/* * This source code is a product of Sun Microsystems, Inc. and is provided * for unrestricted use.  Users may copy or modify this source code without * charge. * * SUN SOURCE CODE IS PROVIDED AS IS WITH NO WARRANTIES OF ANY KIND INCLUDING * THE WARRANTIES OF DESIGN, MERCHANTIBILITY AND FITNESS FOR A PARTICULAR * PURPOSE, OR ARISING FROM A COURSE OF DEALING, USAGE OR TRADE PRACTICE. * * Sun source code is provided with no support and without any obligation on * the part of Sun Microsystems, Inc. to assist in its use, correction, * modification or enhancement. * * SUN MICROSYSTEMS, INC. SHALL HAVE NO LIABILITY WITH RESPECT TO THE * INFRINGEMENT OF COPYRIGHTS, TRADE SECRETS OR ANY PATENTS BY THIS SOFTWARE * OR ANY PART THEREOF. * * In no event will Sun Microsystems, Inc. be liable for any lost revenue * or profits or other special, indirect and consequential damages, even if * Sun has been advised of the possibility of such damages. * * Sun Microsystems, Inc. * 2550 Garcia Avenue * Mountain View, California  94043 *//* 16kbps version created, used 24kbps code and changing as little as possible. * G.726 specs are available from ITU's gopher or WWW site (http://www.itu.ch) * If any errors are found, please contact me at mrand@tamu.edu *      -Marc Randolph *//* * g723_16.c * * Description: * * g723_16_encoder(), g723_16_decoder() * * These routines comprise an implementation of the CCITT G.726 16 Kbps * ADPCM coding algorithm.  Essentially, this implementation is identical to * the bit level description except for a few deviations which take advantage * of workstation attributes, such as hardware 2's complement arithmetic. * */#include "g72x.h"#include "private.h"/* * Maps G.723_16 code word to reconstructed scale factor normalized log * magnitude values.  Comes from Table 11/G.726 */static short   _dqlntab[4] = { 116, 365, 365, 116}; /* Maps G.723_16 code word to log of scale factor multiplier. * * _witab[4] is actually {-22 , 439, 439, -22}, but FILTD wants it * as WI << 5  (multiplied by 32), so we'll do that here  */static short   _witab[4] = {-704, 14048, 14048, -704};/* * Maps G.723_16 code words to a set of values whose long and short * term averages are computed and then compared to give an indication * how stationary (steady state) the signal is. *//* Comes from FUNCTF */static short   _fitab[4] = {0, 0xE00, 0xE00, 0};/* Comes from quantizer decision level tables (Table 7/G.726) */static short qtab_723_16[1] = {261};/* * g723_16_encoder() * * Encodes a linear PCM, A-law or u-law input sample and returns its 2-bit code. * Returns -1 if invalid input coding value. */intg723_16_encoder(       int             sl,       G72x_STATE *state_ptr){       short           sei, sezi, se, sez;     /* ACCUM */       short           d;                      /* SUBTA */       short           y;                      /* MIX */       short           sr;                     /* ADDB */       short           dqsez;                  /* ADDC */       short           dq, i;		/* linearize input sample to 14-bit PCM */		sl >>= 2;               /* sl of 14-bit dynamic range */       sezi = predictor_zero(state_ptr);       sez = sezi >> 1;       sei = sezi + predictor_pole(state_ptr);       se = sei >> 1;                  /* se = estimated signal */       d = sl - se;                    /* d = estimation diff. */       /* quantize prediction difference d */       y = step_size(state_ptr);       /* quantizer step size */       i = quantize(d, y, qtab_723_16, 1);  /* i = ADPCM code */             /* Since quantize() only produces a three level output              * (1, 2, or 3), we must create the fourth one on our own              */       if (i == 3)                          /* i code for the zero region */         if ((d & 0x8000) == 0)             /* If d > 0, i=3 isn't right... */           i = 0;                  dq = reconstruct(i & 2, _dqlntab[i], y); /* quantized diff. */       sr = (dq < 0) ? se - (dq & 0x3FFF) : se + dq; /* reconstructed signal */       dqsez = sr + sez - se;          /* pole prediction diff. */       update(2, y, _witab[i], _fitab[i], dq, sr, dqsez, state_ptr);       return (i);}/* * g723_16_decoder() * * Decodes a 2-bit CCITT G.723_16 ADPCM code and returns * the resulting 16-bit linear PCM, A-law or u-law sample value. * -1 is returned if the output coding is unknown. */intg723_16_decoder(       int             i,       G72x_STATE *state_ptr){       short           sezi, sei, sez, se;     /* ACCUM */       short           y;                      /* MIX */       short           sr;                     /* ADDB */       short           dq;       short           dqsez;       i &= 0x03;                      /* mask to get proper bits */       sezi = predictor_zero(state_ptr);       sez = sezi >> 1;       sei = sezi + predictor_pole(state_ptr);       se = sei >> 1;                  /* se = estimated signal */       y = step_size(state_ptr);       /* adaptive quantizer step size */       dq = reconstruct(i & 0x02, _dqlntab[i], y); /* unquantize pred diff */       sr = (dq < 0) ? (se - (dq & 0x3FFF)) : (se + dq); /* reconst. signal */       dqsez = sr - se + sez;                  /* pole prediction diff. */       update(2, y, _witab[i], _fitab[i], dq, sr, dqsez, state_ptr);		/* sr was of 14-bit dynamic range */		return (sr << 2);       }