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->lfe_on = hdr.lfe_on;
289 s->bit_alloc_params.sr_shift = hdr.sr_shift;
290 s->sample_rate = hdr.sample_rate;
291 s->bit_rate = hdr.bit_rate;
292 s->channels = hdr.channels;
293 s->fbw_channels = s->channels - s->lfe_on;
294 s->lfe_ch = s->fbw_channels + 1;
295 s->frame_size = hdr.frame_size;
296 s->center_mix_level = hdr.center_mix_level;
297 s->surround_mix_level = hdr.surround_mix_level;
298 s->num_blocks = hdr.num_blocks;
299 s->frame_type = hdr.frame_type;
300 s->substreamid = hdr.substreamid;
303 s->start_freq[s->lfe_ch] = 0;
304 s->end_freq[s->lfe_ch] = 7;
305 s->num_exp_groups[s->lfe_ch] = 2;
306 s->channel_in_cpl[s->lfe_ch] = 0;
309 if (hdr.bitstream_id <= 10) {
311 s->snr_offset_strategy = 2;
312 s->block_switch_syntax = 1;
313 s->dither_flag_syntax = 1;
314 s->bit_allocation_syntax = 1;
315 s->fast_gain_syntax = 0;
316 s->first_cpl_leak = 0;
319 memset(s->channel_uses_aht, 0, sizeof(s->channel_uses_aht));
320 return ac3_parse_header(s);
323 return ff_eac3_parse_header(s);
328 * Set stereo downmixing coefficients based on frame header info.
329 * reference: Section 7.8.2 Downmixing Into Two Channels
331 static void set_downmix_coeffs(AC3DecodeContext *s)
334 float cmix = gain_levels[center_levels[s->center_mix_level]];
335 float smix = gain_levels[surround_levels[s->surround_mix_level]];
338 for(i=0; i<s->fbw_channels; i++) {
339 s->downmix_coeffs[i][0] = gain_levels[ac3_default_coeffs[s->channel_mode][i][0]];
340 s->downmix_coeffs[i][1] = gain_levels[ac3_default_coeffs[s->channel_mode][i][1]];
342 if(s->channel_mode > 1 && s->channel_mode & 1) {
343 s->downmix_coeffs[1][0] = s->downmix_coeffs[1][1] = cmix;
345 if(s->channel_mode == AC3_CHMODE_2F1R || s->channel_mode == AC3_CHMODE_3F1R) {
346 int nf = s->channel_mode - 2;
347 s->downmix_coeffs[nf][0] = s->downmix_coeffs[nf][1] = smix * LEVEL_MINUS_3DB;
349 if(s->channel_mode == AC3_CHMODE_2F2R || s->channel_mode == AC3_CHMODE_3F2R) {
350 int nf = s->channel_mode - 4;
351 s->downmix_coeffs[nf][0] = s->downmix_coeffs[nf+1][1] = smix;
356 for(i=0; i<s->fbw_channels; i++) {
357 norm0 += s->downmix_coeffs[i][0];
358 norm1 += s->downmix_coeffs[i][1];
360 norm0 = 1.0f / norm0;
361 norm1 = 1.0f / norm1;
362 for(i=0; i<s->fbw_channels; i++) {
363 s->downmix_coeffs[i][0] *= norm0;
364 s->downmix_coeffs[i][1] *= norm1;
367 if(s->output_mode == AC3_CHMODE_MONO) {
368 for(i=0; i<s->fbw_channels; i++)
369 s->downmix_coeffs[i][0] = (s->downmix_coeffs[i][0] + s->downmix_coeffs[i][1]) * LEVEL_MINUS_3DB;
374 * Decode the grouped exponents according to exponent strategy.
375 * reference: Section 7.1.3 Exponent Decoding
377 static int decode_exponents(GetBitContext *gbc, int exp_strategy, int ngrps,
378 uint8_t absexp, int8_t *dexps)
380 int i, j, grp, group_size;
385 group_size = exp_strategy + (exp_strategy == EXP_D45);
386 for(grp=0,i=0; grp<ngrps; grp++) {
387 expacc = get_bits(gbc, 7);
388 dexp[i++] = ungroup_3_in_7_bits_tab[expacc][0];
389 dexp[i++] = ungroup_3_in_7_bits_tab[expacc][1];
390 dexp[i++] = ungroup_3_in_7_bits_tab[expacc][2];
393 /* convert to absolute exps and expand groups */
395 for(i=0,j=0; i<ngrps*3; i++) {
396 prevexp += dexp[i] - 2;
399 switch (group_size) {
400 case 4: dexps[j++] = prevexp;
401 dexps[j++] = prevexp;
402 case 2: dexps[j++] = prevexp;
403 case 1: dexps[j++] = prevexp;
410 * Generate transform coefficients for each coupled channel in the coupling
411 * range using the coupling coefficients and coupling coordinates.
412 * reference: Section 7.4.3 Coupling Coordinate Format
414 static void calc_transform_coeffs_cpl(AC3DecodeContext *s)
416 int i, j, ch, bnd, subbnd;
419 i = s->start_freq[CPL_CH];
420 for(bnd=0; bnd<s->num_cpl_bands; bnd++) {
423 for(j=0; j<12; j++) {
424 for(ch=1; ch<=s->fbw_channels; ch++) {
425 if(s->channel_in_cpl[ch]) {
426 s->fixed_coeffs[ch][i] = ((int64_t)s->fixed_coeffs[CPL_CH][i] * (int64_t)s->cpl_coords[ch][bnd]) >> 23;
427 if (ch == 2 && s->phase_flags[bnd])
428 s->fixed_coeffs[ch][i] = -s->fixed_coeffs[ch][i];
433 } while(s->cpl_band_struct[subbnd]);
438 * Grouped mantissas for 3-level 5-level and 11-level quantization
450 * Decode the transform coefficients for a particular channel
451 * reference: Section 7.3 Quantization and Decoding of Mantissas
453 static void ac3_decode_transform_coeffs_ch(AC3DecodeContext *s, int ch_index, mant_groups *m)
455 GetBitContext *gbc = &s->gbc;
456 int i, gcode, tbap, start, end;
461 exps = s->dexps[ch_index];
462 bap = s->bap[ch_index];
463 coeffs = s->fixed_coeffs[ch_index];
464 start = s->start_freq[ch_index];
465 end = s->end_freq[ch_index];
467 for (i = start; i < end; i++) {
471 coeffs[i] = (av_lfg_get(&s->dith_state) & 0x7FFFFF) - 0x400000;
476 gcode = get_bits(gbc, 5);
477 m->b1_mant[0] = b1_mantissas[gcode][0];
478 m->b1_mant[1] = b1_mantissas[gcode][1];
479 m->b1_mant[2] = b1_mantissas[gcode][2];
482 coeffs[i] = m->b1_mant[m->b1ptr++];
487 gcode = get_bits(gbc, 7);
488 m->b2_mant[0] = b2_mantissas[gcode][0];
489 m->b2_mant[1] = b2_mantissas[gcode][1];
490 m->b2_mant[2] = b2_mantissas[gcode][2];
493 coeffs[i] = m->b2_mant[m->b2ptr++];
497 coeffs[i] = b3_mantissas[get_bits(gbc, 3)];
502 gcode = get_bits(gbc, 7);
503 m->b4_mant[0] = b4_mantissas[gcode][0];
504 m->b4_mant[1] = b4_mantissas[gcode][1];
507 coeffs[i] = m->b4_mant[m->b4ptr++];
511 coeffs[i] = b5_mantissas[get_bits(gbc, 4)];
515 /* asymmetric dequantization */
516 int qlevel = quantization_tab[tbap];
517 coeffs[i] = get_sbits(gbc, qlevel) << (24 - qlevel);
521 coeffs[i] >>= exps[i];
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] >> s->dexps[ch][bin];
576 * Decode the transform coefficients.
578 static void decode_transform_coeffs(AC3DecodeContext *s, int blk)
584 m.b1ptr = m.b2ptr = m.b4ptr = 3;
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_subbands number of subbands (optionally NULL)
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, int *num_subbands,
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_subbands = n_subbands;
779 *num_bands = n_bands;
781 memcpy(band_sizes, bnd_sz, n_bands);
785 * Decode a single audio block from the AC-3 bitstream.
787 static int decode_audio_block(AC3DecodeContext *s, int blk)
789 int fbw_channels = s->fbw_channels;
790 int channel_mode = s->channel_mode;
792 int different_transforms;
795 GetBitContext *gbc = &s->gbc;
796 uint8_t bit_alloc_stages[AC3_MAX_CHANNELS];
798 memset(bit_alloc_stages, 0, AC3_MAX_CHANNELS);
800 /* block switch flags */
801 different_transforms = 0;
802 if (s->block_switch_syntax) {
803 for (ch = 1; ch <= fbw_channels; ch++) {
804 s->block_switch[ch] = get_bits1(gbc);
805 if(ch > 1 && s->block_switch[ch] != s->block_switch[1])
806 different_transforms = 1;
810 /* dithering flags */
811 if (s->dither_flag_syntax) {
812 for (ch = 1; ch <= fbw_channels; ch++) {
813 s->dither_flag[ch] = get_bits1(gbc);
818 i = !(s->channel_mode);
821 s->dynamic_range[i] = ((dynamic_range_tab[get_bits(gbc, 8)]-1.0) *
822 s->avctx->drc_scale)+1.0;
823 } else if(blk == 0) {
824 s->dynamic_range[i] = 1.0f;
828 /* spectral extension strategy */
829 if (s->eac3 && (!blk || get_bits1(gbc))) {
830 if (get_bits1(gbc)) {
831 ff_log_missing_feature(s->avctx, "Spectral extension", 1);
834 /* TODO: parse spectral extension strategy info */
837 /* TODO: spectral extension coordinates */
839 /* coupling strategy */
840 if (s->eac3 ? s->cpl_strategy_exists[blk] : get_bits1(gbc)) {
841 memset(bit_alloc_stages, 3, AC3_MAX_CHANNELS);
843 s->cpl_in_use[blk] = get_bits1(gbc);
844 if (s->cpl_in_use[blk]) {
845 /* coupling in use */
846 int cpl_start_subband, cpl_end_subband;
848 if (channel_mode < AC3_CHMODE_STEREO) {
849 av_log(s->avctx, AV_LOG_ERROR, "coupling not allowed in mono or dual-mono\n");
853 /* check for enhanced coupling */
854 if (s->eac3 && get_bits1(gbc)) {
855 /* TODO: parse enhanced coupling strategy info */
856 ff_log_missing_feature(s->avctx, "Enhanced coupling", 1);
860 /* determine which channels are coupled */
861 if (s->eac3 && s->channel_mode == AC3_CHMODE_STEREO) {
862 s->channel_in_cpl[1] = 1;
863 s->channel_in_cpl[2] = 1;
865 for (ch = 1; ch <= fbw_channels; ch++)
866 s->channel_in_cpl[ch] = get_bits1(gbc);
869 /* phase flags in use */
870 if (channel_mode == AC3_CHMODE_STEREO)
871 s->phase_flags_in_use = get_bits1(gbc);
873 /* coupling frequency range */
874 /* TODO: modify coupling end freq if spectral extension is used */
875 cpl_start_subband = get_bits(gbc, 4);
876 cpl_end_subband = get_bits(gbc, 4) + 3;
877 s->num_cpl_subbands = cpl_end_subband - cpl_start_subband;
878 if (s->num_cpl_subbands < 0) {
879 av_log(s->avctx, AV_LOG_ERROR, "invalid coupling range (%d > %d)\n",
880 cpl_start_subband, cpl_end_subband);
883 s->start_freq[CPL_CH] = cpl_start_subband * 12 + 37;
884 s->end_freq[CPL_CH] = cpl_end_subband * 12 + 37;
886 decode_band_structure(gbc, blk, s->eac3, 0,
887 cpl_start_subband, cpl_end_subband,
888 ff_eac3_default_cpl_band_struct,
889 s->cpl_band_struct, &s->num_cpl_subbands,
890 &s->num_cpl_bands, NULL);
892 /* coupling not in use */
893 for (ch = 1; ch <= fbw_channels; ch++) {
894 s->channel_in_cpl[ch] = 0;
895 s->first_cpl_coords[ch] = 1;
897 s->first_cpl_leak = s->eac3;
898 s->phase_flags_in_use = 0;
900 } else if (!s->eac3) {
902 av_log(s->avctx, AV_LOG_ERROR, "new coupling strategy must be present in block 0\n");
905 s->cpl_in_use[blk] = s->cpl_in_use[blk-1];
908 cpl_in_use = s->cpl_in_use[blk];
910 /* coupling coordinates */
912 int cpl_coords_exist = 0;
914 for (ch = 1; ch <= fbw_channels; ch++) {
915 if (s->channel_in_cpl[ch]) {
916 if ((s->eac3 && s->first_cpl_coords[ch]) || get_bits1(gbc)) {
917 int master_cpl_coord, cpl_coord_exp, cpl_coord_mant;
918 s->first_cpl_coords[ch] = 0;
919 cpl_coords_exist = 1;
920 master_cpl_coord = 3 * get_bits(gbc, 2);
921 for (bnd = 0; bnd < s->num_cpl_bands; bnd++) {
922 cpl_coord_exp = get_bits(gbc, 4);
923 cpl_coord_mant = get_bits(gbc, 4);
924 if (cpl_coord_exp == 15)
925 s->cpl_coords[ch][bnd] = cpl_coord_mant << 22;
927 s->cpl_coords[ch][bnd] = (cpl_coord_mant + 16) << 21;
928 s->cpl_coords[ch][bnd] >>= (cpl_coord_exp + master_cpl_coord);
931 av_log(s->avctx, AV_LOG_ERROR, "new coupling coordinates must be present in block 0\n");
935 /* channel not in coupling */
936 s->first_cpl_coords[ch] = 1;
940 if (channel_mode == AC3_CHMODE_STEREO && cpl_coords_exist) {
941 for (bnd = 0; bnd < s->num_cpl_bands; bnd++) {
942 s->phase_flags[bnd] = s->phase_flags_in_use? get_bits1(gbc) : 0;
947 /* stereo rematrixing strategy and band structure */
948 if (channel_mode == AC3_CHMODE_STEREO) {
949 if ((s->eac3 && !blk) || get_bits1(gbc)) {
950 s->num_rematrixing_bands = 4;
951 if(cpl_in_use && s->start_freq[CPL_CH] <= 61)
952 s->num_rematrixing_bands -= 1 + (s->start_freq[CPL_CH] == 37);
953 for(bnd=0; bnd<s->num_rematrixing_bands; bnd++)
954 s->rematrixing_flags[bnd] = get_bits1(gbc);
956 av_log(s->avctx, AV_LOG_ERROR, "new rematrixing strategy must be present in block 0\n");
961 /* exponent strategies for each channel */
962 for (ch = !cpl_in_use; ch <= s->channels; ch++) {
964 s->exp_strategy[blk][ch] = get_bits(gbc, 2 - (ch == s->lfe_ch));
965 if(s->exp_strategy[blk][ch] != EXP_REUSE)
966 bit_alloc_stages[ch] = 3;
969 /* channel bandwidth */
970 for (ch = 1; ch <= fbw_channels; ch++) {
971 s->start_freq[ch] = 0;
972 if (s->exp_strategy[blk][ch] != EXP_REUSE) {
974 int prev = s->end_freq[ch];
975 if (s->channel_in_cpl[ch])
976 s->end_freq[ch] = s->start_freq[CPL_CH];
978 int bandwidth_code = get_bits(gbc, 6);
979 if (bandwidth_code > 60) {
980 av_log(s->avctx, AV_LOG_ERROR, "bandwidth code = %d > 60\n", bandwidth_code);
983 s->end_freq[ch] = bandwidth_code * 3 + 73;
985 group_size = 3 << (s->exp_strategy[blk][ch] - 1);
986 s->num_exp_groups[ch] = (s->end_freq[ch]+group_size-4) / group_size;
987 if(blk > 0 && s->end_freq[ch] != prev)
988 memset(bit_alloc_stages, 3, AC3_MAX_CHANNELS);
991 if (cpl_in_use && s->exp_strategy[blk][CPL_CH] != EXP_REUSE) {
992 s->num_exp_groups[CPL_CH] = (s->end_freq[CPL_CH] - s->start_freq[CPL_CH]) /
993 (3 << (s->exp_strategy[blk][CPL_CH] - 1));
996 /* decode exponents for each channel */
997 for (ch = !cpl_in_use; ch <= s->channels; ch++) {
998 if (s->exp_strategy[blk][ch] != EXP_REUSE) {
999 s->dexps[ch][0] = get_bits(gbc, 4) << !ch;
1000 if (decode_exponents(gbc, s->exp_strategy[blk][ch],
1001 s->num_exp_groups[ch], s->dexps[ch][0],
1002 &s->dexps[ch][s->start_freq[ch]+!!ch])) {
1003 av_log(s->avctx, AV_LOG_ERROR, "exponent out-of-range\n");
1006 if(ch != CPL_CH && ch != s->lfe_ch)
1007 skip_bits(gbc, 2); /* skip gainrng */
1011 /* bit allocation information */
1012 if (s->bit_allocation_syntax) {
1013 if (get_bits1(gbc)) {
1014 s->bit_alloc_params.slow_decay = ff_ac3_slow_decay_tab[get_bits(gbc, 2)] >> s->bit_alloc_params.sr_shift;
1015 s->bit_alloc_params.fast_decay = ff_ac3_fast_decay_tab[get_bits(gbc, 2)] >> s->bit_alloc_params.sr_shift;
1016 s->bit_alloc_params.slow_gain = ff_ac3_slow_gain_tab[get_bits(gbc, 2)];
1017 s->bit_alloc_params.db_per_bit = ff_ac3_db_per_bit_tab[get_bits(gbc, 2)];
1018 s->bit_alloc_params.floor = ff_ac3_floor_tab[get_bits(gbc, 3)];
1019 for(ch=!cpl_in_use; ch<=s->channels; ch++)
1020 bit_alloc_stages[ch] = FFMAX(bit_alloc_stages[ch], 2);
1022 av_log(s->avctx, AV_LOG_ERROR, "new bit allocation info must be present in block 0\n");
1027 /* signal-to-noise ratio offsets and fast gains (signal-to-mask ratios) */
1028 if(!s->eac3 || !blk){
1029 if(s->snr_offset_strategy && get_bits1(gbc)) {
1032 csnr = (get_bits(gbc, 6) - 15) << 4;
1033 for (i = ch = !cpl_in_use; ch <= s->channels; ch++) {
1035 if (ch == i || s->snr_offset_strategy == 2)
1036 snr = (csnr + get_bits(gbc, 4)) << 2;
1037 /* run at least last bit allocation stage if snr offset changes */
1038 if(blk && s->snr_offset[ch] != snr) {
1039 bit_alloc_stages[ch] = FFMAX(bit_alloc_stages[ch], 1);
1041 s->snr_offset[ch] = snr;
1043 /* fast gain (normal AC-3 only) */
1045 int prev = s->fast_gain[ch];
1046 s->fast_gain[ch] = ff_ac3_fast_gain_tab[get_bits(gbc, 3)];
1047 /* run last 2 bit allocation stages if fast gain changes */
1048 if(blk && prev != s->fast_gain[ch])
1049 bit_alloc_stages[ch] = FFMAX(bit_alloc_stages[ch], 2);
1052 } else if (!s->eac3 && !blk) {
1053 av_log(s->avctx, AV_LOG_ERROR, "new snr offsets must be present in block 0\n");
1058 /* fast gain (E-AC-3 only) */
1059 if (s->fast_gain_syntax && get_bits1(gbc)) {
1060 for (ch = !cpl_in_use; ch <= s->channels; ch++) {
1061 int prev = s->fast_gain[ch];
1062 s->fast_gain[ch] = ff_ac3_fast_gain_tab[get_bits(gbc, 3)];
1063 /* run last 2 bit allocation stages if fast gain changes */
1064 if(blk && prev != s->fast_gain[ch])
1065 bit_alloc_stages[ch] = FFMAX(bit_alloc_stages[ch], 2);
1067 } else if (s->eac3 && !blk) {
1068 for (ch = !cpl_in_use; ch <= s->channels; ch++)
1069 s->fast_gain[ch] = ff_ac3_fast_gain_tab[4];
1072 /* E-AC-3 to AC-3 converter SNR offset */
1073 if (s->frame_type == EAC3_FRAME_TYPE_INDEPENDENT && get_bits1(gbc)) {
1074 skip_bits(gbc, 10); // skip converter snr offset
1077 /* coupling leak information */
1079 if (s->first_cpl_leak || get_bits1(gbc)) {
1080 int fl = get_bits(gbc, 3);
1081 int sl = get_bits(gbc, 3);
1082 /* run last 2 bit allocation stages for coupling channel if
1083 coupling leak changes */
1084 if(blk && (fl != s->bit_alloc_params.cpl_fast_leak ||
1085 sl != s->bit_alloc_params.cpl_slow_leak)) {
1086 bit_alloc_stages[CPL_CH] = FFMAX(bit_alloc_stages[CPL_CH], 2);
1088 s->bit_alloc_params.cpl_fast_leak = fl;
1089 s->bit_alloc_params.cpl_slow_leak = sl;
1090 } else if (!s->eac3 && !blk) {
1091 av_log(s->avctx, AV_LOG_ERROR, "new coupling leak info must be present in block 0\n");
1094 s->first_cpl_leak = 0;
1097 /* delta bit allocation information */
1098 if (s->dba_syntax && get_bits1(gbc)) {
1099 /* delta bit allocation exists (strategy) */
1100 for (ch = !cpl_in_use; ch <= fbw_channels; ch++) {
1101 s->dba_mode[ch] = get_bits(gbc, 2);
1102 if (s->dba_mode[ch] == DBA_RESERVED) {
1103 av_log(s->avctx, AV_LOG_ERROR, "delta bit allocation strategy reserved\n");
1106 bit_alloc_stages[ch] = FFMAX(bit_alloc_stages[ch], 2);
1108 /* channel delta offset, len and bit allocation */
1109 for (ch = !cpl_in_use; ch <= fbw_channels; ch++) {
1110 if (s->dba_mode[ch] == DBA_NEW) {
1111 s->dba_nsegs[ch] = get_bits(gbc, 3);
1112 for (seg = 0; seg <= s->dba_nsegs[ch]; seg++) {
1113 s->dba_offsets[ch][seg] = get_bits(gbc, 5);
1114 s->dba_lengths[ch][seg] = get_bits(gbc, 4);
1115 s->dba_values[ch][seg] = get_bits(gbc, 3);
1117 /* run last 2 bit allocation stages if new dba values */
1118 bit_alloc_stages[ch] = FFMAX(bit_alloc_stages[ch], 2);
1121 } else if(blk == 0) {
1122 for(ch=0; ch<=s->channels; ch++) {
1123 s->dba_mode[ch] = DBA_NONE;
1127 /* Bit allocation */
1128 for(ch=!cpl_in_use; ch<=s->channels; ch++) {
1129 if(bit_alloc_stages[ch] > 2) {
1130 /* Exponent mapping into PSD and PSD integration */
1131 ff_ac3_bit_alloc_calc_psd(s->dexps[ch],
1132 s->start_freq[ch], s->end_freq[ch],
1133 s->psd[ch], s->band_psd[ch]);
1135 if(bit_alloc_stages[ch] > 1) {
1136 /* Compute excitation function, Compute masking curve, and
1137 Apply delta bit allocation */
1138 if (ff_ac3_bit_alloc_calc_mask(&s->bit_alloc_params, s->band_psd[ch],
1139 s->start_freq[ch], s->end_freq[ch],
1140 s->fast_gain[ch], (ch == s->lfe_ch),
1141 s->dba_mode[ch], s->dba_nsegs[ch],
1142 s->dba_offsets[ch], s->dba_lengths[ch],
1143 s->dba_values[ch], s->mask[ch])) {
1144 av_log(s->avctx, AV_LOG_ERROR, "error in bit allocation\n");
1148 if(bit_alloc_stages[ch] > 0) {
1149 /* Compute bit allocation */
1150 const uint8_t *bap_tab = s->channel_uses_aht[ch] ?
1151 ff_eac3_hebap_tab : ff_ac3_bap_tab;
1152 ff_ac3_bit_alloc_calc_bap(s->mask[ch], s->psd[ch],
1153 s->start_freq[ch], s->end_freq[ch],
1155 s->bit_alloc_params.floor,
1156 bap_tab, s->bap[ch]);
1160 /* unused dummy data */
1161 if (s->skip_syntax && get_bits1(gbc)) {
1162 int skipl = get_bits(gbc, 9);
1167 /* unpack the transform coefficients
1168 this also uncouples channels if coupling is in use. */
1169 decode_transform_coeffs(s, blk);
1171 /* TODO: generate enhanced coupling coordinates and uncouple */
1173 /* TODO: apply spectral extension */
1175 /* recover coefficients if rematrixing is in use */
1176 if(s->channel_mode == AC3_CHMODE_STEREO)
1179 /* apply scaling to coefficients (headroom, dynrng) */
1180 for(ch=1; ch<=s->channels; ch++) {
1181 float gain = s->mul_bias / 4194304.0f;
1182 if(s->channel_mode == AC3_CHMODE_DUALMONO) {
1183 gain *= s->dynamic_range[ch-1];
1185 gain *= s->dynamic_range[0];
1187 s->dsp.int32_to_float_fmul_scalar(s->transform_coeffs[ch], s->fixed_coeffs[ch], gain, 256);
1190 /* downmix and MDCT. order depends on whether block switching is used for
1191 any channel in this block. this is because coefficients for the long
1192 and short transforms cannot be mixed. */
1193 downmix_output = s->channels != s->out_channels &&
1194 !((s->output_mode & AC3_OUTPUT_LFEON) &&
1195 s->fbw_channels == s->out_channels);
1196 if(different_transforms) {
1197 /* the delay samples have already been downmixed, so we upmix the delay
1198 samples in order to reconstruct all channels before downmixing. */
1204 do_imdct(s, s->channels);
1206 if(downmix_output) {
1207 s->dsp.ac3_downmix(s->output, s->downmix_coeffs, s->out_channels, s->fbw_channels, 256);
1210 if(downmix_output) {
1211 s->dsp.ac3_downmix(s->transform_coeffs+1, s->downmix_coeffs, s->out_channels, s->fbw_channels, 256);
1214 if(downmix_output && !s->downmixed) {
1216 s->dsp.ac3_downmix(s->delay, s->downmix_coeffs, s->out_channels, s->fbw_channels, 128);
1219 do_imdct(s, s->out_channels);
1226 * Decode a single AC-3 frame.
1228 static int ac3_decode_frame(AVCodecContext * avctx, void *data, int *data_size,
1229 const uint8_t *buf, int buf_size)
1231 AC3DecodeContext *s = avctx->priv_data;
1232 int16_t *out_samples = (int16_t *)data;
1235 /* initialize the GetBitContext with the start of valid AC-3 Frame */
1236 if (s->input_buffer) {
1237 /* copy input buffer to decoder context to avoid reading past the end
1238 of the buffer, which can be caused by a damaged input stream. */
1239 memcpy(s->input_buffer, buf, FFMIN(buf_size, AC3_FRAME_BUFFER_SIZE));
1240 init_get_bits(&s->gbc, s->input_buffer, buf_size * 8);
1242 init_get_bits(&s->gbc, buf, buf_size * 8);
1245 /* parse the syncinfo */
1247 err = parse_frame_header(s);
1249 /* check that reported frame size fits in input buffer */
1250 if(s->frame_size > buf_size) {
1251 av_log(avctx, AV_LOG_ERROR, "incomplete frame\n");
1252 err = AAC_AC3_PARSE_ERROR_FRAME_SIZE;
1255 /* check for crc mismatch */
1256 if(err != AAC_AC3_PARSE_ERROR_FRAME_SIZE && avctx->error_recognition >= FF_ER_CAREFUL) {
1257 if(av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0, &buf[2], s->frame_size-2)) {
1258 av_log(avctx, AV_LOG_ERROR, "frame CRC mismatch\n");
1259 err = AAC_AC3_PARSE_ERROR_CRC;
1263 if(err && err != AAC_AC3_PARSE_ERROR_CRC) {
1265 case AAC_AC3_PARSE_ERROR_SYNC:
1266 av_log(avctx, AV_LOG_ERROR, "frame sync error\n");
1268 case AAC_AC3_PARSE_ERROR_BSID:
1269 av_log(avctx, AV_LOG_ERROR, "invalid bitstream id\n");
1271 case AAC_AC3_PARSE_ERROR_SAMPLE_RATE:
1272 av_log(avctx, AV_LOG_ERROR, "invalid sample rate\n");
1274 case AAC_AC3_PARSE_ERROR_FRAME_SIZE:
1275 av_log(avctx, AV_LOG_ERROR, "invalid frame size\n");
1277 case AAC_AC3_PARSE_ERROR_FRAME_TYPE:
1278 /* skip frame if CRC is ok. otherwise use error concealment. */
1279 /* TODO: add support for substreams and dependent frames */
1280 if(s->frame_type == EAC3_FRAME_TYPE_DEPENDENT || s->substreamid) {
1281 av_log(avctx, AV_LOG_ERROR, "unsupported frame type : skipping frame\n");
1282 return s->frame_size;
1284 av_log(avctx, AV_LOG_ERROR, "invalid frame type\n");
1288 av_log(avctx, AV_LOG_ERROR, "invalid header\n");
1293 /* if frame is ok, set audio parameters */
1295 avctx->sample_rate = s->sample_rate;
1296 avctx->bit_rate = s->bit_rate;
1298 /* channel config */
1299 s->out_channels = s->channels;
1300 s->output_mode = s->channel_mode;
1302 s->output_mode |= AC3_OUTPUT_LFEON;
1303 if (avctx->request_channels > 0 && avctx->request_channels <= 2 &&
1304 avctx->request_channels < s->channels) {
1305 s->out_channels = avctx->request_channels;
1306 s->output_mode = avctx->request_channels == 1 ? AC3_CHMODE_MONO : AC3_CHMODE_STEREO;
1308 avctx->channels = s->out_channels;
1310 /* set downmixing coefficients if needed */
1311 if(s->channels != s->out_channels && !((s->output_mode & AC3_OUTPUT_LFEON) &&
1312 s->fbw_channels == s->out_channels)) {
1313 set_downmix_coeffs(s);
1315 } else if (!s->out_channels) {
1316 s->out_channels = avctx->channels;
1317 if(s->out_channels < s->channels)
1318 s->output_mode = s->out_channels == 1 ? AC3_CHMODE_MONO : AC3_CHMODE_STEREO;
1321 /* decode the audio blocks */
1322 for (blk = 0; blk < s->num_blocks; blk++) {
1323 const float *output[s->out_channels];
1324 if (!err && decode_audio_block(s, blk)) {
1325 av_log(avctx, AV_LOG_ERROR, "error decoding the audio block\n");
1328 for (ch = 0; ch < s->out_channels; ch++)
1329 output[ch] = s->output[ch];
1330 s->dsp.float_to_int16_interleave(out_samples, output, 256, s->out_channels);
1331 out_samples += 256 * s->out_channels;
1333 *data_size = s->num_blocks * 256 * avctx->channels * sizeof (int16_t);
1334 return s->frame_size;
1338 * Uninitialize the AC-3 decoder.
1340 static av_cold int ac3_decode_end(AVCodecContext *avctx)
1342 AC3DecodeContext *s = avctx->priv_data;
1343 ff_mdct_end(&s->imdct_512);
1344 ff_mdct_end(&s->imdct_256);
1346 av_freep(&s->input_buffer);
1351 AVCodec ac3_decoder = {
1353 .type = CODEC_TYPE_AUDIO,
1355 .priv_data_size = sizeof (AC3DecodeContext),
1356 .init = ac3_decode_init,
1357 .close = ac3_decode_end,
1358 .decode = ac3_decode_frame,
1359 .long_name = NULL_IF_CONFIG_SMALL("ATSC A/52A (AC-3)"),
1362 AVCodec eac3_decoder = {
1364 .type = CODEC_TYPE_AUDIO,
1365 .id = CODEC_ID_EAC3,
1366 .priv_data_size = sizeof (AC3DecodeContext),
1367 .init = ac3_decode_init,
1368 .close = ac3_decode_end,
1369 .decode = ac3_decode_frame,
1370 .long_name = NULL_IF_CONFIG_SMALL("ATSC A/52B (AC-3, E-AC-3)"),