utils/wxMMedia2/lib/g721.cpp

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   3  * for unrestricted use.  Users may copy or modify this source code without
   4  * charge.
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  12  * modification or enhancement.
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  15  * INFRINGEMENT OF COPYRIGHTS, TRADE SECRETS OR ANY PATENTS BY THIS SOFTWARE
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  17  *
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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 #include <wx/wxprec.h>
  28
  29 /*
  30  * g721.c
  31  *
  32  * Description:
  33  *
  34  * g721_encoder(), g721_decoder()
  35  *
  36  * These routines comprise an implementation of the CCITT G.721 ADPCM
  37  * coding algorithm.  Essentially, this implementation is identical to
  38  * the bit level description except for a few deviations which
  39  * take advantage of work station attributes, such as hardware 2's
  40  * complement arithmetic and large memory.  Specifically, certain time
  41  * consuming operations such as multiplications are replaced
  42  * with lookup tables and software 2's complement operations are
  43  * replaced with hardware 2's complement.
  44  *
  45  * The deviation from the bit level specification (lookup tables)
  46  * preserves the bit level performance specifications.
  47  *
  48  * As outlined in the G.721 Recommendation, the algorithm is broken
  49  * down into modules.  Each section of code below is preceded by
  50  * the name of the module which it is implementing.
  51  *
  52  */
  53 #include "g72x.h"
  54
  55 static short qtab_721[7] = {-124, 80, 178, 246, 300, 349, 400};
  56 /*
  57  * Maps G.721 code word to reconstructed scale factor normalized log
  58  * magnitude values.
  59  */
  60 static short    _dqlntab[16] = {-2048, 4, 135, 213, 273, 323, 373, 425,
  61                                 425, 373, 323, 273, 213, 135, 4, -2048};
  62
  63 /* Maps G.721 code word to log of scale factor multiplier. */
  64 static short    _witab[16] = {-12, 18, 41, 64, 112, 198, 355, 1122,
  65                                 1122, 355, 198, 112, 64, 41, 18, -12};
  66 /*
  67  * Maps G.721 code words to a set of values whose long and short
  68  * term averages are computed and then compared to give an indication
  69  * how stationary (steady state) the signal is.
  70  */
  71 static short    _fitab[16] = {0, 0, 0, 0x200, 0x200, 0x200, 0x600, 0xE00,
  72                                 0xE00, 0x600, 0x200, 0x200, 0x200, 0, 0, 0};
  73
  74 /*
  75  * g721_encoder()
  76  *
  77  * Encodes the input vale of linear PCM, A-law or u-law data sl and returns
  78  * the resulting code. -1 is returned for unknown input coding value.
  79  */
  80 int
  81 g721_encoder(
  82         int             sl,
  83         int             in_coding,
  84         struct g72x_state *state_ptr)
  85 {
  86         short           sezi, se, sez;          /* ACCUM */
  87         short           d;                      /* SUBTA */
  88         short           sr;                     /* ADDB */
  89         short           y;                      /* MIX */
  90         short           dqsez;                  /* ADDC */
  91         short           dq, i;
  92
  93         switch (in_coding) {    /* linearize input sample to 14-bit PCM */
  94         case AUDIO_ENCODING_ALAW:
  95                 sl = alaw2linear(sl) >> 2;
  96                 break;
  97         case AUDIO_ENCODING_ULAW:
  98                 sl = ulaw2linear(sl) >> 2;
  99                 break;
 100         case AUDIO_ENCODING_LINEAR:
 101                 sl = ((short)sl) >> 2;          /* 14-bit dynamic range */
 102                 break;
 103         default:
 104                 return (-1);
 105         }
 106
 107         sezi = predictor_zero(state_ptr);
 108         sez = sezi >> 1;
 109         se = (sezi + predictor_pole(state_ptr)) >> 1;   /* estimated signal */
 110
 111         d = sl - se;                            /* estimation difference */
 112
 113         /* quantize the prediction difference */
 114         y = step_size(state_ptr);               /* quantizer step size */
 115         i = quantize(d, y, qtab_721, 7);        /* i = ADPCM code */
 116
 117         dq = reconstruct(i & 8, _dqlntab[i], y);        /* quantized est diff */
 118
 119         sr = (dq < 0) ? se - (dq & 0x3FFF) : se + dq;   /* reconst. signal */
 120
 121         dqsez = sr + sez - se;                  /* pole prediction diff. */
 122
 123         update(4, y, _witab[i] << 5, _fitab[i], dq, sr, dqsez, state_ptr);
 124
 125         return (i);
 126 }
 127
 128 /*
 129  * g721_decoder()
 130  *
 131  * Description:
 132  *
 133  * Decodes a 4-bit code of G.721 encoded data of i and
 134  * returns the resulting linear PCM, A-law or u-law value.
 135  * return -1 for unknown out_coding value.
 136  */
 137 int
 138 g721_decoder(
 139         int             i,
 140         int             out_coding,
 141         struct g72x_state *state_ptr)
 142 {
 143         short           sezi, sei, sez, se;     /* ACCUM */
 144         short           y;                      /* MIX */
 145         short           sr;                     /* ADDB */
 146         short           dq;
 147         short           dqsez;
 148
 149         i &= 0x0f;                      /* mask to get proper bits */
 150         sezi = predictor_zero(state_ptr);
 151         sez = sezi >> 1;
 152         sei = sezi + predictor_pole(state_ptr);
 153         se = sei >> 1;                  /* se = estimated signal */
 154
 155         y = step_size(state_ptr);       /* dynamic quantizer step size */
 156
 157         dq = reconstruct(i & 0x08, _dqlntab[i], y); /* quantized diff. */
 158
 159         sr = (dq < 0) ? (se - (dq & 0x3FFF)) : se + dq; /* reconst. signal */
 160
 161         dqsez = sr - se + sez;                  /* pole prediction diff. */
 162
 163         update(4, y, _witab[i] << 5, _fitab[i], dq, sr, dqsez, state_ptr);
 164
 165         switch (out_coding) {
 166         case AUDIO_ENCODING_ALAW:
 167                 return (tandem_adjust_alaw(sr, se, y, i, 8, qtab_721));
 168         case AUDIO_ENCODING_ULAW:
 169                 return (tandem_adjust_ulaw(sr, se, y, i, 8, qtab_721));
 170         case AUDIO_ENCODING_LINEAR:
 171                 return (sr << 2);       /* sr was 14-bit dynamic range */
 172         default:
 173                 return (-1);
 174         }
 175 }