ref: 8791cbd4a9f89b06f87ea3f85f8c2d2432bf8903
dir: /src/g723_24.c/
/* * 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 */ /* * g723_24.c * * Description: * * g723_24_encoder(), g723_24_decoder() * * These routines comprise an implementation of the CCITT G.723 24 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 "st.h" #include "libst.h" #include "g72x.h" /* * Maps G.723_24 code word to reconstructed scale factor normalized log * magnitude values. */ static short _dqlntab[8] = {-2048, 135, 273, 373, 373, 273, 135, -2048}; /* Maps G.723_24 code word to log of scale factor multiplier. */ static short _witab[8] = {-128, 960, 4384, 18624, 18624, 4384, 960, -128}; /* * Maps G.723_24 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. */ static short _fitab[8] = {0, 0x200, 0x400, 0xE00, 0xE00, 0x400, 0x200, 0}; static short qtab_723_24[3] = {8, 218, 331}; /* * g723_24_encoder() * * Encodes a linear PCM, A-law or u-law input sample and returns its 3-bit code. * Returns -1 if invalid input coding value. */ int g723_24_encoder(sl, in_coding, state_ptr) int sl; int in_coding; struct 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; switch (in_coding) { /* linearize input sample to 14-bit PCM */ case AUDIO_ENCODING_ALAW: sl = st_Alaw_to_linear(sl) >> 2; break; case AUDIO_ENCODING_ULAW: sl = st_ulaw_to_linear(sl) >> 2; break; case AUDIO_ENCODING_LINEAR: sl >>= 2; /* sl of 14-bit dynamic range */ break; default: return (-1); } 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_24, 3); /* i = ADPCM code */ dq = reconstruct(i & 4, _dqlntab[i], y); /* quantized diff. */ sr = (dq < 0) ? se - (dq & 0x3FFF) : se + dq; /* reconstructed signal */ dqsez = sr + sez - se; /* pole prediction diff. */ update(3, y, _witab[i], _fitab[i], dq, sr, dqsez, state_ptr); return (i); } /* * g723_24_decoder() * * Decodes a 3-bit CCITT G.723_24 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. */ int g723_24_decoder(i, out_coding, state_ptr) int i; int out_coding; struct g72x_state *state_ptr; { short sezi, sei, sez, se; /* ACCUM */ short y; /* MIX */ short sr; /* ADDB */ short dq; short dqsez; i &= 0x07; /* 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 & 0x04, _dqlntab[i], y); /* unquantize pred diff */ sr = (dq < 0) ? (se - (dq & 0x3FFF)) : (se + dq); /* reconst. signal */ dqsez = sr - se + sez; /* pole prediction diff. */ update(3, y, _witab[i], _fitab[i], dq, sr, dqsez, state_ptr); switch (out_coding) { case AUDIO_ENCODING_ALAW: return (tandem_adjust_alaw(sr, se, y, i, 4, qtab_723_24)); case AUDIO_ENCODING_ULAW: return (tandem_adjust_ulaw(sr, se, y, i, 4, qtab_723_24)); case AUDIO_ENCODING_LINEAR: return (sr << 2); /* sr was of 14-bit dynamic range */ default: return (-1); } }