utils/wxMMedia/adpcm/g723_24.cpp

   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  * g723_24.c
  29  *
  30  * Description:
  31  *
  32  * g723_24_encoder(), g723_24_decoder()
  33  *
  34  * These routines comprise an implementation of the CCITT G.723 24 Kbps
  35  * ADPCM coding algorithm.  Essentially, this implementation is identical to
  36  * the bit level description except for a few deviations which take advantage
  37  * of workstation attributes, such as hardware 2's complement arithmetic.
  38  *
  39  */
  40 #include "g72x.h"
  41
  42 /*
  43  * Maps G.723_24 code word to reconstructed scale factor normalized log
  44  * magnitude values.
  45  */
  46 static short    _dqlntab[8] = {-2048, 135, 273, 373, 373, 273, 135, -2048};
  47
  48 /* Maps G.723_24 code word to log of scale factor multiplier. */
  49 static short    _witab[8] = {-128, 960, 4384, 18624, 18624, 4384, 960, -128};
  50
  51 /*
  52  * Maps G.723_24 code words to a set of values whose long and short
  53  * term averages are computed and then compared to give an indication
  54  * how stationary (steady state) the signal is.
  55  */
  56 static short    _fitab[8] = {0, 0x200, 0x400, 0xE00, 0xE00, 0x400, 0x200, 0};
  57
  58 static short qtab_723_24[3] = {8, 218, 331};
  59
  60 /*
  61  * g723_24_encoder()
  62  *
  63  * Encodes a linear PCM, A-law or u-law input sample and returns its 3-bit code.
  64  * Returns -1 if invalid input coding value.
  65  */
  66 int
  67 g723_24_encoder(
  68         int             sl,
  69         int             in_coding,
  70         struct g72x_state *state_ptr)
  71 {
  72         short           sei, sezi, se, sez;     /* ACCUM */
  73         short           d;                      /* SUBTA */
  74         short           y;                      /* MIX */
  75         short           sr;                     /* ADDB */
  76         short           dqsez;                  /* ADDC */
  77         short           dq, i;
  78
  79         switch (in_coding) {    /* linearize input sample to 14-bit PCM */
  80         case AUDIO_ENCODING_ALAW:
  81                 sl = alaw2linear(sl) >> 2;
  82                 break;
  83         case AUDIO_ENCODING_ULAW:
  84                 sl = ulaw2linear(sl) >> 2;
  85                 break;
  86         case AUDIO_ENCODING_LINEAR:
  87                 sl = ((short)sl) >> 2;          /* sl of 14-bit dynamic range */
  88                 break;
  89         default:
  90                 return (-1);
  91         }
  92
  93         sezi = predictor_zero(state_ptr);
  94         sez = sezi >> 1;
  95         sei = sezi + predictor_pole(state_ptr);
  96         se = sei >> 1;                  /* se = estimated signal */
  97
  98         d = sl - se;                    /* d = estimation diff. */
  99
 100         /* quantize prediction difference d */
 101         y = step_size(state_ptr);       /* quantizer step size */
 102         i = quantize(d, y, qtab_723_24, 3);     /* i = ADPCM code */
 103         dq = reconstruct(i & 4, _dqlntab[i], y); /* quantized diff. */
 104
 105         sr = (dq < 0) ? se - (dq & 0x3FFF) : se + dq; /* reconstructed signal */
 106
 107         dqsez = sr + sez - se;          /* pole prediction diff. */
 108
 109         update(3, y, _witab[i], _fitab[i], dq, sr, dqsez, state_ptr);
 110
 111         return (i);
 112 }
 113
 114 /*
 115  * g723_24_decoder()
 116  *
 117  * Decodes a 3-bit CCITT G.723_24 ADPCM code and returns
 118  * the resulting 16-bit linear PCM, A-law or u-law sample value.
 119  * -1 is returned if the output coding is unknown.
 120  */
 121 int
 122 g723_24_decoder(
 123         int             i,
 124         int             out_coding,
 125         struct g72x_state *state_ptr)
 126 {
 127         short           sezi, sei, sez, se;     /* ACCUM */
 128         short           y;                      /* MIX */
 129         short           sr;                     /* ADDB */
 130         short           dq;
 131         short           dqsez;
 132
 133         i &= 0x07;                      /* mask to get proper bits */
 134         sezi = predictor_zero(state_ptr);
 135         sez = sezi >> 1;
 136         sei = sezi + predictor_pole(state_ptr);
 137         se = sei >> 1;                  /* se = estimated signal */
 138
 139         y = step_size(state_ptr);       /* adaptive quantizer step size */
 140         dq = reconstruct(i & 0x04, _dqlntab[i], y); /* unquantize pred diff */
 141
 142         sr = (dq < 0) ? (se - (dq & 0x3FFF)) : (se + dq); /* reconst. signal */
 143
 144         dqsez = sr - se + sez;                  /* pole prediction diff. */
 145
 146         update(3, y, _witab[i], _fitab[i], dq, sr, dqsez, state_ptr);
 147
 148         switch (out_coding) {
 149         case AUDIO_ENCODING_ALAW:
 150                 return (tandem_adjust_alaw(sr, se, y, i, 4, qtab_723_24));
 151         case AUDIO_ENCODING_ULAW:
 152                 return (tandem_adjust_ulaw(sr, se, y, i, 4, qtab_723_24));
 153         case AUDIO_ENCODING_LINEAR:
 154                 return (sr << 2);       /* sr was of 14-bit dynamic range */
 155         default:
 156                 return (-1);
 157         }
 158 }