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 "get_bits.h" 27#include "put_bits.h" 28 29/** 30 * G.726 11bit float. 31 * G.726 Standard uses rather odd 11bit floating point arithmentic for 32 * numerous occasions. It's a mistery to me why they did it this way 33 * instead of simply using 32bit integer arithmetic. 34 */ 35typedef struct Float11 { 36 uint8_t sign; /**< 1bit sign */ 37 uint8_t exp; /**< 4bit exponent */ 38 uint8_t mant; /**< 6bit mantissa */ 39} Float11; 40 41static inline Float11* i2f(int i, Float11* f) 42{ 43 f->sign = (i < 0); 44 if (f->sign) 45 i = -i; 46 f->exp = av_log2_16bit(i) + !!i; 47 f->mant = i? (i<<6) >> f->exp : 1<<5; 48 return f; 49} 50 51static inline int16_t mult(Float11* f1, Float11* f2) 52{ 53 int res, exp; 54 55 exp = f1->exp + f2->exp; 56 res = (((f1->mant * f2->mant) + 0x30) >> 4); 57 res = exp > 19 ? res << (exp - 19) : res >> (19 - exp); 58 return (f1->sign ^ f2->sign) ? -res : res; 59} 60 61static inline int sgn(int value) 62{ 63 return (value < 0) ? -1 : 1; 64} 65 66typedef struct G726Tables { 67 const int* quant; /**< quantization table */ 68 const int16_t* iquant; /**< inverse quantization table */ 69 const int16_t* W; /**< special table #1 ;-) */ 70 const uint8_t* F; /**< special table #2 */ 71} G726Tables; 72 73typedef struct G726Context { 74 G726Tables tbls; /**< static tables needed for computation */ 75 76 Float11 sr[2]; /**< prev. reconstructed samples */ 77 Float11 dq[6]; /**< prev. difference */ 78 int a[2]; /**< second order predictor coeffs */ 79 int b[6]; /**< sixth order predictor coeffs */ 80 int pk[2]; /**< signs of prev. 2 sez + dq */ 81 82 int ap; /**< scale factor control */ 83 int yu; /**< fast scale factor */ 84 int yl; /**< slow scale factor */ 85 int dms; /**< short average magnitude of F[i] */ 86 int dml; /**< long average magnitude of F[i] */ 87 int td; /**< tone detect */ 88 89 int se; /**< estimated signal for the next iteration */ 90 int sez; /**< estimated second order prediction */ 91 int y; /**< quantizer scaling factor for the next iteration */ 92 int code_size; 93} G726Context; 94 95static const int quant_tbl16[] = /**< 16kbit/s 2bits per sample */ 96 { 260, INT_MAX }; 97static const int16_t iquant_tbl16[] = 98 { 116, 365, 365, 116 }; 99static const int16_t W_tbl16[] = 100 { -22, 439, 439, -22 }; 101static const uint8_t F_tbl16[] = 102 { 0, 7, 7, 0 }; 103 104static const int quant_tbl24[] = /**< 24kbit/s 3bits per sample */ 105 { 7, 217, 330, INT_MAX }; 106static const int16_t iquant_tbl24[] = 107 { INT16_MIN, 135, 273, 373, 373, 273, 135, INT16_MIN }; 108static const int16_t W_tbl24[] = 109 { -4, 30, 137, 582, 582, 137, 30, -4 }; 110static const uint8_t F_tbl24[] = 111 { 0, 1, 2, 7, 7, 2, 1, 0 }; 112 113static const int quant_tbl32[] = /**< 32kbit/s 4bits per sample */ 114 { -125, 79, 177, 245, 299, 348, 399, INT_MAX }; 115static const int16_t iquant_tbl32[] = 116 { INT16_MIN, 4, 135, 213, 273, 323, 373, 425, 117 425, 373, 323, 273, 213, 135, 4, INT16_MIN }; 118static const int16_t W_tbl32[] = 119 { -12, 18, 41, 64, 112, 198, 355, 1122, 120 1122, 355, 198, 112, 64, 41, 18, -12}; 121static const uint8_t F_tbl32[] = 122 { 0, 0, 0, 1, 1, 1, 3, 7, 7, 3, 1, 1, 1, 0, 0, 0 }; 123 124static const int quant_tbl40[] = /**< 40kbit/s 5bits per sample */ 125 { -122, -16, 67, 138, 197, 249, 297, 338, 126 377, 412, 444, 474, 501, 527, 552, INT_MAX }; 127static const int16_t iquant_tbl40[] = 128 { INT16_MIN, -66, 28, 104, 169, 224, 274, 318, 129 358, 395, 429, 459, 488, 514, 539, 566, 130 566, 539, 514, 488, 459, 429, 395, 358, 131 318, 274, 224, 169, 104, 28, -66, INT16_MIN }; 132static const int16_t W_tbl40[] = 133 { 14, 14, 24, 39, 40, 41, 58, 100, 134 141, 179, 219, 280, 358, 440, 529, 696, 135 696, 529, 440, 358, 280, 219, 179, 141, 136 100, 58, 41, 40, 39, 24, 14, 14 }; 137static const uint8_t F_tbl40[] = 138 { 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 2, 3, 4, 5, 6, 6, 139 6, 6, 5, 4, 3, 2, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0 }; 140 141static const G726Tables G726Tables_pool[] = 142 {{ quant_tbl16, iquant_tbl16, W_tbl16, F_tbl16 }, 143 { quant_tbl24, iquant_tbl24, W_tbl24, F_tbl24 }, 144 { quant_tbl32, iquant_tbl32, W_tbl32, F_tbl32 }, 145 { quant_tbl40, iquant_tbl40, W_tbl40, F_tbl40 }}; 146 147 148/** 149 * Para 4.2.2 page 18: Adaptive quantizer. 150 */ 151static inline uint8_t quant(G726Context* c, int d) 152{ 153 int sign, exp, i, dln; 154 155 sign = i = 0; 156 if (d < 0) { 157 sign = 1; 158 d = -d; 159 } 160 exp = av_log2_16bit(d); 161 dln = ((exp<<7) + (((d<<7)>>exp)&0x7f)) - (c->y>>2); 162 163 while (c->tbls.quant[i] < INT_MAX && c->tbls.quant[i] < dln) 164 ++i; 165 166 if (sign) 167 i = ~i; 168 if (c->code_size != 2 && i == 0) /* I'm not sure this is a good idea */ 169 i = 0xff; 170 171 return i; 172} 173 174/** 175 * Para 4.2.3 page 22: Inverse adaptive quantizer. 176 */ 177static inline int16_t inverse_quant(G726Context* c, int i) 178{ 179 int dql, dex, dqt; 180 181 dql = c->tbls.iquant[i] + (c->y >> 2); 182 dex = (dql>>7) & 0xf; /* 4bit exponent */ 183 dqt = (1<<7) + (dql & 0x7f); /* log2 -> linear */ 184 return (dql < 0) ? 0 : ((dqt<<dex) >> 7); 185} 186 187static int16_t g726_decode(G726Context* c, int I) 188{ 189 int dq, re_signal, pk0, fa1, i, tr, ylint, ylfrac, thr2, al, dq0; 190 Float11 f; 191 int I_sig= I >> (c->code_size - 1); 192 193 dq = inverse_quant(c, I); 194 195 /* Transition detect */ 196 ylint = (c->yl >> 15); 197 ylfrac = (c->yl >> 10) & 0x1f; 198 thr2 = (ylint > 9) ? 0x1f << 10 : (0x20 + ylfrac) << ylint; 199 tr= (c->td == 1 && dq > ((3*thr2)>>2)); 200 201 if (I_sig) /* get the sign */ 202 dq = -dq; 203 re_signal = c->se + dq; 204 205 /* Update second order predictor coefficient A2 and A1 */ 206 pk0 = (c->sez + dq) ? sgn(c->sez + dq) : 0; 207 dq0 = dq ? sgn(dq) : 0; 208 if (tr) { 209 c->a[0] = 0; 210 c->a[1] = 0; 211 for (i=0; i<6; i++) 212 c->b[i] = 0; 213 } else { 214 /* This is a bit crazy, but it really is +255 not +256 */ 215 fa1 = av_clip((-c->a[0]*c->pk[0]*pk0)>>5, -256, 255); 216 217 c->a[1] += 128*pk0*c->pk[1] + fa1 - (c->a[1]>>7); 218 c->a[1] = av_clip(c->a[1], -12288, 12288); 219 c->a[0] += 64*3*pk0*c->pk[0] - (c->a[0] >> 8); 220 c->a[0] = av_clip(c->a[0], -(15360 - c->a[1]), 15360 - c->a[1]); 221 222 for (i=0; i<6; i++) 223 c->b[i] += 128*dq0*sgn(-c->dq[i].sign) - (c->b[i]>>8); 224 } 225 226 /* Update Dq and Sr and Pk */ 227 c->pk[1] = c->pk[0]; 228 c->pk[0] = pk0 ? pk0 : 1; 229 c->sr[1] = c->sr[0]; 230 i2f(re_signal, &c->sr[0]); 231 for (i=5; i>0; i--) 232 c->dq[i] = c->dq[i-1]; 233 i2f(dq, &c->dq[0]); 234 c->dq[0].sign = I_sig; /* Isn't it crazy ?!?! */ 235 236 c->td = c->a[1] < -11776; 237 238 /* Update Ap */ 239 c->dms += (c->tbls.F[I]<<4) + ((- c->dms) >> 5); 240 c->dml += (c->tbls.F[I]<<4) + ((- c->dml) >> 7); 241 if (tr) 242 c->ap = 256; 243 else { 244 c->ap += (-c->ap) >> 4; 245 if (c->y <= 1535 || c->td || abs((c->dms << 2) - c->dml) >= (c->dml >> 3)) 246 c->ap += 0x20; 247 } 248 249 /* Update Yu and Yl */ 250 c->yu = av_clip(c->y + c->tbls.W[I] + ((-c->y)>>5), 544, 5120); 251 c->yl += c->yu + ((-c->yl)>>6); 252 253 /* Next iteration for Y */ 254 al = (c->ap >= 256) ? 1<<6 : c->ap >> 2; 255 c->y = (c->yl + (c->yu - (c->yl>>6))*al) >> 6; 256 257 /* Next iteration for SE and SEZ */ 258 c->se = 0; 259 for (i=0; i<6; i++) 260 c->se += mult(i2f(c->b[i] >> 2, &f), &c->dq[i]); 261 c->sez = c->se >> 1; 262 for (i=0; i<2; i++) 263 c->se += mult(i2f(c->a[i] >> 2, &f), &c->sr[i]); 264 c->se >>= 1; 265 266 return av_clip(re_signal << 2, -0xffff, 0xffff); 267} 268 269static av_cold int g726_reset(G726Context* c, int index) 270{ 271 int i; 272 273 c->tbls = G726Tables_pool[index]; 274 for (i=0; i<2; i++) { 275 c->sr[i].mant = 1<<5; 276 c->pk[i] = 1; 277 } 278 for (i=0; i<6; i++) { 279 c->dq[i].mant = 1<<5; 280 } 281 c->yu = 544; 282 c->yl = 34816; 283 284 c->y = 544; 285 286 return 0; 287} 288 289#if CONFIG_ADPCM_G726_ENCODER 290static int16_t g726_encode(G726Context* c, int16_t sig) 291{ 292 uint8_t i; 293 294 i = quant(c, sig/4 - c->se) & ((1<<c->code_size) - 1); 295 g726_decode(c, i); 296 return i; 297} 298#endif 299 300/* Interfacing to the libavcodec */ 301 302static av_cold int g726_init(AVCodecContext * avctx) 303{ 304 G726Context* c = avctx->priv_data; 305 unsigned int index; 306 307 if (avctx->sample_rate <= 0) { 308 av_log(avctx, AV_LOG_ERROR, "Samplerate is invalid\n"); 309 return -1; 310 } 311 312 index = (avctx->bit_rate + avctx->sample_rate/2) / avctx->sample_rate - 2; 313 314 if (avctx->bit_rate % avctx->sample_rate && avctx->codec->encode) { 315 av_log(avctx, AV_LOG_ERROR, "Bitrate - Samplerate combination is invalid\n"); 316 return -1; 317 } 318 if(avctx->channels != 1){ 319 av_log(avctx, AV_LOG_ERROR, "Only mono is supported\n"); 320 return -1; 321 } 322 if(index>3){ 323 av_log(avctx, AV_LOG_ERROR, "Unsupported number of bits %d\n", index+2); 324 return -1; 325 } 326 g726_reset(c, index); 327 c->code_size = index+2; 328 329 avctx->coded_frame = avcodec_alloc_frame(); 330 if (!avctx->coded_frame) 331 return AVERROR(ENOMEM); 332 avctx->coded_frame->key_frame = 1; 333 334 if (avctx->codec->decode) 335 avctx->sample_fmt = SAMPLE_FMT_S16; 336 337 return 0; 338} 339 340static av_cold int g726_close(AVCodecContext *avctx) 341{ 342 av_freep(&avctx->coded_frame); 343 return 0; 344} 345 346#if CONFIG_ADPCM_G726_ENCODER 347static int g726_encode_frame(AVCodecContext *avctx, 348 uint8_t *dst, int buf_size, void *data) 349{ 350 G726Context *c = avctx->priv_data; 351 short *samples = data; 352 PutBitContext pb; 353 354 init_put_bits(&pb, dst, 1024*1024); 355 356 for (; buf_size; buf_size--) 357 put_bits(&pb, c->code_size, g726_encode(c, *samples++)); 358 359 flush_put_bits(&pb); 360 361 return put_bits_count(&pb)>>3; 362} 363#endif 364 365static int g726_decode_frame(AVCodecContext *avctx, 366 void *data, int *data_size, 367 AVPacket *avpkt) 368{ 369 const uint8_t *buf = avpkt->data; 370 int buf_size = avpkt->size; 371 G726Context *c = avctx->priv_data; 372 short *samples = data; 373 GetBitContext gb; 374 375 init_get_bits(&gb, buf, buf_size * 8); 376 377 while (get_bits_count(&gb) + c->code_size <= buf_size*8) 378 *samples++ = g726_decode(c, get_bits(&gb, c->code_size)); 379 380 if(buf_size*8 != get_bits_count(&gb)) 381 av_log(avctx, AV_LOG_ERROR, "Frame invalidly split, missing parser?\n"); 382 383 *data_size = (uint8_t*)samples - (uint8_t*)data; 384 return buf_size; 385} 386 387#if CONFIG_ADPCM_G726_ENCODER 388AVCodec adpcm_g726_encoder = { 389 "g726", 390 AVMEDIA_TYPE_AUDIO, 391 CODEC_ID_ADPCM_G726, 392 sizeof(G726Context), 393 g726_init, 394 g726_encode_frame, 395 g726_close, 396 NULL, 397 .sample_fmts = (const enum SampleFormat[]){SAMPLE_FMT_S16,SAMPLE_FMT_NONE}, 398 .long_name = NULL_IF_CONFIG_SMALL("G.726 ADPCM"), 399}; 400#endif 401 402AVCodec adpcm_g726_decoder = { 403 "g726", 404 AVMEDIA_TYPE_AUDIO, 405 CODEC_ID_ADPCM_G726, 406 sizeof(G726Context), 407 g726_init, 408 NULL, 409 g726_close, 410 g726_decode_frame, 411 .long_name = NULL_IF_CONFIG_SMALL("G.726 ADPCM"), 412}; 413