contrib/src/mmedia/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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  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 "wx/mmedia/internal/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 }