Imported Debian version 2.5.3~trusty1
[deb_ffmpeg.git] / ffmpeg / libavcodec / eac3dec.c
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 * Dependent Streams
35 * Only the independent stream is currently decoded. Any dependent
36 * streams are skipped. We have only come across two examples of this, and
37 * they are both just test streams, one for HD-DVD and the other for
38 * Blu-ray.
39 *
40 * Transient Pre-noise Processing
41 * This is side information which a decoder should use to reduce artifacts
42 * caused by transients. There are samples which are known to have this
43 * information, but this decoder currently ignores it.
44 */
45
46
47 #include "avcodec.h"
48 #include "internal.h"
49 #include "aac_ac3_parser.h"
50 #include "ac3.h"
51 #include "ac3_parser.h"
52 #include "ac3dec.h"
53 #include "ac3dec_data.h"
54 #include "eac3_data.h"
55
56 /** gain adaptive quantization mode */
57 typedef enum {
58 EAC3_GAQ_NO =0,
59 EAC3_GAQ_12,
60 EAC3_GAQ_14,
61 EAC3_GAQ_124
62 } EAC3GaqMode;
63
64 #define EAC3_SR_CODE_REDUCED 3
65
66 void ff_eac3_apply_spectral_extension(AC3DecodeContext *s)
67 {
68 int bin, bnd, ch, i;
69 uint8_t wrapflag[SPX_MAX_BANDS]={1,0,}, num_copy_sections, copy_sizes[SPX_MAX_BANDS];
70 float rms_energy[SPX_MAX_BANDS];
71
72 /* Set copy index mapping table. Set wrap flags to apply a notch filter at
73 wrap points later on. */
74 bin = s->spx_dst_start_freq;
75 num_copy_sections = 0;
76 for (bnd = 0; bnd < s->num_spx_bands; bnd++) {
77 int copysize;
78 int bandsize = s->spx_band_sizes[bnd];
79 if (bin + bandsize > s->spx_src_start_freq) {
80 copy_sizes[num_copy_sections++] = bin - s->spx_dst_start_freq;
81 bin = s->spx_dst_start_freq;
82 wrapflag[bnd] = 1;
83 }
84 for (i = 0; i < bandsize; i += copysize) {
85 if (bin == s->spx_src_start_freq) {
86 copy_sizes[num_copy_sections++] = bin - s->spx_dst_start_freq;
87 bin = s->spx_dst_start_freq;
88 }
89 copysize = FFMIN(bandsize - i, s->spx_src_start_freq - bin);
90 bin += copysize;
91 }
92 }
93 copy_sizes[num_copy_sections++] = bin - s->spx_dst_start_freq;
94
95 for (ch = 1; ch <= s->fbw_channels; ch++) {
96 if (!s->channel_uses_spx[ch])
97 continue;
98
99 /* Copy coeffs from normal bands to extension bands */
100 bin = s->spx_src_start_freq;
101 for (i = 0; i < num_copy_sections; i++) {
102 memcpy(&s->transform_coeffs[ch][bin],
103 &s->transform_coeffs[ch][s->spx_dst_start_freq],
104 copy_sizes[i]*sizeof(float));
105 bin += copy_sizes[i];
106 }
107
108 /* Calculate RMS energy for each SPX band. */
109 bin = s->spx_src_start_freq;
110 for (bnd = 0; bnd < s->num_spx_bands; bnd++) {
111 int bandsize = s->spx_band_sizes[bnd];
112 float accum = 0.0f;
113 for (i = 0; i < bandsize; i++) {
114 float coeff = s->transform_coeffs[ch][bin++];
115 accum += coeff * coeff;
116 }
117 rms_energy[bnd] = sqrtf(accum / bandsize);
118 }
119
120 /* Apply a notch filter at transitions between normal and extension
121 bands and at all wrap points. */
122 if (s->spx_atten_code[ch] >= 0) {
123 const float *atten_tab = ff_eac3_spx_atten_tab[s->spx_atten_code[ch]];
124 bin = s->spx_src_start_freq - 2;
125 for (bnd = 0; bnd < s->num_spx_bands; bnd++) {
126 if (wrapflag[bnd]) {
127 float *coeffs = &s->transform_coeffs[ch][bin];
128 coeffs[0] *= atten_tab[0];
129 coeffs[1] *= atten_tab[1];
130 coeffs[2] *= atten_tab[2];
131 coeffs[3] *= atten_tab[1];
132 coeffs[4] *= atten_tab[0];
133 }
134 bin += s->spx_band_sizes[bnd];
135 }
136 }
137
138 /* Apply noise-blended coefficient scaling based on previously
139 calculated RMS energy, blending factors, and SPX coordinates for
140 each band. */
141 bin = s->spx_src_start_freq;
142 for (bnd = 0; bnd < s->num_spx_bands; bnd++) {
143 float nscale = s->spx_noise_blend[ch][bnd] * rms_energy[bnd] * (1.0f / INT32_MIN);
144 float sscale = s->spx_signal_blend[ch][bnd];
145 for (i = 0; i < s->spx_band_sizes[bnd]; i++) {
146 float noise = nscale * (int32_t)av_lfg_get(&s->dith_state);
147 s->transform_coeffs[ch][bin] *= sscale;
148 s->transform_coeffs[ch][bin++] += noise;
149 }
150 }
151 }
152 }
153
154
155 /** lrint(M_SQRT2*cos(2*M_PI/12)*(1<<23)) */
156 #define COEFF_0 10273905LL
157
158 /** lrint(M_SQRT2*cos(0*M_PI/12)*(1<<23)) = lrint(M_SQRT2*(1<<23)) */
159 #define COEFF_1 11863283LL
160
161 /** lrint(M_SQRT2*cos(5*M_PI/12)*(1<<23)) */
162 #define COEFF_2 3070444LL
163
164 /**
165 * Calculate 6-point IDCT of the pre-mantissas.
166 * All calculations are 24-bit fixed-point.
167 */
168 static void idct6(int pre_mant[6])
169 {
170 int tmp;
171 int even0, even1, even2, odd0, odd1, odd2;
172
173 odd1 = pre_mant[1] - pre_mant[3] - pre_mant[5];
174
175 even2 = ( pre_mant[2] * COEFF_0) >> 23;
176 tmp = ( pre_mant[4] * COEFF_1) >> 23;
177 odd0 = ((pre_mant[1] + pre_mant[5]) * COEFF_2) >> 23;
178
179 even0 = pre_mant[0] + (tmp >> 1);
180 even1 = pre_mant[0] - tmp;
181
182 tmp = even0;
183 even0 = tmp + even2;
184 even2 = tmp - even2;
185
186 tmp = odd0;
187 odd0 = tmp + pre_mant[1] + pre_mant[3];
188 odd2 = tmp + pre_mant[5] - pre_mant[3];
189
190 pre_mant[0] = even0 + odd0;
191 pre_mant[1] = even1 + odd1;
192 pre_mant[2] = even2 + odd2;
193 pre_mant[3] = even2 - odd2;
194 pre_mant[4] = even1 - odd1;
195 pre_mant[5] = even0 - odd0;
196 }
197
198 void ff_eac3_decode_transform_coeffs_aht_ch(AC3DecodeContext *s, int ch)
199 {
200 int bin, blk, gs;
201 int end_bap, gaq_mode;
202 GetBitContext *gbc = &s->gbc;
203 int gaq_gain[AC3_MAX_COEFS];
204
205 gaq_mode = get_bits(gbc, 2);
206 end_bap = (gaq_mode < 2) ? 12 : 17;
207
208 /* if GAQ gain is used, decode gain codes for bins with hebap between
209 8 and end_bap */
210 gs = 0;
211 if (gaq_mode == EAC3_GAQ_12 || gaq_mode == EAC3_GAQ_14) {
212 /* read 1-bit GAQ gain codes */
213 for (bin = s->start_freq[ch]; bin < s->end_freq[ch]; bin++) {
214 if (s->bap[ch][bin] > 7 && s->bap[ch][bin] < end_bap)
215 gaq_gain[gs++] = get_bits1(gbc) << (gaq_mode-1);
216 }
217 } else if (gaq_mode == EAC3_GAQ_124) {
218 /* read 1.67-bit GAQ gain codes (3 codes in 5 bits) */
219 int gc = 2;
220 for (bin = s->start_freq[ch]; bin < s->end_freq[ch]; bin++) {
221 if (s->bap[ch][bin] > 7 && s->bap[ch][bin] < 17) {
222 if (gc++ == 2) {
223 int group_code = get_bits(gbc, 5);
224 if (group_code > 26) {
225 av_log(s->avctx, AV_LOG_WARNING, "GAQ gain group code out-of-range\n");
226 group_code = 26;
227 }
228 gaq_gain[gs++] = ff_ac3_ungroup_3_in_5_bits_tab[group_code][0];
229 gaq_gain[gs++] = ff_ac3_ungroup_3_in_5_bits_tab[group_code][1];
230 gaq_gain[gs++] = ff_ac3_ungroup_3_in_5_bits_tab[group_code][2];
231 gc = 0;
232 }
233 }
234 }
235 }
236
237 gs=0;
238 for (bin = s->start_freq[ch]; bin < s->end_freq[ch]; bin++) {
239 int hebap = s->bap[ch][bin];
240 int bits = ff_eac3_bits_vs_hebap[hebap];
241 if (!hebap) {
242 /* zero-mantissa dithering */
243 for (blk = 0; blk < 6; blk++) {
244 s->pre_mantissa[ch][bin][blk] = (av_lfg_get(&s->dith_state) & 0x7FFFFF) - 0x400000;
245 }
246 } else if (hebap < 8) {
247 /* Vector Quantization */
248 int v = get_bits(gbc, bits);
249 for (blk = 0; blk < 6; blk++) {
250 s->pre_mantissa[ch][bin][blk] = ff_eac3_mantissa_vq[hebap][v][blk] << 8;
251 }
252 } else {
253 /* Gain Adaptive Quantization */
254 int gbits, log_gain;
255 if (gaq_mode != EAC3_GAQ_NO && hebap < end_bap) {
256 log_gain = gaq_gain[gs++];
257 } else {
258 log_gain = 0;
259 }
260 gbits = bits - log_gain;
261
262 for (blk = 0; blk < 6; blk++) {
263 int mant = get_sbits(gbc, gbits);
264 if (log_gain && mant == -(1 << (gbits-1))) {
265 /* large mantissa */
266 int b;
267 int mbits = bits - (2 - log_gain);
268 mant = get_sbits(gbc, mbits);
269 mant <<= (23 - (mbits - 1));
270 /* remap mantissa value to correct for asymmetric quantization */
271 if (mant >= 0)
272 b = 1 << (23 - log_gain);
273 else
274 b = ff_eac3_gaq_remap_2_4_b[hebap-8][log_gain-1] << 8;
275 mant += ((ff_eac3_gaq_remap_2_4_a[hebap-8][log_gain-1] * (int64_t)mant) >> 15) + b;
276 } else {
277 /* small mantissa, no GAQ, or Gk=1 */
278 mant <<= 24 - bits;
279 if (!log_gain) {
280 /* remap mantissa value for no GAQ or Gk=1 */
281 mant += (ff_eac3_gaq_remap_1[hebap-8] * (int64_t)mant) >> 15;
282 }
283 }
284 s->pre_mantissa[ch][bin][blk] = mant;
285 }
286 }
287 idct6(s->pre_mantissa[ch][bin]);
288 }
289 }
290
291 int ff_eac3_parse_header(AC3DecodeContext *s)
292 {
293 int i, blk, ch;
294 int ac3_exponent_strategy, parse_aht_info, parse_spx_atten_data;
295 int parse_transient_proc_info;
296 int num_cpl_blocks;
297 GetBitContext *gbc = &s->gbc;
298
299 /* An E-AC-3 stream can have multiple independent streams which the
300 application can select from. each independent stream can also contain
301 dependent streams which are used to add or replace channels. */
302 if (s->frame_type == EAC3_FRAME_TYPE_DEPENDENT) {
303 avpriv_request_sample(s->avctx, "Dependent substream decoding");
304 return AAC_AC3_PARSE_ERROR_FRAME_TYPE;
305 } else if (s->frame_type == EAC3_FRAME_TYPE_RESERVED) {
306 av_log(s->avctx, AV_LOG_ERROR, "Reserved frame type\n");
307 return AAC_AC3_PARSE_ERROR_FRAME_TYPE;
308 }
309
310 /* The substream id indicates which substream this frame belongs to. each
311 independent stream has its own substream id, and the dependent streams
312 associated to an independent stream have matching substream id's. */
313 if (s->substreamid) {
314 /* only decode substream with id=0. skip any additional substreams. */
315 avpriv_request_sample(s->avctx, "Additional substreams");
316 return AAC_AC3_PARSE_ERROR_FRAME_TYPE;
317 }
318
319 if (s->bit_alloc_params.sr_code == EAC3_SR_CODE_REDUCED) {
320 /* The E-AC-3 specification does not tell how to handle reduced sample
321 rates in bit allocation. The best assumption would be that it is
322 handled like AC-3 DolbyNet, but we cannot be sure until we have a
323 sample which utilizes this feature. */
324 avpriv_request_sample(s->avctx, "Reduced sampling rate");
325 return AVERROR_PATCHWELCOME;
326 }
327 skip_bits(gbc, 5); // skip bitstream id
328
329 /* volume control params */
330 for (i = 0; i < (s->channel_mode ? 1 : 2); i++) {
331 skip_bits(gbc, 5); // skip dialog normalization
332 if (get_bits1(gbc)) {
333 skip_bits(gbc, 8); // skip compression gain word
334 }
335 }
336
337 /* dependent stream channel map */
338 if (s->frame_type == EAC3_FRAME_TYPE_DEPENDENT) {
339 if (get_bits1(gbc)) {
340 skip_bits(gbc, 16); // skip custom channel map
341 }
342 }
343
344 /* mixing metadata */
345 if (get_bits1(gbc)) {
346 /* center and surround mix levels */
347 if (s->channel_mode > AC3_CHMODE_STEREO) {
348 s->preferred_downmix = get_bits(gbc, 2);
349 if (s->channel_mode & 1) {
350 /* if three front channels exist */
351 s->center_mix_level_ltrt = get_bits(gbc, 3);
352 s->center_mix_level = get_bits(gbc, 3);
353 }
354 if (s->channel_mode & 4) {
355 /* if a surround channel exists */
356 s->surround_mix_level_ltrt = av_clip(get_bits(gbc, 3), 3, 7);
357 s->surround_mix_level = av_clip(get_bits(gbc, 3), 3, 7);
358 }
359 }
360
361 /* lfe mix level */
362 if (s->lfe_on && (s->lfe_mix_level_exists = get_bits1(gbc))) {
363 s->lfe_mix_level = get_bits(gbc, 5);
364 }
365
366 /* info for mixing with other streams and substreams */
367 if (s->frame_type == EAC3_FRAME_TYPE_INDEPENDENT) {
368 for (i = 0; i < (s->channel_mode ? 1 : 2); i++) {
369 // TODO: apply program scale factor
370 if (get_bits1(gbc)) {
371 skip_bits(gbc, 6); // skip program scale factor
372 }
373 }
374 if (get_bits1(gbc)) {
375 skip_bits(gbc, 6); // skip external program scale factor
376 }
377 /* skip mixing parameter data */
378 switch(get_bits(gbc, 2)) {
379 case 1: skip_bits(gbc, 5); break;
380 case 2: skip_bits(gbc, 12); break;
381 case 3: {
382 int mix_data_size = (get_bits(gbc, 5) + 2) << 3;
383 skip_bits_long(gbc, mix_data_size);
384 break;
385 }
386 }
387 /* skip pan information for mono or dual mono source */
388 if (s->channel_mode < AC3_CHMODE_STEREO) {
389 for (i = 0; i < (s->channel_mode ? 1 : 2); i++) {
390 if (get_bits1(gbc)) {
391 /* note: this is not in the ATSC A/52B specification
392 reference: ETSI TS 102 366 V1.1.1
393 section: E.1.3.1.25 */
394 skip_bits(gbc, 8); // skip pan mean direction index
395 skip_bits(gbc, 6); // skip reserved paninfo bits
396 }
397 }
398 }
399 /* skip mixing configuration information */
400 if (get_bits1(gbc)) {
401 for (blk = 0; blk < s->num_blocks; blk++) {
402 if (s->num_blocks == 1 || get_bits1(gbc)) {
403 skip_bits(gbc, 5);
404 }
405 }
406 }
407 }
408 }
409
410 /* informational metadata */
411 if (get_bits1(gbc)) {
412 s->bitstream_mode = get_bits(gbc, 3);
413 skip_bits(gbc, 2); // skip copyright bit and original bitstream bit
414 if (s->channel_mode == AC3_CHMODE_STEREO) {
415 s->dolby_surround_mode = get_bits(gbc, 2);
416 s->dolby_headphone_mode = get_bits(gbc, 2);
417 }
418 if (s->channel_mode >= AC3_CHMODE_2F2R) {
419 s->dolby_surround_ex_mode = get_bits(gbc, 2);
420 }
421 for (i = 0; i < (s->channel_mode ? 1 : 2); i++) {
422 if (get_bits1(gbc)) {
423 skip_bits(gbc, 8); // skip mix level, room type, and A/D converter type
424 }
425 }
426 if (s->bit_alloc_params.sr_code != EAC3_SR_CODE_REDUCED) {
427 skip_bits1(gbc); // skip source sample rate code
428 }
429 }
430
431 /* converter synchronization flag
432 If frames are less than six blocks, this bit should be turned on
433 once every 6 blocks to indicate the start of a frame set.
434 reference: RFC 4598, Section 2.1.3 Frame Sets */
435 if (s->frame_type == EAC3_FRAME_TYPE_INDEPENDENT && s->num_blocks != 6) {
436 skip_bits1(gbc); // skip converter synchronization flag
437 }
438
439 /* original frame size code if this stream was converted from AC-3 */
440 if (s->frame_type == EAC3_FRAME_TYPE_AC3_CONVERT &&
441 (s->num_blocks == 6 || get_bits1(gbc))) {
442 skip_bits(gbc, 6); // skip frame size code
443 }
444
445 /* additional bitstream info */
446 if (get_bits1(gbc)) {
447 int addbsil = get_bits(gbc, 6);
448 for (i = 0; i < addbsil + 1; i++) {
449 skip_bits(gbc, 8); // skip additional bit stream info
450 }
451 }
452
453 /* audio frame syntax flags, strategy data, and per-frame data */
454
455 if (s->num_blocks == 6) {
456 ac3_exponent_strategy = get_bits1(gbc);
457 parse_aht_info = get_bits1(gbc);
458 } else {
459 /* less than 6 blocks, so use AC-3-style exponent strategy syntax, and
460 do not use AHT */
461 ac3_exponent_strategy = 1;
462 parse_aht_info = 0;
463 }
464
465 s->snr_offset_strategy = get_bits(gbc, 2);
466 parse_transient_proc_info = get_bits1(gbc);
467
468 s->block_switch_syntax = get_bits1(gbc);
469 if (!s->block_switch_syntax)
470 memset(s->block_switch, 0, sizeof(s->block_switch));
471
472 s->dither_flag_syntax = get_bits1(gbc);
473 if (!s->dither_flag_syntax) {
474 for (ch = 1; ch <= s->fbw_channels; ch++)
475 s->dither_flag[ch] = 1;
476 }
477 s->dither_flag[CPL_CH] = s->dither_flag[s->lfe_ch] = 0;
478
479 s->bit_allocation_syntax = get_bits1(gbc);
480 if (!s->bit_allocation_syntax) {
481 /* set default bit allocation parameters */
482 s->bit_alloc_params.slow_decay = ff_ac3_slow_decay_tab[2];
483 s->bit_alloc_params.fast_decay = ff_ac3_fast_decay_tab[1];
484 s->bit_alloc_params.slow_gain = ff_ac3_slow_gain_tab [1];
485 s->bit_alloc_params.db_per_bit = ff_ac3_db_per_bit_tab[2];
486 s->bit_alloc_params.floor = ff_ac3_floor_tab [7];
487 }
488
489 s->fast_gain_syntax = get_bits1(gbc);
490 s->dba_syntax = get_bits1(gbc);
491 s->skip_syntax = get_bits1(gbc);
492 parse_spx_atten_data = get_bits1(gbc);
493
494 /* coupling strategy occurrence and coupling use per block */
495 num_cpl_blocks = 0;
496 if (s->channel_mode > 1) {
497 for (blk = 0; blk < s->num_blocks; blk++) {
498 s->cpl_strategy_exists[blk] = (!blk || get_bits1(gbc));
499 if (s->cpl_strategy_exists[blk]) {
500 s->cpl_in_use[blk] = get_bits1(gbc);
501 } else {
502 s->cpl_in_use[blk] = s->cpl_in_use[blk-1];
503 }
504 num_cpl_blocks += s->cpl_in_use[blk];
505 }
506 } else {
507 memset(s->cpl_in_use, 0, sizeof(s->cpl_in_use));
508 }
509
510 /* exponent strategy data */
511 if (ac3_exponent_strategy) {
512 /* AC-3-style exponent strategy syntax */
513 for (blk = 0; blk < s->num_blocks; blk++) {
514 for (ch = !s->cpl_in_use[blk]; ch <= s->fbw_channels; ch++) {
515 s->exp_strategy[blk][ch] = get_bits(gbc, 2);
516 }
517 }
518 } else {
519 /* LUT-based exponent strategy syntax */
520 for (ch = !((s->channel_mode > 1) && num_cpl_blocks); ch <= s->fbw_channels; ch++) {
521 int frmchexpstr = get_bits(gbc, 5);
522 for (blk = 0; blk < 6; blk++) {
523 s->exp_strategy[blk][ch] = ff_eac3_frm_expstr[frmchexpstr][blk];
524 }
525 }
526 }
527 /* LFE exponent strategy */
528 if (s->lfe_on) {
529 for (blk = 0; blk < s->num_blocks; blk++) {
530 s->exp_strategy[blk][s->lfe_ch] = get_bits1(gbc);
531 }
532 }
533 /* original exponent strategies if this stream was converted from AC-3 */
534 if (s->frame_type == EAC3_FRAME_TYPE_INDEPENDENT &&
535 (s->num_blocks == 6 || get_bits1(gbc))) {
536 skip_bits(gbc, 5 * s->fbw_channels); // skip converter channel exponent strategy
537 }
538
539 /* determine which channels use AHT */
540 if (parse_aht_info) {
541 /* For AHT to be used, all non-zero blocks must reuse exponents from
542 the first block. Furthermore, for AHT to be used in the coupling
543 channel, all blocks must use coupling and use the same coupling
544 strategy. */
545 s->channel_uses_aht[CPL_CH]=0;
546 for (ch = (num_cpl_blocks != 6); ch <= s->channels; ch++) {
547 int use_aht = 1;
548 for (blk = 1; blk < 6; blk++) {
549 if ((s->exp_strategy[blk][ch] != EXP_REUSE) ||
550 (!ch && s->cpl_strategy_exists[blk])) {
551 use_aht = 0;
552 break;
553 }
554 }
555 s->channel_uses_aht[ch] = use_aht && get_bits1(gbc);
556 }
557 } else {
558 memset(s->channel_uses_aht, 0, sizeof(s->channel_uses_aht));
559 }
560
561 /* per-frame SNR offset */
562 if (!s->snr_offset_strategy) {
563 int csnroffst = (get_bits(gbc, 6) - 15) << 4;
564 int snroffst = (csnroffst + get_bits(gbc, 4)) << 2;
565 for (ch = 0; ch <= s->channels; ch++)
566 s->snr_offset[ch] = snroffst;
567 }
568
569 /* transient pre-noise processing data */
570 if (parse_transient_proc_info) {
571 for (ch = 1; ch <= s->fbw_channels; ch++) {
572 if (get_bits1(gbc)) { // channel in transient processing
573 skip_bits(gbc, 10); // skip transient processing location
574 skip_bits(gbc, 8); // skip transient processing length
575 }
576 }
577 }
578
579 /* spectral extension attenuation data */
580 for (ch = 1; ch <= s->fbw_channels; ch++) {
581 if (parse_spx_atten_data && get_bits1(gbc)) {
582 s->spx_atten_code[ch] = get_bits(gbc, 5);
583 } else {
584 s->spx_atten_code[ch] = -1;
585 }
586 }
587
588 /* block start information */
589 if (s->num_blocks > 1 && get_bits1(gbc)) {
590 /* reference: Section E2.3.2.27
591 nblkstrtbits = (numblks - 1) * (4 + ceiling(log2(words_per_frame)))
592 The spec does not say what this data is or what it's used for.
593 It is likely the offset of each block within the frame. */
594 int block_start_bits = (s->num_blocks-1) * (4 + av_log2(s->frame_size-2));
595 skip_bits_long(gbc, block_start_bits);
596 avpriv_request_sample(s->avctx, "Block start info");
597 }
598
599 /* syntax state initialization */
600 for (ch = 1; ch <= s->fbw_channels; ch++) {
601 s->first_spx_coords[ch] = 1;
602 s->first_cpl_coords[ch] = 1;
603 }
604 s->first_cpl_leak = 1;
605
606 return 0;
607 }