3 * This code was developed as part of Google Summer of Code 2006.
4 * E-AC-3 support was added as part of Google Summer of Code 2007.
6 * Copyright (c) 2006 Kartikey Mahendra BHATT (bhattkm at gmail dot com)
7 * Copyright (c) 2007-2008 Bartlomiej Wolowiec <bartek.wolowiec@gmail.com>
8 * Copyright (c) 2007 Justin Ruggles <justin.ruggles@gmail.com>
10 * Portions of this code are derived from liba52
11 * http://liba52.sourceforge.net
12 * Copyright (C) 2000-2003 Michel Lespinasse <walken@zoy.org>
13 * Copyright (C) 1999-2000 Aaron Holtzman <aholtzma@ess.engr.uvic.ca>
15 * This file is part of FFmpeg.
17 * FFmpeg is free software; you can redistribute it and/or
18 * modify it under the terms of the GNU General Public
19 * License as published by the Free Software Foundation; either
20 * version 2 of the License, or (at your option) any later version.
22 * FFmpeg is distributed in the hope that it will be useful,
23 * but WITHOUT ANY WARRANTY; without even the implied warranty of
24 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
25 * General Public License for more details.
27 * You should have received a copy of the GNU General Public
28 * License along with FFmpeg; if not, write to the Free Software
29 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
37 #include "libavutil/crc.h"
39 #include "aac_ac3_parser.h"
40 #include "ac3_parser.h"
42 #include "ac3dec_data.h"
44 /** Large enough for maximum possible frame size when the specification limit is ignored */
45 #define AC3_FRAME_BUFFER_SIZE 32768
48 * table for ungrouping 3 values in 7 bits.
49 * used for exponents and bap=2 mantissas
51 static uint8_t ungroup_3_in_7_bits_tab[128][3];
54 /** tables for ungrouping mantissas */
55 static int b1_mantissas[32][3];
56 static int b2_mantissas[128][3];
57 static int b3_mantissas[8];
58 static int b4_mantissas[128][2];
59 static int b5_mantissas[16];
62 * Quantization table: levels for symmetric. bits for asymmetric.
63 * reference: Table 7.18 Mapping of bap to Quantizer
65 static const uint8_t quantization_tab[16] = {
67 5, 6, 7, 8, 9, 10, 11, 12, 14, 16
70 /** dynamic range table. converts codes to scale factors. */
71 static float dynamic_range_tab[256];
73 /** Adjustments in dB gain */
74 #define LEVEL_PLUS_3DB 1.4142135623730950
75 #define LEVEL_PLUS_1POINT5DB 1.1892071150027209
76 #define LEVEL_MINUS_1POINT5DB 0.8408964152537145
77 #define LEVEL_MINUS_3DB 0.7071067811865476
78 #define LEVEL_MINUS_4POINT5DB 0.5946035575013605
79 #define LEVEL_MINUS_6DB 0.5000000000000000
80 #define LEVEL_MINUS_9DB 0.3535533905932738
81 #define LEVEL_ZERO 0.0000000000000000
82 #define LEVEL_ONE 1.0000000000000000
84 static const float gain_levels[9] = {
88 LEVEL_MINUS_1POINT5DB,
90 LEVEL_MINUS_4POINT5DB,
97 * Table for center mix levels
98 * reference: Section 5.4.2.4 cmixlev
100 static const uint8_t center_levels[4] = { 4, 5, 6, 5 };
103 * Table for surround mix levels
104 * reference: Section 5.4.2.5 surmixlev
106 static const uint8_t surround_levels[4] = { 4, 6, 7, 6 };
109 * Table for default stereo downmixing coefficients
110 * reference: Section 7.8.2 Downmixing Into Two Channels
112 static const uint8_t ac3_default_coeffs[8][5][2] = {
113 { { 2, 7 }, { 7, 2 }, },
115 { { 2, 7 }, { 7, 2 }, },
116 { { 2, 7 }, { 5, 5 }, { 7, 2 }, },
117 { { 2, 7 }, { 7, 2 }, { 6, 6 }, },
118 { { 2, 7 }, { 5, 5 }, { 7, 2 }, { 8, 8 }, },
119 { { 2, 7 }, { 7, 2 }, { 6, 7 }, { 7, 6 }, },
120 { { 2, 7 }, { 5, 5 }, { 7, 2 }, { 6, 7 }, { 7, 6 }, },
124 * Symmetrical Dequantization
125 * reference: Section 7.3.3 Expansion of Mantissas for Symmetrical Quantization
126 * Tables 7.19 to 7.23
129 symmetric_dequant(int code, int levels)
131 return ((code - (levels >> 1)) << 24) / levels;
135 * Initialize tables at runtime.
137 static av_cold void ac3_tables_init(void)
141 /* generate table for ungrouping 3 values in 7 bits
142 reference: Section 7.1.3 Exponent Decoding */
143 for(i=0; i<128; i++) {
144 ungroup_3_in_7_bits_tab[i][0] = i / 25;
145 ungroup_3_in_7_bits_tab[i][1] = (i % 25) / 5;
146 ungroup_3_in_7_bits_tab[i][2] = (i % 25) % 5;
149 /* generate grouped mantissa tables
150 reference: Section 7.3.5 Ungrouping of Mantissas */
151 for(i=0; i<32; i++) {
152 /* bap=1 mantissas */
153 b1_mantissas[i][0] = symmetric_dequant(ff_ac3_ungroup_3_in_5_bits_tab[i][0], 3);
154 b1_mantissas[i][1] = symmetric_dequant(ff_ac3_ungroup_3_in_5_bits_tab[i][1], 3);
155 b1_mantissas[i][2] = symmetric_dequant(ff_ac3_ungroup_3_in_5_bits_tab[i][2], 3);
157 for(i=0; i<128; i++) {
158 /* bap=2 mantissas */
159 b2_mantissas[i][0] = symmetric_dequant(ungroup_3_in_7_bits_tab[i][0], 5);
160 b2_mantissas[i][1] = symmetric_dequant(ungroup_3_in_7_bits_tab[i][1], 5);
161 b2_mantissas[i][2] = symmetric_dequant(ungroup_3_in_7_bits_tab[i][2], 5);
163 /* bap=4 mantissas */
164 b4_mantissas[i][0] = symmetric_dequant(i / 11, 11);
165 b4_mantissas[i][1] = symmetric_dequant(i % 11, 11);
167 /* generate ungrouped mantissa tables
168 reference: Tables 7.21 and 7.23 */
170 /* bap=3 mantissas */
171 b3_mantissas[i] = symmetric_dequant(i, 7);
173 for(i=0; i<15; i++) {
174 /* bap=5 mantissas */
175 b5_mantissas[i] = symmetric_dequant(i, 15);
178 /* generate dynamic range table
179 reference: Section 7.7.1 Dynamic Range Control */
180 for(i=0; i<256; i++) {
181 int v = (i >> 5) - ((i >> 7) << 3) - 5;
182 dynamic_range_tab[i] = powf(2.0f, v) * ((i & 0x1F) | 0x20);
188 * AVCodec initialization
190 static av_cold int ac3_decode_init(AVCodecContext *avctx)
192 AC3DecodeContext *s = avctx->priv_data;
197 ff_mdct_init(&s->imdct_256, 8, 1, 1.0);
198 ff_mdct_init(&s->imdct_512, 9, 1, 1.0);
199 ff_kbd_window_init(s->window, 5.0, 256);
200 dsputil_init(&s->dsp, avctx);
201 av_lfg_init(&s->dith_state, 0);
203 /* set bias values for float to int16 conversion */
204 if(s->dsp.float_to_int16_interleave == ff_float_to_int16_interleave_c) {
205 s->add_bias = 385.0f;
209 s->mul_bias = 32767.0f;
212 /* allow downmixing to stereo or mono */
213 if (avctx->channels > 0 && avctx->request_channels > 0 &&
214 avctx->request_channels < avctx->channels &&
215 avctx->request_channels <= 2) {
216 avctx->channels = avctx->request_channels;
220 /* allocate context input buffer */
221 if (avctx->error_recognition >= FF_ER_CAREFUL) {
222 s->input_buffer = av_mallocz(AC3_FRAME_BUFFER_SIZE + FF_INPUT_BUFFER_PADDING_SIZE);
223 if (!s->input_buffer)
224 return AVERROR_NOMEM;
227 avctx->sample_fmt = SAMPLE_FMT_S16;
232 * Parse the 'sync info' and 'bit stream info' from the AC-3 bitstream.
233 * GetBitContext within AC3DecodeContext must point to
234 * the start of the synchronized AC-3 bitstream.
236 static int ac3_parse_header(AC3DecodeContext *s)
238 GetBitContext *gbc = &s->gbc;
241 /* read the rest of the bsi. read twice for dual mono mode. */
242 i = !(s->channel_mode);
244 skip_bits(gbc, 5); // skip dialog normalization
246 skip_bits(gbc, 8); //skip compression
248 skip_bits(gbc, 8); //skip language code
250 skip_bits(gbc, 7); //skip audio production information
253 skip_bits(gbc, 2); //skip copyright bit and original bitstream bit
255 /* skip the timecodes (or extra bitstream information for Alternate Syntax)
256 TODO: read & use the xbsi1 downmix levels */
258 skip_bits(gbc, 14); //skip timecode1 / xbsi1
260 skip_bits(gbc, 14); //skip timecode2 / xbsi2
262 /* skip additional bitstream info */
263 if (get_bits1(gbc)) {
264 i = get_bits(gbc, 6);
274 * Common function to parse AC-3 or E-AC-3 frame header
276 static int parse_frame_header(AC3DecodeContext *s)
281 err = ff_ac3_parse_header(&s->gbc, &hdr);
285 /* get decoding parameters from header info */
286 s->bit_alloc_params.sr_code = hdr.sr_code;
287 s->channel_mode = hdr.channel_mode;
288 s->channel_layout = hdr.channel_layout;
289 s->lfe_on = hdr.lfe_on;
290 s->bit_alloc_params.sr_shift = hdr.sr_shift;
291 s->sample_rate = hdr.sample_rate;
292 s->bit_rate = hdr.bit_rate;
293 s->channels = hdr.channels;
294 s->fbw_channels = s->channels - s->lfe_on;
295 s->lfe_ch = s->fbw_channels + 1;
296 s->frame_size = hdr.frame_size;
297 s->center_mix_level = hdr.center_mix_level;
298 s->surround_mix_level = hdr.surround_mix_level;
299 s->num_blocks = hdr.num_blocks;
300 s->frame_type = hdr.frame_type;
301 s->substreamid = hdr.substreamid;
304 s->start_freq[s->lfe_ch] = 0;
305 s->end_freq[s->lfe_ch] = 7;
306 s->num_exp_groups[s->lfe_ch] = 2;
307 s->channel_in_cpl[s->lfe_ch] = 0;
310 if (hdr.bitstream_id <= 10) {
312 s->snr_offset_strategy = 2;
313 s->block_switch_syntax = 1;
314 s->dither_flag_syntax = 1;
315 s->bit_allocation_syntax = 1;
316 s->fast_gain_syntax = 0;
317 s->first_cpl_leak = 0;
320 memset(s->channel_uses_aht, 0, sizeof(s->channel_uses_aht));
321 return ac3_parse_header(s);
324 return ff_eac3_parse_header(s);
329 * Set stereo downmixing coefficients based on frame header info.
330 * reference: Section 7.8.2 Downmixing Into Two Channels
332 static void set_downmix_coeffs(AC3DecodeContext *s)
335 float cmix = gain_levels[center_levels[s->center_mix_level]];
336 float smix = gain_levels[surround_levels[s->surround_mix_level]];
339 for(i=0; i<s->fbw_channels; i++) {
340 s->downmix_coeffs[i][0] = gain_levels[ac3_default_coeffs[s->channel_mode][i][0]];
341 s->downmix_coeffs[i][1] = gain_levels[ac3_default_coeffs[s->channel_mode][i][1]];
343 if(s->channel_mode > 1 && s->channel_mode & 1) {
344 s->downmix_coeffs[1][0] = s->downmix_coeffs[1][1] = cmix;
346 if(s->channel_mode == AC3_CHMODE_2F1R || s->channel_mode == AC3_CHMODE_3F1R) {
347 int nf = s->channel_mode - 2;
348 s->downmix_coeffs[nf][0] = s->downmix_coeffs[nf][1] = smix * LEVEL_MINUS_3DB;
350 if(s->channel_mode == AC3_CHMODE_2F2R || s->channel_mode == AC3_CHMODE_3F2R) {
351 int nf = s->channel_mode - 4;
352 s->downmix_coeffs[nf][0] = s->downmix_coeffs[nf+1][1] = smix;
357 for(i=0; i<s->fbw_channels; i++) {
358 norm0 += s->downmix_coeffs[i][0];
359 norm1 += s->downmix_coeffs[i][1];
361 norm0 = 1.0f / norm0;
362 norm1 = 1.0f / norm1;
363 for(i=0; i<s->fbw_channels; i++) {
364 s->downmix_coeffs[i][0] *= norm0;
365 s->downmix_coeffs[i][1] *= norm1;
368 if(s->output_mode == AC3_CHMODE_MONO) {
369 for(i=0; i<s->fbw_channels; i++)
370 s->downmix_coeffs[i][0] = (s->downmix_coeffs[i][0] + s->downmix_coeffs[i][1]) * LEVEL_MINUS_3DB;
375 * Decode the grouped exponents according to exponent strategy.
376 * reference: Section 7.1.3 Exponent Decoding
378 static int decode_exponents(GetBitContext *gbc, int exp_strategy, int ngrps,
379 uint8_t absexp, int8_t *dexps)
381 int i, j, grp, group_size;
386 group_size = exp_strategy + (exp_strategy == EXP_D45);
387 for(grp=0,i=0; grp<ngrps; grp++) {
388 expacc = get_bits(gbc, 7);
389 dexp[i++] = ungroup_3_in_7_bits_tab[expacc][0];
390 dexp[i++] = ungroup_3_in_7_bits_tab[expacc][1];
391 dexp[i++] = ungroup_3_in_7_bits_tab[expacc][2];
394 /* convert to absolute exps and expand groups */
396 for(i=0,j=0; i<ngrps*3; i++) {
397 prevexp += dexp[i] - 2;
400 switch (group_size) {
401 case 4: dexps[j++] = prevexp;
402 dexps[j++] = prevexp;
403 case 2: dexps[j++] = prevexp;
404 case 1: dexps[j++] = prevexp;
411 * Generate transform coefficients for each coupled channel in the coupling
412 * range using the coupling coefficients and coupling coordinates.
413 * reference: Section 7.4.3 Coupling Coordinate Format
415 static void calc_transform_coeffs_cpl(AC3DecodeContext *s)
417 int i, j, ch, bnd, subbnd;
420 i = s->start_freq[CPL_CH];
421 for(bnd=0; bnd<s->num_cpl_bands; bnd++) {
424 for(j=0; j<12; j++) {
425 for(ch=1; ch<=s->fbw_channels; ch++) {
426 if(s->channel_in_cpl[ch]) {
427 s->fixed_coeffs[ch][i] = ((int64_t)s->fixed_coeffs[CPL_CH][i] * (int64_t)s->cpl_coords[ch][bnd]) >> 23;
428 if (ch == 2 && s->phase_flags[bnd])
429 s->fixed_coeffs[ch][i] = -s->fixed_coeffs[ch][i];
434 } while(s->cpl_band_struct[subbnd]);
439 * Grouped mantissas for 3-level 5-level and 11-level quantization
451 * Decode the transform coefficients for a particular channel
452 * reference: Section 7.3 Quantization and Decoding of Mantissas
454 static void ac3_decode_transform_coeffs_ch(AC3DecodeContext *s, int ch_index, mant_groups *m)
456 int start_freq = s->start_freq[ch_index];
457 int end_freq = s->end_freq[ch_index];
458 uint8_t *baps = s->bap[ch_index];
459 int8_t *exps = s->dexps[ch_index];
460 int *coeffs = s->fixed_coeffs[ch_index];
461 GetBitContext *gbc = &s->gbc;
464 for(freq = start_freq; freq < end_freq; freq++){
465 int bap = baps[freq];
469 mantissa = (av_lfg_get(&s->dith_state) & 0x7FFFFF) - 0x400000;
474 mantissa = m->b1_mant[m->b1];
477 int bits = get_bits(gbc, 5);
478 mantissa = b1_mantissas[bits][0];
479 m->b1_mant[1] = b1_mantissas[bits][1];
480 m->b1_mant[0] = b1_mantissas[bits][2];
487 mantissa = m->b2_mant[m->b2];
490 int bits = get_bits(gbc, 7);
491 mantissa = b2_mantissas[bits][0];
492 m->b2_mant[1] = b2_mantissas[bits][1];
493 m->b2_mant[0] = b2_mantissas[bits][2];
498 mantissa = b3_mantissas[get_bits(gbc, 3)];
503 mantissa = m->b4_mant;
506 int bits = get_bits(gbc, 7);
507 mantissa = b4_mantissas[bits][0];
508 m->b4_mant = b4_mantissas[bits][1];
513 mantissa = b5_mantissas[get_bits(gbc, 4)];
515 default: /* 6 to 15 */
516 mantissa = get_bits(gbc, quantization_tab[bap]);
517 /* Shift mantissa and sign-extend it. */
518 mantissa = (mantissa << (32-quantization_tab[bap]))>>8;
521 coeffs[freq] = mantissa >> exps[freq];
526 * Remove random dithering from coefficients with zero-bit mantissas
527 * reference: Section 7.3.4 Dither for Zero Bit Mantissas (bap=0)
529 static void remove_dithering(AC3DecodeContext *s) {
535 for(ch=1; ch<=s->fbw_channels; ch++) {
536 if(!s->dither_flag[ch]) {
537 coeffs = s->fixed_coeffs[ch];
539 if(s->channel_in_cpl[ch])
540 end = s->start_freq[CPL_CH];
542 end = s->end_freq[ch];
543 for(i=0; i<end; i++) {
547 if(s->channel_in_cpl[ch]) {
548 bap = s->bap[CPL_CH];
549 for(; i<s->end_freq[CPL_CH]; i++) {
558 static void decode_transform_coeffs_ch(AC3DecodeContext *s, int blk, int ch,
561 if (!s->channel_uses_aht[ch]) {
562 ac3_decode_transform_coeffs_ch(s, ch, m);
564 /* if AHT is used, mantissas for all blocks are encoded in the first
565 block of the frame. */
568 ff_eac3_decode_transform_coeffs_aht_ch(s, ch);
569 for (bin = s->start_freq[ch]; bin < s->end_freq[ch]; bin++) {
570 s->fixed_coeffs[ch][bin] = (s->pre_mantissa[ch][bin][blk] << 8) >> s->dexps[ch][bin];
576 * Decode the transform coefficients.
578 static void decode_transform_coeffs(AC3DecodeContext *s, int blk)
584 m.b1 = m.b2 = m.b4 = 0;
586 for (ch = 1; ch <= s->channels; ch++) {
587 /* transform coefficients for full-bandwidth channel */
588 decode_transform_coeffs_ch(s, blk, ch, &m);
589 /* tranform coefficients for coupling channel come right after the
590 coefficients for the first coupled channel*/
591 if (s->channel_in_cpl[ch]) {
593 decode_transform_coeffs_ch(s, blk, CPL_CH, &m);
594 calc_transform_coeffs_cpl(s);
597 end = s->end_freq[CPL_CH];
599 end = s->end_freq[ch];
602 s->fixed_coeffs[ch][end] = 0;
606 /* zero the dithered coefficients for appropriate channels */
611 * Stereo rematrixing.
612 * reference: Section 7.5.4 Rematrixing : Decoding Technique
614 static void do_rematrixing(AC3DecodeContext *s)
620 end = FFMIN(s->end_freq[1], s->end_freq[2]);
622 for(bnd=0; bnd<s->num_rematrixing_bands; bnd++) {
623 if(s->rematrixing_flags[bnd]) {
624 bndend = FFMIN(end, ff_ac3_rematrix_band_tab[bnd+1]);
625 for(i=ff_ac3_rematrix_band_tab[bnd]; i<bndend; i++) {
626 tmp0 = s->fixed_coeffs[1][i];
627 tmp1 = s->fixed_coeffs[2][i];
628 s->fixed_coeffs[1][i] = tmp0 + tmp1;
629 s->fixed_coeffs[2][i] = tmp0 - tmp1;
636 * Inverse MDCT Transform.
637 * Convert frequency domain coefficients to time-domain audio samples.
638 * reference: Section 7.9.4 Transformation Equations
640 static inline void do_imdct(AC3DecodeContext *s, int channels)
643 float add_bias = s->add_bias;
644 if(s->out_channels==1 && channels>1)
645 add_bias *= LEVEL_MINUS_3DB; // compensate for the gain in downmix
647 for (ch=1; ch<=channels; ch++) {
648 if (s->block_switch[ch]) {
650 float *x = s->tmp_output+128;
652 x[i] = s->transform_coeffs[ch][2*i];
653 ff_imdct_half(&s->imdct_256, s->tmp_output, x);
654 s->dsp.vector_fmul_window(s->output[ch-1], s->delay[ch-1], s->tmp_output, s->window, add_bias, 128);
656 x[i] = s->transform_coeffs[ch][2*i+1];
657 ff_imdct_half(&s->imdct_256, s->delay[ch-1], x);
659 ff_imdct_half(&s->imdct_512, s->tmp_output, s->transform_coeffs[ch]);
660 s->dsp.vector_fmul_window(s->output[ch-1], s->delay[ch-1], s->tmp_output, s->window, add_bias, 128);
661 memcpy(s->delay[ch-1], s->tmp_output+128, 128*sizeof(float));
667 * Downmix the output to mono or stereo.
669 void ff_ac3_downmix_c(float (*samples)[256], float (*matrix)[2], int out_ch, int in_ch, int len)
674 for(i=0; i<len; i++) {
676 for(j=0; j<in_ch; j++) {
677 v0 += samples[j][i] * matrix[j][0];
678 v1 += samples[j][i] * matrix[j][1];
683 } else if(out_ch == 1) {
684 for(i=0; i<len; i++) {
686 for(j=0; j<in_ch; j++)
687 v0 += samples[j][i] * matrix[j][0];
694 * Upmix delay samples from stereo to original channel layout.
696 static void ac3_upmix_delay(AC3DecodeContext *s)
698 int channel_data_size = sizeof(s->delay[0]);
699 switch(s->channel_mode) {
700 case AC3_CHMODE_DUALMONO:
701 case AC3_CHMODE_STEREO:
702 /* upmix mono to stereo */
703 memcpy(s->delay[1], s->delay[0], channel_data_size);
705 case AC3_CHMODE_2F2R:
706 memset(s->delay[3], 0, channel_data_size);
707 case AC3_CHMODE_2F1R:
708 memset(s->delay[2], 0, channel_data_size);
710 case AC3_CHMODE_3F2R:
711 memset(s->delay[4], 0, channel_data_size);
712 case AC3_CHMODE_3F1R:
713 memset(s->delay[3], 0, channel_data_size);
715 memcpy(s->delay[2], s->delay[1], channel_data_size);
716 memset(s->delay[1], 0, channel_data_size);
722 * Decode band structure for coupling, spectral extension, or enhanced coupling.
723 * @param[in] gbc bit reader context
724 * @param[in] blk block number
725 * @param[in] eac3 flag to indicate E-AC-3
726 * @param[in] ecpl flag to indicate enhanced coupling
727 * @param[in] start_subband subband number for start of range
728 * @param[in] end_subband subband number for end of range
729 * @param[in] default_band_struct default band structure table
730 * @param[out] band_struct decoded band structure
731 * @param[out] num_bands number of bands (optionally NULL)
732 * @param[out] band_sizes array containing the number of bins in each band (optionally NULL)
734 static void decode_band_structure(GetBitContext *gbc, int blk, int eac3,
735 int ecpl, int start_subband, int end_subband,
736 const uint8_t *default_band_struct,
737 uint8_t *band_struct, int *num_bands,
740 int subbnd, bnd, n_subbands, n_bands=0;
743 n_subbands = end_subband - start_subband;
745 /* decode band structure from bitstream or use default */
746 if (!eac3 || get_bits1(gbc)) {
747 for (subbnd = 0; subbnd < n_subbands - 1; subbnd++) {
748 band_struct[subbnd] = get_bits1(gbc);
752 &default_band_struct[start_subband+1],
755 band_struct[n_subbands-1] = 0;
757 /* calculate number of bands and band sizes based on band structure.
758 note that the first 4 subbands in enhanced coupling span only 6 bins
760 if (num_bands || band_sizes ) {
761 n_bands = n_subbands;
762 bnd_sz[0] = ecpl ? 6 : 12;
763 for (bnd = 0, subbnd = 1; subbnd < n_subbands; subbnd++) {
764 int subbnd_size = (ecpl && subbnd < 4) ? 6 : 12;
765 if (band_struct[subbnd-1]) {
767 bnd_sz[bnd] += subbnd_size;
769 bnd_sz[++bnd] = subbnd_size;
774 /* set optional output params */
776 *num_bands = n_bands;
778 memcpy(band_sizes, bnd_sz, n_bands);
782 * Decode a single audio block from the AC-3 bitstream.
784 static int decode_audio_block(AC3DecodeContext *s, int blk)
786 int fbw_channels = s->fbw_channels;
787 int channel_mode = s->channel_mode;
789 int different_transforms;
792 GetBitContext *gbc = &s->gbc;
793 uint8_t bit_alloc_stages[AC3_MAX_CHANNELS];
795 memset(bit_alloc_stages, 0, AC3_MAX_CHANNELS);
797 /* block switch flags */
798 different_transforms = 0;
799 if (s->block_switch_syntax) {
800 for (ch = 1; ch <= fbw_channels; ch++) {
801 s->block_switch[ch] = get_bits1(gbc);
802 if(ch > 1 && s->block_switch[ch] != s->block_switch[1])
803 different_transforms = 1;
807 /* dithering flags */
808 if (s->dither_flag_syntax) {
809 for (ch = 1; ch <= fbw_channels; ch++) {
810 s->dither_flag[ch] = get_bits1(gbc);
815 i = !(s->channel_mode);
818 s->dynamic_range[i] = ((dynamic_range_tab[get_bits(gbc, 8)]-1.0) *
819 s->avctx->drc_scale)+1.0;
820 } else if(blk == 0) {
821 s->dynamic_range[i] = 1.0f;
825 /* spectral extension strategy */
826 if (s->eac3 && (!blk || get_bits1(gbc))) {
827 if (get_bits1(gbc)) {
828 ff_log_missing_feature(s->avctx, "Spectral extension", 1);
831 /* TODO: parse spectral extension strategy info */
834 /* TODO: spectral extension coordinates */
836 /* coupling strategy */
837 if (s->eac3 ? s->cpl_strategy_exists[blk] : get_bits1(gbc)) {
838 memset(bit_alloc_stages, 3, AC3_MAX_CHANNELS);
840 s->cpl_in_use[blk] = get_bits1(gbc);
841 if (s->cpl_in_use[blk]) {
842 /* coupling in use */
843 int cpl_start_subband, cpl_end_subband;
845 if (channel_mode < AC3_CHMODE_STEREO) {
846 av_log(s->avctx, AV_LOG_ERROR, "coupling not allowed in mono or dual-mono\n");
850 /* check for enhanced coupling */
851 if (s->eac3 && get_bits1(gbc)) {
852 /* TODO: parse enhanced coupling strategy info */
853 ff_log_missing_feature(s->avctx, "Enhanced coupling", 1);
857 /* determine which channels are coupled */
858 if (s->eac3 && s->channel_mode == AC3_CHMODE_STEREO) {
859 s->channel_in_cpl[1] = 1;
860 s->channel_in_cpl[2] = 1;
862 for (ch = 1; ch <= fbw_channels; ch++)
863 s->channel_in_cpl[ch] = get_bits1(gbc);
866 /* phase flags in use */
867 if (channel_mode == AC3_CHMODE_STEREO)
868 s->phase_flags_in_use = get_bits1(gbc);
870 /* coupling frequency range */
871 /* TODO: modify coupling end freq if spectral extension is used */
872 cpl_start_subband = get_bits(gbc, 4);
873 cpl_end_subband = get_bits(gbc, 4) + 3;
874 if (cpl_start_subband >= cpl_end_subband) {
875 av_log(s->avctx, AV_LOG_ERROR, "invalid coupling range (%d >= %d)\n",
876 cpl_start_subband, cpl_end_subband);
879 s->start_freq[CPL_CH] = cpl_start_subband * 12 + 37;
880 s->end_freq[CPL_CH] = cpl_end_subband * 12 + 37;
882 decode_band_structure(gbc, blk, s->eac3, 0, cpl_start_subband,
884 ff_eac3_default_cpl_band_struct,
885 s->cpl_band_struct, &s->num_cpl_bands, NULL);
887 /* coupling not in use */
888 for (ch = 1; ch <= fbw_channels; ch++) {
889 s->channel_in_cpl[ch] = 0;
890 s->first_cpl_coords[ch] = 1;
892 s->first_cpl_leak = s->eac3;
893 s->phase_flags_in_use = 0;
895 } else if (!s->eac3) {
897 av_log(s->avctx, AV_LOG_ERROR, "new coupling strategy must be present in block 0\n");
900 s->cpl_in_use[blk] = s->cpl_in_use[blk-1];
903 cpl_in_use = s->cpl_in_use[blk];
905 /* coupling coordinates */
907 int cpl_coords_exist = 0;
909 for (ch = 1; ch <= fbw_channels; ch++) {
910 if (s->channel_in_cpl[ch]) {
911 if ((s->eac3 && s->first_cpl_coords[ch]) || get_bits1(gbc)) {
912 int master_cpl_coord, cpl_coord_exp, cpl_coord_mant;
913 s->first_cpl_coords[ch] = 0;
914 cpl_coords_exist = 1;
915 master_cpl_coord = 3 * get_bits(gbc, 2);
916 for (bnd = 0; bnd < s->num_cpl_bands; bnd++) {
917 cpl_coord_exp = get_bits(gbc, 4);
918 cpl_coord_mant = get_bits(gbc, 4);
919 if (cpl_coord_exp == 15)
920 s->cpl_coords[ch][bnd] = cpl_coord_mant << 22;
922 s->cpl_coords[ch][bnd] = (cpl_coord_mant + 16) << 21;
923 s->cpl_coords[ch][bnd] >>= (cpl_coord_exp + master_cpl_coord);
926 av_log(s->avctx, AV_LOG_ERROR, "new coupling coordinates must be present in block 0\n");
930 /* channel not in coupling */
931 s->first_cpl_coords[ch] = 1;
935 if (channel_mode == AC3_CHMODE_STEREO && cpl_coords_exist) {
936 for (bnd = 0; bnd < s->num_cpl_bands; bnd++) {
937 s->phase_flags[bnd] = s->phase_flags_in_use? get_bits1(gbc) : 0;
942 /* stereo rematrixing strategy and band structure */
943 if (channel_mode == AC3_CHMODE_STEREO) {
944 if ((s->eac3 && !blk) || get_bits1(gbc)) {
945 s->num_rematrixing_bands = 4;
946 if(cpl_in_use && s->start_freq[CPL_CH] <= 61)
947 s->num_rematrixing_bands -= 1 + (s->start_freq[CPL_CH] == 37);
948 for(bnd=0; bnd<s->num_rematrixing_bands; bnd++)
949 s->rematrixing_flags[bnd] = get_bits1(gbc);
951 av_log(s->avctx, AV_LOG_ERROR, "new rematrixing strategy must be present in block 0\n");
956 /* exponent strategies for each channel */
957 for (ch = !cpl_in_use; ch <= s->channels; ch++) {
959 s->exp_strategy[blk][ch] = get_bits(gbc, 2 - (ch == s->lfe_ch));
960 if(s->exp_strategy[blk][ch] != EXP_REUSE)
961 bit_alloc_stages[ch] = 3;
964 /* channel bandwidth */
965 for (ch = 1; ch <= fbw_channels; ch++) {
966 s->start_freq[ch] = 0;
967 if (s->exp_strategy[blk][ch] != EXP_REUSE) {
969 int prev = s->end_freq[ch];
970 if (s->channel_in_cpl[ch])
971 s->end_freq[ch] = s->start_freq[CPL_CH];
973 int bandwidth_code = get_bits(gbc, 6);
974 if (bandwidth_code > 60) {
975 av_log(s->avctx, AV_LOG_ERROR, "bandwidth code = %d > 60\n", bandwidth_code);
978 s->end_freq[ch] = bandwidth_code * 3 + 73;
980 group_size = 3 << (s->exp_strategy[blk][ch] - 1);
981 s->num_exp_groups[ch] = (s->end_freq[ch]+group_size-4) / group_size;
982 if(blk > 0 && s->end_freq[ch] != prev)
983 memset(bit_alloc_stages, 3, AC3_MAX_CHANNELS);
986 if (cpl_in_use && s->exp_strategy[blk][CPL_CH] != EXP_REUSE) {
987 s->num_exp_groups[CPL_CH] = (s->end_freq[CPL_CH] - s->start_freq[CPL_CH]) /
988 (3 << (s->exp_strategy[blk][CPL_CH] - 1));
991 /* decode exponents for each channel */
992 for (ch = !cpl_in_use; ch <= s->channels; ch++) {
993 if (s->exp_strategy[blk][ch] != EXP_REUSE) {
994 s->dexps[ch][0] = get_bits(gbc, 4) << !ch;
995 if (decode_exponents(gbc, s->exp_strategy[blk][ch],
996 s->num_exp_groups[ch], s->dexps[ch][0],
997 &s->dexps[ch][s->start_freq[ch]+!!ch])) {
998 av_log(s->avctx, AV_LOG_ERROR, "exponent out-of-range\n");
1001 if(ch != CPL_CH && ch != s->lfe_ch)
1002 skip_bits(gbc, 2); /* skip gainrng */
1006 /* bit allocation information */
1007 if (s->bit_allocation_syntax) {
1008 if (get_bits1(gbc)) {
1009 s->bit_alloc_params.slow_decay = ff_ac3_slow_decay_tab[get_bits(gbc, 2)] >> s->bit_alloc_params.sr_shift;
1010 s->bit_alloc_params.fast_decay = ff_ac3_fast_decay_tab[get_bits(gbc, 2)] >> s->bit_alloc_params.sr_shift;
1011 s->bit_alloc_params.slow_gain = ff_ac3_slow_gain_tab[get_bits(gbc, 2)];
1012 s->bit_alloc_params.db_per_bit = ff_ac3_db_per_bit_tab[get_bits(gbc, 2)];
1013 s->bit_alloc_params.floor = ff_ac3_floor_tab[get_bits(gbc, 3)];
1014 for(ch=!cpl_in_use; ch<=s->channels; ch++)
1015 bit_alloc_stages[ch] = FFMAX(bit_alloc_stages[ch], 2);
1017 av_log(s->avctx, AV_LOG_ERROR, "new bit allocation info must be present in block 0\n");
1022 /* signal-to-noise ratio offsets and fast gains (signal-to-mask ratios) */
1023 if(!s->eac3 || !blk){
1024 if(s->snr_offset_strategy && get_bits1(gbc)) {
1027 csnr = (get_bits(gbc, 6) - 15) << 4;
1028 for (i = ch = !cpl_in_use; ch <= s->channels; ch++) {
1030 if (ch == i || s->snr_offset_strategy == 2)
1031 snr = (csnr + get_bits(gbc, 4)) << 2;
1032 /* run at least last bit allocation stage if snr offset changes */
1033 if(blk && s->snr_offset[ch] != snr) {
1034 bit_alloc_stages[ch] = FFMAX(bit_alloc_stages[ch], 1);
1036 s->snr_offset[ch] = snr;
1038 /* fast gain (normal AC-3 only) */
1040 int prev = s->fast_gain[ch];
1041 s->fast_gain[ch] = ff_ac3_fast_gain_tab[get_bits(gbc, 3)];
1042 /* run last 2 bit allocation stages if fast gain changes */
1043 if(blk && prev != s->fast_gain[ch])
1044 bit_alloc_stages[ch] = FFMAX(bit_alloc_stages[ch], 2);
1047 } else if (!s->eac3 && !blk) {
1048 av_log(s->avctx, AV_LOG_ERROR, "new snr offsets must be present in block 0\n");
1053 /* fast gain (E-AC-3 only) */
1054 if (s->fast_gain_syntax && get_bits1(gbc)) {
1055 for (ch = !cpl_in_use; ch <= s->channels; ch++) {
1056 int prev = s->fast_gain[ch];
1057 s->fast_gain[ch] = ff_ac3_fast_gain_tab[get_bits(gbc, 3)];
1058 /* run last 2 bit allocation stages if fast gain changes */
1059 if(blk && prev != s->fast_gain[ch])
1060 bit_alloc_stages[ch] = FFMAX(bit_alloc_stages[ch], 2);
1062 } else if (s->eac3 && !blk) {
1063 for (ch = !cpl_in_use; ch <= s->channels; ch++)
1064 s->fast_gain[ch] = ff_ac3_fast_gain_tab[4];
1067 /* E-AC-3 to AC-3 converter SNR offset */
1068 if (s->frame_type == EAC3_FRAME_TYPE_INDEPENDENT && get_bits1(gbc)) {
1069 skip_bits(gbc, 10); // skip converter snr offset
1072 /* coupling leak information */
1074 if (s->first_cpl_leak || get_bits1(gbc)) {
1075 int fl = get_bits(gbc, 3);
1076 int sl = get_bits(gbc, 3);
1077 /* run last 2 bit allocation stages for coupling channel if
1078 coupling leak changes */
1079 if(blk && (fl != s->bit_alloc_params.cpl_fast_leak ||
1080 sl != s->bit_alloc_params.cpl_slow_leak)) {
1081 bit_alloc_stages[CPL_CH] = FFMAX(bit_alloc_stages[CPL_CH], 2);
1083 s->bit_alloc_params.cpl_fast_leak = fl;
1084 s->bit_alloc_params.cpl_slow_leak = sl;
1085 } else if (!s->eac3 && !blk) {
1086 av_log(s->avctx, AV_LOG_ERROR, "new coupling leak info must be present in block 0\n");
1089 s->first_cpl_leak = 0;
1092 /* delta bit allocation information */
1093 if (s->dba_syntax && get_bits1(gbc)) {
1094 /* delta bit allocation exists (strategy) */
1095 for (ch = !cpl_in_use; ch <= fbw_channels; ch++) {
1096 s->dba_mode[ch] = get_bits(gbc, 2);
1097 if (s->dba_mode[ch] == DBA_RESERVED) {
1098 av_log(s->avctx, AV_LOG_ERROR, "delta bit allocation strategy reserved\n");
1101 bit_alloc_stages[ch] = FFMAX(bit_alloc_stages[ch], 2);
1103 /* channel delta offset, len and bit allocation */
1104 for (ch = !cpl_in_use; ch <= fbw_channels; ch++) {
1105 if (s->dba_mode[ch] == DBA_NEW) {
1106 s->dba_nsegs[ch] = get_bits(gbc, 3);
1107 for (seg = 0; seg <= s->dba_nsegs[ch]; seg++) {
1108 s->dba_offsets[ch][seg] = get_bits(gbc, 5);
1109 s->dba_lengths[ch][seg] = get_bits(gbc, 4);
1110 s->dba_values[ch][seg] = get_bits(gbc, 3);
1112 /* run last 2 bit allocation stages if new dba values */
1113 bit_alloc_stages[ch] = FFMAX(bit_alloc_stages[ch], 2);
1116 } else if(blk == 0) {
1117 for(ch=0; ch<=s->channels; ch++) {
1118 s->dba_mode[ch] = DBA_NONE;
1122 /* Bit allocation */
1123 for(ch=!cpl_in_use; ch<=s->channels; ch++) {
1124 if(bit_alloc_stages[ch] > 2) {
1125 /* Exponent mapping into PSD and PSD integration */
1126 ff_ac3_bit_alloc_calc_psd(s->dexps[ch],
1127 s->start_freq[ch], s->end_freq[ch],
1128 s->psd[ch], s->band_psd[ch]);
1130 if(bit_alloc_stages[ch] > 1) {
1131 /* Compute excitation function, Compute masking curve, and
1132 Apply delta bit allocation */
1133 if (ff_ac3_bit_alloc_calc_mask(&s->bit_alloc_params, s->band_psd[ch],
1134 s->start_freq[ch], s->end_freq[ch],
1135 s->fast_gain[ch], (ch == s->lfe_ch),
1136 s->dba_mode[ch], s->dba_nsegs[ch],
1137 s->dba_offsets[ch], s->dba_lengths[ch],
1138 s->dba_values[ch], s->mask[ch])) {
1139 av_log(s->avctx, AV_LOG_ERROR, "error in bit allocation\n");
1143 if(bit_alloc_stages[ch] > 0) {
1144 /* Compute bit allocation */
1145 const uint8_t *bap_tab = s->channel_uses_aht[ch] ?
1146 ff_eac3_hebap_tab : ff_ac3_bap_tab;
1147 ff_ac3_bit_alloc_calc_bap(s->mask[ch], s->psd[ch],
1148 s->start_freq[ch], s->end_freq[ch],
1150 s->bit_alloc_params.floor,
1151 bap_tab, s->bap[ch]);
1155 /* unused dummy data */
1156 if (s->skip_syntax && get_bits1(gbc)) {
1157 int skipl = get_bits(gbc, 9);
1162 /* unpack the transform coefficients
1163 this also uncouples channels if coupling is in use. */
1164 decode_transform_coeffs(s, blk);
1166 /* TODO: generate enhanced coupling coordinates and uncouple */
1168 /* TODO: apply spectral extension */
1170 /* recover coefficients if rematrixing is in use */
1171 if(s->channel_mode == AC3_CHMODE_STEREO)
1174 /* apply scaling to coefficients (headroom, dynrng) */
1175 for(ch=1; ch<=s->channels; ch++) {
1176 float gain = s->mul_bias / 4194304.0f;
1177 if(s->channel_mode == AC3_CHMODE_DUALMONO) {
1178 gain *= s->dynamic_range[ch-1];
1180 gain *= s->dynamic_range[0];
1182 s->dsp.int32_to_float_fmul_scalar(s->transform_coeffs[ch], s->fixed_coeffs[ch], gain, 256);
1185 /* downmix and MDCT. order depends on whether block switching is used for
1186 any channel in this block. this is because coefficients for the long
1187 and short transforms cannot be mixed. */
1188 downmix_output = s->channels != s->out_channels &&
1189 !((s->output_mode & AC3_OUTPUT_LFEON) &&
1190 s->fbw_channels == s->out_channels);
1191 if(different_transforms) {
1192 /* the delay samples have already been downmixed, so we upmix the delay
1193 samples in order to reconstruct all channels before downmixing. */
1199 do_imdct(s, s->channels);
1201 if(downmix_output) {
1202 s->dsp.ac3_downmix(s->output, s->downmix_coeffs, s->out_channels, s->fbw_channels, 256);
1205 if(downmix_output) {
1206 s->dsp.ac3_downmix(s->transform_coeffs+1, s->downmix_coeffs, s->out_channels, s->fbw_channels, 256);
1209 if(downmix_output && !s->downmixed) {
1211 s->dsp.ac3_downmix(s->delay, s->downmix_coeffs, s->out_channels, s->fbw_channels, 128);
1214 do_imdct(s, s->out_channels);
1221 * Decode a single AC-3 frame.
1223 static int ac3_decode_frame(AVCodecContext * avctx, void *data, int *data_size,
1226 const uint8_t *buf = avpkt->data;
1227 int buf_size = avpkt->size;
1228 AC3DecodeContext *s = avctx->priv_data;
1229 int16_t *out_samples = (int16_t *)data;
1231 const uint8_t *channel_map;
1232 const float *output[AC3_MAX_CHANNELS];
1234 /* initialize the GetBitContext with the start of valid AC-3 Frame */
1235 if (s->input_buffer) {
1236 /* copy input buffer to decoder context to avoid reading past the end
1237 of the buffer, which can be caused by a damaged input stream. */
1238 memcpy(s->input_buffer, buf, FFMIN(buf_size, AC3_FRAME_BUFFER_SIZE));
1239 init_get_bits(&s->gbc, s->input_buffer, buf_size * 8);
1241 init_get_bits(&s->gbc, buf, buf_size * 8);
1244 /* parse the syncinfo */
1246 err = parse_frame_header(s);
1248 /* check that reported frame size fits in input buffer */
1249 if(s->frame_size > buf_size) {
1250 av_log(avctx, AV_LOG_ERROR, "incomplete frame\n");
1251 err = AAC_AC3_PARSE_ERROR_FRAME_SIZE;
1254 /* check for crc mismatch */
1255 if(err != AAC_AC3_PARSE_ERROR_FRAME_SIZE && avctx->error_recognition >= FF_ER_CAREFUL) {
1256 if(av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0, &buf[2], s->frame_size-2)) {
1257 av_log(avctx, AV_LOG_ERROR, "frame CRC mismatch\n");
1258 err = AAC_AC3_PARSE_ERROR_CRC;
1262 if(err && err != AAC_AC3_PARSE_ERROR_CRC) {
1264 case AAC_AC3_PARSE_ERROR_SYNC:
1265 av_log(avctx, AV_LOG_ERROR, "frame sync error\n");
1267 case AAC_AC3_PARSE_ERROR_BSID:
1268 av_log(avctx, AV_LOG_ERROR, "invalid bitstream id\n");
1270 case AAC_AC3_PARSE_ERROR_SAMPLE_RATE:
1271 av_log(avctx, AV_LOG_ERROR, "invalid sample rate\n");
1273 case AAC_AC3_PARSE_ERROR_FRAME_SIZE:
1274 av_log(avctx, AV_LOG_ERROR, "invalid frame size\n");
1276 case AAC_AC3_PARSE_ERROR_FRAME_TYPE:
1277 /* skip frame if CRC is ok. otherwise use error concealment. */
1278 /* TODO: add support for substreams and dependent frames */
1279 if(s->frame_type == EAC3_FRAME_TYPE_DEPENDENT || s->substreamid) {
1280 av_log(avctx, AV_LOG_ERROR, "unsupported frame type : skipping frame\n");
1281 return s->frame_size;
1283 av_log(avctx, AV_LOG_ERROR, "invalid frame type\n");
1287 av_log(avctx, AV_LOG_ERROR, "invalid header\n");
1292 /* if frame is ok, set audio parameters */
1294 avctx->sample_rate = s->sample_rate;
1295 avctx->bit_rate = s->bit_rate;
1297 /* channel config */
1298 s->out_channels = s->channels;
1299 s->output_mode = s->channel_mode;
1301 s->output_mode |= AC3_OUTPUT_LFEON;
1302 if (avctx->request_channels > 0 && avctx->request_channels <= 2 &&
1303 avctx->request_channels < s->channels) {
1304 s->out_channels = avctx->request_channels;
1305 s->output_mode = avctx->request_channels == 1 ? AC3_CHMODE_MONO : AC3_CHMODE_STEREO;
1306 s->channel_layout = ff_ac3_channel_layout_tab[s->output_mode];
1308 avctx->channels = s->out_channels;
1309 avctx->channel_layout = s->channel_layout;
1311 /* set downmixing coefficients if needed */
1312 if(s->channels != s->out_channels && !((s->output_mode & AC3_OUTPUT_LFEON) &&
1313 s->fbw_channels == s->out_channels)) {
1314 set_downmix_coeffs(s);
1316 } else if (!s->out_channels) {
1317 s->out_channels = avctx->channels;
1318 if(s->out_channels < s->channels)
1319 s->output_mode = s->out_channels == 1 ? AC3_CHMODE_MONO : AC3_CHMODE_STEREO;
1322 /* decode the audio blocks */
1323 channel_map = ff_ac3_dec_channel_map[s->output_mode & ~AC3_OUTPUT_LFEON][s->lfe_on];
1324 for (ch = 0; ch < s->out_channels; ch++)
1325 output[ch] = s->output[channel_map[ch]];
1326 for (blk = 0; blk < s->num_blocks; blk++) {
1327 if (!err && decode_audio_block(s, blk)) {
1328 av_log(avctx, AV_LOG_ERROR, "error decoding the audio block\n");
1331 s->dsp.float_to_int16_interleave(out_samples, output, 256, s->out_channels);
1332 out_samples += 256 * s->out_channels;
1334 *data_size = s->num_blocks * 256 * avctx->channels * sizeof (int16_t);
1335 return s->frame_size;
1339 * Uninitialize the AC-3 decoder.
1341 static av_cold int ac3_decode_end(AVCodecContext *avctx)
1343 AC3DecodeContext *s = avctx->priv_data;
1344 ff_mdct_end(&s->imdct_512);
1345 ff_mdct_end(&s->imdct_256);
1347 av_freep(&s->input_buffer);
1352 AVCodec ac3_decoder = {
1354 .type = CODEC_TYPE_AUDIO,
1356 .priv_data_size = sizeof (AC3DecodeContext),
1357 .init = ac3_decode_init,
1358 .close = ac3_decode_end,
1359 .decode = ac3_decode_frame,
1360 .long_name = NULL_IF_CONFIG_SMALL("ATSC A/52A (AC-3)"),
1363 AVCodec eac3_decoder = {
1365 .type = CODEC_TYPE_AUDIO,
1366 .id = CODEC_ID_EAC3,
1367 .priv_data_size = sizeof (AC3DecodeContext),
1368 .init = ac3_decode_init,
1369 .close = ac3_decode_end,
1370 .decode = ac3_decode_frame,
1371 .long_name = NULL_IF_CONFIG_SMALL("ATSC A/52B (AC-3, E-AC-3)"),