1/* 2 * E-AC-3 decoder 3 * Copyright (c) 2007 Bartlomiej Wolowiec <bartek.wolowiec@gmail.com> 4 * Copyright (c) 2008 Justin Ruggles 5 * 6 * This file is part of FFmpeg. 7 * 8 * FFmpeg is free software; you can redistribute it and/or 9 * modify it under the terms of the GNU Lesser General Public 10 * License as published by the Free Software Foundation; either 11 * version 2.1 of the License, or (at your option) any later version. 12 * 13 * FFmpeg is distributed in the hope that it will be useful, 14 * but WITHOUT ANY WARRANTY; without even the implied warranty of 15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 16 * Lesser General Public License for more details. 17 * 18 * You should have received a copy of the GNU Lesser General Public 19 * License along with FFmpeg; if not, write to the Free Software 20 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA 21 */ 22 23/* 24 * There are several features of E-AC-3 that this decoder does not yet support. 25 * 26 * Enhanced Coupling 27 * No known samples exist. If any ever surface, this feature should not be 28 * too difficult to implement. 29 * 30 * Reduced Sample Rates 31 * No known samples exist. The spec also does not give clear information 32 * on how this is to be implemented. 33 * 34 * Transient Pre-noise Processing 35 * This is side information which a decoder should use to reduce artifacts 36 * caused by transients. There are samples which are known to have this 37 * information, but this decoder currently ignores it. 38 */ 39 40 41#include "avcodec.h" 42#include "aac_ac3_parser.h" 43#include "ac3.h" 44#include "ac3dec.h" 45#include "ac3dec_data.h" 46#include "eac3_data.h" 47 48/** gain adaptive quantization mode */ 49typedef enum { 50 EAC3_GAQ_NO =0, 51 EAC3_GAQ_12, 52 EAC3_GAQ_14, 53 EAC3_GAQ_124 54} EAC3GaqMode; 55 56#define EAC3_SR_CODE_REDUCED 3 57 58static void ff_eac3_apply_spectral_extension(AC3DecodeContext *s) 59{ 60 int bin, bnd, ch, i; 61 uint8_t wrapflag[SPX_MAX_BANDS]={1,0,}, num_copy_sections, copy_sizes[SPX_MAX_BANDS]; 62 float rms_energy[SPX_MAX_BANDS]; 63 64 /* Set copy index mapping table. Set wrap flags to apply a notch filter at 65 wrap points later on. */ 66 bin = s->spx_dst_start_freq; 67 num_copy_sections = 0; 68 for (bnd = 0; bnd < s->num_spx_bands; bnd++) { 69 int copysize; 70 int bandsize = s->spx_band_sizes[bnd]; 71 if (bin + bandsize > s->spx_src_start_freq) { 72 copy_sizes[num_copy_sections++] = bin - s->spx_dst_start_freq; 73 bin = s->spx_dst_start_freq; 74 wrapflag[bnd] = 1; 75 } 76 for (i = 0; i < bandsize; i += copysize) { 77 if (bin == s->spx_src_start_freq) { 78 copy_sizes[num_copy_sections++] = bin - s->spx_dst_start_freq; 79 bin = s->spx_dst_start_freq; 80 } 81 copysize = FFMIN(bandsize - i, s->spx_src_start_freq - bin); 82 bin += copysize; 83 } 84 } 85 copy_sizes[num_copy_sections++] = bin - s->spx_dst_start_freq; 86 87 for (ch = 1; ch <= s->fbw_channels; ch++) { 88 if (!s->channel_uses_spx[ch]) 89 continue; 90 91 /* Copy coeffs from normal bands to extension bands */ 92 bin = s->spx_src_start_freq; 93 for (i = 0; i < num_copy_sections; i++) { 94 memcpy(&s->transform_coeffs[ch][bin], 95 &s->transform_coeffs[ch][s->spx_dst_start_freq], 96 copy_sizes[i]*sizeof(INTFLOAT)); 97 bin += copy_sizes[i]; 98 } 99 100 /* Calculate RMS energy for each SPX band. */ 101 bin = s->spx_src_start_freq; 102 for (bnd = 0; bnd < s->num_spx_bands; bnd++) { 103 int bandsize = s->spx_band_sizes[bnd]; 104 float accum = 0.0f; 105 for (i = 0; i < bandsize; i++) { 106 float coeff = s->transform_coeffs[ch][bin++]; 107 accum += coeff * coeff; 108 } 109 rms_energy[bnd] = sqrtf(accum / bandsize); 110 } 111 112 /* Apply a notch filter at transitions between normal and extension 113 bands and at all wrap points. */ 114 if (s->spx_atten_code[ch] >= 0) { 115 const float *atten_tab = ff_eac3_spx_atten_tab[s->spx_atten_code[ch]]; 116 bin = s->spx_src_start_freq - 2; 117 for (bnd = 0; bnd < s->num_spx_bands; bnd++) { 118 if (wrapflag[bnd]) { 119 INTFLOAT *coeffs = &s->transform_coeffs[ch][bin]; 120 coeffs[0] *= atten_tab[0]; 121 coeffs[1] *= atten_tab[1]; 122 coeffs[2] *= atten_tab[2]; 123 coeffs[3] *= atten_tab[1]; 124 coeffs[4] *= atten_tab[0]; 125 } 126 bin += s->spx_band_sizes[bnd]; 127 } 128 } 129 130 /* Apply noise-blended coefficient scaling based on previously 131 calculated RMS energy, blending factors, and SPX coordinates for 132 each band. */ 133 bin = s->spx_src_start_freq; 134 for (bnd = 0; bnd < s->num_spx_bands; bnd++) { 135 float nscale = s->spx_noise_blend[ch][bnd] * rms_energy[bnd] * (1.0f / INT32_MIN); 136 float sscale = s->spx_signal_blend[ch][bnd]; 137#if USE_FIXED 138 // spx_noise_blend and spx_signal_blend are both FP.23 139 nscale *= 1.0 / (1<<23); 140 sscale *= 1.0 / (1<<23); 141 if (nscale < -1.0) 142 nscale = -1.0; 143#endif 144 for (i = 0; i < s->spx_band_sizes[bnd]; i++) { 145 UINTFLOAT noise = (INTFLOAT)(nscale * (int32_t)av_lfg_get(&s->dith_state)); 146 s->transform_coeffs[ch][bin] *= sscale; 147 s->transform_coeffs[ch][bin++] += noise; 148 } 149 } 150 } 151} 152 153 154/** lrint(M_SQRT2*cos(2*M_PI/12)*(1<<23)) */ 155#define COEFF_0 10273905LL 156 157/** lrint(M_SQRT2*cos(0*M_PI/12)*(1<<23)) = lrint(M_SQRT2*(1<<23)) */ 158#define COEFF_1 11863283LL 159 160/** lrint(M_SQRT2*cos(5*M_PI/12)*(1<<23)) */ 161#define COEFF_2 3070444LL 162 163/** 164 * Calculate 6-point IDCT of the pre-mantissas. 165 * All calculations are 24-bit fixed-point. 166 */ 167static void idct6(int pre_mant[6]) 168{ 169 int tmp; 170 int even0, even1, even2, odd0, odd1, odd2; 171 172 odd1 = pre_mant[1] - pre_mant[3] - pre_mant[5]; 173 174 even2 = ( pre_mant[2] * COEFF_0) >> 23; 175 tmp = ( pre_mant[4] * COEFF_1) >> 23; 176 odd0 = ((pre_mant[1] + pre_mant[5]) * COEFF_2) >> 23; 177 178 even0 = pre_mant[0] + (tmp >> 1); 179 even1 = pre_mant[0] - tmp; 180 181 tmp = even0; 182 even0 = tmp + even2; 183 even2 = tmp - even2; 184 185 tmp = odd0; 186 odd0 = tmp + pre_mant[1] + pre_mant[3]; 187 odd2 = tmp + pre_mant[5] - pre_mant[3]; 188 189 pre_mant[0] = even0 + odd0; 190 pre_mant[1] = even1 + odd1; 191 pre_mant[2] = even2 + odd2; 192 pre_mant[3] = even2 - odd2; 193 pre_mant[4] = even1 - odd1; 194 pre_mant[5] = even0 - odd0; 195} 196 197static void ff_eac3_decode_transform_coeffs_aht_ch(AC3DecodeContext *s, int ch) 198{ 199 int bin, blk, gs; 200 int end_bap, gaq_mode; 201 GetBitContext *gbc = &s->gbc; 202 int gaq_gain[AC3_MAX_COEFS]; 203 204 gaq_mode = get_bits(gbc, 2); 205 end_bap = (gaq_mode < 2) ? 12 : 17; 206 207 /* if GAQ gain is used, decode gain codes for bins with hebap between 208 8 and end_bap */ 209 gs = 0; 210 if (gaq_mode == EAC3_GAQ_12 || gaq_mode == EAC3_GAQ_14) { 211 /* read 1-bit GAQ gain codes */ 212 for (bin = s->start_freq[ch]; bin < s->end_freq[ch]; bin++) { 213 if (s->bap[ch][bin] > 7 && s->bap[ch][bin] < end_bap) 214 gaq_gain[gs++] = get_bits1(gbc) << (gaq_mode-1); 215 } 216 } else if (gaq_mode == EAC3_GAQ_124) { 217 /* read 1.67-bit GAQ gain codes (3 codes in 5 bits) */ 218 int gc = 2; 219 for (bin = s->start_freq[ch]; bin < s->end_freq[ch]; bin++) { 220 if (s->bap[ch][bin] > 7 && s->bap[ch][bin] < 17) { 221 if (gc++ == 2) { 222 int group_code = get_bits(gbc, 5); 223 if (group_code > 26) { 224 av_log(s->avctx, AV_LOG_WARNING, "GAQ gain group code out-of-range\n"); 225 group_code = 26; 226 } 227 gaq_gain[gs++] = ff_ac3_ungroup_3_in_5_bits_tab[group_code][0]; 228 gaq_gain[gs++] = ff_ac3_ungroup_3_in_5_bits_tab[group_code][1]; 229 gaq_gain[gs++] = ff_ac3_ungroup_3_in_5_bits_tab[group_code][2]; 230 gc = 0; 231 } 232 } 233 } 234 } 235 236 gs=0; 237 for (bin = s->start_freq[ch]; bin < s->end_freq[ch]; bin++) { 238 int hebap = s->bap[ch][bin]; 239 int bits = ff_eac3_bits_vs_hebap[hebap]; 240 if (!hebap) { 241 /* zero-mantissa dithering */ 242 for (blk = 0; blk < 6; blk++) { 243 s->pre_mantissa[ch][bin][blk] = (av_lfg_get(&s->dith_state) & 0x7FFFFF) - 0x400000; 244 } 245 } else if (hebap < 8) { 246 /* Vector Quantization */ 247 int v = get_bits(gbc, bits); 248 for (blk = 0; blk < 6; blk++) { 249 s->pre_mantissa[ch][bin][blk] = ff_eac3_mantissa_vq[hebap][v][blk] * (1 << 8); 250 } 251 } else { 252 /* Gain Adaptive Quantization */ 253 int gbits, log_gain; 254 if (gaq_mode != EAC3_GAQ_NO && hebap < end_bap) { 255 log_gain = gaq_gain[gs++]; 256 } else { 257 log_gain = 0; 258 } 259 gbits = bits - log_gain; 260 261 for (blk = 0; blk < 6; blk++) { 262 int mant = get_sbits(gbc, gbits); 263 if (log_gain && mant == -(1 << (gbits-1))) { 264 /* large mantissa */ 265 int b; 266 int mbits = bits - (2 - log_gain); 267 mant = get_sbits(gbc, mbits); 268 mant = ((unsigned)mant) << (23 - (mbits - 1)); 269 /* remap mantissa value to correct for asymmetric quantization */ 270 if (mant >= 0) 271 b = 1 << (23 - log_gain); 272 else 273 b = ff_eac3_gaq_remap_2_4_b[hebap-8][log_gain-1] * (1 << 8); 274 mant += ((ff_eac3_gaq_remap_2_4_a[hebap-8][log_gain-1] * (int64_t)mant) >> 15) + b; 275 } else { 276 /* small mantissa, no GAQ, or Gk=1 */ 277 mant *= (1 << 24 - bits); 278 if (!log_gain) { 279 /* remap mantissa value for no GAQ or Gk=1 */ 280 mant += (ff_eac3_gaq_remap_1[hebap-8] * (int64_t)mant) >> 15; 281 } 282 } 283 s->pre_mantissa[ch][bin][blk] = mant; 284 } 285 } 286 idct6(s->pre_mantissa[ch][bin]); 287 } 288} 289 290static int ff_eac3_parse_header(AC3DecodeContext *s) 291{ 292 int i, blk, ch; 293 int ac3_exponent_strategy, parse_aht_info, parse_spx_atten_data; 294 int parse_transient_proc_info; 295 int num_cpl_blocks; 296 GetBitContext *gbc = &s->gbc; 297 298 /* An E-AC-3 stream can have multiple independent streams which the 299 application can select from. each independent stream can also contain 300 dependent streams which are used to add or replace channels. */ 301 if (s->frame_type == EAC3_FRAME_TYPE_RESERVED) { 302 av_log(s->avctx, AV_LOG_ERROR, "Reserved frame type\n"); 303 return AAC_AC3_PARSE_ERROR_FRAME_TYPE; 304 } 305 306 /* The substream id indicates which substream this frame belongs to. each 307 independent stream has its own substream id, and the dependent streams 308 associated to an independent stream have matching substream id's. */ 309 if (s->substreamid) { 310 /* only decode substream with id=0. skip any additional substreams. */ 311 if (!s->eac3_subsbtreamid_found) { 312 s->eac3_subsbtreamid_found = 1; 313 avpriv_request_sample(s->avctx, "Additional substreams"); 314 } 315 return AAC_AC3_PARSE_ERROR_FRAME_TYPE; 316 } 317 318 if (s->bit_alloc_params.sr_code == EAC3_SR_CODE_REDUCED) { 319 /* The E-AC-3 specification does not tell how to handle reduced sample 320 rates in bit allocation. The best assumption would be that it is 321 handled like AC-3 DolbyNet, but we cannot be sure until we have a 322 sample which utilizes this feature. */ 323 avpriv_request_sample(s->avctx, "Reduced sampling rate"); 324 return AVERROR_PATCHWELCOME; 325 } 326 skip_bits(gbc, 5); // skip bitstream id 327 328 /* volume control params */ 329 for (i = 0; i < (s->channel_mode ? 1 : 2); i++) { 330 s->dialog_normalization[i] = -get_bits(gbc, 5); 331 if (s->dialog_normalization[i] == 0) { 332 s->dialog_normalization[i] = -31; 333 } 334 if (s->target_level != 0) { 335 s->level_gain[i] = powf(2.0f, 336 (float)(s->target_level - s->dialog_normalization[i])/6.0f); 337 } 338 s->compression_exists[i] = get_bits1(gbc); 339 if (s->compression_exists[i]) { 340 s->heavy_dynamic_range[i] = AC3_HEAVY_RANGE(get_bits(gbc, 8)); 341 } 342 } 343 344 /* dependent stream channel map */ 345 if (s->frame_type == EAC3_FRAME_TYPE_DEPENDENT) { 346 if (get_bits1(gbc)) { 347 int64_t channel_layout = 0; 348 int channel_map = get_bits(gbc, 16); 349 av_log(s->avctx, AV_LOG_DEBUG, "channel_map: %0X\n", channel_map); 350 351 for (i = 0; i < 16; i++) 352 if (channel_map & (1 << (EAC3_MAX_CHANNELS - i - 1))) 353 channel_layout |= ff_eac3_custom_channel_map_locations[i][1]; 354 355 if (av_popcount64(channel_layout) > EAC3_MAX_CHANNELS) { 356 return AVERROR_INVALIDDATA; 357 } 358 s->channel_map = channel_map; 359 } 360 } 361 362 /* mixing metadata */ 363 if (get_bits1(gbc)) { 364 /* center and surround mix levels */ 365 if (s->channel_mode > AC3_CHMODE_STEREO) { 366 s->preferred_downmix = get_bits(gbc, 2); 367 if (s->channel_mode & 1) { 368 /* if three front channels exist */ 369 s->center_mix_level_ltrt = get_bits(gbc, 3); 370 s->center_mix_level = get_bits(gbc, 3); 371 } 372 if (s->channel_mode & 4) { 373 /* if a surround channel exists */ 374 s->surround_mix_level_ltrt = av_clip(get_bits(gbc, 3), 3, 7); 375 s->surround_mix_level = av_clip(get_bits(gbc, 3), 3, 7); 376 } 377 } 378 379 /* lfe mix level */ 380 if (s->lfe_on && (s->lfe_mix_level_exists = get_bits1(gbc))) { 381 s->lfe_mix_level = get_bits(gbc, 5); 382 } 383 384 /* info for mixing with other streams and substreams */ 385 if (s->frame_type == EAC3_FRAME_TYPE_INDEPENDENT) { 386 for (i = 0; i < (s->channel_mode ? 1 : 2); i++) { 387 // TODO: apply program scale factor 388 if (get_bits1(gbc)) { 389 skip_bits(gbc, 6); // skip program scale factor 390 } 391 } 392 if (get_bits1(gbc)) { 393 skip_bits(gbc, 6); // skip external program scale factor 394 } 395 /* skip mixing parameter data */ 396 switch(get_bits(gbc, 2)) { 397 case 1: skip_bits(gbc, 5); break; 398 case 2: skip_bits(gbc, 12); break; 399 case 3: { 400 int mix_data_size = (get_bits(gbc, 5) + 2) << 3; 401 skip_bits_long(gbc, mix_data_size); 402 break; 403 } 404 } 405 /* skip pan information for mono or dual mono source */ 406 if (s->channel_mode < AC3_CHMODE_STEREO) { 407 for (i = 0; i < (s->channel_mode ? 1 : 2); i++) { 408 if (get_bits1(gbc)) { 409 /* note: this is not in the ATSC A/52B specification 410 reference: ETSI TS 102 366 V1.1.1 411 section: E.1.3.1.25 */ 412 skip_bits(gbc, 8); // skip pan mean direction index 413 skip_bits(gbc, 6); // skip reserved paninfo bits 414 } 415 } 416 } 417 /* skip mixing configuration information */ 418 if (get_bits1(gbc)) { 419 for (blk = 0; blk < s->num_blocks; blk++) { 420 if (s->num_blocks == 1 || get_bits1(gbc)) { 421 skip_bits(gbc, 5); 422 } 423 } 424 } 425 } 426 } 427 428 /* informational metadata */ 429 if (get_bits1(gbc)) { 430 s->bitstream_mode = get_bits(gbc, 3); 431 skip_bits(gbc, 2); // skip copyright bit and original bitstream bit 432 if (s->channel_mode == AC3_CHMODE_STEREO) { 433 s->dolby_surround_mode = get_bits(gbc, 2); 434 s->dolby_headphone_mode = get_bits(gbc, 2); 435 } 436 if (s->channel_mode >= AC3_CHMODE_2F2R) { 437 s->dolby_surround_ex_mode = get_bits(gbc, 2); 438 } 439 for (i = 0; i < (s->channel_mode ? 1 : 2); i++) { 440 if (get_bits1(gbc)) { 441 skip_bits(gbc, 8); // skip mix level, room type, and A/D converter type 442 } 443 } 444 if (s->bit_alloc_params.sr_code != EAC3_SR_CODE_REDUCED) { 445 skip_bits1(gbc); // skip source sample rate code 446 } 447 } 448 449 /* converter synchronization flag 450 If frames are less than six blocks, this bit should be turned on 451 once every 6 blocks to indicate the start of a frame set. 452 reference: RFC 4598, Section 2.1.3 Frame Sets */ 453 if (s->frame_type == EAC3_FRAME_TYPE_INDEPENDENT && s->num_blocks != 6) { 454 skip_bits1(gbc); // skip converter synchronization flag 455 } 456 457 /* original frame size code if this stream was converted from AC-3 */ 458 if (s->frame_type == EAC3_FRAME_TYPE_AC3_CONVERT && 459 (s->num_blocks == 6 || get_bits1(gbc))) { 460 skip_bits(gbc, 6); // skip frame size code 461 } 462 463 /* additional bitstream info */ 464 if (get_bits1(gbc)) { 465 int addbsil = get_bits(gbc, 6); 466 for (i = 0; i < addbsil + 1; i++) { 467 skip_bits(gbc, 8); // skip additional bit stream info 468 } 469 } 470 471 /* audio frame syntax flags, strategy data, and per-frame data */ 472 473 if (s->num_blocks == 6) { 474 ac3_exponent_strategy = get_bits1(gbc); 475 parse_aht_info = get_bits1(gbc); 476 } else { 477 /* less than 6 blocks, so use AC-3-style exponent strategy syntax, and 478 do not use AHT */ 479 ac3_exponent_strategy = 1; 480 parse_aht_info = 0; 481 } 482 483 s->snr_offset_strategy = get_bits(gbc, 2); 484 parse_transient_proc_info = get_bits1(gbc); 485 486 s->block_switch_syntax = get_bits1(gbc); 487 if (!s->block_switch_syntax) 488 memset(s->block_switch, 0, sizeof(s->block_switch)); 489 490 s->dither_flag_syntax = get_bits1(gbc); 491 if (!s->dither_flag_syntax) { 492 for (ch = 1; ch <= s->fbw_channels; ch++) 493 s->dither_flag[ch] = 1; 494 } 495 s->dither_flag[CPL_CH] = s->dither_flag[s->lfe_ch] = 0; 496 497 s->bit_allocation_syntax = get_bits1(gbc); 498 if (!s->bit_allocation_syntax) { 499 /* set default bit allocation parameters */ 500 s->bit_alloc_params.slow_decay = ff_ac3_slow_decay_tab[2]; 501 s->bit_alloc_params.fast_decay = ff_ac3_fast_decay_tab[1]; 502 s->bit_alloc_params.slow_gain = ff_ac3_slow_gain_tab [1]; 503 s->bit_alloc_params.db_per_bit = ff_ac3_db_per_bit_tab[2]; 504 s->bit_alloc_params.floor = ff_ac3_floor_tab [7]; 505 } 506 507 s->fast_gain_syntax = get_bits1(gbc); 508 s->dba_syntax = get_bits1(gbc); 509 s->skip_syntax = get_bits1(gbc); 510 parse_spx_atten_data = get_bits1(gbc); 511 512 /* coupling strategy occurrence and coupling use per block */ 513 num_cpl_blocks = 0; 514 if (s->channel_mode > 1) { 515 for (blk = 0; blk < s->num_blocks; blk++) { 516 s->cpl_strategy_exists[blk] = (!blk || get_bits1(gbc)); 517 if (s->cpl_strategy_exists[blk]) { 518 s->cpl_in_use[blk] = get_bits1(gbc); 519 } else { 520 s->cpl_in_use[blk] = s->cpl_in_use[blk-1]; 521 } 522 num_cpl_blocks += s->cpl_in_use[blk]; 523 } 524 } else { 525 memset(s->cpl_in_use, 0, sizeof(s->cpl_in_use)); 526 } 527 528 /* exponent strategy data */ 529 if (ac3_exponent_strategy) { 530 /* AC-3-style exponent strategy syntax */ 531 for (blk = 0; blk < s->num_blocks; blk++) { 532 for (ch = !s->cpl_in_use[blk]; ch <= s->fbw_channels; ch++) { 533 s->exp_strategy[blk][ch] = get_bits(gbc, 2); 534 } 535 } 536 } else { 537 /* LUT-based exponent strategy syntax */ 538 for (ch = !((s->channel_mode > 1) && num_cpl_blocks); ch <= s->fbw_channels; ch++) { 539 int frmchexpstr = get_bits(gbc, 5); 540 for (blk = 0; blk < 6; blk++) { 541 s->exp_strategy[blk][ch] = ff_eac3_frm_expstr[frmchexpstr][blk]; 542 } 543 } 544 } 545 /* LFE exponent strategy */ 546 if (s->lfe_on) { 547 for (blk = 0; blk < s->num_blocks; blk++) { 548 s->exp_strategy[blk][s->lfe_ch] = get_bits1(gbc); 549 } 550 } 551 /* original exponent strategies if this stream was converted from AC-3 */ 552 if (s->frame_type == EAC3_FRAME_TYPE_INDEPENDENT && 553 (s->num_blocks == 6 || get_bits1(gbc))) { 554 skip_bits(gbc, 5 * s->fbw_channels); // skip converter channel exponent strategy 555 } 556 557 /* determine which channels use AHT */ 558 if (parse_aht_info) { 559 /* For AHT to be used, all non-zero blocks must reuse exponents from 560 the first block. Furthermore, for AHT to be used in the coupling 561 channel, all blocks must use coupling and use the same coupling 562 strategy. */ 563 s->channel_uses_aht[CPL_CH]=0; 564 for (ch = (num_cpl_blocks != 6); ch <= s->channels; ch++) { 565 int use_aht = 1; 566 for (blk = 1; blk < 6; blk++) { 567 if ((s->exp_strategy[blk][ch] != EXP_REUSE) || 568 (!ch && s->cpl_strategy_exists[blk])) { 569 use_aht = 0; 570 break; 571 } 572 } 573 s->channel_uses_aht[ch] = use_aht && get_bits1(gbc); 574 } 575 } else { 576 memset(s->channel_uses_aht, 0, sizeof(s->channel_uses_aht)); 577 } 578 579 /* per-frame SNR offset */ 580 if (!s->snr_offset_strategy) { 581 int csnroffst = (get_bits(gbc, 6) - 15) << 4; 582 int snroffst = (csnroffst + get_bits(gbc, 4)) << 2; 583 for (ch = 0; ch <= s->channels; ch++) 584 s->snr_offset[ch] = snroffst; 585 } 586 587 /* transient pre-noise processing data */ 588 if (parse_transient_proc_info) { 589 for (ch = 1; ch <= s->fbw_channels; ch++) { 590 if (get_bits1(gbc)) { // channel in transient processing 591 skip_bits(gbc, 10); // skip transient processing location 592 skip_bits(gbc, 8); // skip transient processing length 593 } 594 } 595 } 596 597 /* spectral extension attenuation data */ 598 for (ch = 1; ch <= s->fbw_channels; ch++) { 599 if (parse_spx_atten_data && get_bits1(gbc)) { 600 s->spx_atten_code[ch] = get_bits(gbc, 5); 601 } else { 602 s->spx_atten_code[ch] = -1; 603 } 604 } 605 606 /* block start information */ 607 if (s->num_blocks > 1 && get_bits1(gbc)) { 608 /* reference: Section E2.3.2.27 609 nblkstrtbits = (numblks - 1) * (4 + ceiling(log2(words_per_frame))) 610 The spec does not say what this data is or what it's used for. 611 It is likely the offset of each block within the frame. */ 612 int block_start_bits = (s->num_blocks-1) * (4 + av_log2(s->frame_size-2)); 613 skip_bits_long(gbc, block_start_bits); 614 avpriv_request_sample(s->avctx, "Block start info"); 615 } 616 617 /* syntax state initialization */ 618 for (ch = 1; ch <= s->fbw_channels; ch++) { 619 s->first_spx_coords[ch] = 1; 620 s->first_cpl_coords[ch] = 1; 621 } 622 s->first_cpl_leak = 1; 623 624 return 0; 625} 626