/project/jni/sndfile/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 */
 53static 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 */
 60static 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 */
 69static short   _fitab[4] = {0, 0xE00, 0xE00, 0};
 70
 71/* Comes from quantizer decision level tables (Table 7/G.726)
 72 */
 73static 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 */
 82int
 83g723_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 */
133int
134g723_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