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);
198 ff_mdct_init(&s->imdct_512, 9, 1);
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 GetBitContext *gbc = &s->gbc;
457 int i, gcode, tbap, start, end;
462 exps = s->dexps[ch_index];
463 bap = s->bap[ch_index];
464 coeffs = s->fixed_coeffs[ch_index];
465 start = s->start_freq[ch_index];
466 end = s->end_freq[ch_index];
468 for (i = start; i < end; i++) {
472 coeffs[i] = (av_lfg_get(&s->dith_state) & 0x7FFFFF) - 0x400000;
477 gcode = get_bits(gbc, 5);
478 m->b1_mant[0] = b1_mantissas[gcode][0];
479 m->b1_mant[1] = b1_mantissas[gcode][1];
480 m->b1_mant[2] = b1_mantissas[gcode][2];
483 coeffs[i] = m->b1_mant[m->b1ptr++];
488 gcode = get_bits(gbc, 7);
489 m->b2_mant[0] = b2_mantissas[gcode][0];
490 m->b2_mant[1] = b2_mantissas[gcode][1];
491 m->b2_mant[2] = b2_mantissas[gcode][2];
494 coeffs[i] = m->b2_mant[m->b2ptr++];
498 coeffs[i] = b3_mantissas[get_bits(gbc, 3)];
503 gcode = get_bits(gbc, 7);
504 m->b4_mant[0] = b4_mantissas[gcode][0];
505 m->b4_mant[1] = b4_mantissas[gcode][1];
508 coeffs[i] = m->b4_mant[m->b4ptr++];
512 coeffs[i] = b5_mantissas[get_bits(gbc, 4)];
516 /* asymmetric dequantization */
517 int qlevel = quantization_tab[tbap];
518 coeffs[i] = get_sbits(gbc, qlevel) << (24 - qlevel);
522 coeffs[i] >>= exps[i];
527 * Remove random dithering from coefficients with zero-bit mantissas
528 * reference: Section 7.3.4 Dither for Zero Bit Mantissas (bap=0)
530 static void remove_dithering(AC3DecodeContext *s) {
536 for(ch=1; ch<=s->fbw_channels; ch++) {
537 if(!s->dither_flag[ch]) {
538 coeffs = s->fixed_coeffs[ch];
540 if(s->channel_in_cpl[ch])
541 end = s->start_freq[CPL_CH];
543 end = s->end_freq[ch];
544 for(i=0; i<end; i++) {
548 if(s->channel_in_cpl[ch]) {
549 bap = s->bap[CPL_CH];
550 for(; i<s->end_freq[CPL_CH]; i++) {
559 static void decode_transform_coeffs_ch(AC3DecodeContext *s, int blk, int ch,
562 if (!s->channel_uses_aht[ch]) {
563 ac3_decode_transform_coeffs_ch(s, ch, m);
565 /* if AHT is used, mantissas for all blocks are encoded in the first
566 block of the frame. */
569 ff_eac3_decode_transform_coeffs_aht_ch(s, ch);
570 for (bin = s->start_freq[ch]; bin < s->end_freq[ch]; bin++) {
571 s->fixed_coeffs[ch][bin] = s->pre_mantissa[ch][bin][blk] >> s->dexps[ch][bin];
577 * Decode the transform coefficients.
579 static void decode_transform_coeffs(AC3DecodeContext *s, int blk)
585 m.b1ptr = m.b2ptr = m.b4ptr = 3;
587 for (ch = 1; ch <= s->channels; ch++) {
588 /* transform coefficients for full-bandwidth channel */
589 decode_transform_coeffs_ch(s, blk, ch, &m);
590 /* tranform coefficients for coupling channel come right after the
591 coefficients for the first coupled channel*/
592 if (s->channel_in_cpl[ch]) {
594 decode_transform_coeffs_ch(s, blk, CPL_CH, &m);
595 calc_transform_coeffs_cpl(s);
598 end = s->end_freq[CPL_CH];
600 end = s->end_freq[ch];
603 s->fixed_coeffs[ch][end] = 0;
607 /* zero the dithered coefficients for appropriate channels */
612 * Stereo rematrixing.
613 * reference: Section 7.5.4 Rematrixing : Decoding Technique
615 static void do_rematrixing(AC3DecodeContext *s)
621 end = FFMIN(s->end_freq[1], s->end_freq[2]);
623 for(bnd=0; bnd<s->num_rematrixing_bands; bnd++) {
624 if(s->rematrixing_flags[bnd]) {
625 bndend = FFMIN(end, ff_ac3_rematrix_band_tab[bnd+1]);
626 for(i=ff_ac3_rematrix_band_tab[bnd]; i<bndend; i++) {
627 tmp0 = s->fixed_coeffs[1][i];
628 tmp1 = s->fixed_coeffs[2][i];
629 s->fixed_coeffs[1][i] = tmp0 + tmp1;
630 s->fixed_coeffs[2][i] = tmp0 - tmp1;
637 * Inverse MDCT Transform.
638 * Convert frequency domain coefficients to time-domain audio samples.
639 * reference: Section 7.9.4 Transformation Equations
641 static inline void do_imdct(AC3DecodeContext *s, int channels)
644 float add_bias = s->add_bias;
645 if(s->out_channels==1 && channels>1)
646 add_bias *= LEVEL_MINUS_3DB; // compensate for the gain in downmix
648 for (ch=1; ch<=channels; ch++) {
649 if (s->block_switch[ch]) {
651 float *x = s->tmp_output+128;
653 x[i] = s->transform_coeffs[ch][2*i];
654 ff_imdct_half(&s->imdct_256, s->tmp_output, x);
655 s->dsp.vector_fmul_window(s->output[ch-1], s->delay[ch-1], s->tmp_output, s->window, add_bias, 128);
657 x[i] = s->transform_coeffs[ch][2*i+1];
658 ff_imdct_half(&s->imdct_256, s->delay[ch-1], x);
660 ff_imdct_half(&s->imdct_512, s->tmp_output, s->transform_coeffs[ch]);
661 s->dsp.vector_fmul_window(s->output[ch-1], s->delay[ch-1], s->tmp_output, s->window, add_bias, 128);
662 memcpy(s->delay[ch-1], s->tmp_output+128, 128*sizeof(float));
668 * Downmix the output to mono or stereo.
670 void ff_ac3_downmix_c(float (*samples)[256], float (*matrix)[2], int out_ch, int in_ch, int len)
675 for(i=0; i<len; i++) {
677 for(j=0; j<in_ch; j++) {
678 v0 += samples[j][i] * matrix[j][0];
679 v1 += samples[j][i] * matrix[j][1];
684 } else if(out_ch == 1) {
685 for(i=0; i<len; i++) {
687 for(j=0; j<in_ch; j++)
688 v0 += samples[j][i] * matrix[j][0];
695 * Upmix delay samples from stereo to original channel layout.
697 static void ac3_upmix_delay(AC3DecodeContext *s)
699 int channel_data_size = sizeof(s->delay[0]);
700 switch(s->channel_mode) {
701 case AC3_CHMODE_DUALMONO:
702 case AC3_CHMODE_STEREO:
703 /* upmix mono to stereo */
704 memcpy(s->delay[1], s->delay[0], channel_data_size);
706 case AC3_CHMODE_2F2R:
707 memset(s->delay[3], 0, channel_data_size);
708 case AC3_CHMODE_2F1R:
709 memset(s->delay[2], 0, channel_data_size);
711 case AC3_CHMODE_3F2R:
712 memset(s->delay[4], 0, channel_data_size);
713 case AC3_CHMODE_3F1R:
714 memset(s->delay[3], 0, channel_data_size);
716 memcpy(s->delay[2], s->delay[1], channel_data_size);
717 memset(s->delay[1], 0, channel_data_size);
723 * Decode band structure for coupling, spectral extension, or enhanced coupling.
724 * @param[in] gbc bit reader context
725 * @param[in] blk block number
726 * @param[in] eac3 flag to indicate E-AC-3
727 * @param[in] ecpl flag to indicate enhanced coupling
728 * @param[in] start_subband subband number for start of range
729 * @param[in] end_subband subband number for end of range
730 * @param[in] default_band_struct default band structure table
731 * @param[out] band_struct decoded band structure
732 * @param[out] num_bands number of bands (optionally NULL)
733 * @param[out] band_sizes array containing the number of bins in each band (optionally NULL)
735 static void decode_band_structure(GetBitContext *gbc, int blk, int eac3,
736 int ecpl, int start_subband, int end_subband,
737 const uint8_t *default_band_struct,
738 uint8_t *band_struct,
739 int *num_bands, uint8_t *band_sizes)
741 int subbnd, bnd, n_subbands, n_bands=0;
744 n_subbands = end_subband - start_subband;
746 /* decode band structure from bitstream or use default */
747 if (!eac3 || get_bits1(gbc)) {
748 for (subbnd = 0; subbnd < n_subbands - 1; subbnd++) {
749 band_struct[subbnd] = get_bits1(gbc);
753 &default_band_struct[start_subband+1],
756 band_struct[n_subbands-1] = 0;
758 /* calculate number of bands and band sizes based on band structure.
759 note that the first 4 subbands in enhanced coupling span only 6 bins
761 if (num_bands || band_sizes ) {
762 n_bands = n_subbands;
763 bnd_sz[0] = ecpl ? 6 : 12;
764 for (bnd = 0, subbnd = 1; subbnd < n_subbands; subbnd++) {
765 int subbnd_size = (ecpl && subbnd < 4) ? 6 : 12;
766 if (band_struct[subbnd-1]) {
768 bnd_sz[bnd] += subbnd_size;
770 bnd_sz[++bnd] = subbnd_size;
775 /* set optional output params */
777 *num_bands = n_bands;
779 memcpy(band_sizes, bnd_sz, n_bands);
783 * Decode a single audio block from the AC-3 bitstream.
785 static int decode_audio_block(AC3DecodeContext *s, int blk)
787 int fbw_channels = s->fbw_channels;
788 int channel_mode = s->channel_mode;
790 int different_transforms;
793 GetBitContext *gbc = &s->gbc;
794 uint8_t bit_alloc_stages[AC3_MAX_CHANNELS];
796 memset(bit_alloc_stages, 0, AC3_MAX_CHANNELS);
798 /* block switch flags */
799 different_transforms = 0;
800 if (s->block_switch_syntax) {
801 for (ch = 1; ch <= fbw_channels; ch++) {
802 s->block_switch[ch] = get_bits1(gbc);
803 if(ch > 1 && s->block_switch[ch] != s->block_switch[1])
804 different_transforms = 1;
808 /* dithering flags */
809 if (s->dither_flag_syntax) {
810 for (ch = 1; ch <= fbw_channels; ch++) {
811 s->dither_flag[ch] = get_bits1(gbc);
816 i = !(s->channel_mode);
819 s->dynamic_range[i] = ((dynamic_range_tab[get_bits(gbc, 8)]-1.0) *
820 s->avctx->drc_scale)+1.0;
821 } else if(blk == 0) {
822 s->dynamic_range[i] = 1.0f;
826 /* spectral extension strategy */
827 if (s->eac3 && (!blk || get_bits1(gbc))) {
828 if (get_bits1(gbc)) {
829 ff_log_missing_feature(s->avctx, "Spectral extension", 1);
832 /* TODO: parse spectral extension strategy info */
835 /* TODO: spectral extension coordinates */
837 /* coupling strategy */
838 if (s->eac3 ? s->cpl_strategy_exists[blk] : get_bits1(gbc)) {
839 memset(bit_alloc_stages, 3, AC3_MAX_CHANNELS);
841 s->cpl_in_use[blk] = get_bits1(gbc);
842 if (s->cpl_in_use[blk]) {
843 /* coupling in use */
844 int cpl_start_subband, cpl_end_subband;
846 if (channel_mode < AC3_CHMODE_STEREO) {
847 av_log(s->avctx, AV_LOG_ERROR, "coupling not allowed in mono or dual-mono\n");
851 /* check for enhanced coupling */
852 if (s->eac3 && get_bits1(gbc)) {
853 /* TODO: parse enhanced coupling strategy info */
854 ff_log_missing_feature(s->avctx, "Enhanced coupling", 1);
858 /* determine which channels are coupled */
859 if (s->eac3 && s->channel_mode == AC3_CHMODE_STEREO) {
860 s->channel_in_cpl[1] = 1;
861 s->channel_in_cpl[2] = 1;
863 for (ch = 1; ch <= fbw_channels; ch++)
864 s->channel_in_cpl[ch] = get_bits1(gbc);
867 /* phase flags in use */
868 if (channel_mode == AC3_CHMODE_STEREO)
869 s->phase_flags_in_use = get_bits1(gbc);
871 /* coupling frequency range */
872 /* TODO: modify coupling end freq if spectral extension is used */
873 cpl_start_subband = get_bits(gbc, 4);
874 cpl_end_subband = get_bits(gbc, 4) + 3;
875 if (cpl_start_subband > cpl_end_subband) {
876 av_log(s->avctx, AV_LOG_ERROR, "invalid coupling range (%d > %d)\n",
877 cpl_start_subband, cpl_end_subband);
880 s->start_freq[CPL_CH] = cpl_start_subband * 12 + 37;
881 s->end_freq[CPL_CH] = cpl_end_subband * 12 + 37;
883 decode_band_structure(gbc, blk, s->eac3, 0,
884 cpl_start_subband, cpl_end_subband,
885 ff_eac3_default_cpl_band_struct,
887 &s->num_cpl_bands, NULL);
889 /* coupling not in use */
890 for (ch = 1; ch <= fbw_channels; ch++) {
891 s->channel_in_cpl[ch] = 0;
892 s->first_cpl_coords[ch] = 1;
894 s->first_cpl_leak = s->eac3;
895 s->phase_flags_in_use = 0;
897 } else if (!s->eac3) {
899 av_log(s->avctx, AV_LOG_ERROR, "new coupling strategy must be present in block 0\n");
902 s->cpl_in_use[blk] = s->cpl_in_use[blk-1];
905 cpl_in_use = s->cpl_in_use[blk];
907 /* coupling coordinates */
909 int cpl_coords_exist = 0;
911 for (ch = 1; ch <= fbw_channels; ch++) {
912 if (s->channel_in_cpl[ch]) {
913 if ((s->eac3 && s->first_cpl_coords[ch]) || get_bits1(gbc)) {
914 int master_cpl_coord, cpl_coord_exp, cpl_coord_mant;
915 s->first_cpl_coords[ch] = 0;
916 cpl_coords_exist = 1;
917 master_cpl_coord = 3 * get_bits(gbc, 2);
918 for (bnd = 0; bnd < s->num_cpl_bands; bnd++) {
919 cpl_coord_exp = get_bits(gbc, 4);
920 cpl_coord_mant = get_bits(gbc, 4);
921 if (cpl_coord_exp == 15)
922 s->cpl_coords[ch][bnd] = cpl_coord_mant << 22;
924 s->cpl_coords[ch][bnd] = (cpl_coord_mant + 16) << 21;
925 s->cpl_coords[ch][bnd] >>= (cpl_coord_exp + master_cpl_coord);
928 av_log(s->avctx, AV_LOG_ERROR, "new coupling coordinates must be present in block 0\n");
932 /* channel not in coupling */
933 s->first_cpl_coords[ch] = 1;
937 if (channel_mode == AC3_CHMODE_STEREO && cpl_coords_exist) {
938 for (bnd = 0; bnd < s->num_cpl_bands; bnd++) {
939 s->phase_flags[bnd] = s->phase_flags_in_use? get_bits1(gbc) : 0;
944 /* stereo rematrixing strategy and band structure */
945 if (channel_mode == AC3_CHMODE_STEREO) {
946 if ((s->eac3 && !blk) || get_bits1(gbc)) {
947 s->num_rematrixing_bands = 4;
948 if(cpl_in_use && s->start_freq[CPL_CH] <= 61)
949 s->num_rematrixing_bands -= 1 + (s->start_freq[CPL_CH] == 37);
950 for(bnd=0; bnd<s->num_rematrixing_bands; bnd++)
951 s->rematrixing_flags[bnd] = get_bits1(gbc);
953 av_log(s->avctx, AV_LOG_ERROR, "new rematrixing strategy must be present in block 0\n");
958 /* exponent strategies for each channel */
959 for (ch = !cpl_in_use; ch <= s->channels; ch++) {
961 s->exp_strategy[blk][ch] = get_bits(gbc, 2 - (ch == s->lfe_ch));
962 if(s->exp_strategy[blk][ch] != EXP_REUSE)
963 bit_alloc_stages[ch] = 3;
966 /* channel bandwidth */
967 for (ch = 1; ch <= fbw_channels; ch++) {
968 s->start_freq[ch] = 0;
969 if (s->exp_strategy[blk][ch] != EXP_REUSE) {
971 int prev = s->end_freq[ch];
972 if (s->channel_in_cpl[ch])
973 s->end_freq[ch] = s->start_freq[CPL_CH];
975 int bandwidth_code = get_bits(gbc, 6);
976 if (bandwidth_code > 60) {
977 av_log(s->avctx, AV_LOG_ERROR, "bandwidth code = %d > 60\n", bandwidth_code);
980 s->end_freq[ch] = bandwidth_code * 3 + 73;
982 group_size = 3 << (s->exp_strategy[blk][ch] - 1);
983 s->num_exp_groups[ch] = (s->end_freq[ch]+group_size-4) / group_size;
984 if(blk > 0 && s->end_freq[ch] != prev)
985 memset(bit_alloc_stages, 3, AC3_MAX_CHANNELS);
988 if (cpl_in_use && s->exp_strategy[blk][CPL_CH] != EXP_REUSE) {
989 s->num_exp_groups[CPL_CH] = (s->end_freq[CPL_CH] - s->start_freq[CPL_CH]) /
990 (3 << (s->exp_strategy[blk][CPL_CH] - 1));
993 /* decode exponents for each channel */
994 for (ch = !cpl_in_use; ch <= s->channels; ch++) {
995 if (s->exp_strategy[blk][ch] != EXP_REUSE) {
996 s->dexps[ch][0] = get_bits(gbc, 4) << !ch;
997 if (decode_exponents(gbc, s->exp_strategy[blk][ch],
998 s->num_exp_groups[ch], s->dexps[ch][0],
999 &s->dexps[ch][s->start_freq[ch]+!!ch])) {
1000 av_log(s->avctx, AV_LOG_ERROR, "exponent out-of-range\n");
1003 if(ch != CPL_CH && ch != s->lfe_ch)
1004 skip_bits(gbc, 2); /* skip gainrng */
1008 /* bit allocation information */
1009 if (s->bit_allocation_syntax) {
1010 if (get_bits1(gbc)) {
1011 s->bit_alloc_params.slow_decay = ff_ac3_slow_decay_tab[get_bits(gbc, 2)] >> s->bit_alloc_params.sr_shift;
1012 s->bit_alloc_params.fast_decay = ff_ac3_fast_decay_tab[get_bits(gbc, 2)] >> s->bit_alloc_params.sr_shift;
1013 s->bit_alloc_params.slow_gain = ff_ac3_slow_gain_tab[get_bits(gbc, 2)];
1014 s->bit_alloc_params.db_per_bit = ff_ac3_db_per_bit_tab[get_bits(gbc, 2)];
1015 s->bit_alloc_params.floor = ff_ac3_floor_tab[get_bits(gbc, 3)];
1016 for(ch=!cpl_in_use; ch<=s->channels; ch++)
1017 bit_alloc_stages[ch] = FFMAX(bit_alloc_stages[ch], 2);
1019 av_log(s->avctx, AV_LOG_ERROR, "new bit allocation info must be present in block 0\n");
1024 /* signal-to-noise ratio offsets and fast gains (signal-to-mask ratios) */
1025 if(!s->eac3 || !blk){
1026 if(s->snr_offset_strategy && get_bits1(gbc)) {
1029 csnr = (get_bits(gbc, 6) - 15) << 4;
1030 for (i = ch = !cpl_in_use; ch <= s->channels; ch++) {
1032 if (ch == i || s->snr_offset_strategy == 2)
1033 snr = (csnr + get_bits(gbc, 4)) << 2;
1034 /* run at least last bit allocation stage if snr offset changes */
1035 if(blk && s->snr_offset[ch] != snr) {
1036 bit_alloc_stages[ch] = FFMAX(bit_alloc_stages[ch], 1);
1038 s->snr_offset[ch] = snr;
1040 /* fast gain (normal AC-3 only) */
1042 int prev = s->fast_gain[ch];
1043 s->fast_gain[ch] = ff_ac3_fast_gain_tab[get_bits(gbc, 3)];
1044 /* run last 2 bit allocation stages if fast gain changes */
1045 if(blk && prev != s->fast_gain[ch])
1046 bit_alloc_stages[ch] = FFMAX(bit_alloc_stages[ch], 2);
1049 } else if (!s->eac3 && !blk) {
1050 av_log(s->avctx, AV_LOG_ERROR, "new snr offsets must be present in block 0\n");
1055 /* fast gain (E-AC-3 only) */
1056 if (s->fast_gain_syntax && get_bits1(gbc)) {
1057 for (ch = !cpl_in_use; ch <= s->channels; ch++) {
1058 int prev = s->fast_gain[ch];
1059 s->fast_gain[ch] = ff_ac3_fast_gain_tab[get_bits(gbc, 3)];
1060 /* run last 2 bit allocation stages if fast gain changes */
1061 if(blk && prev != s->fast_gain[ch])
1062 bit_alloc_stages[ch] = FFMAX(bit_alloc_stages[ch], 2);
1064 } else if (s->eac3 && !blk) {
1065 for (ch = !cpl_in_use; ch <= s->channels; ch++)
1066 s->fast_gain[ch] = ff_ac3_fast_gain_tab[4];
1069 /* E-AC-3 to AC-3 converter SNR offset */
1070 if (s->frame_type == EAC3_FRAME_TYPE_INDEPENDENT && get_bits1(gbc)) {
1071 skip_bits(gbc, 10); // skip converter snr offset
1074 /* coupling leak information */
1076 if (s->first_cpl_leak || get_bits1(gbc)) {
1077 int fl = get_bits(gbc, 3);
1078 int sl = get_bits(gbc, 3);
1079 /* run last 2 bit allocation stages for coupling channel if
1080 coupling leak changes */
1081 if(blk && (fl != s->bit_alloc_params.cpl_fast_leak ||
1082 sl != s->bit_alloc_params.cpl_slow_leak)) {
1083 bit_alloc_stages[CPL_CH] = FFMAX(bit_alloc_stages[CPL_CH], 2);
1085 s->bit_alloc_params.cpl_fast_leak = fl;
1086 s->bit_alloc_params.cpl_slow_leak = sl;
1087 } else if (!s->eac3 && !blk) {
1088 av_log(s->avctx, AV_LOG_ERROR, "new coupling leak info must be present in block 0\n");
1091 s->first_cpl_leak = 0;
1094 /* delta bit allocation information */
1095 if (s->dba_syntax && get_bits1(gbc)) {
1096 /* delta bit allocation exists (strategy) */
1097 for (ch = !cpl_in_use; ch <= fbw_channels; ch++) {
1098 s->dba_mode[ch] = get_bits(gbc, 2);
1099 if (s->dba_mode[ch] == DBA_RESERVED) {
1100 av_log(s->avctx, AV_LOG_ERROR, "delta bit allocation strategy reserved\n");
1103 bit_alloc_stages[ch] = FFMAX(bit_alloc_stages[ch], 2);
1105 /* channel delta offset, len and bit allocation */
1106 for (ch = !cpl_in_use; ch <= fbw_channels; ch++) {
1107 if (s->dba_mode[ch] == DBA_NEW) {
1108 s->dba_nsegs[ch] = get_bits(gbc, 3);
1109 for (seg = 0; seg <= s->dba_nsegs[ch]; seg++) {
1110 s->dba_offsets[ch][seg] = get_bits(gbc, 5);
1111 s->dba_lengths[ch][seg] = get_bits(gbc, 4);
1112 s->dba_values[ch][seg] = get_bits(gbc, 3);
1114 /* run last 2 bit allocation stages if new dba values */
1115 bit_alloc_stages[ch] = FFMAX(bit_alloc_stages[ch], 2);
1118 } else if(blk == 0) {
1119 for(ch=0; ch<=s->channels; ch++) {
1120 s->dba_mode[ch] = DBA_NONE;
1124 /* Bit allocation */
1125 for(ch=!cpl_in_use; ch<=s->channels; ch++) {
1126 if(bit_alloc_stages[ch] > 2) {
1127 /* Exponent mapping into PSD and PSD integration */
1128 ff_ac3_bit_alloc_calc_psd(s->dexps[ch],
1129 s->start_freq[ch], s->end_freq[ch],
1130 s->psd[ch], s->band_psd[ch]);
1132 if(bit_alloc_stages[ch] > 1) {
1133 /* Compute excitation function, Compute masking curve, and
1134 Apply delta bit allocation */
1135 if (ff_ac3_bit_alloc_calc_mask(&s->bit_alloc_params, s->band_psd[ch],
1136 s->start_freq[ch], s->end_freq[ch],
1137 s->fast_gain[ch], (ch == s->lfe_ch),
1138 s->dba_mode[ch], s->dba_nsegs[ch],
1139 s->dba_offsets[ch], s->dba_lengths[ch],
1140 s->dba_values[ch], s->mask[ch])) {
1141 av_log(s->avctx, AV_LOG_ERROR, "error in bit allocation\n");
1145 if(bit_alloc_stages[ch] > 0) {
1146 /* Compute bit allocation */
1147 const uint8_t *bap_tab = s->channel_uses_aht[ch] ?
1148 ff_eac3_hebap_tab : ff_ac3_bap_tab;
1149 ff_ac3_bit_alloc_calc_bap(s->mask[ch], s->psd[ch],
1150 s->start_freq[ch], s->end_freq[ch],
1152 s->bit_alloc_params.floor,
1153 bap_tab, s->bap[ch]);
1157 /* unused dummy data */
1158 if (s->skip_syntax && get_bits1(gbc)) {
1159 int skipl = get_bits(gbc, 9);
1164 /* unpack the transform coefficients
1165 this also uncouples channels if coupling is in use. */
1166 decode_transform_coeffs(s, blk);
1168 /* TODO: generate enhanced coupling coordinates and uncouple */
1170 /* TODO: apply spectral extension */
1172 /* recover coefficients if rematrixing is in use */
1173 if(s->channel_mode == AC3_CHMODE_STEREO)
1176 /* apply scaling to coefficients (headroom, dynrng) */
1177 for(ch=1; ch<=s->channels; ch++) {
1178 float gain = s->mul_bias / 4194304.0f;
1179 if(s->channel_mode == AC3_CHMODE_DUALMONO) {
1180 gain *= s->dynamic_range[ch-1];
1182 gain *= s->dynamic_range[0];
1184 s->dsp.int32_to_float_fmul_scalar(s->transform_coeffs[ch], s->fixed_coeffs[ch], gain, 256);
1187 /* downmix and MDCT. order depends on whether block switching is used for
1188 any channel in this block. this is because coefficients for the long
1189 and short transforms cannot be mixed. */
1190 downmix_output = s->channels != s->out_channels &&
1191 !((s->output_mode & AC3_OUTPUT_LFEON) &&
1192 s->fbw_channels == s->out_channels);
1193 if(different_transforms) {
1194 /* the delay samples have already been downmixed, so we upmix the delay
1195 samples in order to reconstruct all channels before downmixing. */
1201 do_imdct(s, s->channels);
1203 if(downmix_output) {
1204 s->dsp.ac3_downmix(s->output, s->downmix_coeffs, s->out_channels, s->fbw_channels, 256);
1207 if(downmix_output) {
1208 s->dsp.ac3_downmix(s->transform_coeffs+1, s->downmix_coeffs, s->out_channels, s->fbw_channels, 256);
1211 if(downmix_output && !s->downmixed) {
1213 s->dsp.ac3_downmix(s->delay, s->downmix_coeffs, s->out_channels, s->fbw_channels, 128);
1216 do_imdct(s, s->out_channels);
1223 * Decode a single AC-3 frame.
1225 static int ac3_decode_frame(AVCodecContext * avctx, void *data, int *data_size,
1228 const uint8_t *buf = avpkt->data;
1229 int buf_size = avpkt->size;
1230 AC3DecodeContext *s = avctx->priv_data;
1231 int16_t *out_samples = (int16_t *)data;
1233 const uint8_t *channel_map;
1234 const float *output[AC3_MAX_CHANNELS];
1236 /* initialize the GetBitContext with the start of valid AC-3 Frame */
1237 if (s->input_buffer) {
1238 /* copy input buffer to decoder context to avoid reading past the end
1239 of the buffer, which can be caused by a damaged input stream. */
1240 memcpy(s->input_buffer, buf, FFMIN(buf_size, AC3_FRAME_BUFFER_SIZE));
1241 init_get_bits(&s->gbc, s->input_buffer, buf_size * 8);
1243 init_get_bits(&s->gbc, buf, buf_size * 8);
1246 /* parse the syncinfo */
1248 err = parse_frame_header(s);
1250 /* check that reported frame size fits in input buffer */
1251 if(s->frame_size > buf_size) {
1252 av_log(avctx, AV_LOG_ERROR, "incomplete frame\n");
1253 err = AAC_AC3_PARSE_ERROR_FRAME_SIZE;
1256 /* check for crc mismatch */
1257 if(err != AAC_AC3_PARSE_ERROR_FRAME_SIZE && avctx->error_recognition >= FF_ER_CAREFUL) {
1258 if(av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0, &buf[2], s->frame_size-2)) {
1259 av_log(avctx, AV_LOG_ERROR, "frame CRC mismatch\n");
1260 err = AAC_AC3_PARSE_ERROR_CRC;
1264 if(err && err != AAC_AC3_PARSE_ERROR_CRC) {
1266 case AAC_AC3_PARSE_ERROR_SYNC:
1267 av_log(avctx, AV_LOG_ERROR, "frame sync error\n");
1269 case AAC_AC3_PARSE_ERROR_BSID:
1270 av_log(avctx, AV_LOG_ERROR, "invalid bitstream id\n");
1272 case AAC_AC3_PARSE_ERROR_SAMPLE_RATE:
1273 av_log(avctx, AV_LOG_ERROR, "invalid sample rate\n");
1275 case AAC_AC3_PARSE_ERROR_FRAME_SIZE:
1276 av_log(avctx, AV_LOG_ERROR, "invalid frame size\n");
1278 case AAC_AC3_PARSE_ERROR_FRAME_TYPE:
1279 /* skip frame if CRC is ok. otherwise use error concealment. */
1280 /* TODO: add support for substreams and dependent frames */
1281 if(s->frame_type == EAC3_FRAME_TYPE_DEPENDENT || s->substreamid) {
1282 av_log(avctx, AV_LOG_ERROR, "unsupported frame type : skipping frame\n");
1283 return s->frame_size;
1285 av_log(avctx, AV_LOG_ERROR, "invalid frame type\n");
1289 av_log(avctx, AV_LOG_ERROR, "invalid header\n");
1294 /* if frame is ok, set audio parameters */
1296 avctx->sample_rate = s->sample_rate;
1297 avctx->bit_rate = s->bit_rate;
1299 /* channel config */
1300 s->out_channels = s->channels;
1301 s->output_mode = s->channel_mode;
1303 s->output_mode |= AC3_OUTPUT_LFEON;
1304 if (avctx->request_channels > 0 && avctx->request_channels <= 2 &&
1305 avctx->request_channels < s->channels) {
1306 s->out_channels = avctx->request_channels;
1307 s->output_mode = avctx->request_channels == 1 ? AC3_CHMODE_MONO : AC3_CHMODE_STEREO;
1308 s->channel_layout = ff_ac3_channel_layout_tab[s->output_mode];
1310 avctx->channels = s->out_channels;
1311 avctx->channel_layout = s->channel_layout;
1313 /* set downmixing coefficients if needed */
1314 if(s->channels != s->out_channels && !((s->output_mode & AC3_OUTPUT_LFEON) &&
1315 s->fbw_channels == s->out_channels)) {
1316 set_downmix_coeffs(s);
1318 } else if (!s->out_channels) {
1319 s->out_channels = avctx->channels;
1320 if(s->out_channels < s->channels)
1321 s->output_mode = s->out_channels == 1 ? AC3_CHMODE_MONO : AC3_CHMODE_STEREO;
1324 /* decode the audio blocks */
1325 channel_map = ff_ac3_dec_channel_map[s->output_mode & ~AC3_OUTPUT_LFEON][s->lfe_on];
1326 for (ch = 0; ch < s->out_channels; ch++)
1327 output[ch] = s->output[channel_map[ch]];
1328 for (blk = 0; blk < s->num_blocks; blk++) {
1329 if (!err && decode_audio_block(s, blk)) {
1330 av_log(avctx, AV_LOG_ERROR, "error decoding the audio block\n");
1333 s->dsp.float_to_int16_interleave(out_samples, output, 256, s->out_channels);
1334 out_samples += 256 * s->out_channels;
1336 *data_size = s->num_blocks * 256 * avctx->channels * sizeof (int16_t);
1337 return s->frame_size;
1341 * Uninitialize the AC-3 decoder.
1343 static av_cold int ac3_decode_end(AVCodecContext *avctx)
1345 AC3DecodeContext *s = avctx->priv_data;
1346 ff_mdct_end(&s->imdct_512);
1347 ff_mdct_end(&s->imdct_256);
1349 av_freep(&s->input_buffer);
1354 AVCodec ac3_decoder = {
1356 .type = CODEC_TYPE_AUDIO,
1358 .priv_data_size = sizeof (AC3DecodeContext),
1359 .init = ac3_decode_init,
1360 .close = ac3_decode_end,
1361 .decode = ac3_decode_frame,
1362 .long_name = NULL_IF_CONFIG_SMALL("ATSC A/52A (AC-3)"),
1365 AVCodec eac3_decoder = {
1367 .type = CODEC_TYPE_AUDIO,
1368 .id = CODEC_ID_EAC3,
1369 .priv_data_size = sizeof (AC3DecodeContext),
1370 .init = ac3_decode_init,
1371 .close = ac3_decode_end,
1372 .decode = ac3_decode_frame,
1373 .long_name = NULL_IF_CONFIG_SMALL("ATSC A/52B (AC-3, E-AC-3)"),