utils/wxMMedia2/lib/g723_24.cpp

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   3  * for unrestricted use.  Users may copy or modify this source code without
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  12  * modification or enhancement.
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  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
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  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 <wx/wxprec.h>
  41 #include "g72x.h"
  42
  43 /*
  44  * Maps G.723_24 code word to reconstructed scale factor normalized log
  45  * magnitude values.
  46  */
  47 static short    _dqlntab[8] = {-2048, 135, 273, 373, 373, 273, 135, -2048};
  48
  49 /* Maps G.723_24 code word to log of scale factor multiplier. */
  50 static short    _witab[8] = {-128, 960, 4384, 18624, 18624, 4384, 960, -128};
  51
  52 /*
  53  * Maps G.723_24 code words to a set of values whose long and short
  54  * term averages are computed and then compared to give an indication
  55  * how stationary (steady state) the signal is.
  56  */
  57 static short    _fitab[8] = {0, 0x200, 0x400, 0xE00, 0xE00, 0x400, 0x200, 0};
  58
  59 static short qtab_723_24[3] = {8, 218, 331};
  60
  61 /*
  62  * g723_24_encoder()
  63  *
  64  * Encodes a linear PCM, A-law or u-law input sample and returns its 3-bit code.
  65  * Returns -1 if invalid input coding value.
  66  */
  67 int
  68 g723_24_encoder(
  69         int             sl,
  70         int             in_coding,
  71         struct g72x_state *state_ptr)
  72 {
  73         short           sei, sezi, se, sez;     /* ACCUM */
  74         short           d;                      /* SUBTA */
  75         short           y;                      /* MIX */
  76         short           sr;                     /* ADDB */
  77         short           dqsez;                  /* ADDC */
  78         short           dq, i;
  79
  80         switch (in_coding) {    /* linearize input sample to 14-bit PCM */
  81         case AUDIO_ENCODING_ALAW:
  82                 sl = alaw2linear(sl) >> 2;
  83                 break;
  84         case AUDIO_ENCODING_ULAW:
  85                 sl = ulaw2linear(sl) >> 2;
  86                 break;
  87         case AUDIO_ENCODING_LINEAR:
  88                 sl = ((short)sl) >> 2;          /* sl of 14-bit dynamic range */
  89                 break;
  90         default:
  91                 return (-1);
  92         }
  93
  94         sezi = predictor_zero(state_ptr);
  95         sez = sezi >> 1;
  96         sei = sezi + predictor_pole(state_ptr);
  97         se = sei >> 1;                  /* se = estimated signal */
  98
  99         d = sl - se;                    /* d = estimation diff. */
 100
 101         /* quantize prediction difference d */
 102         y = step_size(state_ptr);       /* quantizer step size */
 103         i = quantize(d, y, qtab_723_24, 3);     /* i = ADPCM code */
 104         dq = reconstruct(i & 4, _dqlntab[i], y); /* quantized diff. */
 105
 106         sr = (dq < 0) ? se - (dq & 0x3FFF) : se + dq; /* reconstructed signal */
 107
 108         dqsez = sr + sez - se;          /* pole prediction diff. */
 109
 110         update(3, y, _witab[i], _fitab[i], dq, sr, dqsez, state_ptr);
 111
 112         return (i);
 113 }
 114
 115 /*
 116  * g723_24_decoder()
 117  *
 118  * Decodes a 3-bit CCITT G.723_24 ADPCM code and returns
 119  * the resulting 16-bit linear PCM, A-law or u-law sample value.
 120  * -1 is returned if the output coding is unknown.
 121  */
 122 int
 123 g723_24_decoder(
 124         int             i,
 125         int             out_coding,
 126         struct g72x_state *state_ptr)
 127 {
 128         short           sezi, sei, sez, se;     /* ACCUM */
 129         short           y;                      /* MIX */
 130         short           sr;                     /* ADDB */
 131         short           dq;
 132         short           dqsez;
 133
 134         i &= 0x07;                      /* mask to get proper bits */
 135         sezi = predictor_zero(state_ptr);
 136         sez = sezi >> 1;
 137         sei = sezi + predictor_pole(state_ptr);
 138         se = sei >> 1;                  /* se = estimated signal */
 139
 140         y = step_size(state_ptr);       /* adaptive quantizer step size */
 141         dq = reconstruct(i & 0x04, _dqlntab[i], y); /* unquantize pred diff */
 142
 143         sr = (dq < 0) ? (se - (dq & 0x3FFF)) : (se + dq); /* reconst. signal */
 144
 145         dqsez = sr - se + sez;                  /* pole prediction diff. */
 146
 147         update(3, y, _witab[i], _fitab[i], dq, sr, dqsez, state_ptr);
 148
 149         switch (out_coding) {
 150         case AUDIO_ENCODING_ALAW:
 151                 return (tandem_adjust_alaw(sr, se, y, i, 4, qtab_723_24));
 152         case AUDIO_ENCODING_ULAW:
 153                 return (tandem_adjust_ulaw(sr, se, y, i, 4, qtab_723_24));
 154         case AUDIO_ENCODING_LINEAR:
 155                 return (sr << 2);       /* sr was of 14-bit dynamic range */
 156         default:
 157                 return (-1);
 158         }
 159 }