1/* 2 * G.726 ADPCM audio codec 3 * Copyright (c) 2004 Roman Shaposhnik 4 * 5 * This is a very straightforward rendition of the G.726 6 * Section 4 "Computational Details". 7 * 8 * This file is part of FFmpeg. 9 * 10 * FFmpeg is free software; you can redistribute it and/or 11 * modify it under the terms of the GNU Lesser General Public 12 * License as published by the Free Software Foundation; either 13 * version 2.1 of the License, or (at your option) any later version. 14 * 15 * FFmpeg is distributed in the hope that it will be useful, 16 * but WITHOUT ANY WARRANTY; without even the implied warranty of 17 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 18 * Lesser General Public License for more details. 19 * 20 * You should have received a copy of the GNU Lesser General Public 21 * License along with FFmpeg; if not, write to the Free Software 22 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA 23 */ 24#include <limits.h> 25#include "avcodec.h" 26#include "bitstream.h" 27 28/** 29 * G.726 11bit float. 30 * G.726 Standard uses rather odd 11bit floating point arithmentic for 31 * numerous occasions. It's a mistery to me why they did it this way 32 * instead of simply using 32bit integer arithmetic. 33 */ 34typedef struct Float11 { 35 uint8_t sign; /**< 1bit sign */ 36 uint8_t exp; /**< 4bit exponent */ 37 uint8_t mant; /**< 6bit mantissa */ 38} Float11; 39 40static inline Float11* i2f(int i, Float11* f) 41{ 42 f->sign = (i < 0); 43 if (f->sign) 44 i = -i; 45 f->exp = av_log2_16bit(i) + !!i; 46 f->mant = i? (i<<6) >> f->exp : 1<<5; 47 return f; 48} 49 50static inline int16_t mult(Float11* f1, Float11* f2) 51{ 52 int res, exp; 53 54 exp = f1->exp + f2->exp; 55 res = (((f1->mant * f2->mant) + 0x30) >> 4); 56 res = exp > 19 ? res << (exp - 19) : res >> (19 - exp); 57 return (f1->sign ^ f2->sign) ? -res : res; 58} 59 60static inline int sgn(int value) 61{ 62 return (value < 0) ? -1 : 1; 63} 64 65typedef struct G726Tables { 66 const int* quant; /**< quantization table */ 67 const int16_t* iquant; /**< inverse quantization table */ 68 const int16_t* W; /**< special table #1 ;-) */ 69 const uint8_t* F; /**< special table #2 */ 70} G726Tables; 71 72typedef struct G726Context { 73 G726Tables tbls; /**< static tables needed for computation */ 74 75 Float11 sr[2]; /**< prev. reconstructed samples */ 76 Float11 dq[6]; /**< prev. difference */ 77 int a[2]; /**< second order predictor coeffs */ 78 int b[6]; /**< sixth order predictor coeffs */ 79 int pk[2]; /**< signs of prev. 2 sez + dq */ 80 81 int ap; /**< scale factor control */ 82 int yu; /**< fast scale factor */ 83 int yl; /**< slow scale factor */ 84 int dms; /**< short average magnitude of F[i] */ 85 int dml; /**< long average magnitude of F[i] */ 86 int td; /**< tone detect */ 87 88 int se; /**< estimated signal for the next iteration */ 89 int sez; /**< estimated second order prediction */ 90 int y; /**< quantizer scaling factor for the next iteration */ 91 int code_size; 92} G726Context; 93 94static const int quant_tbl16[] = /**< 16kbit/s 2bits per sample */ 95 { 260, INT_MAX }; 96static const int16_t iquant_tbl16[] = 97 { 116, 365, 365, 116 }; 98static const int16_t W_tbl16[] = 99 { -22, 439, 439, -22 }; 100static const uint8_t F_tbl16[] = 101 { 0, 7, 7, 0 }; 102 103static const int quant_tbl24[] = /**< 24kbit/s 3bits per sample */ 104 { 7, 217, 330, INT_MAX }; 105static const int16_t iquant_tbl24[] = 106 { INT16_MIN, 135, 273, 373, 373, 273, 135, INT16_MIN }; 107static const int16_t W_tbl24[] = 108 { -4, 30, 137, 582, 582, 137, 30, -4 }; 109static const uint8_t F_tbl24[] = 110 { 0, 1, 2, 7, 7, 2, 1, 0 }; 111 112static const int quant_tbl32[] = /**< 32kbit/s 4bits per sample */ 113 { -125, 79, 177, 245, 299, 348, 399, INT_MAX }; 114static const int16_t iquant_tbl32[] = 115 { INT16_MIN, 4, 135, 213, 273, 323, 373, 425, 116 425, 373, 323, 273, 213, 135, 4, INT16_MIN }; 117static const int16_t W_tbl32[] = 118 { -12, 18, 41, 64, 112, 198, 355, 1122, 119 1122, 355, 198, 112, 64, 41, 18, -12}; 120static const uint8_t F_tbl32[] = 121 { 0, 0, 0, 1, 1, 1, 3, 7, 7, 3, 1, 1, 1, 0, 0, 0 }; 122 123static const int quant_tbl40[] = /**< 40kbit/s 5bits per sample */ 124 { -122, -16, 67, 138, 197, 249, 297, 338, 125 377, 412, 444, 474, 501, 527, 552, INT_MAX }; 126static const int16_t iquant_tbl40[] = 127 { INT16_MIN, -66, 28, 104, 169, 224, 274, 318, 128 358, 395, 429, 459, 488, 514, 539, 566, 129 566, 539, 514, 488, 459, 429, 395, 358, 130 318, 274, 224, 169, 104, 28, -66, INT16_MIN }; 131static const int16_t W_tbl40[] = 132 { 14, 14, 24, 39, 40, 41, 58, 100, 133 141, 179, 219, 280, 358, 440, 529, 696, 134 696, 529, 440, 358, 280, 219, 179, 141, 135 100, 58, 41, 40, 39, 24, 14, 14 }; 136static const uint8_t F_tbl40[] = 137 { 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 2, 3, 4, 5, 6, 6, 138 6, 6, 5, 4, 3, 2, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0 }; 139 140static const G726Tables G726Tables_pool[] = 141 {{ quant_tbl16, iquant_tbl16, W_tbl16, F_tbl16 }, 142 { quant_tbl24, iquant_tbl24, W_tbl24, F_tbl24 }, 143 { quant_tbl32, iquant_tbl32, W_tbl32, F_tbl32 }, 144 { quant_tbl40, iquant_tbl40, W_tbl40, F_tbl40 }}; 145 146 147/** 148 * Para 4.2.2 page 18: Adaptive quantizer. 149 */ 150static inline uint8_t quant(G726Context* c, int d) 151{ 152 int sign, exp, i, dln; 153 154 sign = i = 0; 155 if (d < 0) { 156 sign = 1; 157 d = -d; 158 } 159 exp = av_log2_16bit(d); 160 dln = ((exp<<7) + (((d<<7)>>exp)&0x7f)) - (c->y>>2); 161 162 while (c->tbls.quant[i] < INT_MAX && c->tbls.quant[i] < dln) 163 ++i; 164 165 if (sign) 166 i = ~i; 167 if (c->code_size != 2 && i == 0) /* I'm not sure this is a good idea */ 168 i = 0xff; 169 170 return i; 171} 172 173/** 174 * Para 4.2.3 page 22: Inverse adaptive quantizer. 175 */ 176static inline int16_t inverse_quant(G726Context* c, int i) 177{ 178 int dql, dex, dqt; 179 180 dql = c->tbls.iquant[i] + (c->y >> 2); 181 dex = (dql>>7) & 0xf; /* 4bit exponent */ 182 dqt = (1<<7) + (dql & 0x7f); /* log2 -> linear */ 183 return (dql < 0) ? 0 : ((dqt<<dex) >> 7); 184} 185 186static int16_t g726_decode(G726Context* c, int I) 187{ 188 int dq, re_signal, pk0, fa1, i, tr, ylint, ylfrac, thr2, al, dq0; 189 Float11 f; 190 int I_sig= I >> (c->code_size - 1); 191 192 dq = inverse_quant(c, I); 193 194 /* Transition detect */ 195 ylint = (c->yl >> 15); 196 ylfrac = (c->yl >> 10) & 0x1f; 197 thr2 = (ylint > 9) ? 0x1f << 10 : (0x20 + ylfrac) << ylint; 198 tr= (c->td == 1 && dq > ((3*thr2)>>2)); 199 200 if (I_sig) /* get the sign */ 201 dq = -dq; 202 re_signal = c->se + dq; 203 204 /* Update second order predictor coefficient A2 and A1 */ 205 pk0 = (c->sez + dq) ? sgn(c->sez + dq) : 0; 206 dq0 = dq ? sgn(dq) : 0; 207 if (tr) { 208 c->a[0] = 0; 209 c->a[1] = 0; 210 for (i=0; i<6; i++) 211 c->b[i] = 0; 212 } else { 213 /* This is a bit crazy, but it really is +255 not +256 */ 214 fa1 = av_clip((-c->a[0]*c->pk[0]*pk0)>>5, -256, 255); 215 216 c->a[1] += 128*pk0*c->pk[1] + fa1 - (c->a[1]>>7); 217 c->a[1] = av_clip(c->a[1], -12288, 12288); 218 c->a[0] += 64*3*pk0*c->pk[0] - (c->a[0] >> 8); 219 c->a[0] = av_clip(c->a[0], -(15360 - c->a[1]), 15360 - c->a[1]); 220 221 for (i=0; i<6; i++) 222 c->b[i] += 128*dq0*sgn(-c->dq[i].sign) - (c->b[i]>>8); 223 } 224 225 /* Update Dq and Sr and Pk */ 226 c->pk[1] = c->pk[0]; 227 c->pk[0] = pk0 ? pk0 : 1; 228 c->sr[1] = c->sr[0]; 229 i2f(re_signal, &c->sr[0]); 230 for (i=5; i>0; i--) 231 c->dq[i] = c->dq[i-1]; 232 i2f(dq, &c->dq[0]); 233 c->dq[0].sign = I_sig; /* Isn't it crazy ?!?! */ 234 235 c->td = c->a[1] < -11776; 236 237 /* Update Ap */ 238 c->dms += (c->tbls.F[I]<<4) + ((- c->dms) >> 5); 239 c->dml += (c->tbls.F[I]<<4) + ((- c->dml) >> 7); 240 if (tr) 241 c->ap = 256; 242 else { 243 c->ap += (-c->ap) >> 4; 244 if (c->y <= 1535 || c->td || abs((c->dms << 2) - c->dml) >= (c->dml >> 3)) 245 c->ap += 0x20; 246 } 247 248 /* Update Yu and Yl */ 249 c->yu = av_clip(c->y + c->tbls.W[I] + ((-c->y)>>5), 544, 5120); 250 c->yl += c->yu + ((-c->yl)>>6); 251 252 /* Next iteration for Y */ 253 al = (c->ap >= 256) ? 1<<6 : c->ap >> 2; 254 c->y = (c->yl + (c->yu - (c->yl>>6))*al) >> 6; 255 256 /* Next iteration for SE and SEZ */ 257 c->se = 0; 258 for (i=0; i<6; i++) 259 c->se += mult(i2f(c->b[i] >> 2, &f), &c->dq[i]); 260 c->sez = c->se >> 1; 261 for (i=0; i<2; i++) 262 c->se += mult(i2f(c->a[i] >> 2, &f), &c->sr[i]); 263 c->se >>= 1; 264 265 return av_clip(re_signal << 2, -0xffff, 0xffff); 266} 267 268static av_cold int g726_reset(G726Context* c, int index) 269{ 270 int i; 271 272 c->tbls = G726Tables_pool[index]; 273 for (i=0; i<2; i++) { 274 c->sr[i].mant = 1<<5; 275 c->pk[i] = 1; 276 } 277 for (i=0; i<6; i++) { 278 c->dq[i].mant = 1<<5; 279 } 280 c->yu = 544; 281 c->yl = 34816; 282 283 c->y = 544; 284 285 return 0; 286} 287 288#if CONFIG_ADPCM_G726_ENCODER 289static int16_t g726_encode(G726Context* c, int16_t sig) 290{ 291 uint8_t i; 292 293 i = quant(c, sig/4 - c->se) & ((1<<c->code_size) - 1); 294 g726_decode(c, i); 295 return i; 296} 297#endif 298 299/* Interfacing to the libavcodec */ 300 301static av_cold int g726_init(AVCodecContext * avctx) 302{ 303 G726Context* c = avctx->priv_data; 304 unsigned int index; 305 306 if (avctx->sample_rate <= 0) { 307 av_log(avctx, AV_LOG_ERROR, "Samplerate is invalid\n"); 308 return -1; 309 } 310 311 index = (avctx->bit_rate + avctx->sample_rate/2) / avctx->sample_rate - 2; 312 313 if (avctx->bit_rate % avctx->sample_rate && avctx->codec->encode) { 314 av_log(avctx, AV_LOG_ERROR, "Bitrate - Samplerate combination is invalid\n"); 315 return -1; 316 } 317 if(avctx->channels != 1){ 318 av_log(avctx, AV_LOG_ERROR, "Only mono is supported\n"); 319 return -1; 320 } 321 if(index>3){ 322 av_log(avctx, AV_LOG_ERROR, "Unsupported number of bits %d\n", index+2); 323 return -1; 324 } 325 g726_reset(c, index); 326 c->code_size = index+2; 327 328 avctx->coded_frame = avcodec_alloc_frame(); 329 if (!avctx->coded_frame) 330 return AVERROR(ENOMEM); 331 avctx->coded_frame->key_frame = 1; 332 333 if (avctx->codec->decode) 334 avctx->sample_fmt = SAMPLE_FMT_S16; 335 336 return 0; 337} 338 339static av_cold int g726_close(AVCodecContext *avctx) 340{ 341 av_freep(&avctx->coded_frame); 342 return 0; 343} 344 345#if CONFIG_ADPCM_G726_ENCODER 346static int g726_encode_frame(AVCodecContext *avctx, 347 uint8_t *dst, int buf_size, void *data) 348{ 349 G726Context *c = avctx->priv_data; 350 short *samples = data; 351 PutBitContext pb; 352 353 init_put_bits(&pb, dst, 1024*1024); 354 355 for (; buf_size; buf_size--) 356 put_bits(&pb, c->code_size, g726_encode(c, *samples++)); 357 358 flush_put_bits(&pb); 359 360 return put_bits_count(&pb)>>3; 361} 362#endif 363 364static int g726_decode_frame(AVCodecContext *avctx, 365 void *data, int *data_size, 366 const uint8_t *buf, int buf_size) 367{ 368 G726Context *c = avctx->priv_data; 369 short *samples = data; 370 GetBitContext gb; 371 372 init_get_bits(&gb, buf, buf_size * 8); 373 374 while (get_bits_count(&gb) + c->code_size <= buf_size*8) 375 *samples++ = g726_decode(c, get_bits(&gb, c->code_size)); 376 377 if(buf_size*8 != get_bits_count(&gb)) 378 av_log(avctx, AV_LOG_ERROR, "Frame invalidly split, missing parser?\n"); 379 380 *data_size = (uint8_t*)samples - (uint8_t*)data; 381 return buf_size; 382} 383 384#if CONFIG_ADPCM_G726_ENCODER 385AVCodec adpcm_g726_encoder = { 386 "g726", 387 CODEC_TYPE_AUDIO, 388 CODEC_ID_ADPCM_G726, 389 sizeof(G726Context), 390 g726_init, 391 g726_encode_frame, 392 g726_close, 393 NULL, 394 .sample_fmts = (enum SampleFormat[]){SAMPLE_FMT_S16,SAMPLE_FMT_NONE}, 395 .long_name = NULL_IF_CONFIG_SMALL("G.726 ADPCM"), 396}; 397#endif 398 399AVCodec adpcm_g726_decoder = { 400 "g726", 401 CODEC_TYPE_AUDIO, 402 CODEC_ID_ADPCM_G726, 403 sizeof(G726Context), 404 g726_init, 405 NULL, 406 g726_close, 407 g726_decode_frame, 408 .long_name = NULL_IF_CONFIG_SMALL("G.726 ADPCM"), 409}; 410