 2 to 6: Interpolation between first
  1.9484 +              and second set of lsf coefficients */
  1.9485 +
  1.9486 +           pos = lp_length;
  1.9487 +           for (i = 1; i < iLBCenc_inst->nsub; i++) {
  1.9488 +               LSFinterpolate2a_enc(lp, lsfdeq, lsfdeq2,
  1.9489 +                   lsf_weightTbl_30ms[i], length);
  1.9490 +               memcpy(syntdenum + pos,lp,lp_length*sizeof(float));
  1.9491 +
  1.9492 +               LSFinterpolate2a_enc(lp, lsf, lsf2,
  1.9493 +                   lsf_weightTbl_30ms[i], length);
  1.9494 +               bwexpand(weightdenum + pos, lp,
  1.9495 +                   LPC_CHIRP_WEIGHTDENUM, lp_length);
  1.9496 +               pos += lp_length;
  1.9497 +           }
  1.9498 +       }
  1.9499 +       else {
  1.9500 +           pos = 0;
  1.9501 +           for (i = 0; i < iLBCenc_inst->nsub; i++) {
  1.9502 +               LSFinterpolate2a_enc(lp, lsfdeqold, lsfdeq,
  1.9503 +                   lsf_weightTbl_20ms[i], length);
  1.9504 +               memcpy(syntdenum+pos,lp,lp_length*sizeof(float));
  1.9505 +               LSFinterpolate2a_enc(lp, lsfold, lsf,
  1.9506 +                   lsf_weightTbl_20ms[i], length);
  1.9507 +               bwexpand(weightdenum+pos, lp,
  1.9508 +                   LPC_CHIRP_WEIGHTDENUM, lp_length);
  1.9509 +               pos += lp_length;
  1.9510 +           }
  1.9511 +       }
  1.9512 +
  1.9513 +       /* update memory */
  1.9514 +
  1.9515 +       if (iLBCenc_inst->mode==30) {
  1.9516 +           memcpy(lsfold, lsf2, length*sizeof(float));
  1.9517 +           memcpy(lsfdeqold, lsfdeq2, length*sizeof(float));
  1.9518 +       }
  1.9519 +       else {
  1.9520 +           memcpy(lsfold, lsf, length*sizeof(float));
  1.9521 +           memcpy(lsfdeqold, lsfdeq, length*sizeof(float));
  1.9522 +
  1.9523 +
  1.9524 +
  1.9525 +Andersen, et al.              Experimental                    [Page 170]
  1.9526 +
  1.9527 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.9528 +
  1.9529 +
  1.9530 +       }
  1.9531 +   }
  1.9532 +
  1.9533 +   /*----------------------------------------------------------------*
  1.9534 +    *  lsf quantizer (subrutine to LPCencode)
  1.9535 +    *---------------------------------------------------------------*/
  1.9536 +
  1.9537 +   void SimplelsfQ(
  1.9538 +       float *lsfdeq,    /* (o) dequantized lsf coefficients
  1.9539 +                              (dimension FILTERORDER) */
  1.9540 +       int *index,     /* (o) quantization index */
  1.9541 +       float *lsf,      /* (i) the lsf coefficient vector to be
  1.9542 +                              quantized (dimension FILTERORDER ) */
  1.9543 +       int lpc_n     /* (i) number of lsf sets to quantize */
  1.9544 +   ){
  1.9545 +       /* Quantize first LSF with memoryless split VQ */
  1.9546 +       SplitVQ(lsfdeq, index, lsf, lsfCbTbl, LSF_NSPLIT,
  1.9547 +           dim_lsfCbTbl, size_lsfCbTbl);
  1.9548 +
  1.9549 +       if (lpc_n==2) {
  1.9550 +           /* Quantize second LSF with memoryless split VQ */
  1.9551 +           SplitVQ(lsfdeq + LPC_FILTERORDER, index + LSF_NSPLIT,
  1.9552 +               lsf + LPC_FILTERORDER, lsfCbTbl, LSF_NSPLIT,
  1.9553 +               dim_lsfCbTbl, size_lsfCbTbl);
  1.9554 +       }
  1.9555 +   }
  1.9556 +
  1.9557 +   /*----------------------------------------------------------------*
  1.9558 +    *  lpc encoder
  1.9559 +    *---------------------------------------------------------------*/
  1.9560 +
  1.9561 +   void LPCencode(
  1.9562 +       float *syntdenum, /* (i/o) synthesis filter coefficients
  1.9563 +                                  before/after encoding */
  1.9564 +       float *weightdenum, /* (i/o) weighting denumerator
  1.9565 +                                  coefficients before/after
  1.9566 +                                  encoding */
  1.9567 +       int *lsf_index,     /* (o) lsf quantization index */
  1.9568 +       float *data,    /* (i) lsf coefficients to quantize */
  1.9569 +       iLBC_Enc_Inst_t *iLBCenc_inst
  1.9570 +                           /* (i/o) the encoder state structure */
  1.9571 +   ){
  1.9572 +       float lsf[LPC_FILTERORDER * LPC_N_MAX];
  1.9573 +       float lsfdeq[LPC_FILTERORDER * LPC_N_MAX];
  1.9574 +       int change=0;
  1.9575 +
  1.9576 +       SimpleAnalysis(lsf, data, iLBCenc_inst);
  1.9577 +       SimplelsfQ(lsfdeq, lsf_index, lsf, iLBCenc_inst->lpc_n);
  1.9578 +
  1.9579 +
  1.9580 +
  1.9581 +Andersen, et al.              Experimental                    [Page 171]
  1.9582 +
  1.9583 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.9584 +
  1.9585 +
  1.9586 +       change=LSF_check(lsfdeq, LPC_FILTERORDER, iLBCenc_inst->lpc_n);
  1.9587 +       SimpleInterpolateLSF(syntdenum, weightdenum,
  1.9588 +           lsf, lsfdeq, iLBCenc_inst->lsfold,
  1.9589 +           iLBCenc_inst->lsfdeqold, LPC_FILTERORDER, iLBCenc_inst);
  1.9590 +   }
  1.9591 +
  1.9592 +A.39.  lsf.h
  1.9593 +
  1.9594 +   /******************************************************************
  1.9595 +
  1.9596 +       iLBC Speech Coder ANSI-C Source Code
  1.9597 +
  1.9598 +       lsf.h
  1.9599 +
  1.9600 +       Copyright (C) The Internet Society (2004).
  1.9601 +       All Rights Reserved.
  1.9602 +
  1.9603 +   ******************************************************************/
  1.9604 +
  1.9605 +   #ifndef __iLBC_LSF_H
  1.9606 +   #define __iLBC_LSF_H
  1.9607 +
  1.9608 +   void a2lsf(
  1.9609 +       float *freq,/* (o) lsf coefficients */
  1.9610 +       float *a    /* (i) lpc coefficients */
  1.9611 +   );
  1.9612 +
  1.9613 +   void lsf2a(
  1.9614 +       float *a_coef,  /* (o) lpc coefficients */
  1.9615 +       float *freq     /* (i) lsf coefficients */
  1.9616 +   );
  1.9617 +
  1.9618 +   #endif
  1.9619 +
  1.9620 +A.40.  lsf.c
  1.9621 +
  1.9622 +   /******************************************************************
  1.9623 +
  1.9624 +       iLBC Speech Coder ANSI-C Source Code
  1.9625 +
  1.9626 +       lsf.c
  1.9627 +
  1.9628 +       Copyright (C) The Internet Society (2004).
  1.9629 +       All Rights Reserved.
  1.9630 +
  1.9631 +   ******************************************************************/
  1.9632 +
  1.9633 +   #include <string.h>
  1.9634 +
  1.9635 +
  1.9636 +
  1.9637 +Andersen, et al.              Experimental                    [Page 172]
  1.9638 +
  1.9639 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.9640 +
  1.9641 +
  1.9642 +   #include <math.h>
  1.9643 +
  1.9644 +   #include "iLBC_define.h"
  1.9645 +
  1.9646 +   /*----------------------------------------------------------------*
  1.9647 +    *  conversion from lpc coefficients to lsf coefficients
  1.9648 +    *---------------------------------------------------------------*/
  1.9649 +
  1.9650 +   void a2lsf(
  1.9651 +       float *freq,/* (o) lsf coefficients */
  1.9652 +       float *a    /* (i) lpc coefficients */
  1.9653 +   ){
  1.9654 +       float steps[LSF_NUMBER_OF_STEPS] =
  1.9655 +           {(float)0.00635, (float)0.003175, (float)0.0015875,
  1.9656 +           (float)0.00079375};
  1.9657 +       float step;
  1.9658 +       int step_idx;
  1.9659 +       int lsp_index;
  1.9660 +       float p[LPC_HALFORDER];
  1.9661 +       float q[LPC_HALFORDER];
  1.9662 +       float p_pre[LPC_HALFORDER];
  1.9663 +       float q_pre[LPC_HALFORDER];
  1.9664 +       float old_p, old_q, *old;
  1.9665 +       float *pq_coef;
  1.9666 +       float omega, old_omega;
  1.9667 +       int i;
  1.9668 +       float hlp, hlp1, hlp2, hlp3, hlp4, hlp5;
  1.9669 +
  1.9670 +       for (i=0; i<LPC_HALFORDER; i++) {
  1.9671 +           p[i] = (float)-1.0 * (a[i + 1] + a[LPC_FILTERORDER - i]);
  1.9672 +           q[i] = a[LPC_FILTERORDER - i] - a[i + 1];
  1.9673 +       }
  1.9674 +
  1.9675 +       p_pre[0] = (float)-1.0 - p[0];
  1.9676 +       p_pre[1] = - p_pre[0] - p[1];
  1.9677 +       p_pre[2] = - p_pre[1] - p[2];
  1.9678 +       p_pre[3] = - p_pre[2] - p[3];
  1.9679 +       p_pre[4] = - p_pre[3] - p[4];
  1.9680 +       p_pre[4] = p_pre[4] / 2;
  1.9681 +
  1.9682 +       q_pre[0] = (float)1.0 - q[0];
  1.9683 +       q_pre[1] = q_pre[0] - q[1];
  1.9684 +       q_pre[2] = q_pre[1] - q[2];
  1.9685 +       q_pre[3] = q_pre[2] - q[3];
  1.9686 +       q_pre[4] = q_pre[3] - q[4];
  1.9687 +       q_pre[4] = q_pre[4] / 2;
  1.9688 +
  1.9689 +       omega = 0.0;
  1.9690 +
  1.9691 +
  1.9692 +
  1.9693 +Andersen, et al.              Experimental                    [Page 173]
  1.9694 +
  1.9695 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.9696 +
  1.9697 +
  1.9698 +       old_omega = 0.0;
  1.9699 +
  1.9700 +       old_p = FLOAT_MAX;
  1.9701 +       old_q = FLOAT_MAX;
  1.9702 +
  1.9703 +       /* Here we loop through lsp_index to find all the
  1.9704 +          LPC_FILTERORDER roots for omega. */
  1.9705 +
  1.9706 +       for (lsp_index = 0; lsp_index<LPC_FILTERORDER; lsp_index++) {
  1.9707 +
  1.9708 +           /* Depending on lsp_index being even or odd, we
  1.9709 +           alternatively solve the roots for the two LSP equations. */
  1.9710 +
  1.9711 +
  1.9712 +           if ((lsp_index & 0x1) == 0) {
  1.9713 +               pq_coef = p_pre;
  1.9714 +               old = &old_p;
  1.9715 +           } else {
  1.9716 +               pq_coef = q_pre;
  1.9717 +               old = &old_q;
  1.9718 +           }
  1.9719 +
  1.9720 +           /* Start with low resolution grid */
  1.9721 +
  1.9722 +           for (step_idx = 0, step = steps[step_idx];
  1.9723 +               step_idx < LSF_NUMBER_OF_STEPS;){
  1.9724 +
  1.9725 +               /*  cos(10piw) + pq(0)cos(8piw) + pq(1)cos(6piw) +
  1.9726 +               pq(2)cos(4piw) + pq(3)cod(2piw) + pq(4) */
  1.9727 +
  1.9728 +               hlp = (float)cos(omega * TWO_PI);
  1.9729 +               hlp1 = (float)2.0 * hlp + pq_coef[0];
  1.9730 +               hlp2 = (float)2.0 * hlp * hlp1 - (float)1.0 +
  1.9731 +                   pq_coef[1];
  1.9732 +               hlp3 = (float)2.0 * hlp * hlp2 - hlp1 + pq_coef[2];
  1.9733 +               hlp4 = (float)2.0 * hlp * hlp3 - hlp2 + pq_coef[3];
  1.9734 +               hlp5 = hlp * hlp4 - hlp3 + pq_coef[4];
  1.9735 +
  1.9736 +
  1.9737 +               if (((hlp5 * (*old)) <= 0.0) || (omega >= 0.5)){
  1.9738 +
  1.9739 +                   if (step_idx == (LSF_NUMBER_OF_STEPS - 1)){
  1.9740 +
  1.9741 +                       if (fabs(hlp5) >= fabs(*old)) {
  1.9742 +                           freq[lsp_index] = omega - step;
  1.9743 +                       } else {
  1.9744 +                           freq[lsp_index] = omega;
  1.9745 +                       }
  1.9746 +
  1.9747 +
  1.9748 +
  1.9749 +Andersen, et al.              Experimental                    [Page 174]
  1.9750 +
  1.9751 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.9752 +
  1.9753 +
  1.9754 +
  1.9755 +
  1.9756 +                       if ((*old) >= 0.0){
  1.9757 +                           *old = (float)-1.0 * FLOAT_MAX;
  1.9758 +                       } else {
  1.9759 +                           *old = FLOAT_MAX;
  1.9760 +                       }
  1.9761 +
  1.9762 +                       omega = old_omega;
  1.9763 +                       step_idx = 0;
  1.9764 +
  1.9765 +                       step_idx = LSF_NUMBER_OF_STEPS;
  1.9766 +                   } else {
  1.9767 +
  1.9768 +                       if (step_idx == 0) {
  1.9769 +                           old_omega = omega;
  1.9770 +                       }
  1.9771 +
  1.9772 +                       step_idx++;
  1.9773 +                       omega -= steps[step_idx];
  1.9774 +
  1.9775 +                       /* Go back one grid step */
  1.9776 +
  1.9777 +                       step = steps[step_idx];
  1.9778 +                   }
  1.9779 +               } else {
  1.9780 +
  1.9781 +               /* increment omega until they are of different sign,
  1.9782 +               and we know there is at least one root between omega
  1.9783 +               and old_omega */
  1.9784 +                   *old = hlp5;
  1.9785 +                   omega += step;
  1.9786 +               }
  1.9787 +           }
  1.9788 +       }
  1.9789 +
  1.9790 +       for (i = 0; i<LPC_FILTERORDER; i++) {
  1.9791 +           freq[i] = freq[i] * TWO_PI;
  1.9792 +       }
  1.9793 +   }
  1.9794 +
  1.9795 +   /*----------------------------------------------------------------*
  1.9796 +    *  conversion from lsf coefficients to lpc coefficients
  1.9797 +    *---------------------------------------------------------------*/
  1.9798 +
  1.9799 +   void lsf2a(
  1.9800 +       float *a_coef,  /* (o) lpc coefficients */
  1.9801 +       float *freq     /* (i) lsf coefficients */
  1.9802 +
  1.9803 +
  1.9804 +
  1.9805 +Andersen, et al.              Experimental                    [Page 175]
  1.9806 +
  1.9807 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.9808 +
  1.9809 +
  1.9810 +   ){
  1.9811 +       int i, j;
  1.9812 +       float hlp;
  1.9813 +       float p[LPC_HALFORDER], q[LPC_HALFORDER];
  1.9814 +       float a[LPC_HALFORDER + 1], a1[LPC_HALFORDER],
  1.9815 +           a2[LPC_HALFORDER];
  1.9816 +       float b[LPC_HALFORDER + 1], b1[LPC_HALFORDER],
  1.9817 +           b2[LPC_HALFORDER];
  1.9818 +
  1.9819 +       for (i=0; i<LPC_FILTERORDER; i++) {
  1.9820 +           freq[i] = freq[i] * PI2;
  1.9821 +       }
  1.9822 +
  1.9823 +       /* Check input for ill-conditioned cases.  This part is not
  1.9824 +       found in the TIA standard.  It involves the following 2 IF
  1.9825 +       blocks.  If "freq" is judged ill-conditioned, then we first
  1.9826 +       modify freq[0] and freq[LPC_HALFORDER-1] (normally
  1.9827 +       LPC_HALFORDER = 10 for LPC applications), then we adjust
  1.9828 +       the other "freq" values slightly */
  1.9829 +
  1.9830 +
  1.9831 +       if ((freq[0] <= 0.0) || (freq[LPC_FILTERORDER - 1] >= 0.5)){
  1.9832 +
  1.9833 +
  1.9834 +           if (freq[0] <= 0.0) {
  1.9835 +               freq[0] = (float)0.022;
  1.9836 +           }
  1.9837 +
  1.9838 +
  1.9839 +           if (freq[LPC_FILTERORDER - 1] >= 0.5) {
  1.9840 +               freq[LPC_FILTERORDER - 1] = (float)0.499;
  1.9841 +           }
  1.9842 +
  1.9843 +           hlp = (freq[LPC_FILTERORDER - 1] - freq[0]) /
  1.9844 +               (float) (LPC_FILTERORDER - 1);
  1.9845 +
  1.9846 +           for (i=1; i<LPC_FILTERORDER; i++) {
  1.9847 +               freq[i] = freq[i - 1] + hlp;
  1.9848 +           }
  1.9849 +       }
  1.9850 +
  1.9851 +       memset(a1, 0, LPC_HALFORDER*sizeof(float));
  1.9852 +       memset(a2, 0, LPC_HALFORDER*sizeof(float));
  1.9853 +       memset(b1, 0, LPC_HALFORDER*sizeof(float));
  1.9854 +       memset(b2, 0, LPC_HALFORDER*sizeof(float));
  1.9855 +       memset(a, 0, (LPC_HALFORDER+1)*sizeof(float));
  1.9856 +       memset(b, 0, (LPC_HALFORDER+1)*sizeof(float));
  1.9857 +
  1.9858 +
  1.9859 +
  1.9860 +
  1.9861 +Andersen, et al.              Experimental                    [Page 176]
  1.9862 +
  1.9863 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.9864 +
  1.9865 +
  1.9866 +       /* p[i] and q[i] compute cos(2*pi*omega_{2j}) and
  1.9867 +       cos(2*pi*omega_{2j-1} in eqs. 4.2.2.2-1 and 4.2.2.2-2.
  1.9868 +       Note that for this code p[i] specifies the coefficients
  1.9869 +       used in .Q_A(z) while q[i] specifies the coefficients used
  1.9870 +       in .P_A(z) */
  1.9871 +
  1.9872 +       for (i=0; i<LPC_HALFORDER; i++) {
  1.9873 +           p[i] = (float)cos(TWO_PI * freq[2 * i]);
  1.9874 +           q[i] = (float)cos(TWO_PI * freq[2 * i + 1]);
  1.9875 +       }
  1.9876 +
  1.9877 +       a[0] = 0.25;
  1.9878 +       b[0] = 0.25;
  1.9879 +
  1.9880 +       for (i= 0; i<LPC_HALFORDER; i++) {
  1.9881 +           a[i + 1] = a[i] - 2 * p[i] * a1[i] + a2[i];
  1.9882 +           b[i + 1] = b[i] - 2 * q[i] * b1[i] + b2[i];
  1.9883 +           a2[i] = a1[i];
  1.9884 +           a1[i] = a[i];
  1.9885 +           b2[i] = b1[i];
  1.9886 +           b1[i] = b[i];
  1.9887 +       }
  1.9888 +
  1.9889 +       for (j=0; j<LPC_FILTERORDER; j++) {
  1.9890 +
  1.9891 +           if (j == 0) {
  1.9892 +               a[0] = 0.25;
  1.9893 +               b[0] = -0.25;
  1.9894 +           } else {
  1.9895 +               a[0] = b[0] = 0.0;
  1.9896 +           }
  1.9897 +
  1.9898 +           for (i=0; i<LPC_HALFORDER; i++) {
  1.9899 +               a[i + 1] = a[i] - 2 * p[i] * a1[i] + a2[i];
  1.9900 +               b[i + 1] = b[i] - 2 * q[i] * b1[i] + b2[i];
  1.9901 +               a2[i] = a1[i];
  1.9902 +               a1[i] = a[i];
  1.9903 +               b2[i] = b1[i];
  1.9904 +               b1[i] = b[i];
  1.9905 +           }
  1.9906 +
  1.9907 +           a_coef[j + 1] = 2 * (a[LPC_HALFORDER] + b[LPC_HALFORDER]);
  1.9908 +       }
  1.9909 +
  1.9910 +       a_coef[0] = 1.0;
  1.9911 +   }
  1.9912 +
  1.9913 +
  1.9914 +
  1.9915 +
  1.9916 +
  1.9917 +Andersen, et al.              Experimental                    [Page 177]
  1.9918 +
  1.9919 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.9920 +
  1.9921 +
  1.9922 +A.41.  packing.h
  1.9923 +
  1.9924 +   /******************************************************************
  1.9925 +
  1.9926 +       iLBC Speech Coder ANSI-C Source Code
  1.9927 +
  1.9928 +       packing.h
  1.9929 +
  1.9930 +       Copyright (C) The Internet Society (2004).
  1.9931 +       All Rights Reserved.
  1.9932 +
  1.9933 +   ******************************************************************/
  1.9934 +
  1.9935 +   #ifndef __PACKING_H
  1.9936 +   #define __PACKING_H
  1.9937 +
  1.9938 +   void packsplit(
  1.9939 +       int *index,                 /* (i) the value to split */
  1.9940 +       int *firstpart,             /* (o) the value specified by most
  1.9941 +                                          significant bits */
  1.9942 +       int *rest,                  /* (o) the value specified by least
  1.9943 +                                          significant bits */
  1.9944 +       int bitno_firstpart,    /* (i) number of bits in most
  1.9945 +                                          significant part */
  1.9946 +       int bitno_total             /* (i) number of bits in full range
  1.9947 +                                          of value */
  1.9948 +   );
  1.9949 +
  1.9950 +   void packcombine(
  1.9951 +       int *index,                 /* (i/o) the msb value in the
  1.9952 +                                          combined value out */
  1.9953 +       int rest,                   /* (i) the lsb value */
  1.9954 +       int bitno_rest              /* (i) the number of bits in the
  1.9955 +                                          lsb part */
  1.9956 +   );
  1.9957 +
  1.9958 +   void dopack(
  1.9959 +       unsigned char **bitstream,  /* (i/o) on entrance pointer to
  1.9960 +                                          place in bitstream to pack
  1.9961 +                                          new data, on exit pointer
  1.9962 +                                          to place in bitstream to
  1.9963 +                                          pack future data */
  1.9964 +       int index,                  /* (i) the value to pack */
  1.9965 +       int bitno,                  /* (i) the number of bits that the
  1.9966 +                                          value will fit within */
  1.9967 +       int *pos                /* (i/o) write position in the
  1.9968 +                                          current byte */
  1.9969 +   );
  1.9970 +
  1.9971 +
  1.9972 +
  1.9973 +Andersen, et al.              Experimental                    [Page 178]
  1.9974 +
  1.9975 +RFC 3951              Internet Low Bit Rate Codec          December 2004
  1.9976 +
  1.9977 +
  1.9978 +   void unpack(
  1.9979 +       unsigned char **bitstream,  /* (i/o) on entrance pointer to
  1.9980 +                                          place in bitstream to
  1.9981 +                                          unpack new data from, on
  1.9982 +                                          exit pointer to place in
  1.9983 +                                          bitstream to unpack future
  1.9984 +                                          data from */
  1.9985 +       int *index,                 /* (o) resulting value */
  1.9986 +       int bitno,                  /* (i) number of bits used to
  1.9987 +                                          represent the value */
  1.9988 +       int *pos                /* (i/o) read position in the
  1.9989 +                                          current byte */
  1.9990 +   );
  1.9991 +
  1.9992 +   #endif
  1.9993 +
  1.9994 +A.42.  packing.c
  1.9995 +
  1.9996 +   /******************************************************************
  1.9997 +
  1.9998 +       iLBC Speech Coder ANSI-C Source Code
  1.9999 +
 1.10000 +       packing.c
 1.10001 +
 1.10002 +       Copyright (C) The Internet Society (2004).
 1.10003 +       All Rights Reserved.
 1.10004 +
 1.10005 +   ******************************************************************/
 1.10006 +
 1.10007 +   #include <math.h>
 1.10008 +   #include <stdlib.h>
 1.10009 +
 1.10010 +   #include "iLBC_define.h"
 1.10011 +   #include "constants.h"
 1.10012 +   #include "helpfun.h"
 1.10013 +   #include "string.h"
 1.10014 +
 1.10015 +   /*----------------------------------------------------------------*
 1.10016 +    *  splitting an integer into first most significant bits and
 1.10017 +    *  remaining least significant bits
 1.10018 +    *---------------------------------------------------------------*/
 1.10019 +
 1.10020 +   void packsplit(
 1.10021 +       int *index,                 /* (i) the value to split */
 1.10022 +       int *firstpart,             /* (o) the value specified by most
 1.10023 +                                          significant bits */
 1.10024 +       int *rest,                  /* (o) the value specified by least
 1.10025 +                                          significant bits */
 1.10026 +
 1.10027 +
 1.10028 +
 1.10029 +Andersen, et al.              Experimental                    [Page 179]
 1.10030 +
 1.10031 +RFC 3951              Internet Low Bit Rate Codec          December 2004
 1.10032 +
 1.10033 +
 1.10034 +       int bitno_firstpart,    /* (i) number of bits in most
 1.10035 +                                          significant part */
 1.10036 +       int bitno_total             /* (i) number of bits in full range
 1.10037 +                                          of value */
 1.10038 +   ){
 1.10039 +       int bitno_rest = bitno_total-bitno_firstpart;
 1.10040 +
 1.10041 +       *firstpart = *index>>(bitno_rest);
 1.10042 +       *rest = *index-(*firstpart<<(bitno_rest));
 1.10043 +   }
 1.10044 +
 1.10045 +   /*----------------------------------------------------------------*
 1.10046 +    *  combining a value corresponding to msb's with a value
 1.10047 +    *  corresponding to lsb's
 1.10048 +    *---------------------------------------------------------------*/
 1.10049 +
 1.10050 +   void packcombine(
 1.10051 +       int *index,                 /* (i/o) the msb value in the
 1.10052 +                                          combined value out */
 1.10053 +       int rest,                   /* (i) the lsb value */
 1.10054 +       int bitno_rest              /* (i) the number of bits in the
 1.10055 +                                          lsb part */
 1.10056 +   ){
 1.10057 +       *index = *index<<bitno_rest;
 1.10058 +       *index += rest;
 1.10059 +   }
 1.10060 +
 1.10061 +   /*----------------------------------------------------------------*
 1.10062 +    *  packing of bits into bitstream, i.e., vector of bytes
 1.10063 +    *---------------------------------------------------------------*/
 1.10064 +
 1.10065 +   void dopack(
 1.10066 +       unsigned char **bitstream,  /* (i/o) on entrance pointer to
 1.10067 +                                          place in bitstream to pack
 1.10068 +                                          new data, on exit pointer
 1.10069 +                                          to place in bitstream to
 1.10070 +                                          pack future data */
 1.10071 +       int index,                  /* (i) the value to pack */
 1.10072 +       int bitno,                  /* (i) the number of bits that the
 1.10073 +                                          value will fit within */
 1.10074 +       int *pos                /* (i/o) write position in the
 1.10075 +                                          current byte */
 1.10076 +   ){
 1.10077 +       int posLeft;
 1.10078 +
 1.10079 +       /* Clear the bits before starting in a new byte */
 1.10080 +
 1.10081 +       if ((*pos)==0) {
 1.10082 +
 1.10083 +
 1.10084 +
 1.10085 +Andersen, et al.              Experimental                    [Page 180]
 1.10086 +
 1.10087 +RFC 3951              Internet Low Bit Rate Codec          December 2004
 1.10088 +
 1.10089 +
 1.10090 +           **bitstream=0;
 1.10091 +       }
 1.10092 +
 1.10093 +       while (bitno>0) {
 1.10094 +
 1.10095 +           /* Jump to the next byte if end of this byte is reached*/
 1.10096 +
 1.10097 +           if (*pos==8) {
 1.10098 +               *pos=0;
 1.10099 +               (*bitstream)++;
 1.10100 +               **bitstream=0;
 1.10101 +           }
 1.10102 +
 1.10103 +           posLeft=8-(*pos);
 1.10104 +
 1.10105 +           /* Insert index into the bitstream */
 1.10106 +
 1.10107 +           if (bitno <= posLeft) {
 1.10108 +               **bitstream |= (unsigned char)(index<<(posLeft-bitno));
 1.10109 +               *pos+=bitno;
 1.10110 +               bitno=0;
 1.10111 +           } else {
 1.10112 +               **bitstream |= (unsigned char)(index>>(bitno-posLeft));
 1.10113 +
 1.10114 +               *pos=8;
 1.10115 +               index-=((index>>(bitno-posLeft))<<(bitno-posLeft));
 1.10116 +
 1.10117 +               bitno-=posLeft;
 1.10118 +           }
 1.10119 +       }
 1.10120 +   }
 1.10121 +
 1.10122 +   /*----------------------------------------------------------------*
 1.10123 +    *  unpacking of bits from bitstream, i.e., vector of bytes
 1.10124 +    *---------------------------------------------------------------*/
 1.10125 +
 1.10126 +   void unpack(
 1.10127 +       unsigned char **bitstream,  /* (i/o) on entrance pointer to
 1.10128 +                                          place in bitstream to
 1.10129 +                                          unpack new data from, on
 1.10130 +                                          exit pointer to place in
 1.10131 +                                          bitstream to unpack future
 1.10132 +                                          data from */
 1.10133 +       int *index,                 /* (o) resulting value */
 1.10134 +       int bitno,                  /* (i) number of bits used to
 1.10135 +                                          represent the value */
 1.10136 +       int *pos                /* (i/o) read position in the
 1.10137 +                                          current byte */
 1.10138 +
 1.10139 +
 1.10140 +
 1.10141 +Andersen, et al.              Experimental                    [Page 181]
 1.10142 +
 1.10143 +RFC 3951              Internet Low Bit Rate Codec          December 2004
 1.10144 +
 1.10145 +
 1.10146 +   ){
 1.10147 +       int BitsLeft;
 1.10148 +
 1.10149 +       *index=0;
 1.10150 +
 1.10151 +       while (bitno>0) {
 1.10152 +
 1.10153 +           /* move forward in bitstream when the end of the
 1.10154 +              byte is reached */
 1.10155 +
 1.10156 +           if (*pos==8) {
 1.10157 +               *pos=0;
 1.10158 +               (*bitstream)++;
 1.10159 +           }
 1.10160 +
 1.10161 +           BitsLeft=8-(*pos);
 1.10162 +
 1.10163 +           /* Extract bits to index */
 1.10164 +
 1.10165 +           if (BitsLeft>=bitno) {
 1.10166 +               *index+=((((**bitstream)<<(*pos)) & 0xFF)>>(8-bitno));
 1.10167 +
 1.10168 +               *pos+=bitno;
 1.10169 +               bitno=0;
 1.10170 +           } else {
 1.10171 +
 1.10172 +               if ((8-bitno)>0) {
 1.10173 +                   *index+=((((**bitstream)<<(*pos)) & 0xFF)>>
 1.10174 +                       (8-bitno));
 1.10175 +                   *pos=8;
 1.10176 +               } else {
 1.10177 +                   *index+=(((int)(((**bitstream)<<(*pos)) & 0xFF))<<
 1.10178 +                       (bitno-8));
 1.10179 +                   *pos=8;
 1.10180 +               }
 1.10181 +               bitno-=BitsLeft;
 1.10182 +           }
 1.10183 +       }
 1.10184 +   }
 1.10185 +
 1.10186 +A.43.  StateConstructW.h
 1.10187 +
 1.10188 +   /******************************************************************
 1.10189 +
 1.10190 +       iLBC Speech Coder ANSI-C Source Code
 1.10191 +
 1.10192 +       StateConstructW.h
 1.10193 +
 1.10194 +
 1.10195 +
 1.10196 +
 1.10197 +Andersen, et al.              Experimental                    [Page 182]
 1.10198 +
 1.10199 +RFC 3951              Internet Low Bit Rate Codec          December 2004
 1.10200 +
 1.10201 +
 1.10202 +       Copyright (C) The Internet Society (2004).
 1.10203 +       All Rights Reserved.
 1.10204 +
 1.10205 +   ******************************************************************/
 1.10206 +
 1.10207 +   #ifndef __iLBC_STATECONSTRUCTW_H
 1.10208 +   #define __iLBC_STATECONSTRUCTW_H
 1.10209 +
 1.10210 +   void StateConstructW(
 1.10211 +       int idxForMax,      /* (i) 6-bit index for the quantization of
 1.10212 +                                  max amplitude */
 1.10213 +       int *idxVec,    /* (i) vector of quantization indexes */
 1.10214 +       float *syntDenum,   /* (i) synthesis filter denumerator */
 1.10215 +       float *out,         /* (o) the decoded state vector */
 1.10216 +       int len             /* (i) length of a state vector */
 1.10217 +   );
 1.10218 +
 1.10219 +   #endif
 1.10220 +
 1.10221 +A.44.  StateConstructW.c
 1.10222 +
 1.10223 +   /******************************************************************
 1.10224 +
 1.10225 +       iLBC Speech Coder ANSI-C Source Code
 1.10226 +
 1.10227 +       StateConstructW.c
 1.10228 +
 1.10229 +       Copyright (C) The Internet Society (2004).
 1.10230 +       All Rights Reserved.
 1.10231 +
 1.10232 +   ******************************************************************/
 1.10233 +
 1.10234 +   #include <math.h>
 1.10235 +   #include <string.h>
 1.10236 +
 1.10237 +   #include "iLBC_define.h"
 1.10238 +   #include "constants.h"
 1.10239 +   #include "filter.h"
 1.10240 +
 1.10241 +   /*----------------------------------------------------------------*
 1.10242 +    *  decoding of the start state
 1.10243 +    *---------------------------------------------------------------*/
 1.10244 +
 1.10245 +   void StateConstructW(
 1.10246 +       int idxForMax,      /* (i) 6-bit index for the quantization of
 1.10247 +                                  max amplitude */
 1.10248 +       int *idxVec,    /* (i) vector of quantization indexes */
 1.10249 +       float *syntDenum,   /* (i) synthesis filter denumerator */
 1.10250 +
 1.10251 +
 1.10252 +
 1.10253 +Andersen, et al.              Experimental                    [Page 183]
 1.10254 +
 1.10255 +RFC 3951              Internet Low Bit Rate Codec          December 2004
 1.10256 +
 1.10257 +
 1.10258 +       float *out,         /* (o) the decoded state vector */
 1.10259 +       int len             /* (i) length of a state vector */
 1.10260 +   ){
 1.10261 +       float maxVal, tmpbuf[LPC_FILTERORDER+2*STATE_LEN], *tmp,
 1.10262 +           numerator[LPC_FILTERORDER+1];
 1.10263 +       float foutbuf[LPC_FILTERORDER+2*STATE_LEN], *fout;
 1.10264 +       int k,tmpi;
 1.10265 +
 1.10266 +       /* decoding of the maximum value */
 1.10267 +
 1.10268 +       maxVal = state_frgqTbl[idxForMax];
 1.10269 +       maxVal = (float)pow(10,maxVal)/(float)4.5;
 1.10270 +
 1.10271 +       /* initialization of buffers and coefficients */
 1.10272 +
 1.10273 +       memset(tmpbuf, 0, LPC_FILTERORDER*sizeof(float));
 1.10274 +       memset(foutbuf, 0, LPC_FILTERORDER*sizeof(float));
 1.10275 +       for (k=0; k<LPC_FILTERORDER; k++) {
 1.10276 +           numerator[k]=syntDenum[LPC_FILTERORDER-k];
 1.10277 +       }
 1.10278 +       numerator[LPC_FILTERORDER]=syntDenum[0];
 1.10279 +       tmp = &tmpbuf[LPC_FILTERORDER];
 1.10280 +       fout = &foutbuf[LPC_FILTERORDER];
 1.10281 +
 1.10282 +       /* decoding of the sample values */
 1.10283 +
 1.10284 +       for (k=0; k<len; k++) {
 1.10285 +           tmpi = len-1-k;
 1.10286 +           /* maxVal = 1/scal */
 1.10287 +           tmp[k] = maxVal*state_sq3Tbl[idxVec[tmpi]];
 1.10288 +       }
 1.10289 +
 1.10290 +       /* circular convolution with all-pass filter */
 1.10291 +
 1.10292 +       memset(tmp+len, 0, len*sizeof(float));
 1.10293 +       ZeroPoleFilter(tmp, numerator, syntDenum, 2*len,
 1.10294 +           LPC_FILTERORDER, fout);
 1.10295 +       for (k=0;k<len;k++) {
 1.10296 +           out[k] = fout[len-1-k]+fout[2*len-1-k];
 1.10297 +       }
 1.10298 +   }
 1.10299 +
 1.10300 +
 1.10301 +
 1.10302 +
 1.10303 +
 1.10304 +
 1.10305 +
 1.10306 +
 1.10307 +
 1.10308 +
 1.10309 +Andersen, et al.              Experimental                    [Page 184]
 1.10310 +
 1.10311 +RFC 3951              Internet Low Bit Rate Codec          December 2004
 1.10312 +
 1.10313 +
 1.10314 +A.45.  StateSearchW.h
 1.10315 +
 1.10316 +   /******************************************************************
 1.10317 +
 1.10318 +       iLBC Speech Coder ANSI-C Source Code
 1.10319 +
 1.10320 +       StateSearchW.h
 1.10321 +
 1.10322 +       Copyright (C) The Internet Society (2004).
 1.10323 +       All Rights Reserved.
 1.10324 +
 1.10325 +   ******************************************************************/
 1.10326 +
 1.10327 +   #ifndef __iLBC_STATESEARCHW_H
 1.10328 +   #define __iLBC_STATESEARCHW_H
 1.10329 +
 1.10330 +   void AbsQuantW(
 1.10331 +       iLBC_Enc_Inst_t *iLBCenc_inst,
 1.10332 +                           /* (i) Encoder instance */
 1.10333 +       float *in,          /* (i) vector to encode */
 1.10334 +       float *syntDenum,   /* (i) denominator of synthesis filter */
 1.10335 +       float *weightDenum, /* (i) denominator of weighting filter */
 1.10336 +       int *out,           /* (o) vector of quantizer indexes */
 1.10337 +       int len,        /* (i) length of vector to encode and
 1.10338 +                                  vector of quantizer indexes */
 1.10339 +       int state_first     /* (i) position of start state in the
 1.10340 +                                  80 vec */
 1.10341 +   );
 1.10342 +
 1.10343 +   void StateSearchW(
 1.10344 +       iLBC_Enc_Inst_t *iLBCenc_inst,
 1.10345 +                           /* (i) Encoder instance */
 1.10346 +       float *residual,/* (i) target residual vector */
 1.10347 +       float *syntDenum,   /* (i) lpc synthesis filter */
 1.10348 +       float *weightDenum, /* (i) weighting filter denuminator */
 1.10349 +       int *idxForMax,     /* (o) quantizer index for maximum
 1.10350 +                                  amplitude */
 1.10351 +       int *idxVec,    /* (o) vector of quantization indexes */
 1.10352 +       int len,        /* (i) length of all vectors */
 1.10353 +       int state_first     /* (i) position of start state in the
 1.10354 +                                  80 vec */
 1.10355 +   );
 1.10356 +
 1.10357 +
 1.10358 +   #endif
 1.10359 +
 1.10360 +
 1.10361 +
 1.10362 +
 1.10363 +
 1.10364 +
 1.10365 +Andersen, et al.              Experimental                    [Page 185]
 1.10366 +
 1.10367 +RFC 3951              Internet Low Bit Rate Codec          December 2004
 1.10368 +
 1.10369 +
 1.10370 +A.46.  StateSearchW.c
 1.10371 +
 1.10372 +   /******************************************************************
 1.10373 +
 1.10374 +       iLBC Speech Coder ANSI-C Source Code
 1.10375 +
 1.10376 +       StateSearchW.c
 1.10377 +
 1.10378 +       Copyright (C) The Internet Society (2004).
 1.10379 +       All Rights Reserved.
 1.10380 +
 1.10381 +   ******************************************************************/
 1.10382 +
 1.10383 +   #include <math.h>
 1.10384 +   #include <string.h>
 1.10385 +
 1.10386 +   #include "iLBC_define.h"
 1.10387 +   #include "constants.h"
 1.10388 +   #include "filter.h"
 1.10389 +   #include "helpfun.h"
 1.10390 +
 1.10391 +   /*----------------------------------------------------------------*
 1.10392 +    *  predictive noise shaping encoding of scaled start state
 1.10393 +    *  (subrutine for StateSearchW)
 1.10394 +    *---------------------------------------------------------------*/
 1.10395 +
 1.10396 +   void AbsQuantW(
 1.10397 +       iLBC_Enc_Inst_t *iLBCenc_inst,
 1.10398 +                           /* (i) Encoder instance */
 1.10399 +       float *in,          /* (i) vector to encode */
 1.10400 +       float *syntDenum,   /* (i) denominator of synthesis filter */
 1.10401 +       float *weightDenum, /* (i) denominator of weighting filter */
 1.10402 +       int *out,           /* (o) vector of quantizer indexes */
 1.10403 +       int len,        /* (i) length of vector to encode and
 1.10404 +                                  vector of quantizer indexes */
 1.10405 +       int state_first     /* (i) position of start state in the
 1.10406 +                                  80 vec */
 1.10407 +   ){
 1.10408 +       float *syntOut;
 1.10409 +       float syntOutBuf[LPC_FILTERORDER+STATE_SHORT_LEN_30MS];
 1.10410 +       float toQ, xq;
 1.10411 +       int n;
 1.10412 +       int index;
 1.10413 +
 1.10414 +       /* initialization of buffer for filtering */
 1.10415 +
 1.10416 +       memset(syntOutBuf, 0, LPC_FILTERORDER*sizeof(float));
 1.10417 +
 1.10418 +
 1.10419 +
 1.10420 +
 1.10421 +Andersen, et al.              Experimental                    [Page 186]
 1.10422 +
 1.10423 +RFC 3951              Internet Low Bit Rate Codec          December 2004
 1.10424 +
 1.10425 +
 1.10426 +       /* initialization of pointer for filtering */
 1.10427 +
 1.10428 +       syntOut = &syntOutBuf[LPC_FILTERORDER];
 1.10429 +
 1.10430 +       /* synthesis and weighting filters on input */
 1.10431 +
 1.10432 +       if (state_first) {
 1.10433 +           AllPoleFilter (in, weightDenum, SUBL, LPC_FILTERORDER);
 1.10434 +       } else {
 1.10435 +           AllPoleFilter (in, weightDenum,
 1.10436 +               iLBCenc_inst->state_short_len-SUBL,
 1.10437 +               LPC_FILTERORDER);
 1.10438 +       }
 1.10439 +
 1.10440 +       /* encoding loop */
 1.10441 +
 1.10442 +       for (n=0; n<len; n++) {
 1.10443 +
 1.10444 +           /* time update of filter coefficients */
 1.10445 +
 1.10446 +           if ((state_first)&&(n==SUBL)){
 1.10447 +               syntDenum += (LPC_FILTERORDER+1);
 1.10448 +               weightDenum += (LPC_FILTERORDER+1);
 1.10449 +
 1.10450 +               /* synthesis and weighting filters on input */
 1.10451 +               AllPoleFilter (&in[n], weightDenum, len-n,
 1.10452 +                   LPC_FILTERORDER);
 1.10453 +
 1.10454 +           } else if ((state_first==0)&&
 1.10455 +               (n==(iLBCenc_inst->state_short_len-SUBL))) {
 1.10456 +               syntDenum += (LPC_FILTERORDER+1);
 1.10457 +               weightDenum += (LPC_FILTERORDER+1);
 1.10458 +
 1.10459 +               /* synthesis and weighting filters on input */
 1.10460 +               AllPoleFilter (&in[n], weightDenum, len-n,
 1.10461 +                   LPC_FILTERORDER);
 1.10462 +
 1.10463 +           }
 1.10464 +
 1.10465 +           /* prediction of synthesized and weighted input */
 1.10466 +
 1.10467 +           syntOut[n] = 0.0;
 1.10468 +           AllPoleFilter (&syntOut[n], weightDenum, 1,
 1.10469 +               LPC_FILTERORDER);
 1.10470 +
 1.10471 +           /* quantization */
 1.10472 +
 1.10473 +           toQ = in[n]-syntOut[n];
 1.10474 +
 1.10475 +
 1.10476 +
 1.10477 +Andersen, et al.              Experimental                    [Page 187]
 1.10478 +
 1.10479 +RFC 3951              Internet Low Bit Rate Codec          December 2004
 1.10480 +
 1.10481 +
 1.10482 +           sort_sq(&xq, &index, toQ, state_sq3Tbl, 8);
 1.10483 +           out[n]=index;
 1.10484 +           syntOut[n] = state_sq3Tbl[out[n]];
 1.10485 +
 1.10486 +           /* update of the prediction filter */
 1.10487 +
 1.10488 +           AllPoleFilter(&syntOut[n], weightDenum, 1,
 1.10489 +               LPC_FILTERORDER);
 1.10490 +       }
 1.10491 +   }
 1.10492 +
 1.10493 +   /*----------------------------------------------------------------*
 1.10494 +    *  encoding of start state
 1.10495 +    *---------------------------------------------------------------*/
 1.10496 +
 1.10497 +   void StateSearchW(
 1.10498 +       iLBC_Enc_Inst_t *iLBCenc_inst,
 1.10499 +                           /* (i) Encoder instance */
 1.10500 +       float *residual,/* (i) target residual vector */
 1.10501 +       float *syntDenum,   /* (i) lpc synthesis filter */
 1.10502 +       float *weightDenum, /* (i) weighting filter denuminator */
 1.10503 +       int *idxForMax,     /* (o) quantizer index for maximum
 1.10504 +                                  amplitude */
 1.10505 +       int *idxVec,    /* (o) vector of quantization indexes */
 1.10506 +       int len,        /* (i) length of all vectors */
 1.10507 +       int state_first     /* (i) position of start state in the
 1.10508 +                                  80 vec */
 1.10509 +   ){
 1.10510 +       float dtmp, maxVal;
 1.10511 +       float tmpbuf[LPC_FILTERORDER+2*STATE_SHORT_LEN_30MS];
 1.10512 +       float *tmp, numerator[1+LPC_FILTERORDER];
 1.10513 +       float foutbuf[LPC_FILTERORDER+2*STATE_SHORT_LEN_30MS], *fout;
 1.10514 +       int k;
 1.10515 +       float qmax, scal;
 1.10516 +
 1.10517 +       /* initialization of buffers and filter coefficients */
 1.10518 +
 1.10519 +       memset(tmpbuf, 0, LPC_FILTERORDER*sizeof(float));
 1.10520 +       memset(foutbuf, 0, LPC_FILTERORDER*sizeof(float));
 1.10521 +       for (k=0; k<LPC_FILTERORDER; k++) {
 1.10522 +           numerator[k]=syntDenum[LPC_FILTERORDER-k];
 1.10523 +       }
 1.10524 +       numerator[LPC_FILTERORDER]=syntDenum[0];
 1.10525 +       tmp = &tmpbuf[LPC_FILTERORDER];
 1.10526 +       fout = &foutbuf[LPC_FILTERORDER];
 1.10527 +
 1.10528 +       /* circular convolution with the all-pass filter */
 1.10529 +
 1.10530 +
 1.10531 +
 1.10532 +
 1.10533 +Andersen, et al.              Experimental                    [Page 188]
 1.10534 +
 1.10535 +RFC 3951              Internet Low Bit Rate Codec          December 2004
 1.10536 +
 1.10537 +
 1.10538 +       memcpy(tmp, residual, len*sizeof(float));
 1.10539 +       memset(tmp+len, 0, len*sizeof(float));
 1.10540 +       ZeroPoleFilter(tmp, numerator, syntDenum, 2*len,
 1.10541 +           LPC_FILTERORDER, fout);
 1.10542 +       for (k=0; k<len; k++) {
 1.10543 +           fout[k] += fout[k+len];
 1.10544 +       }
 1.10545 +
 1.10546 +       /* identification of the maximum amplitude value */
 1.10547 +
 1.10548 +       maxVal = fout[0];
 1.10549 +       for (k=1; k<len; k++) {
 1.10550 +
 1.10551 +           if (fout[k]*fout[k] > maxVal*maxVal){
 1.10552 +               maxVal = fout[k];
 1.10553 +           }
 1.10554 +       }
 1.10555 +       maxVal=(float)fabs(maxVal);
 1.10556 +
 1.10557 +       /* encoding of the maximum amplitude value */
 1.10558 +
 1.10559 +       if (maxVal < 10.0) {
 1.10560 +           maxVal = 10.0;
 1.10561 +       }
 1.10562 +       maxVal = (float)log10(maxVal);
 1.10563 +       sort_sq(&dtmp, idxForMax, maxVal, state_frgqTbl, 64);
 1.10564 +
 1.10565 +       /* decoding of the maximum amplitude representation value,
 1.10566 +          and corresponding scaling of start state */
 1.10567 +
 1.10568 +       maxVal=state_frgqTbl[*idxForMax];
 1.10569 +       qmax = (float)pow(10,maxVal);
 1.10570 +       scal = (float)(4.5)/qmax;
 1.10571 +       for (k=0; k<len; k++){
 1.10572 +           fout[k] *= scal;
 1.10573 +       }
 1.10574 +
 1.10575 +       /* predictive noise shaping encoding of scaled start state */
 1.10576 +
 1.10577 +       AbsQuantW(iLBCenc_inst, fout,syntDenum,
 1.10578 +           weightDenum,idxVec, len, state_first);
 1.10579 +   }
 1.10580 +
 1.10581 +
 1.10582 +
 1.10583 +
 1.10584 +
 1.10585 +
 1.10586 +
 1.10587 +
 1.10588 +
 1.10589 +Andersen, et al.              Experimental                    [Page 189]
 1.10590 +
 1.10591 +RFC 3951              Internet Low Bit Rate Codec          December 2004
 1.10592 +
 1.10593 +
 1.10594 +A.47.  syntFilter.h
 1.10595 +
 1.10596 +   /******************************************************************
 1.10597 +
 1.10598 +       iLBC Speech Coder ANSI-C Source Code
 1.10599 +
 1.10600 +       syntFilter.h
 1.10601 +
 1.10602 +       Copyright (C) The Internet Society (2004).
 1.10603 +       All Rights Reserved.
 1.10604 +
 1.10605 +   ******************************************************************/
 1.10606 +
 1.10607 +   #ifndef __iLBC_SYNTFILTER_H
 1.10608 +   #define __iLBC_SYNTFILTER_H
 1.10609 +
 1.10610 +   void syntFilter(
 1.10611 +       float *Out,     /* (i/o) Signal to be filtered */
 1.10612 +       float *a,       /* (i) LP parameters */
 1.10613 +       int len,    /* (i) Length of signal */
 1.10614 +       float *mem      /* (i/o) Filter state */
 1.10615 +   );
 1.10616 +
 1.10617 +   #endif
 1.10618 +
 1.10619 +A.48.  syntFilter.c
 1.10620 +
 1.10621 +   /******************************************************************
 1.10622 +
 1.10623 +       iLBC Speech Coder ANSI-C Source Code
 1.10624 +
 1.10625 +       syntFilter.c
 1.10626 +
 1.10627 +       Copyright (C) The Internet Society (2004).
 1.10628 +       All Rights Reserved.
 1.10629 +
 1.10630 +   ******************************************************************/
 1.10631 +
 1.10632 +   #include "iLBC_define.h"
 1.10633 +
 1.10634 +   /*----------------------------------------------------------------*
 1.10635 +    *  LP synthesis filter.
 1.10636 +    *---------------------------------------------------------------*/
 1.10637 +
 1.10638 +   void syntFilter(
 1.10639 +       float *Out,     /* (i/o) Signal to be filtered */
 1.10640 +       float *a,       /* (i) LP parameters */
 1.10641 +       int len,    /* (i) Length of signal */
 1.10642 +
 1.10643 +
 1.10644 +
 1.10645 +Andersen, et al.              Experimental                    [Page 190]
 1.10646 +
 1.10647 +RFC 3951              Internet Low Bit Rate Codec          December 2004
 1.10648 +
 1.10649 +
 1.10650 +       float *mem      /* (i/o) Filter state */
 1.10651 +   ){
 1.10652 +       int i, j;
 1.10653 +       float *po, *pi, *pa, *pm;
 1.10654 +
 1.10655 +       po=Out;
 1.10656 +
 1.10657 +       /* Filter first part using memory from past */
 1.10658 +
 1.10659 +       for (i=0; i<LPC_FILTERORDER; i++) {
 1.10660 +           pi=&Out[i-1];
 1.10661 +           pa=&a[1];
 1.10662 +           pm=&mem[LPC_FILTERORDER-1];
 1.10663 +           for (j=1; j<=i; j++) {
 1.10664 +               *po-=(*pa++)*(*pi--);
 1.10665 +           }
 1.10666 +           for (j=i+1; j<LPC_FILTERORDER+1; j++) {
 1.10667 +               *po-=(*pa++)*(*pm--);
 1.10668 +           }
 1.10669 +           po++;
 1.10670 +       }
 1.10671 +
 1.10672 +       /* Filter last part where the state is entirely in
 1.10673 +          the output vector */
 1.10674 +
 1.10675 +       for (i=LPC_FILTERORDER; i<len; i++) {
 1.10676 +           pi=&Out[i-1];
 1.10677 +           pa=&a[1];
 1.10678 +           for (j=1; j<LPC_FILTERORDER+1; j++) {
 1.10679 +               *po-=(*pa++)*(*pi--);
 1.10680 +           }
 1.10681 +           po++;
 1.10682 +       }
 1.10683 +
 1.10684 +       /* Update state vector */
 1.10685 +
 1.10686 +       memcpy(mem, &Out[len-LPC_FILTERORDER],
 1.10687 +           LPC_FILTERORDER*sizeof(float));
 1.10688 +   }
 1.10689 +
 1.10690 +
 1.10691 +
 1.10692 +
 1.10693 +
 1.10694 +
 1.10695 +
 1.10696 +
 1.10697 +
 1.10698 +
 1.10699 +
 1.10700 +
 1.10701 +Andersen, et al.              Experimental                    [Page 191]
 1.10702 +
 1.10703 +RFC 3951              Internet Low Bit Rate Codec          December 2004
 1.10704 +
 1.10705 +
 1.10706 +Authors' Addresses
 1.10707 +
 1.10708 +   Soren Vang Andersen
 1.10709 +   Department of Communication Technology
 1.10710 +   Aalborg University
 1.10711 +   Fredrik Bajers Vej 7A
 1.10712 +   9200 Aalborg
 1.10713 +   Denmark
 1.10714 +
 1.10715 +   Phone:  ++45 9 6358627
 1.10716 +   EMail:  sva@kom.auc.dk
 1.10717 +
 1.10718 +
 1.10719 +   Alan Duric
 1.10720 +   Telio AS
 1.10721 +   Stoperigt. 2
 1.10722 +   Oslo, N-0250
 1.10723 +   Norway
 1.10724 +
 1.10725 +   Phone:  +47 21673555
 1.10726 +   EMail:  alan.duric@telio.no
 1.10727 +
 1.10728 +
 1.10729 +   Henrik Astrom
 1.10730 +   Global IP Sound AB
 1.10731 +   Olandsgatan 42
 1.10732 +   Stockholm, S-11663
 1.10733 +   Sweden
 1.10734 +
 1.10735 +   Phone:  +46 8 54553040
 1.10736 +   EMail:  henrik.astrom@globalipsound.com
 1.10737 +
 1.10738 +
 1.10739 +   Roar Hagen
 1.10740 +   Global IP Sound AB
 1.10741 +   Olandsgatan 42
 1.10742 +   Stockholm, S-11663
 1.10743 +   Sweden
 1.10744 +
 1.10745 +   Phone:  +46 8 54553040
 1.10746 +   EMail:  roar.hagen@globalipsound.com
 1.10747 +
 1.10748 +
 1.10749 +
 1.10750 +
 1.10751 +
 1.10752 +
 1.10753 +
 1.10754 +
 1.10755 +
 1.10756 +
 1.10757 +Andersen, et al.              Experimental                    [Page 192]
 1.10758 +
 1.10759 +RFC 3951              Internet Low Bit Rate Codec          December 2004
 1.10760 +
 1.10761 +
 1.10762 +   W. Bastiaan Kleijn
 1.10763 +   Global IP Sound AB
 1.10764 +   Olandsgatan 42
 1.10765 +   Stockholm, S-11663
 1.10766 +   Sweden
 1.10767 +
 1.10768 +   Phone:  +46 8 54553040
 1.10769 +   EMail:  bastiaan.kleijn@globalipsound.com
 1.10770 +
 1.10771 +
 1.10772 +   Jan Linden
 1.10773 +   Global IP Sound Inc.
 1.10774 +   900 Kearny Street, suite 500
 1.10775 +   San Francisco, CA-94133
 1.10776 +   USA
 1.10777 +
 1.10778 +   Phone: +1 415 397 2555
 1.10779 +   EMail: jan.linden@globalipsound.com
 1.10780 +
 1.10781 +
 1.10782 +
 1.10783 +
 1.10784 +
 1.10785 +
 1.10786 +
 1.10787 +
 1.10788 +
 1.10789 +
 1.10790 +
 1.10791 +
 1.10792 +
 1.10793 +
 1.10794 +
 1.10795 +
 1.10796 +
 1.10797 +
 1.10798 +
 1.10799 +
 1.10800 +
 1.10801 +
 1.10802 +
 1.10803 +
 1.10804 +
 1.10805 +
 1.10806 +
 1.10807 +
 1.10808 +
 1.10809 +
 1.10810 +
 1.10811 +
 1.10812 +
 1.10813 +Andersen, et al.              Experimental                    [Page 193]
 1.10814 +
 1.10815 +RFC 3951              Internet Low Bit Rate Codec          December 2004
 1.10816 +
 1.10817 +
 1.10818 +Full Copyright Statement
 1.10819 +
 1.10820 +   Copyright (C) The Internet Society (2004).
 1.10821 +
 1.10822 +   This document is subject to the rights, licenses and restrictions
 1.10823 +   contained in BCP 78, and except as set forth therein, the authors
 1.10824 +   retain all their rights.
 1.10825 +
 1.10826 +   This document and the information contained herein are provided on an
 1.10827 +   "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
 1.10828 +   OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
 1.10829 +   ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
 1.10830 +   INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
 1.10831 +   INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
 1.10832 +   WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
 1.10833 +
 1.10834 +Intellectual Property
 1.10835 +
 1.10836 +   The IETF takes no position regarding the validity or scope of any
 1.10837 +   Intellectual Property Rights or other rights that might be claimed to
 1.10838 +   pertain to the implementation or use of the technology described in
 1.10839 +   this document or the extent to which any license under such rights
 1.10840 +   might or might not be available; nor does it represent that it has
 1.10841 +   made any independent effort to identify any such rights.  Information
 1.10842 +   on the IETF's procedures with respect to rights in IETF Documents can
 1.10843 +   be found in BCP 78 and BCP 79.
 1.10844 +
 1.10845 +   Copies of IPR disclosures made to the IETF Secretariat and any
 1.10846 +   assurances of licenses to be made available, or the result of an
 1.10847 +   attempt made to obtain a general license or permission for the use of
 1.10848 +   such proprietary rights by implementers or users of this
 1.10849 +   specification can be obtained from the IETF on-line IPR repository at
 1.10850 +   http://www.ietf.org/ipr.
 1.10851 +
 1.10852 +   The IETF invites any interested party to bring to its attention any
 1.10853 +   copyrights, patents or patent applications, or other proprietary
 1.10854 +   rights that may cover technology that may be required to implement
 1.10855 +   this standard.  Please address the information to the IETF at ietf-
 1.10856 +   ipr@ietf.org.
 1.10857 +
 1.10858 +
 1.10859 +Acknowledgement
 1.10860 +
 1.10861 +   Funding for the RFC Editor function is currently provided by the
 1.10862 +   Internet Society.
 1.10863 +
 1.10864 +
 1.10865 +
 1.10866 +
 1.10867 +
 1.10868 +
 1.10869 +Andersen, et al.              Experimental                    [Page 194]
 1.10870 +