src/g726/g726_40.c

   1 /*
   2  * This source code is a product of Sun Microsystems, Inc. and is provided
   3  * for unrestricted use.  Users may copy or modify this source code without
   4  * charge.
   5  *
   6  * SUN SOURCE CODE IS PROVIDED AS IS WITH NO WARRANTIES OF ANY KIND INCLUDING
   7  * THE WARRANTIES OF DESIGN, MERCHANTIBILITY AND FITNESS FOR A PARTICULAR
   8  * PURPOSE, OR ARISING FROM A COURSE OF DEALING, USAGE OR TRADE PRACTICE.
   9  *
  10  * Sun source code is provided with no support and without any obligation on
  11  * the part of Sun Microsystems, Inc. to assist in its use, correction,
  12  * modification or enhancement.
  13  *
  14  * SUN MICROSYSTEMS, INC. SHALL HAVE NO LIABILITY WITH RESPECT TO THE
  15  * INFRINGEMENT OF COPYRIGHTS, TRADE SECRETS OR ANY PATENTS BY THIS SOFTWARE
  16  * OR ANY PART THEREOF.
  17  *
  18  * In no event will Sun Microsystems, Inc. be liable for any lost revenue
  19  * or profits or other special, indirect and consequential damages, even if
  20  * Sun has been advised of the possibility of such damages.
  21  *
  22  * Sun Microsystems, Inc.
  23  * 2550 Garcia Avenue
  24  * Mountain View, California  94043
  25  */
  26
  27 /*
  28  * g726_40.c
  29  *
  30  * Description:
  31  *
  32  * g723_40_encoder(), g723_40_decoder()
  33  *
  34  * These routines comprise an implementation of the CCITT G.723 40Kbps
  35  * ADPCM coding algorithm.  Essentially, this implementation is identical to
  36  * the bit level description except for a few deviations which
  37  * take advantage of workstation attributes, such as hardware 2's
  38  * complement arithmetic.
  39  *
  40  * The deviation from the bit level specification (lookup tables),
  41  * preserves the bit level performance specifications.
  42  *
  43  * As outlined in the G.723 Recommendation, the algorithm is broken
  44  * down into modules.  Each section of code below is preceded by
  45  * the name of the module which it is implementing.
  46  *
  47  * The ITU-T G.726 coder is an adaptive differential pulse code modulation
  48  * (ADPCM) waveform coding algorithm, suitable for coding of digitized
  49  * telephone bandwidth (0.3-3.4 kHz) speech or audio signals sampled at 8 kHz.
  50  * This coder operates on a sample-by-sample basis. Input samples may be
  51  * represented in linear PCM or companded 8-bit G.711 (m-law/A-law) formats
  52  * (i.e., 64 kbps). For 32 kbps operation, each sample is converted into a
  53  * 4-bit quantized difference signal resulting in a compression ratio of
  54  * 2:1 over the G.711 format. For 24 kbps 40 kbps operation, the quantized
  55  * difference signal is 3 bits and 5 bits, respectively.
  56  *
  57  * $Log$
  58  * Revision 1.4  2002/11/20 04:29:13  robertj
  59  * Included optimisations for G.711 and G.726 codecs, thanks Ted Szoczei
  60  *
  61  * Revision 1.1  2002/02/11 23:24:23  robertj
  62  * Updated to openH323 v1.8.0
  63  *
  64  * Revision 1.2  2002/02/10 21:14:54  dereks
  65  * Add cvs log history to head of the file.
  66  * Ensure file is terminated by a newline.
  67  *
  68  *
  69  *
  70  */
  71
  72 #include "g72x.h"
  73 #include "private.h"
  74
  75 /*
  76  * Maps G.723_40 code word to ructeconstructed scale factor normalized log
  77  * magnitude values.
  78  */
  79 static short    _dqlntab[32] = {-2048, -66, 28, 104, 169, 224, 274, 318,
  80                                 358, 395, 429, 459, 488, 514, 539, 566,
  81                                 566, 539, 514, 488, 459, 429, 395, 358,
  82                                 318, 274, 224, 169, 104, 28, -66, -2048};
  83
  84 /* Maps G.723_40 code word to log of scale factor multiplier. */
  85 static short    _witab[32] = {448, 448, 768, 1248, 1280, 1312, 1856, 3200,
  86                         4512, 5728, 7008, 8960, 11456, 14080, 16928, 22272,
  87                         22272, 16928, 14080, 11456, 8960, 7008, 5728, 4512,
  88                         3200, 1856, 1312, 1280, 1248, 768, 448, 448};
  89
  90 /*
  91  * Maps G.723_40 code words to a set of values whose long and short
  92  * term averages are computed and then compared to give an indication
  93  * how stationary (steady state) the signal is.
  94  */
  95 static short    _fitab[32] = {0, 0, 0, 0, 0, 0x200, 0x200, 0x200,
  96                         0x200, 0x200, 0x400, 0x600, 0x800, 0xA00, 0xC00, 0xC00,
  97                         0xC00, 0xC00, 0xA00, 0x800, 0x600, 0x400, 0x200, 0x200,
  98                         0x200, 0x200, 0x200, 0, 0, 0, 0, 0};
  99
 100 static int qtab_723_40[15] = {-122, -16, 68, 139, 198, 250, 298, 339,
 101                                 378, 413, 445, 475, 502, 528, 553};
 102
 103 /*
 104  * g723_40_encoder()
 105  *
 106  * Encodes a 16-bit linear PCM, A-law or u-law input sample and returns
 107  * the resulting 5-bit CCITT G.723 40Kbps code.
 108  * Returns -1 if the input coding value is invalid.
 109  */
 110 int
 111 g726_40_encoder(
 112         int             sl,
 113         int             in_coding,
 114         g726_state *state_ptr)
 115 {
 116         int             sezi;
 117         int             sez;                    /* ACCUM */
 118         int             sei;
 119         int             se;
 120         int             d;                              /* SUBTA */
 121         int             y;                              /* MIX */
 122         int             i;
 123         int             dq;
 124         int             sr;                             /* ADDB */
 125         int             dqsez;                  /* ADDC */
 126
 127         switch (in_coding) {    /* linearize input sample to 14-bit PCM */
 128         case AUDIO_ENCODING_ALAW:
 129                 sl = alaw2linear(sl) >> 2;
 130                 break;
 131         case AUDIO_ENCODING_ULAW:
 132                 sl = ulaw2linear(sl) >> 2;
 133                 break;
 134         case AUDIO_ENCODING_LINEAR:
 135                 sl >>= 2;               /* sl of 14-bit dynamic range */
 136                 break;
 137         default:
 138                 return (-1);
 139         }
 140
 141         sezi = predictor_zero(state_ptr);
 142         sez = sezi >> 1;
 143         sei = sezi + predictor_pole(state_ptr);
 144         se = sei >> 1;                  /* se = estimated signal */
 145
 146         d = sl - se;                    /* d = estimation difference */
 147
 148         /* quantize prediction difference */
 149         y = step_size(state_ptr);       /* adaptive quantizer step size */
 150         i = quantize(d, y, qtab_723_40, 15);    /* i = ADPCM code */
 151
 152         dq = reconstruct(i & 0x10, _dqlntab[i], y);     /* quantized diff */
 153
 154         sr = (dq < 0) ? se - (dq & 0x7FFF) : se + dq; /* reconstructed signal */
 155
 156         dqsez = sr + sez - se;          /* dqsez = pole prediction diff. */
 157
 158         update(5, y, _witab[i], _fitab[i], dq, sr, dqsez, state_ptr);
 159
 160         return (i);
 161 }
 162
 163 /*
 164  * g723_40_decoder()
 165  *
 166  * Decodes a 5-bit CCITT G.723 40Kbps code and returns
 167  * the resulting 16-bit linear PCM, A-law or u-law sample value.
 168  * -1 is returned if the output coding is unknown.
 169  */
 170 int
 171 g726_40_decoder(
 172         int             i,
 173         int             out_coding,
 174         g726_state *state_ptr)
 175 {
 176         int             sezi;
 177         int             sez;                    /* ACCUM */
 178         int             sei;
 179         int             se;
 180         int             y;                              /* MIX */
 181         int             dq;
 182         int             sr;                             /* ADDB */
 183         int             dqsez;
 184
 185         i &= 0x1f;                              /* mask to get proper bits */
 186         sezi = predictor_zero(state_ptr);
 187         sez = sezi >> 1;
 188         sei = sezi + predictor_pole(state_ptr);
 189         se = sei >> 1;                  /* se = estimated signal */
 190
 191         y = step_size(state_ptr);       /* adaptive quantizer step size */
 192         dq = reconstruct(i & 0x10, _dqlntab[i], y);     /* estimation diff. */
 193
 194         sr = (dq < 0) ? (se - (dq & 0x7FFF)) : (se + dq); /* reconst. signal */
 195
 196         dqsez = sr - se + sez;          /* pole prediction diff. */
 197
 198         update(5, y, _witab[i], _fitab[i], dq, sr, dqsez, state_ptr);
 199
 200         switch (out_coding) {
 201         case AUDIO_ENCODING_ALAW:
 202                 return (tandem_adjust_alaw(sr, se, y, i, 0x10, qtab_723_40));
 203         case AUDIO_ENCODING_ULAW:
 204                 return (tandem_adjust_ulaw(sr, se, y, i, 0x10, qtab_723_40));
 205         case AUDIO_ENCODING_LINEAR:
 206                 return (sr << 2);       /* sr was of 14-bit dynamic range */
 207         default:
 208                 return (-1);
 209         }
 210 }
 211