interpretor/libsndfile-1.0.25/src/G72x/g723_16.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 /* 16kbps version created, used 24kbps code and changing as little as possible.
  27  * G.726 specs are available from ITU's gopher or WWW site (http://www.itu.ch)
  28  * If any errors are found, please contact me at mrand@tamu.edu
  29  *      -Marc Randolph
  30  */
  31
  32 /*
  33  * g723_16.c
  34  *
  35  * Description:
  36  *
  37  * g723_16_encoder(), g723_16_decoder()
  38  *
  39  * These routines comprise an implementation of the CCITT G.726 16 Kbps
  40  * ADPCM coding algorithm.  Essentially, this implementation is identical to
  41  * the bit level description except for a few deviations which take advantage
  42  * of workstation attributes, such as hardware 2's complement arithmetic.
  43  *
  44  */
  45
  46 #include "g72x.h"
  47 #include "g72x_priv.h"
  48
  49 /*
  50  * Maps G.723_16 code word to reconstructed scale factor normalized log
  51  * magnitude values.  Comes from Table 11/G.726
  52  */
  53 static short   _dqlntab[4] = { 116, 365, 365, 116};
  54
  55 /* Maps G.723_16 code word to log of scale factor multiplier.
  56  *
  57  * _witab[4] is actually {-22 , 439, 439, -22}, but FILTD wants it
  58  * as WI << 5  (multiplied by 32), so we'll do that here
  59  */
  60 static short   _witab[4] = {-704, 14048, 14048, -704};
  61
  62 /*
  63  * Maps G.723_16 code words to a set of values whose long and short
  64  * term averages are computed and then compared to give an indication
  65  * how stationary (steady state) the signal is.
  66  */
  67
  68 /* Comes from FUNCTF */
  69 static short   _fitab[4] = {0, 0xE00, 0xE00, 0};
  70
  71 /* Comes from quantizer decision level tables (Table 7/G.726)
  72  */
  73 static short qtab_723_16[1] = {261};
  74
  75
  76 /*
  77  * g723_16_encoder()
  78  *
  79  * Encodes a linear PCM, A-law or u-law input sample and returns its 2-bit code.
  80  * Returns -1 if invalid input coding value.
  81  */
  82 int
  83 g723_16_encoder(
  84        int             sl,
  85        G72x_STATE *state_ptr)
  86 {
  87        short           sei, sezi, se, sez;     /* ACCUM */
  88        short           d;                      /* SUBTA */
  89        short           y;                      /* MIX */
  90        short           sr;                     /* ADDB */
  91        short           dqsez;                  /* ADDC */
  92        short           dq, i;
  93
  94                 /* linearize input sample to 14-bit PCM */
  95                 sl >>= 2;               /* sl of 14-bit dynamic range */
  96
  97        sezi = predictor_zero(state_ptr);
  98        sez = sezi >> 1;
  99        sei = sezi + predictor_pole(state_ptr);
 100        se = sei >> 1;                  /* se = estimated signal */
 101
 102        d = sl - se;                    /* d = estimation diff. */
 103
 104        /* quantize prediction difference d */
 105        y = step_size(state_ptr);       /* quantizer step size */
 106        i = quantize(d, y, qtab_723_16, 1);  /* i = ADPCM code */
 107
 108              /* Since quantize() only produces a three level output
 109               * (1, 2, or 3), we must create the fourth one on our own
 110               */
 111        if (i == 3)                          /* i code for the zero region */
 112          if ((d & 0x8000) == 0)             /* If d > 0, i=3 isn't right... */
 113            i = 0;
 114
 115        dq = reconstruct(i & 2, _dqlntab[i], y); /* quantized diff. */
 116
 117        sr = (dq < 0) ? se - (dq & 0x3FFF) : se + dq; /* reconstructed signal */
 118
 119        dqsez = sr + sez - se;          /* pole prediction diff. */
 120
 121        update(2, y, _witab[i], _fitab[i], dq, sr, dqsez, state_ptr);
 122
 123        return (i);
 124 }
 125
 126 /*
 127  * g723_16_decoder()
 128  *
 129  * Decodes a 2-bit CCITT G.723_16 ADPCM code and returns
 130  * the resulting 16-bit linear PCM, A-law or u-law sample value.
 131  * -1 is returned if the output coding is unknown.
 132  */
 133 int
 134 g723_16_decoder(
 135        int             i,
 136        G72x_STATE *state_ptr)
 137 {
 138        short           sezi, sei, sez, se;     /* ACCUM */
 139        short           y;                      /* MIX */
 140        short           sr;                     /* ADDB */
 141        short           dq;
 142        short           dqsez;
 143
 144        i &= 0x03;                      /* mask to get proper bits */
 145        sezi = predictor_zero(state_ptr);
 146        sez = sezi >> 1;
 147        sei = sezi + predictor_pole(state_ptr);
 148        se = sei >> 1;                  /* se = estimated signal */
 149
 150        y = step_size(state_ptr);       /* adaptive quantizer step size */
 151        dq = reconstruct(i & 0x02, _dqlntab[i], y); /* unquantize pred diff */
 152
 153        sr = (dq < 0) ? (se - (dq & 0x3FFF)) : (se + dq); /* reconst. signal */
 154
 155        dqsez = sr - se + sez;                  /* pole prediction diff. */
 156
 157        update(2, y, _witab[i], _fitab[i], dq, sr, dqsez, state_ptr);
 158
 159                 /* sr was of 14-bit dynamic range */
 160                 return (sr << 2);
 161 }
 162