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libavcodec/g726.c

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00001 /*
00002  * G.726 ADPCM audio codec
00003  * Copyright (c) 2004 Roman Shaposhnik
00004  *
00005  * This is a very straightforward rendition of the G.726
00006  * Section 4 "Computational Details".
00007  *
00008  * This file is part of FFmpeg.
00009  *
00010  * FFmpeg is free software; you can redistribute it and/or
00011  * modify it under the terms of the GNU Lesser General Public
00012  * License as published by the Free Software Foundation; either
00013  * version 2.1 of the License, or (at your option) any later version.
00014  *
00015  * FFmpeg is distributed in the hope that it will be useful,
00016  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00017  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00018  * Lesser General Public License for more details.
00019  *
00020  * You should have received a copy of the GNU Lesser General Public
00021  * License along with FFmpeg; if not, write to the Free Software
00022  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
00023  */
00024 #include <limits.h>
00025 #include "avcodec.h"
00026 #include "bitstream.h"
00027 
00034 typedef struct Float11 {
00035     uint8_t sign;   
00036     uint8_t exp;    
00037     uint8_t mant;   
00038 } Float11;
00039 
00040 static inline Float11* i2f(int i, Float11* f)
00041 {
00042     f->sign = (i < 0);
00043     if (f->sign)
00044         i = -i;
00045     f->exp = av_log2_16bit(i) + !!i;
00046     f->mant = i? (i<<6) >> f->exp : 1<<5;
00047     return f;
00048 }
00049 
00050 static inline int16_t mult(Float11* f1, Float11* f2)
00051 {
00052         int res, exp;
00053 
00054         exp = f1->exp + f2->exp;
00055         res = (((f1->mant * f2->mant) + 0x30) >> 4);
00056         res = exp > 19 ? res << (exp - 19) : res >> (19 - exp);
00057         return (f1->sign ^ f2->sign) ? -res : res;
00058 }
00059 
00060 static inline int sgn(int value)
00061 {
00062     return (value < 0) ? -1 : 1;
00063 }
00064 
00065 typedef struct G726Tables {
00066     const int* quant;         
00067     const int16_t* iquant;    
00068     const int16_t* W;         
00069     const uint8_t* F;         
00070 } G726Tables;
00071 
00072 typedef struct G726Context {
00073     G726Tables tbls;    
00075     Float11 sr[2];      
00076     Float11 dq[6];      
00077     int a[2];           
00078     int b[6];           
00079     int pk[2];          
00081     int ap;             
00082     int yu;             
00083     int yl;             
00084     int dms;            
00085     int dml;            
00086     int td;             
00088     int se;             
00089     int sez;            
00090     int y;              
00091     int code_size;
00092 } G726Context;
00093 
00094 static const int quant_tbl16[] =                  
00095            { 260, INT_MAX };
00096 static const int16_t iquant_tbl16[] =
00097            { 116, 365, 365, 116 };
00098 static const int16_t W_tbl16[] =
00099            { -22, 439, 439, -22 };
00100 static const uint8_t F_tbl16[] =
00101            { 0, 7, 7, 0 };
00102 
00103 static const int quant_tbl24[] =                  
00104            {  7, 217, 330, INT_MAX };
00105 static const int16_t iquant_tbl24[] =
00106            { INT16_MIN, 135, 273, 373, 373, 273, 135, INT16_MIN };
00107 static const int16_t W_tbl24[] =
00108            { -4,  30, 137, 582, 582, 137,  30, -4 };
00109 static const uint8_t F_tbl24[] =
00110            { 0, 1, 2, 7, 7, 2, 1, 0 };
00111 
00112 static const int quant_tbl32[] =                  
00113            { -125,  79, 177, 245, 299, 348, 399, INT_MAX };
00114 static const int16_t iquant_tbl32[] =
00115          { INT16_MIN,   4, 135, 213, 273, 323, 373, 425,
00116                  425, 373, 323, 273, 213, 135,   4, INT16_MIN };
00117 static const int16_t W_tbl32[] =
00118            { -12,  18,  41,  64, 112, 198, 355, 1122,
00119             1122, 355, 198, 112,  64,  41,  18, -12};
00120 static const uint8_t F_tbl32[] =
00121            { 0, 0, 0, 1, 1, 1, 3, 7, 7, 3, 1, 1, 1, 0, 0, 0 };
00122 
00123 static const int quant_tbl40[] =                  
00124            { -122, -16,  67, 138, 197, 249, 297, 338,
00125               377, 412, 444, 474, 501, 527, 552, INT_MAX };
00126 static const int16_t iquant_tbl40[] =
00127          { INT16_MIN, -66,  28, 104, 169, 224, 274, 318,
00128                  358, 395, 429, 459, 488, 514, 539, 566,
00129                  566, 539, 514, 488, 459, 429, 395, 358,
00130                  318, 274, 224, 169, 104,  28, -66, INT16_MIN };
00131 static const int16_t W_tbl40[] =
00132            {   14,  14,  24,  39,  40,  41,   58,  100,
00133               141, 179, 219, 280, 358, 440,  529,  696,
00134               696, 529, 440, 358, 280, 219,  179,  141,
00135               100,  58,  41,  40,  39,  24,   14,   14 };
00136 static const uint8_t F_tbl40[] =
00137            { 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 2, 3, 4, 5, 6, 6,
00138              6, 6, 5, 4, 3, 2, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0 };
00139 
00140 static const G726Tables G726Tables_pool[] =
00141            {{ quant_tbl16, iquant_tbl16, W_tbl16, F_tbl16 },
00142             { quant_tbl24, iquant_tbl24, W_tbl24, F_tbl24 },
00143             { quant_tbl32, iquant_tbl32, W_tbl32, F_tbl32 },
00144             { quant_tbl40, iquant_tbl40, W_tbl40, F_tbl40 }};
00145 
00146 
00150 static inline uint8_t quant(G726Context* c, int d)
00151 {
00152     int sign, exp, i, dln;
00153 
00154     sign = i = 0;
00155     if (d < 0) {
00156         sign = 1;
00157         d = -d;
00158     }
00159     exp = av_log2_16bit(d);
00160     dln = ((exp<<7) + (((d<<7)>>exp)&0x7f)) - (c->y>>2);
00161 
00162     while (c->tbls.quant[i] < INT_MAX && c->tbls.quant[i] < dln)
00163         ++i;
00164 
00165     if (sign)
00166         i = ~i;
00167     if (c->code_size != 2 && i == 0) /* I'm not sure this is a good idea */
00168         i = 0xff;
00169 
00170     return i;
00171 }
00172 
00176 static inline int16_t inverse_quant(G726Context* c, int i)
00177 {
00178     int dql, dex, dqt;
00179 
00180     dql = c->tbls.iquant[i] + (c->y >> 2);
00181     dex = (dql>>7) & 0xf;        /* 4bit exponent */
00182     dqt = (1<<7) + (dql & 0x7f); /* log2 -> linear */
00183     return (dql < 0) ? 0 : ((dqt<<dex) >> 7);
00184 }
00185 
00186 static int16_t g726_decode(G726Context* c, int I)
00187 {
00188     int dq, re_signal, pk0, fa1, i, tr, ylint, ylfrac, thr2, al, dq0;
00189     Float11 f;
00190     int I_sig= I >> (c->code_size - 1);
00191 
00192     dq = inverse_quant(c, I);
00193 
00194     /* Transition detect */
00195     ylint = (c->yl >> 15);
00196     ylfrac = (c->yl >> 10) & 0x1f;
00197     thr2 = (ylint > 9) ? 0x1f << 10 : (0x20 + ylfrac) << ylint;
00198     tr= (c->td == 1 && dq > ((3*thr2)>>2));
00199 
00200     if (I_sig)  /* get the sign */
00201         dq = -dq;
00202     re_signal = c->se + dq;
00203 
00204     /* Update second order predictor coefficient A2 and A1 */
00205     pk0 = (c->sez + dq) ? sgn(c->sez + dq) : 0;
00206     dq0 = dq ? sgn(dq) : 0;
00207     if (tr) {
00208         c->a[0] = 0;
00209         c->a[1] = 0;
00210         for (i=0; i<6; i++)
00211             c->b[i] = 0;
00212     } else {
00213         /* This is a bit crazy, but it really is +255 not +256 */
00214         fa1 = av_clip((-c->a[0]*c->pk[0]*pk0)>>5, -256, 255);
00215 
00216         c->a[1] += 128*pk0*c->pk[1] + fa1 - (c->a[1]>>7);
00217         c->a[1] = av_clip(c->a[1], -12288, 12288);
00218         c->a[0] += 64*3*pk0*c->pk[0] - (c->a[0] >> 8);
00219         c->a[0] = av_clip(c->a[0], -(15360 - c->a[1]), 15360 - c->a[1]);
00220 
00221         for (i=0; i<6; i++)
00222             c->b[i] += 128*dq0*sgn(-c->dq[i].sign) - (c->b[i]>>8);
00223     }
00224 
00225     /* Update Dq and Sr and Pk */
00226     c->pk[1] = c->pk[0];
00227     c->pk[0] = pk0 ? pk0 : 1;
00228     c->sr[1] = c->sr[0];
00229     i2f(re_signal, &c->sr[0]);
00230     for (i=5; i>0; i--)
00231         c->dq[i] = c->dq[i-1];
00232     i2f(dq, &c->dq[0]);
00233     c->dq[0].sign = I_sig; /* Isn't it crazy ?!?! */
00234 
00235     c->td = c->a[1] < -11776;
00236 
00237     /* Update Ap */
00238     c->dms += (c->tbls.F[I]<<4) + ((- c->dms) >> 5);
00239     c->dml += (c->tbls.F[I]<<4) + ((- c->dml) >> 7);
00240     if (tr)
00241         c->ap = 256;
00242     else {
00243         c->ap += (-c->ap) >> 4;
00244         if (c->y <= 1535 || c->td || abs((c->dms << 2) - c->dml) >= (c->dml >> 3))
00245             c->ap += 0x20;
00246     }
00247 
00248     /* Update Yu and Yl */
00249     c->yu = av_clip(c->y + c->tbls.W[I] + ((-c->y)>>5), 544, 5120);
00250     c->yl += c->yu + ((-c->yl)>>6);
00251 
00252     /* Next iteration for Y */
00253     al = (c->ap >= 256) ? 1<<6 : c->ap >> 2;
00254     c->y = (c->yl + (c->yu - (c->yl>>6))*al) >> 6;
00255 
00256     /* Next iteration for SE and SEZ */
00257     c->se = 0;
00258     for (i=0; i<6; i++)
00259         c->se += mult(i2f(c->b[i] >> 2, &f), &c->dq[i]);
00260     c->sez = c->se >> 1;
00261     for (i=0; i<2; i++)
00262         c->se += mult(i2f(c->a[i] >> 2, &f), &c->sr[i]);
00263     c->se >>= 1;
00264 
00265     return av_clip(re_signal << 2, -0xffff, 0xffff);
00266 }
00267 
00268 static av_cold int g726_reset(G726Context* c, int index)
00269 {
00270     int i;
00271 
00272     c->tbls = G726Tables_pool[index];
00273     for (i=0; i<2; i++) {
00274         c->sr[i].mant = 1<<5;
00275         c->pk[i] = 1;
00276     }
00277     for (i=0; i<6; i++) {
00278         c->dq[i].mant = 1<<5;
00279     }
00280     c->yu = 544;
00281     c->yl = 34816;
00282 
00283     c->y = 544;
00284 
00285     return 0;
00286 }
00287 
00288 #if CONFIG_ADPCM_G726_ENCODER
00289 static int16_t g726_encode(G726Context* c, int16_t sig)
00290 {
00291     uint8_t i;
00292 
00293     i = quant(c, sig/4 - c->se) & ((1<<c->code_size) - 1);
00294     g726_decode(c, i);
00295     return i;
00296 }
00297 #endif
00298 
00299 /* Interfacing to the libavcodec */
00300 
00301 static av_cold int g726_init(AVCodecContext * avctx)
00302 {
00303     G726Context* c = avctx->priv_data;
00304     unsigned int index;
00305 
00306     if (avctx->sample_rate <= 0) {
00307         av_log(avctx, AV_LOG_ERROR, "Samplerate is invalid\n");
00308         return -1;
00309     }
00310 
00311     index = (avctx->bit_rate + avctx->sample_rate/2) / avctx->sample_rate - 2;
00312 
00313     if (avctx->bit_rate % avctx->sample_rate && avctx->codec->encode) {
00314         av_log(avctx, AV_LOG_ERROR, "Bitrate - Samplerate combination is invalid\n");
00315         return -1;
00316     }
00317     if(avctx->channels != 1){
00318         av_log(avctx, AV_LOG_ERROR, "Only mono is supported\n");
00319         return -1;
00320     }
00321     if(index>3){
00322         av_log(avctx, AV_LOG_ERROR, "Unsupported number of bits %d\n", index+2);
00323         return -1;
00324     }
00325     g726_reset(c, index);
00326     c->code_size = index+2;
00327 
00328     avctx->coded_frame = avcodec_alloc_frame();
00329     if (!avctx->coded_frame)
00330         return AVERROR(ENOMEM);
00331     avctx->coded_frame->key_frame = 1;
00332 
00333     if (avctx->codec->decode)
00334         avctx->sample_fmt = SAMPLE_FMT_S16;
00335 
00336     return 0;
00337 }
00338 
00339 static av_cold int g726_close(AVCodecContext *avctx)
00340 {
00341     av_freep(&avctx->coded_frame);
00342     return 0;
00343 }
00344 
00345 #if CONFIG_ADPCM_G726_ENCODER
00346 static int g726_encode_frame(AVCodecContext *avctx,
00347                             uint8_t *dst, int buf_size, void *data)
00348 {
00349     G726Context *c = avctx->priv_data;
00350     short *samples = data;
00351     PutBitContext pb;
00352 
00353     init_put_bits(&pb, dst, 1024*1024);
00354 
00355     for (; buf_size; buf_size--)
00356         put_bits(&pb, c->code_size, g726_encode(c, *samples++));
00357 
00358     flush_put_bits(&pb);
00359 
00360     return put_bits_count(&pb)>>3;
00361 }
00362 #endif
00363 
00364 static int g726_decode_frame(AVCodecContext *avctx,
00365                              void *data, int *data_size,
00366                              const uint8_t *buf, int buf_size)
00367 {
00368     G726Context *c = avctx->priv_data;
00369     short *samples = data;
00370     GetBitContext gb;
00371 
00372     init_get_bits(&gb, buf, buf_size * 8);
00373 
00374     while (get_bits_count(&gb) + c->code_size <= buf_size*8)
00375         *samples++ = g726_decode(c, get_bits(&gb, c->code_size));
00376 
00377     if(buf_size*8 != get_bits_count(&gb))
00378         av_log(avctx, AV_LOG_ERROR, "Frame invalidly split, missing parser?\n");
00379 
00380     *data_size = (uint8_t*)samples - (uint8_t*)data;
00381     return buf_size;
00382 }
00383 
00384 #if CONFIG_ADPCM_G726_ENCODER
00385 AVCodec adpcm_g726_encoder = {
00386     "g726",
00387     CODEC_TYPE_AUDIO,
00388     CODEC_ID_ADPCM_G726,
00389     sizeof(G726Context),
00390     g726_init,
00391     g726_encode_frame,
00392     g726_close,
00393     NULL,
00394     .sample_fmts = (enum SampleFormat[]){SAMPLE_FMT_S16,SAMPLE_FMT_NONE},
00395     .long_name = NULL_IF_CONFIG_SMALL("G.726 ADPCM"),
00396 };
00397 #endif
00398 
00399 AVCodec adpcm_g726_decoder = {
00400     "g726",
00401     CODEC_TYPE_AUDIO,
00402     CODEC_ID_ADPCM_G726,
00403     sizeof(G726Context),
00404     g726_init,
00405     NULL,
00406     g726_close,
00407     g726_decode_frame,
00408     .long_name = NULL_IF_CONFIG_SMALL("G.726 ADPCM"),
00409 };

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