ref: 273089322f62e5b01d40228bf8095d9414f5d778
dir: /src/g721.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 */ /* * g721.c * * Description: * * g721_encoder(), g721_decoder() * * These routines comprise an implementation of the CCITT G.721 ADPCM * coding algorithm. Essentially, this implementation is identical to * the bit level description except for a few deviations which * take advantage of work station attributes, such as hardware 2's * complement arithmetic and large memory. Specifically, certain time * consuming operations such as multiplications are replaced * with lookup tables and software 2's complement operations are * replaced with hardware 2's complement. * * The deviation from the bit level specification (lookup tables) * preserves the bit level performance specifications. * * As outlined in the G.721 Recommendation, the algorithm is broken * down into modules. Each section of code below is preceded by * the name of the module which it is implementing. * */ #include "st.h" #include "g72x.h" #include "libst.h" static short qtab_721[7] = {-124, 80, 178, 246, 300, 349, 400}; /* * Maps G.721 code word to reconstructed scale factor normalized log * magnitude values. */ static short _dqlntab[16] = {-2048, 4, 135, 213, 273, 323, 373, 425, 425, 373, 323, 273, 213, 135, 4, -2048}; /* Maps G.721 code word to log of scale factor multiplier. */ static short _witab[16] = {-12, 18, 41, 64, 112, 198, 355, 1122, 1122, 355, 198, 112, 64, 41, 18, -12}; /* * Maps G.721 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[16] = {0, 0, 0, 0x200, 0x200, 0x200, 0x600, 0xE00, 0xE00, 0x600, 0x200, 0x200, 0x200, 0, 0, 0}; /* * g721_encoder() * * Encodes the input vale of linear PCM, A-law or u-law data sl and returns * the resulting code. -1 is returned for unknown input coding value. */ int g721_encoder(sl, in_coding,state_ptr) int sl; int in_coding; struct g72x_state *state_ptr; { short sezi, se, sez; /* ACCUM */ short d; /* SUBTA */ short sr; /* ADDB */ short y; /* MIX */ 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; /* 14-bit dynamic range */ break; default: return (-1); } sezi = predictor_zero(state_ptr); sez = sezi >> 1; se = (sezi + predictor_pole(state_ptr)) >> 1; /* estimated signal */ d = sl - se; /* estimation difference */ /* quantize the prediction difference */ y = step_size(state_ptr); /* quantizer step size */ i = quantize(d, y, qtab_721, 7); /* i = ADPCM code */ dq = reconstruct(i & 8, _dqlntab[i], y); /* quantized est diff */ sr = (dq < 0) ? se - (dq & 0x3FFF) : se + dq; /* reconst. signal */ dqsez = sr + sez - se; /* pole prediction diff. */ update(4, y, _witab[i] << 5, _fitab[i], dq, sr, dqsez, state_ptr); return (i); } /* * g721_decoder() * * Description: * * Decodes a 4-bit code of G.721 encoded data of i and * returns the resulting linear PCM, A-law or u-law value. * return -1 for unknown out_coding value. */ int g721_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 &= 0x0f; /* 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); /* dynamic quantizer step size */ dq = reconstruct(i & 0x08, _dqlntab[i], y); /* quantized diff. */ sr = (dq < 0) ? (se - (dq & 0x3FFF)) : se + dq; /* reconst. signal */ dqsez = sr - se + sez; /* pole prediction diff. */ update(4, y, _witab[i] << 5, _fitab[i], dq, sr, dqsez, state_ptr); switch (out_coding) { case AUDIO_ENCODING_ALAW: return (tandem_adjust_alaw(sr, se, y, i, 8, qtab_721)); case AUDIO_ENCODING_ULAW: return (tandem_adjust_ulaw(sr, se, y, i, 8, qtab_721)); case AUDIO_ENCODING_LINEAR: return (sr << 2); /* sr was 14-bit dynamic range */ default: return (-1); } }