3 * Copyright (c) 2007 Bartlomiej Wolowiec <bartek.wolowiec@gmail.com>
4 * Copyright (c) 2008 Justin Ruggles
6 * This file is part of FFmpeg.
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.
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.
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
24 * There are several features of E-AC-3 that this decoder does not yet support.
27 * No known samples exist. If any ever surface, this feature should not be
28 * too difficult to implement.
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.
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
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.
49 #include "aac_ac3_parser.h"
51 #include "ac3_parser.h"
53 #include "ac3dec_data.h"
54 #include "eac3_data.h"
56 /** gain adaptive quantization mode */
64 #define EAC3_SR_CODE_REDUCED 3
66 static void ff_eac3_apply_spectral_extension(AC3DecodeContext *s)
69 uint8_t wrapflag[SPX_MAX_BANDS]={1,0,}, num_copy_sections, copy_sizes[SPX_MAX_BANDS];
70 float rms_energy[SPX_MAX_BANDS];
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++) {
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;
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;
89 copysize = FFMIN(bandsize - i, s->spx_src_start_freq - bin);
93 copy_sizes[num_copy_sections++] = bin - s->spx_dst_start_freq;
95 for (ch = 1; ch <= s->fbw_channels; ch++) {
96 if (!s->channel_uses_spx[ch])
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(INTFLOAT));
105 bin += copy_sizes[i];
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];
113 for (i = 0; i < bandsize; i++) {
114 float coeff = s->transform_coeffs[ch][bin++];
115 accum += coeff * coeff;
117 rms_energy[bnd] = sqrtf(accum / bandsize);
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++) {
127 INTFLOAT *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];
134 bin += s->spx_band_sizes[bnd];
138 /* Apply noise-blended coefficient scaling based on previously
139 calculated RMS energy, blending factors, and SPX coordinates for
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];
146 // spx_noise_blend and spx_signal_blend are both FP.23
147 nscale *= 1.0 / (1<<23);
148 sscale *= 1.0 / (1<<23);
150 for (i = 0; i < s->spx_band_sizes[bnd]; i++) {
151 float noise = nscale * (int32_t)av_lfg_get(&s->dith_state);
152 s->transform_coeffs[ch][bin] *= sscale;
153 s->transform_coeffs[ch][bin++] += noise;
160 /** lrint(M_SQRT2*cos(2*M_PI/12)*(1<<23)) */
161 #define COEFF_0 10273905LL
163 /** lrint(M_SQRT2*cos(0*M_PI/12)*(1<<23)) = lrint(M_SQRT2*(1<<23)) */
164 #define COEFF_1 11863283LL
166 /** lrint(M_SQRT2*cos(5*M_PI/12)*(1<<23)) */
167 #define COEFF_2 3070444LL
170 * Calculate 6-point IDCT of the pre-mantissas.
171 * All calculations are 24-bit fixed-point.
173 static void idct6(int pre_mant[6])
176 int even0, even1, even2, odd0, odd1, odd2;
178 odd1 = pre_mant[1] - pre_mant[3] - pre_mant[5];
180 even2 = ( pre_mant[2] * COEFF_0) >> 23;
181 tmp = ( pre_mant[4] * COEFF_1) >> 23;
182 odd0 = ((pre_mant[1] + pre_mant[5]) * COEFF_2) >> 23;
184 even0 = pre_mant[0] + (tmp >> 1);
185 even1 = pre_mant[0] - tmp;
192 odd0 = tmp + pre_mant[1] + pre_mant[3];
193 odd2 = tmp + pre_mant[5] - pre_mant[3];
195 pre_mant[0] = even0 + odd0;
196 pre_mant[1] = even1 + odd1;
197 pre_mant[2] = even2 + odd2;
198 pre_mant[3] = even2 - odd2;
199 pre_mant[4] = even1 - odd1;
200 pre_mant[5] = even0 - odd0;
203 static void ff_eac3_decode_transform_coeffs_aht_ch(AC3DecodeContext *s, int ch)
206 int end_bap, gaq_mode;
207 GetBitContext *gbc = &s->gbc;
208 int gaq_gain[AC3_MAX_COEFS];
210 gaq_mode = get_bits(gbc, 2);
211 end_bap = (gaq_mode < 2) ? 12 : 17;
213 /* if GAQ gain is used, decode gain codes for bins with hebap between
216 if (gaq_mode == EAC3_GAQ_12 || gaq_mode == EAC3_GAQ_14) {
217 /* read 1-bit GAQ gain codes */
218 for (bin = s->start_freq[ch]; bin < s->end_freq[ch]; bin++) {
219 if (s->bap[ch][bin] > 7 && s->bap[ch][bin] < end_bap)
220 gaq_gain[gs++] = get_bits1(gbc) << (gaq_mode-1);
222 } else if (gaq_mode == EAC3_GAQ_124) {
223 /* read 1.67-bit GAQ gain codes (3 codes in 5 bits) */
225 for (bin = s->start_freq[ch]; bin < s->end_freq[ch]; bin++) {
226 if (s->bap[ch][bin] > 7 && s->bap[ch][bin] < 17) {
228 int group_code = get_bits(gbc, 5);
229 if (group_code > 26) {
230 av_log(s->avctx, AV_LOG_WARNING, "GAQ gain group code out-of-range\n");
233 gaq_gain[gs++] = ff_ac3_ungroup_3_in_5_bits_tab[group_code][0];
234 gaq_gain[gs++] = ff_ac3_ungroup_3_in_5_bits_tab[group_code][1];
235 gaq_gain[gs++] = ff_ac3_ungroup_3_in_5_bits_tab[group_code][2];
243 for (bin = s->start_freq[ch]; bin < s->end_freq[ch]; bin++) {
244 int hebap = s->bap[ch][bin];
245 int bits = ff_eac3_bits_vs_hebap[hebap];
247 /* zero-mantissa dithering */
248 for (blk = 0; blk < 6; blk++) {
249 s->pre_mantissa[ch][bin][blk] = (av_lfg_get(&s->dith_state) & 0x7FFFFF) - 0x400000;
251 } else if (hebap < 8) {
252 /* Vector Quantization */
253 int v = get_bits(gbc, bits);
254 for (blk = 0; blk < 6; blk++) {
255 s->pre_mantissa[ch][bin][blk] = ff_eac3_mantissa_vq[hebap][v][blk] << 8;
258 /* Gain Adaptive Quantization */
260 if (gaq_mode != EAC3_GAQ_NO && hebap < end_bap) {
261 log_gain = gaq_gain[gs++];
265 gbits = bits - log_gain;
267 for (blk = 0; blk < 6; blk++) {
268 int mant = get_sbits(gbc, gbits);
269 if (log_gain && mant == -(1 << (gbits-1))) {
272 int mbits = bits - (2 - log_gain);
273 mant = get_sbits(gbc, mbits);
274 mant <<= (23 - (mbits - 1));
275 /* remap mantissa value to correct for asymmetric quantization */
277 b = 1 << (23 - log_gain);
279 b = ff_eac3_gaq_remap_2_4_b[hebap-8][log_gain-1] << 8;
280 mant += ((ff_eac3_gaq_remap_2_4_a[hebap-8][log_gain-1] * (int64_t)mant) >> 15) + b;
282 /* small mantissa, no GAQ, or Gk=1 */
285 /* remap mantissa value for no GAQ or Gk=1 */
286 mant += (ff_eac3_gaq_remap_1[hebap-8] * (int64_t)mant) >> 15;
289 s->pre_mantissa[ch][bin][blk] = mant;
292 idct6(s->pre_mantissa[ch][bin]);
296 static int ff_eac3_parse_header(AC3DecodeContext *s)
299 int ac3_exponent_strategy, parse_aht_info, parse_spx_atten_data;
300 int parse_transient_proc_info;
302 GetBitContext *gbc = &s->gbc;
304 /* An E-AC-3 stream can have multiple independent streams which the
305 application can select from. each independent stream can also contain
306 dependent streams which are used to add or replace channels. */
307 if (s->frame_type == EAC3_FRAME_TYPE_DEPENDENT) {
308 if (!s->eac3_frame_dependent_found) {
309 s->eac3_frame_dependent_found = 1;
310 avpriv_request_sample(s->avctx, "Dependent substream decoding");
312 return AAC_AC3_PARSE_ERROR_FRAME_TYPE;
313 } else if (s->frame_type == EAC3_FRAME_TYPE_RESERVED) {
314 av_log(s->avctx, AV_LOG_ERROR, "Reserved frame type\n");
315 return AAC_AC3_PARSE_ERROR_FRAME_TYPE;
318 /* The substream id indicates which substream this frame belongs to. each
319 independent stream has its own substream id, and the dependent streams
320 associated to an independent stream have matching substream id's. */
321 if (s->substreamid) {
322 /* only decode substream with id=0. skip any additional substreams. */
323 if (!s->eac3_subsbtreamid_found) {
324 s->eac3_subsbtreamid_found = 1;
325 avpriv_request_sample(s->avctx, "Additional substreams");
327 return AAC_AC3_PARSE_ERROR_FRAME_TYPE;
330 if (s->bit_alloc_params.sr_code == EAC3_SR_CODE_REDUCED) {
331 /* The E-AC-3 specification does not tell how to handle reduced sample
332 rates in bit allocation. The best assumption would be that it is
333 handled like AC-3 DolbyNet, but we cannot be sure until we have a
334 sample which utilizes this feature. */
335 avpriv_request_sample(s->avctx, "Reduced sampling rate");
336 return AVERROR_PATCHWELCOME;
338 skip_bits(gbc, 5); // skip bitstream id
340 /* volume control params */
341 for (i = 0; i < (s->channel_mode ? 1 : 2); i++) {
342 skip_bits(gbc, 5); // skip dialog normalization
343 if (get_bits1(gbc)) {
344 skip_bits(gbc, 8); // skip compression gain word
348 /* dependent stream channel map */
349 if (s->frame_type == EAC3_FRAME_TYPE_DEPENDENT) {
350 if (get_bits1(gbc)) {
351 skip_bits(gbc, 16); // skip custom channel map
355 /* mixing metadata */
356 if (get_bits1(gbc)) {
357 /* center and surround mix levels */
358 if (s->channel_mode > AC3_CHMODE_STEREO) {
359 s->preferred_downmix = get_bits(gbc, 2);
360 if (s->channel_mode & 1) {
361 /* if three front channels exist */
362 s->center_mix_level_ltrt = get_bits(gbc, 3);
363 s->center_mix_level = get_bits(gbc, 3);
365 if (s->channel_mode & 4) {
366 /* if a surround channel exists */
367 s->surround_mix_level_ltrt = av_clip(get_bits(gbc, 3), 3, 7);
368 s->surround_mix_level = av_clip(get_bits(gbc, 3), 3, 7);
373 if (s->lfe_on && (s->lfe_mix_level_exists = get_bits1(gbc))) {
374 s->lfe_mix_level = get_bits(gbc, 5);
377 /* info for mixing with other streams and substreams */
378 if (s->frame_type == EAC3_FRAME_TYPE_INDEPENDENT) {
379 for (i = 0; i < (s->channel_mode ? 1 : 2); i++) {
380 // TODO: apply program scale factor
381 if (get_bits1(gbc)) {
382 skip_bits(gbc, 6); // skip program scale factor
385 if (get_bits1(gbc)) {
386 skip_bits(gbc, 6); // skip external program scale factor
388 /* skip mixing parameter data */
389 switch(get_bits(gbc, 2)) {
390 case 1: skip_bits(gbc, 5); break;
391 case 2: skip_bits(gbc, 12); break;
393 int mix_data_size = (get_bits(gbc, 5) + 2) << 3;
394 skip_bits_long(gbc, mix_data_size);
398 /* skip pan information for mono or dual mono source */
399 if (s->channel_mode < AC3_CHMODE_STEREO) {
400 for (i = 0; i < (s->channel_mode ? 1 : 2); i++) {
401 if (get_bits1(gbc)) {
402 /* note: this is not in the ATSC A/52B specification
403 reference: ETSI TS 102 366 V1.1.1
404 section: E.1.3.1.25 */
405 skip_bits(gbc, 8); // skip pan mean direction index
406 skip_bits(gbc, 6); // skip reserved paninfo bits
410 /* skip mixing configuration information */
411 if (get_bits1(gbc)) {
412 for (blk = 0; blk < s->num_blocks; blk++) {
413 if (s->num_blocks == 1 || get_bits1(gbc)) {
421 /* informational metadata */
422 if (get_bits1(gbc)) {
423 s->bitstream_mode = get_bits(gbc, 3);
424 skip_bits(gbc, 2); // skip copyright bit and original bitstream bit
425 if (s->channel_mode == AC3_CHMODE_STEREO) {
426 s->dolby_surround_mode = get_bits(gbc, 2);
427 s->dolby_headphone_mode = get_bits(gbc, 2);
429 if (s->channel_mode >= AC3_CHMODE_2F2R) {
430 s->dolby_surround_ex_mode = get_bits(gbc, 2);
432 for (i = 0; i < (s->channel_mode ? 1 : 2); i++) {
433 if (get_bits1(gbc)) {
434 skip_bits(gbc, 8); // skip mix level, room type, and A/D converter type
437 if (s->bit_alloc_params.sr_code != EAC3_SR_CODE_REDUCED) {
438 skip_bits1(gbc); // skip source sample rate code
442 /* converter synchronization flag
443 If frames are less than six blocks, this bit should be turned on
444 once every 6 blocks to indicate the start of a frame set.
445 reference: RFC 4598, Section 2.1.3 Frame Sets */
446 if (s->frame_type == EAC3_FRAME_TYPE_INDEPENDENT && s->num_blocks != 6) {
447 skip_bits1(gbc); // skip converter synchronization flag
450 /* original frame size code if this stream was converted from AC-3 */
451 if (s->frame_type == EAC3_FRAME_TYPE_AC3_CONVERT &&
452 (s->num_blocks == 6 || get_bits1(gbc))) {
453 skip_bits(gbc, 6); // skip frame size code
456 /* additional bitstream info */
457 if (get_bits1(gbc)) {
458 int addbsil = get_bits(gbc, 6);
459 for (i = 0; i < addbsil + 1; i++) {
460 skip_bits(gbc, 8); // skip additional bit stream info
464 /* audio frame syntax flags, strategy data, and per-frame data */
466 if (s->num_blocks == 6) {
467 ac3_exponent_strategy = get_bits1(gbc);
468 parse_aht_info = get_bits1(gbc);
470 /* less than 6 blocks, so use AC-3-style exponent strategy syntax, and
472 ac3_exponent_strategy = 1;
476 s->snr_offset_strategy = get_bits(gbc, 2);
477 parse_transient_proc_info = get_bits1(gbc);
479 s->block_switch_syntax = get_bits1(gbc);
480 if (!s->block_switch_syntax)
481 memset(s->block_switch, 0, sizeof(s->block_switch));
483 s->dither_flag_syntax = get_bits1(gbc);
484 if (!s->dither_flag_syntax) {
485 for (ch = 1; ch <= s->fbw_channels; ch++)
486 s->dither_flag[ch] = 1;
488 s->dither_flag[CPL_CH] = s->dither_flag[s->lfe_ch] = 0;
490 s->bit_allocation_syntax = get_bits1(gbc);
491 if (!s->bit_allocation_syntax) {
492 /* set default bit allocation parameters */
493 s->bit_alloc_params.slow_decay = ff_ac3_slow_decay_tab[2];
494 s->bit_alloc_params.fast_decay = ff_ac3_fast_decay_tab[1];
495 s->bit_alloc_params.slow_gain = ff_ac3_slow_gain_tab [1];
496 s->bit_alloc_params.db_per_bit = ff_ac3_db_per_bit_tab[2];
497 s->bit_alloc_params.floor = ff_ac3_floor_tab [7];
500 s->fast_gain_syntax = get_bits1(gbc);
501 s->dba_syntax = get_bits1(gbc);
502 s->skip_syntax = get_bits1(gbc);
503 parse_spx_atten_data = get_bits1(gbc);
505 /* coupling strategy occurrence and coupling use per block */
507 if (s->channel_mode > 1) {
508 for (blk = 0; blk < s->num_blocks; blk++) {
509 s->cpl_strategy_exists[blk] = (!blk || get_bits1(gbc));
510 if (s->cpl_strategy_exists[blk]) {
511 s->cpl_in_use[blk] = get_bits1(gbc);
513 s->cpl_in_use[blk] = s->cpl_in_use[blk-1];
515 num_cpl_blocks += s->cpl_in_use[blk];
518 memset(s->cpl_in_use, 0, sizeof(s->cpl_in_use));
521 /* exponent strategy data */
522 if (ac3_exponent_strategy) {
523 /* AC-3-style exponent strategy syntax */
524 for (blk = 0; blk < s->num_blocks; blk++) {
525 for (ch = !s->cpl_in_use[blk]; ch <= s->fbw_channels; ch++) {
526 s->exp_strategy[blk][ch] = get_bits(gbc, 2);
530 /* LUT-based exponent strategy syntax */
531 for (ch = !((s->channel_mode > 1) && num_cpl_blocks); ch <= s->fbw_channels; ch++) {
532 int frmchexpstr = get_bits(gbc, 5);
533 for (blk = 0; blk < 6; blk++) {
534 s->exp_strategy[blk][ch] = ff_eac3_frm_expstr[frmchexpstr][blk];
538 /* LFE exponent strategy */
540 for (blk = 0; blk < s->num_blocks; blk++) {
541 s->exp_strategy[blk][s->lfe_ch] = get_bits1(gbc);
544 /* original exponent strategies if this stream was converted from AC-3 */
545 if (s->frame_type == EAC3_FRAME_TYPE_INDEPENDENT &&
546 (s->num_blocks == 6 || get_bits1(gbc))) {
547 skip_bits(gbc, 5 * s->fbw_channels); // skip converter channel exponent strategy
550 /* determine which channels use AHT */
551 if (parse_aht_info) {
552 /* For AHT to be used, all non-zero blocks must reuse exponents from
553 the first block. Furthermore, for AHT to be used in the coupling
554 channel, all blocks must use coupling and use the same coupling
556 s->channel_uses_aht[CPL_CH]=0;
557 for (ch = (num_cpl_blocks != 6); ch <= s->channels; ch++) {
559 for (blk = 1; blk < 6; blk++) {
560 if ((s->exp_strategy[blk][ch] != EXP_REUSE) ||
561 (!ch && s->cpl_strategy_exists[blk])) {
566 s->channel_uses_aht[ch] = use_aht && get_bits1(gbc);
569 memset(s->channel_uses_aht, 0, sizeof(s->channel_uses_aht));
572 /* per-frame SNR offset */
573 if (!s->snr_offset_strategy) {
574 int csnroffst = (get_bits(gbc, 6) - 15) << 4;
575 int snroffst = (csnroffst + get_bits(gbc, 4)) << 2;
576 for (ch = 0; ch <= s->channels; ch++)
577 s->snr_offset[ch] = snroffst;
580 /* transient pre-noise processing data */
581 if (parse_transient_proc_info) {
582 for (ch = 1; ch <= s->fbw_channels; ch++) {
583 if (get_bits1(gbc)) { // channel in transient processing
584 skip_bits(gbc, 10); // skip transient processing location
585 skip_bits(gbc, 8); // skip transient processing length
590 /* spectral extension attenuation data */
591 for (ch = 1; ch <= s->fbw_channels; ch++) {
592 if (parse_spx_atten_data && get_bits1(gbc)) {
593 s->spx_atten_code[ch] = get_bits(gbc, 5);
595 s->spx_atten_code[ch] = -1;
599 /* block start information */
600 if (s->num_blocks > 1 && get_bits1(gbc)) {
601 /* reference: Section E2.3.2.27
602 nblkstrtbits = (numblks - 1) * (4 + ceiling(log2(words_per_frame)))
603 The spec does not say what this data is or what it's used for.
604 It is likely the offset of each block within the frame. */
605 int block_start_bits = (s->num_blocks-1) * (4 + av_log2(s->frame_size-2));
606 skip_bits_long(gbc, block_start_bits);
607 avpriv_request_sample(s->avctx, "Block start info");
610 /* syntax state initialization */
611 for (ch = 1; ch <= s->fbw_channels; ch++) {
612 s->first_spx_coords[ch] = 1;
613 s->first_cpl_coords[ch] = 1;
615 s->first_cpl_leak = 1;