3
* This code is developed as part of Google Summer of Code 2006 Program.
5
* Copyright (c) 2006 Kartikey Mahendra BHATT (bhattkm at gmail dot com).
6
* Copyright (c) 2007 Justin Ruggles
8
* Portions of this code are derived from liba52
9
* http://liba52.sourceforge.net
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* Copyright (C) 2000-2003 Michel Lespinasse <walken@zoy.org>
11
* Copyright (C) 1999-2000 Aaron Holtzman <aholtzma@ess.engr.uvic.ca>
13
* This file is part of FFmpeg.
15
* FFmpeg is free software; you can redistribute it and/or
16
* modify it under the terms of the GNU General Public
17
* License as published by the Free Software Foundation; either
18
* version 2 of the License, or (at your option) any later version.
20
* FFmpeg is distributed in the hope that it will be useful,
21
* but WITHOUT ANY WARRANTY; without even the implied warranty of
22
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
23
* General Public License for more details.
25
* You should have received a copy of the GNU General Public
26
* License along with FFmpeg; if not, write to the Free Software
27
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
36
#include "ac3_parser.h"
37
#include "bitstream.h"
42
/** Maximum possible frame size when the specification limit is ignored */
43
#define AC3_MAX_FRAME_SIZE 21695
46
* Table of bin locations for rematrixing bands
47
* reference: Section 7.5.2 Rematrixing : Frequency Band Definitions
49
static const uint8_t rematrix_band_tab[5] = { 13, 25, 37, 61, 253 };
51
/** table for grouping exponents */
52
static uint8_t exp_ungroup_tab[128][3];
55
/** tables for ungrouping mantissas */
56
static int b1_mantissas[32][3];
57
static int b2_mantissas[128][3];
58
static int b3_mantissas[8];
59
static int b4_mantissas[128][2];
60
static int b5_mantissas[16];
63
* Quantization table: levels for symmetric. bits for asymmetric.
64
* reference: Table 7.18 Mapping of bap to Quantizer
66
static const uint8_t quantization_tab[16] = {
68
5, 6, 7, 8, 9, 10, 11, 12, 14, 16
71
/** dynamic range table. converts codes to scale factors. */
72
static float dynamic_range_tab[256];
74
/** Adjustments in dB gain */
75
#define LEVEL_MINUS_3DB 0.7071067811865476
76
#define LEVEL_MINUS_4POINT5DB 0.5946035575013605
77
#define LEVEL_MINUS_6DB 0.5000000000000000
78
#define LEVEL_MINUS_9DB 0.3535533905932738
79
#define LEVEL_ZERO 0.0000000000000000
80
#define LEVEL_ONE 1.0000000000000000
82
static const float gain_levels[6] = {
86
LEVEL_MINUS_4POINT5DB,
92
* Table for default stereo downmixing coefficients
93
* reference: Section 7.8.2 Downmixing Into Two Channels
95
static const uint8_t ac3_default_coeffs[8][5][2] = {
96
{ { 1, 0 }, { 0, 1 }, },
98
{ { 1, 0 }, { 0, 1 }, },
99
{ { 1, 0 }, { 3, 3 }, { 0, 1 }, },
100
{ { 1, 0 }, { 0, 1 }, { 4, 4 }, },
101
{ { 1, 0 }, { 3, 3 }, { 0, 1 }, { 5, 5 }, },
102
{ { 1, 0 }, { 0, 1 }, { 4, 0 }, { 0, 4 }, },
103
{ { 1, 0 }, { 3, 3 }, { 0, 1 }, { 4, 0 }, { 0, 4 }, },
106
/* override ac3.h to include coupling channel */
107
#undef AC3_MAX_CHANNELS
108
#define AC3_MAX_CHANNELS 7
111
#define AC3_OUTPUT_LFEON 8
114
int channel_mode; ///< channel mode (acmod)
115
int block_switch[AC3_MAX_CHANNELS]; ///< block switch flags
116
int dither_flag[AC3_MAX_CHANNELS]; ///< dither flags
117
int dither_all; ///< true if all channels are dithered
118
int cpl_in_use; ///< coupling in use
119
int channel_in_cpl[AC3_MAX_CHANNELS]; ///< channel in coupling
120
int phase_flags_in_use; ///< phase flags in use
121
int phase_flags[18]; ///< phase flags
122
int cpl_band_struct[18]; ///< coupling band structure
123
int num_rematrixing_bands; ///< number of rematrixing bands
124
int rematrixing_flags[4]; ///< rematrixing flags
125
int exp_strategy[AC3_MAX_CHANNELS]; ///< exponent strategies
126
int snr_offset[AC3_MAX_CHANNELS]; ///< signal-to-noise ratio offsets
127
int fast_gain[AC3_MAX_CHANNELS]; ///< fast gain values (signal-to-mask ratio)
128
int dba_mode[AC3_MAX_CHANNELS]; ///< delta bit allocation mode
129
int dba_nsegs[AC3_MAX_CHANNELS]; ///< number of delta segments
130
uint8_t dba_offsets[AC3_MAX_CHANNELS][8]; ///< delta segment offsets
131
uint8_t dba_lengths[AC3_MAX_CHANNELS][8]; ///< delta segment lengths
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uint8_t dba_values[AC3_MAX_CHANNELS][8]; ///< delta values for each segment
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int sample_rate; ///< sample frequency, in Hz
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int bit_rate; ///< stream bit rate, in bits-per-second
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int frame_size; ///< current frame size, in bytes
138
int channels; ///< number of total channels
139
int fbw_channels; ///< number of full-bandwidth channels
140
int lfe_on; ///< lfe channel in use
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int lfe_ch; ///< index of LFE channel
142
int output_mode; ///< output channel configuration
143
int out_channels; ///< number of output channels
145
int center_mix_level; ///< Center mix level index
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int surround_mix_level; ///< Surround mix level index
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float downmix_coeffs[AC3_MAX_CHANNELS][2]; ///< stereo downmix coefficients
148
float downmix_coeff_adjust[2]; ///< adjustment needed for each output channel when downmixing
149
float dynamic_range[2]; ///< dynamic range
150
int cpl_coords[AC3_MAX_CHANNELS][18]; ///< coupling coordinates
151
int num_cpl_bands; ///< number of coupling bands
152
int num_cpl_subbands; ///< number of coupling sub bands
153
int start_freq[AC3_MAX_CHANNELS]; ///< start frequency bin
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int end_freq[AC3_MAX_CHANNELS]; ///< end frequency bin
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AC3BitAllocParameters bit_alloc_params; ///< bit allocation parameters
157
int8_t dexps[AC3_MAX_CHANNELS][256]; ///< decoded exponents
158
uint8_t bap[AC3_MAX_CHANNELS][256]; ///< bit allocation pointers
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int16_t psd[AC3_MAX_CHANNELS][256]; ///< scaled exponents
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int16_t band_psd[AC3_MAX_CHANNELS][50]; ///< interpolated exponents
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int16_t mask[AC3_MAX_CHANNELS][50]; ///< masking curve values
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int fixed_coeffs[AC3_MAX_CHANNELS][256]; ///> fixed-point transform coefficients
164
DECLARE_ALIGNED_16(float, transform_coeffs[AC3_MAX_CHANNELS][256]); ///< transform coefficients
165
int downmixed; ///< indicates if coeffs are currently downmixed
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MDCTContext imdct_512; ///< for 512 sample IMDCT
169
MDCTContext imdct_256; ///< for 256 sample IMDCT
170
DSPContext dsp; ///< for optimization
171
float add_bias; ///< offset for float_to_int16 conversion
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float mul_bias; ///< scaling for float_to_int16 conversion
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DECLARE_ALIGNED_16(float, output[AC3_MAX_CHANNELS][256]); ///< output after imdct transform and windowing
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DECLARE_ALIGNED_16(short, int_output[AC3_MAX_CHANNELS-1][256]); ///< final 16-bit integer output
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DECLARE_ALIGNED_16(float, delay[AC3_MAX_CHANNELS][256]); ///< delay - added to the next block
177
DECLARE_ALIGNED_16(float, tmp_imdct[256]); ///< temporary storage for imdct transform
178
DECLARE_ALIGNED_16(float, tmp_output[512]); ///< temporary storage for output before windowing
179
DECLARE_ALIGNED_16(float, window[256]); ///< window coefficients
182
GetBitContext gbc; ///< bitstream reader
183
AVRandomState dith_state; ///< for dither generation
184
AVCodecContext *avctx; ///< parent context
185
uint8_t *input_buffer; ///< temp buffer to prevent overread
189
* Symmetrical Dequantization
190
* reference: Section 7.3.3 Expansion of Mantissas for Symmetrical Quantization
191
* Tables 7.19 to 7.23
194
symmetric_dequant(int code, int levels)
196
return ((code - (levels >> 1)) << 24) / levels;
200
* Initialize tables at runtime.
202
static av_cold void ac3_tables_init(void)
206
/* generate grouped mantissa tables
207
reference: Section 7.3.5 Ungrouping of Mantissas */
208
for(i=0; i<32; i++) {
209
/* bap=1 mantissas */
210
b1_mantissas[i][0] = symmetric_dequant( i / 9 , 3);
211
b1_mantissas[i][1] = symmetric_dequant((i % 9) / 3, 3);
212
b1_mantissas[i][2] = symmetric_dequant((i % 9) % 3, 3);
214
for(i=0; i<128; i++) {
215
/* bap=2 mantissas */
216
b2_mantissas[i][0] = symmetric_dequant( i / 25 , 5);
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b2_mantissas[i][1] = symmetric_dequant((i % 25) / 5, 5);
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b2_mantissas[i][2] = symmetric_dequant((i % 25) % 5, 5);
220
/* bap=4 mantissas */
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b4_mantissas[i][0] = symmetric_dequant(i / 11, 11);
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b4_mantissas[i][1] = symmetric_dequant(i % 11, 11);
224
/* generate ungrouped mantissa tables
225
reference: Tables 7.21 and 7.23 */
227
/* bap=3 mantissas */
228
b3_mantissas[i] = symmetric_dequant(i, 7);
230
for(i=0; i<15; i++) {
231
/* bap=5 mantissas */
232
b5_mantissas[i] = symmetric_dequant(i, 15);
235
/* generate dynamic range table
236
reference: Section 7.7.1 Dynamic Range Control */
237
for(i=0; i<256; i++) {
238
int v = (i >> 5) - ((i >> 7) << 3) - 5;
239
dynamic_range_tab[i] = powf(2.0f, v) * ((i & 0x1F) | 0x20);
242
/* generate exponent tables
243
reference: Section 7.1.3 Exponent Decoding */
244
for(i=0; i<128; i++) {
245
exp_ungroup_tab[i][0] = i / 25;
246
exp_ungroup_tab[i][1] = (i % 25) / 5;
247
exp_ungroup_tab[i][2] = (i % 25) % 5;
253
* AVCodec initialization
255
static av_cold int ac3_decode_init(AVCodecContext *avctx)
257
AC3DecodeContext *s = avctx->priv_data;
262
ff_mdct_init(&s->imdct_256, 8, 1);
263
ff_mdct_init(&s->imdct_512, 9, 1);
264
ff_kbd_window_init(s->window, 5.0, 256);
265
dsputil_init(&s->dsp, avctx);
266
av_init_random(0, &s->dith_state);
268
/* set bias values for float to int16 conversion */
269
if(s->dsp.float_to_int16 == ff_float_to_int16_c) {
270
s->add_bias = 385.0f;
274
s->mul_bias = 32767.0f;
277
/* allow downmixing to stereo or mono */
278
if (avctx->channels > 0 && avctx->request_channels > 0 &&
279
avctx->request_channels < avctx->channels &&
280
avctx->request_channels <= 2) {
281
avctx->channels = avctx->request_channels;
285
/* allocate context input buffer */
286
if (avctx->error_resilience >= FF_ER_CAREFUL) {
287
s->input_buffer = av_mallocz(AC3_MAX_FRAME_SIZE + FF_INPUT_BUFFER_PADDING_SIZE);
288
if (!s->input_buffer)
289
return AVERROR_NOMEM;
296
* Parse the 'sync info' and 'bit stream info' from the AC-3 bitstream.
297
* GetBitContext within AC3DecodeContext must point to
298
* start of the synchronized ac3 bitstream.
300
static int ac3_parse_header(AC3DecodeContext *s)
303
GetBitContext *gbc = &s->gbc;
306
err = ff_ac3_parse_header(gbc, &hdr);
310
if(hdr.bitstream_id > 10)
311
return AC3_PARSE_ERROR_BSID;
313
/* get decoding parameters from header info */
314
s->bit_alloc_params.sr_code = hdr.sr_code;
315
s->channel_mode = hdr.channel_mode;
316
s->lfe_on = hdr.lfe_on;
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s->bit_alloc_params.sr_shift = hdr.sr_shift;
318
s->sample_rate = hdr.sample_rate;
319
s->bit_rate = hdr.bit_rate;
320
s->channels = hdr.channels;
321
s->fbw_channels = s->channels - s->lfe_on;
322
s->lfe_ch = s->fbw_channels + 1;
323
s->frame_size = hdr.frame_size;
324
s->center_mix_level = hdr.center_mix_level;
325
s->surround_mix_level = hdr.surround_mix_level;
327
/* set default output to all source channels */
328
s->out_channels = s->channels;
329
s->output_mode = s->channel_mode;
331
s->output_mode |= AC3_OUTPUT_LFEON;
333
/* read the rest of the bsi. read twice for dual mono mode. */
334
i = !(s->channel_mode);
336
skip_bits(gbc, 5); // skip dialog normalization
338
skip_bits(gbc, 8); //skip compression
340
skip_bits(gbc, 8); //skip language code
342
skip_bits(gbc, 7); //skip audio production information
345
skip_bits(gbc, 2); //skip copyright bit and original bitstream bit
347
/* skip the timecodes (or extra bitstream information for Alternate Syntax)
348
TODO: read & use the xbsi1 downmix levels */
350
skip_bits(gbc, 14); //skip timecode1 / xbsi1
352
skip_bits(gbc, 14); //skip timecode2 / xbsi2
354
/* skip additional bitstream info */
355
if (get_bits1(gbc)) {
356
i = get_bits(gbc, 6);
366
* Set stereo downmixing coefficients based on frame header info.
367
* reference: Section 7.8.2 Downmixing Into Two Channels
369
static void set_downmix_coeffs(AC3DecodeContext *s)
372
float cmix = gain_levels[s->center_mix_level];
373
float smix = gain_levels[s->surround_mix_level];
375
for(i=0; i<s->fbw_channels; i++) {
376
s->downmix_coeffs[i][0] = gain_levels[ac3_default_coeffs[s->channel_mode][i][0]];
377
s->downmix_coeffs[i][1] = gain_levels[ac3_default_coeffs[s->channel_mode][i][1]];
379
if(s->channel_mode > 1 && s->channel_mode & 1) {
380
s->downmix_coeffs[1][0] = s->downmix_coeffs[1][1] = cmix;
382
if(s->channel_mode == AC3_CHMODE_2F1R || s->channel_mode == AC3_CHMODE_3F1R) {
383
int nf = s->channel_mode - 2;
384
s->downmix_coeffs[nf][0] = s->downmix_coeffs[nf][1] = smix * LEVEL_MINUS_3DB;
386
if(s->channel_mode == AC3_CHMODE_2F2R || s->channel_mode == AC3_CHMODE_3F2R) {
387
int nf = s->channel_mode - 4;
388
s->downmix_coeffs[nf][0] = s->downmix_coeffs[nf+1][1] = smix;
391
/* calculate adjustment needed for each channel to avoid clipping */
392
s->downmix_coeff_adjust[0] = s->downmix_coeff_adjust[1] = 0.0f;
393
for(i=0; i<s->fbw_channels; i++) {
394
s->downmix_coeff_adjust[0] += s->downmix_coeffs[i][0];
395
s->downmix_coeff_adjust[1] += s->downmix_coeffs[i][1];
397
s->downmix_coeff_adjust[0] = 1.0f / s->downmix_coeff_adjust[0];
398
s->downmix_coeff_adjust[1] = 1.0f / s->downmix_coeff_adjust[1];
402
* Decode the grouped exponents according to exponent strategy.
403
* reference: Section 7.1.3 Exponent Decoding
405
static void decode_exponents(GetBitContext *gbc, int exp_strategy, int ngrps,
406
uint8_t absexp, int8_t *dexps)
408
int i, j, grp, group_size;
413
group_size = exp_strategy + (exp_strategy == EXP_D45);
414
for(grp=0,i=0; grp<ngrps; grp++) {
415
expacc = get_bits(gbc, 7);
416
dexp[i++] = exp_ungroup_tab[expacc][0];
417
dexp[i++] = exp_ungroup_tab[expacc][1];
418
dexp[i++] = exp_ungroup_tab[expacc][2];
421
/* convert to absolute exps and expand groups */
423
for(i=0; i<ngrps*3; i++) {
424
prevexp = av_clip(prevexp + dexp[i]-2, 0, 24);
425
for(j=0; j<group_size; j++) {
426
dexps[(i*group_size)+j] = prevexp;
432
* Generate transform coefficients for each coupled channel in the coupling
433
* range using the coupling coefficients and coupling coordinates.
434
* reference: Section 7.4.3 Coupling Coordinate Format
436
static void uncouple_channels(AC3DecodeContext *s)
438
int i, j, ch, bnd, subbnd;
441
i = s->start_freq[CPL_CH];
442
for(bnd=0; bnd<s->num_cpl_bands; bnd++) {
445
for(j=0; j<12; j++) {
446
for(ch=1; ch<=s->fbw_channels; ch++) {
447
if(s->channel_in_cpl[ch]) {
448
s->fixed_coeffs[ch][i] = ((int64_t)s->fixed_coeffs[CPL_CH][i] * (int64_t)s->cpl_coords[ch][bnd]) >> 23;
449
if (ch == 2 && s->phase_flags[bnd])
450
s->fixed_coeffs[ch][i] = -s->fixed_coeffs[ch][i];
455
} while(s->cpl_band_struct[subbnd]);
460
* Grouped mantissas for 3-level 5-level and 11-level quantization
472
* Get the transform coefficients for a particular channel
473
* reference: Section 7.3 Quantization and Decoding of Mantissas
475
static int get_transform_coeffs_ch(AC3DecodeContext *s, int ch_index, mant_groups *m)
477
GetBitContext *gbc = &s->gbc;
478
int i, gcode, tbap, start, end;
483
exps = s->dexps[ch_index];
484
bap = s->bap[ch_index];
485
coeffs = s->fixed_coeffs[ch_index];
486
start = s->start_freq[ch_index];
487
end = s->end_freq[ch_index];
489
for (i = start; i < end; i++) {
493
coeffs[i] = (av_random(&s->dith_state) & 0x7FFFFF) - 4194304;
498
gcode = get_bits(gbc, 5);
499
m->b1_mant[0] = b1_mantissas[gcode][0];
500
m->b1_mant[1] = b1_mantissas[gcode][1];
501
m->b1_mant[2] = b1_mantissas[gcode][2];
504
coeffs[i] = m->b1_mant[m->b1ptr++];
509
gcode = get_bits(gbc, 7);
510
m->b2_mant[0] = b2_mantissas[gcode][0];
511
m->b2_mant[1] = b2_mantissas[gcode][1];
512
m->b2_mant[2] = b2_mantissas[gcode][2];
515
coeffs[i] = m->b2_mant[m->b2ptr++];
519
coeffs[i] = b3_mantissas[get_bits(gbc, 3)];
524
gcode = get_bits(gbc, 7);
525
m->b4_mant[0] = b4_mantissas[gcode][0];
526
m->b4_mant[1] = b4_mantissas[gcode][1];
529
coeffs[i] = m->b4_mant[m->b4ptr++];
533
coeffs[i] = b5_mantissas[get_bits(gbc, 4)];
537
/* asymmetric dequantization */
538
int qlevel = quantization_tab[tbap];
539
coeffs[i] = get_sbits(gbc, qlevel) << (24 - qlevel);
543
coeffs[i] >>= exps[i];
550
* Remove random dithering from coefficients with zero-bit mantissas
551
* reference: Section 7.3.4 Dither for Zero Bit Mantissas (bap=0)
553
static void remove_dithering(AC3DecodeContext *s) {
559
for(ch=1; ch<=s->fbw_channels; ch++) {
560
if(!s->dither_flag[ch]) {
561
coeffs = s->fixed_coeffs[ch];
563
if(s->channel_in_cpl[ch])
564
end = s->start_freq[CPL_CH];
566
end = s->end_freq[ch];
567
for(i=0; i<end; i++) {
571
if(s->channel_in_cpl[ch]) {
572
bap = s->bap[CPL_CH];
573
for(; i<s->end_freq[CPL_CH]; i++) {
583
* Get the transform coefficients.
585
static int get_transform_coeffs(AC3DecodeContext *s)
591
m.b1ptr = m.b2ptr = m.b4ptr = 3;
593
for (ch = 1; ch <= s->channels; ch++) {
594
/* transform coefficients for full-bandwidth channel */
595
if (get_transform_coeffs_ch(s, ch, &m))
597
/* tranform coefficients for coupling channel come right after the
598
coefficients for the first coupled channel*/
599
if (s->channel_in_cpl[ch]) {
601
if (get_transform_coeffs_ch(s, CPL_CH, &m)) {
602
av_log(s->avctx, AV_LOG_ERROR, "error in decoupling channels\n");
605
uncouple_channels(s);
608
end = s->end_freq[CPL_CH];
610
end = s->end_freq[ch];
613
s->transform_coeffs[ch][end] = 0;
617
/* if any channel doesn't use dithering, zero appropriate coefficients */
625
* Stereo rematrixing.
626
* reference: Section 7.5.4 Rematrixing : Decoding Technique
628
static void do_rematrixing(AC3DecodeContext *s)
634
end = FFMIN(s->end_freq[1], s->end_freq[2]);
636
for(bnd=0; bnd<s->num_rematrixing_bands; bnd++) {
637
if(s->rematrixing_flags[bnd]) {
638
bndend = FFMIN(end, rematrix_band_tab[bnd+1]);
639
for(i=rematrix_band_tab[bnd]; i<bndend; i++) {
640
tmp0 = s->fixed_coeffs[1][i];
641
tmp1 = s->fixed_coeffs[2][i];
642
s->fixed_coeffs[1][i] = tmp0 + tmp1;
643
s->fixed_coeffs[2][i] = tmp0 - tmp1;
650
* Perform the 256-point IMDCT
652
static void do_imdct_256(AC3DecodeContext *s, int chindex)
655
DECLARE_ALIGNED_16(float, x[128]);
657
float *o_ptr = s->tmp_output;
660
/* de-interleave coefficients */
661
for(k=0; k<128; k++) {
662
x[k] = s->transform_coeffs[chindex][2*k+i];
665
/* run standard IMDCT */
666
s->imdct_256.fft.imdct_calc(&s->imdct_256, o_ptr, x, s->tmp_imdct);
668
/* reverse the post-rotation & reordering from standard IMDCT */
669
for(k=0; k<32; k++) {
670
z[i][32+k].re = -o_ptr[128+2*k];
671
z[i][32+k].im = -o_ptr[2*k];
672
z[i][31-k].re = o_ptr[2*k+1];
673
z[i][31-k].im = o_ptr[128+2*k+1];
677
/* apply AC-3 post-rotation & reordering */
678
for(k=0; k<64; k++) {
679
o_ptr[ 2*k ] = -z[0][ k].im;
680
o_ptr[ 2*k+1] = z[0][63-k].re;
681
o_ptr[128+2*k ] = -z[0][ k].re;
682
o_ptr[128+2*k+1] = z[0][63-k].im;
683
o_ptr[256+2*k ] = -z[1][ k].re;
684
o_ptr[256+2*k+1] = z[1][63-k].im;
685
o_ptr[384+2*k ] = z[1][ k].im;
686
o_ptr[384+2*k+1] = -z[1][63-k].re;
691
* Inverse MDCT Transform.
692
* Convert frequency domain coefficients to time-domain audio samples.
693
* reference: Section 7.9.4 Transformation Equations
695
static inline void do_imdct(AC3DecodeContext *s, int channels)
699
for (ch=1; ch<=channels; ch++) {
700
if (s->block_switch[ch]) {
703
s->imdct_512.fft.imdct_calc(&s->imdct_512, s->tmp_output,
704
s->transform_coeffs[ch], s->tmp_imdct);
706
/* For the first half of the block, apply the window, add the delay
707
from the previous block, and send to output */
708
s->dsp.vector_fmul_add_add(s->output[ch-1], s->tmp_output,
709
s->window, s->delay[ch-1], 0, 256, 1);
710
/* For the second half of the block, apply the window and store the
711
samples to delay, to be combined with the next block */
712
s->dsp.vector_fmul_reverse(s->delay[ch-1], s->tmp_output+256,
718
* Downmix the output to mono or stereo.
720
static void ac3_downmix(AC3DecodeContext *s,
721
float samples[AC3_MAX_CHANNELS][256], int ch_offset)
726
for(i=0; i<256; i++) {
728
for(j=0; j<s->fbw_channels; j++) {
729
v0 += samples[j+ch_offset][i] * s->downmix_coeffs[j][0];
730
v1 += samples[j+ch_offset][i] * s->downmix_coeffs[j][1];
732
v0 *= s->downmix_coeff_adjust[0];
733
v1 *= s->downmix_coeff_adjust[1];
734
if(s->output_mode == AC3_CHMODE_MONO) {
735
samples[ch_offset][i] = (v0 + v1) * LEVEL_MINUS_3DB;
736
} else if(s->output_mode == AC3_CHMODE_STEREO) {
737
samples[ ch_offset][i] = v0;
738
samples[1+ch_offset][i] = v1;
744
* Upmix delay samples from stereo to original channel layout.
746
static void ac3_upmix_delay(AC3DecodeContext *s)
748
int channel_data_size = sizeof(s->delay[0]);
749
switch(s->channel_mode) {
750
case AC3_CHMODE_DUALMONO:
751
case AC3_CHMODE_STEREO:
752
/* upmix mono to stereo */
753
memcpy(s->delay[1], s->delay[0], channel_data_size);
755
case AC3_CHMODE_2F2R:
756
memset(s->delay[3], 0, channel_data_size);
757
case AC3_CHMODE_2F1R:
758
memset(s->delay[2], 0, channel_data_size);
760
case AC3_CHMODE_3F2R:
761
memset(s->delay[4], 0, channel_data_size);
762
case AC3_CHMODE_3F1R:
763
memset(s->delay[3], 0, channel_data_size);
765
memcpy(s->delay[2], s->delay[1], channel_data_size);
766
memset(s->delay[1], 0, channel_data_size);
772
* Parse an audio block from AC-3 bitstream.
774
static int ac3_parse_audio_block(AC3DecodeContext *s, int blk)
776
int fbw_channels = s->fbw_channels;
777
int channel_mode = s->channel_mode;
779
int different_transforms;
781
GetBitContext *gbc = &s->gbc;
782
uint8_t bit_alloc_stages[AC3_MAX_CHANNELS];
784
memset(bit_alloc_stages, 0, AC3_MAX_CHANNELS);
786
/* block switch flags */
787
different_transforms = 0;
788
for (ch = 1; ch <= fbw_channels; ch++) {
789
s->block_switch[ch] = get_bits1(gbc);
790
if(ch > 1 && s->block_switch[ch] != s->block_switch[1])
791
different_transforms = 1;
794
/* dithering flags */
796
for (ch = 1; ch <= fbw_channels; ch++) {
797
s->dither_flag[ch] = get_bits1(gbc);
798
if(!s->dither_flag[ch])
803
i = !(s->channel_mode);
806
s->dynamic_range[i] = ((dynamic_range_tab[get_bits(gbc, 8)]-1.0) *
807
s->avctx->drc_scale)+1.0;
808
} else if(blk == 0) {
809
s->dynamic_range[i] = 1.0f;
813
/* coupling strategy */
814
if (get_bits1(gbc)) {
815
memset(bit_alloc_stages, 3, AC3_MAX_CHANNELS);
816
s->cpl_in_use = get_bits1(gbc);
818
/* coupling in use */
819
int cpl_begin_freq, cpl_end_freq;
821
/* determine which channels are coupled */
822
for (ch = 1; ch <= fbw_channels; ch++)
823
s->channel_in_cpl[ch] = get_bits1(gbc);
825
/* phase flags in use */
826
if (channel_mode == AC3_CHMODE_STEREO)
827
s->phase_flags_in_use = get_bits1(gbc);
829
/* coupling frequency range and band structure */
830
cpl_begin_freq = get_bits(gbc, 4);
831
cpl_end_freq = get_bits(gbc, 4);
832
if (3 + cpl_end_freq - cpl_begin_freq < 0) {
833
av_log(s->avctx, AV_LOG_ERROR, "3+cplendf = %d < cplbegf = %d\n", 3+cpl_end_freq, cpl_begin_freq);
836
s->num_cpl_bands = s->num_cpl_subbands = 3 + cpl_end_freq - cpl_begin_freq;
837
s->start_freq[CPL_CH] = cpl_begin_freq * 12 + 37;
838
s->end_freq[CPL_CH] = cpl_end_freq * 12 + 73;
839
for (bnd = 0; bnd < s->num_cpl_subbands - 1; bnd++) {
840
if (get_bits1(gbc)) {
841
s->cpl_band_struct[bnd] = 1;
845
s->cpl_band_struct[s->num_cpl_subbands-1] = 0;
847
/* coupling not in use */
848
for (ch = 1; ch <= fbw_channels; ch++)
849
s->channel_in_cpl[ch] = 0;
853
/* coupling coordinates */
855
int cpl_coords_exist = 0;
857
for (ch = 1; ch <= fbw_channels; ch++) {
858
if (s->channel_in_cpl[ch]) {
859
if (get_bits1(gbc)) {
860
int master_cpl_coord, cpl_coord_exp, cpl_coord_mant;
861
cpl_coords_exist = 1;
862
master_cpl_coord = 3 * get_bits(gbc, 2);
863
for (bnd = 0; bnd < s->num_cpl_bands; bnd++) {
864
cpl_coord_exp = get_bits(gbc, 4);
865
cpl_coord_mant = get_bits(gbc, 4);
866
if (cpl_coord_exp == 15)
867
s->cpl_coords[ch][bnd] = cpl_coord_mant << 22;
869
s->cpl_coords[ch][bnd] = (cpl_coord_mant + 16) << 21;
870
s->cpl_coords[ch][bnd] >>= (cpl_coord_exp + master_cpl_coord);
876
if (channel_mode == AC3_CHMODE_STEREO && cpl_coords_exist) {
877
for (bnd = 0; bnd < s->num_cpl_bands; bnd++) {
878
s->phase_flags[bnd] = s->phase_flags_in_use? get_bits1(gbc) : 0;
883
/* stereo rematrixing strategy and band structure */
884
if (channel_mode == AC3_CHMODE_STEREO) {
885
if (get_bits1(gbc)) {
886
s->num_rematrixing_bands = 4;
887
if(s->cpl_in_use && s->start_freq[CPL_CH] <= 61)
888
s->num_rematrixing_bands -= 1 + (s->start_freq[CPL_CH] == 37);
889
for(bnd=0; bnd<s->num_rematrixing_bands; bnd++)
890
s->rematrixing_flags[bnd] = get_bits1(gbc);
894
/* exponent strategies for each channel */
895
s->exp_strategy[CPL_CH] = EXP_REUSE;
896
s->exp_strategy[s->lfe_ch] = EXP_REUSE;
897
for (ch = !s->cpl_in_use; ch <= s->channels; ch++) {
899
s->exp_strategy[ch] = get_bits(gbc, 1);
901
s->exp_strategy[ch] = get_bits(gbc, 2);
902
if(s->exp_strategy[ch] != EXP_REUSE)
903
bit_alloc_stages[ch] = 3;
906
/* channel bandwidth */
907
for (ch = 1; ch <= fbw_channels; ch++) {
908
s->start_freq[ch] = 0;
909
if (s->exp_strategy[ch] != EXP_REUSE) {
910
int prev = s->end_freq[ch];
911
if (s->channel_in_cpl[ch])
912
s->end_freq[ch] = s->start_freq[CPL_CH];
914
int bandwidth_code = get_bits(gbc, 6);
915
if (bandwidth_code > 60) {
916
av_log(s->avctx, AV_LOG_ERROR, "bandwidth code = %d > 60", bandwidth_code);
919
s->end_freq[ch] = bandwidth_code * 3 + 73;
921
if(blk > 0 && s->end_freq[ch] != prev)
922
memset(bit_alloc_stages, 3, AC3_MAX_CHANNELS);
925
s->start_freq[s->lfe_ch] = 0;
926
s->end_freq[s->lfe_ch] = 7;
928
/* decode exponents for each channel */
929
for (ch = !s->cpl_in_use; ch <= s->channels; ch++) {
930
if (s->exp_strategy[ch] != EXP_REUSE) {
931
int group_size, num_groups;
932
group_size = 3 << (s->exp_strategy[ch] - 1);
934
num_groups = (s->end_freq[ch] - s->start_freq[ch]) / group_size;
935
else if(ch == s->lfe_ch)
938
num_groups = (s->end_freq[ch] + group_size - 4) / group_size;
939
s->dexps[ch][0] = get_bits(gbc, 4) << !ch;
940
decode_exponents(gbc, s->exp_strategy[ch], num_groups, s->dexps[ch][0],
941
&s->dexps[ch][s->start_freq[ch]+!!ch]);
942
if(ch != CPL_CH && ch != s->lfe_ch)
943
skip_bits(gbc, 2); /* skip gainrng */
947
/* bit allocation information */
948
if (get_bits1(gbc)) {
949
s->bit_alloc_params.slow_decay = ff_ac3_slow_decay_tab[get_bits(gbc, 2)] >> s->bit_alloc_params.sr_shift;
950
s->bit_alloc_params.fast_decay = ff_ac3_fast_decay_tab[get_bits(gbc, 2)] >> s->bit_alloc_params.sr_shift;
951
s->bit_alloc_params.slow_gain = ff_ac3_slow_gain_tab[get_bits(gbc, 2)];
952
s->bit_alloc_params.db_per_bit = ff_ac3_db_per_bit_tab[get_bits(gbc, 2)];
953
s->bit_alloc_params.floor = ff_ac3_floor_tab[get_bits(gbc, 3)];
954
for(ch=!s->cpl_in_use; ch<=s->channels; ch++) {
955
bit_alloc_stages[ch] = FFMAX(bit_alloc_stages[ch], 2);
959
/* signal-to-noise ratio offsets and fast gains (signal-to-mask ratios) */
960
if (get_bits1(gbc)) {
962
csnr = (get_bits(gbc, 6) - 15) << 4;
963
for (ch = !s->cpl_in_use; ch <= s->channels; ch++) { /* snr offset and fast gain */
964
s->snr_offset[ch] = (csnr + get_bits(gbc, 4)) << 2;
965
s->fast_gain[ch] = ff_ac3_fast_gain_tab[get_bits(gbc, 3)];
967
memset(bit_alloc_stages, 3, AC3_MAX_CHANNELS);
970
/* coupling leak information */
971
if (s->cpl_in_use && get_bits1(gbc)) {
972
s->bit_alloc_params.cpl_fast_leak = get_bits(gbc, 3);
973
s->bit_alloc_params.cpl_slow_leak = get_bits(gbc, 3);
974
bit_alloc_stages[CPL_CH] = FFMAX(bit_alloc_stages[CPL_CH], 2);
977
/* delta bit allocation information */
978
if (get_bits1(gbc)) {
979
/* delta bit allocation exists (strategy) */
980
for (ch = !s->cpl_in_use; ch <= fbw_channels; ch++) {
981
s->dba_mode[ch] = get_bits(gbc, 2);
982
if (s->dba_mode[ch] == DBA_RESERVED) {
983
av_log(s->avctx, AV_LOG_ERROR, "delta bit allocation strategy reserved\n");
986
bit_alloc_stages[ch] = FFMAX(bit_alloc_stages[ch], 2);
988
/* channel delta offset, len and bit allocation */
989
for (ch = !s->cpl_in_use; ch <= fbw_channels; ch++) {
990
if (s->dba_mode[ch] == DBA_NEW) {
991
s->dba_nsegs[ch] = get_bits(gbc, 3);
992
for (seg = 0; seg <= s->dba_nsegs[ch]; seg++) {
993
s->dba_offsets[ch][seg] = get_bits(gbc, 5);
994
s->dba_lengths[ch][seg] = get_bits(gbc, 4);
995
s->dba_values[ch][seg] = get_bits(gbc, 3);
999
} else if(blk == 0) {
1000
for(ch=0; ch<=s->channels; ch++) {
1001
s->dba_mode[ch] = DBA_NONE;
1005
/* Bit allocation */
1006
for(ch=!s->cpl_in_use; ch<=s->channels; ch++) {
1007
if(bit_alloc_stages[ch] > 2) {
1008
/* Exponent mapping into PSD and PSD integration */
1009
ff_ac3_bit_alloc_calc_psd(s->dexps[ch],
1010
s->start_freq[ch], s->end_freq[ch],
1011
s->psd[ch], s->band_psd[ch]);
1013
if(bit_alloc_stages[ch] > 1) {
1014
/* Compute excitation function, Compute masking curve, and
1015
Apply delta bit allocation */
1016
ff_ac3_bit_alloc_calc_mask(&s->bit_alloc_params, s->band_psd[ch],
1017
s->start_freq[ch], s->end_freq[ch],
1018
s->fast_gain[ch], (ch == s->lfe_ch),
1019
s->dba_mode[ch], s->dba_nsegs[ch],
1020
s->dba_offsets[ch], s->dba_lengths[ch],
1021
s->dba_values[ch], s->mask[ch]);
1023
if(bit_alloc_stages[ch] > 0) {
1024
/* Compute bit allocation */
1025
ff_ac3_bit_alloc_calc_bap(s->mask[ch], s->psd[ch],
1026
s->start_freq[ch], s->end_freq[ch],
1028
s->bit_alloc_params.floor,
1033
/* unused dummy data */
1034
if (get_bits1(gbc)) {
1035
int skipl = get_bits(gbc, 9);
1040
/* unpack the transform coefficients
1041
this also uncouples channels if coupling is in use. */
1042
if (get_transform_coeffs(s)) {
1043
av_log(s->avctx, AV_LOG_ERROR, "Error in routine get_transform_coeffs\n");
1047
/* recover coefficients if rematrixing is in use */
1048
if(s->channel_mode == AC3_CHMODE_STEREO)
1051
/* apply scaling to coefficients (headroom, dynrng) */
1052
for(ch=1; ch<=s->channels; ch++) {
1053
float gain = s->mul_bias / 4194304.0f;
1054
if(s->channel_mode == AC3_CHMODE_DUALMONO) {
1055
gain *= s->dynamic_range[ch-1];
1057
gain *= s->dynamic_range[0];
1059
for(i=0; i<256; i++) {
1060
s->transform_coeffs[ch][i] = s->fixed_coeffs[ch][i] * gain;
1064
/* downmix and MDCT. order depends on whether block switching is used for
1065
any channel in this block. this is because coefficients for the long
1066
and short transforms cannot be mixed. */
1067
downmix_output = s->channels != s->out_channels &&
1068
!((s->output_mode & AC3_OUTPUT_LFEON) &&
1069
s->fbw_channels == s->out_channels);
1070
if(different_transforms) {
1071
/* the delay samples have already been downmixed, so we upmix the delay
1072
samples in order to reconstruct all channels before downmixing. */
1078
do_imdct(s, s->channels);
1080
if(downmix_output) {
1081
ac3_downmix(s, s->output, 0);
1084
if(downmix_output) {
1085
ac3_downmix(s, s->transform_coeffs, 1);
1090
ac3_downmix(s, s->delay, 0);
1093
do_imdct(s, s->out_channels);
1096
/* convert float to 16-bit integer */
1097
for(ch=0; ch<s->out_channels; ch++) {
1098
for(i=0; i<256; i++) {
1099
s->output[ch][i] += s->add_bias;
1101
s->dsp.float_to_int16(s->int_output[ch], s->output[ch], 256);
1108
* Decode a single AC-3 frame.
1110
static int ac3_decode_frame(AVCodecContext * avctx, void *data, int *data_size,
1111
const uint8_t *buf, int buf_size)
1113
AC3DecodeContext *s = avctx->priv_data;
1114
int16_t *out_samples = (int16_t *)data;
1115
int i, blk, ch, err;
1117
/* initialize the GetBitContext with the start of valid AC-3 Frame */
1118
if (s->input_buffer) {
1119
/* copy input buffer to decoder context to avoid reading past the end
1120
of the buffer, which can be caused by a damaged input stream. */
1121
memcpy(s->input_buffer, buf, FFMIN(buf_size, AC3_MAX_FRAME_SIZE));
1122
init_get_bits(&s->gbc, s->input_buffer, buf_size * 8);
1124
init_get_bits(&s->gbc, buf, buf_size * 8);
1127
/* parse the syncinfo */
1128
err = ac3_parse_header(s);
1131
case AC3_PARSE_ERROR_SYNC:
1132
av_log(avctx, AV_LOG_ERROR, "frame sync error\n");
1134
case AC3_PARSE_ERROR_BSID:
1135
av_log(avctx, AV_LOG_ERROR, "invalid bitstream id\n");
1137
case AC3_PARSE_ERROR_SAMPLE_RATE:
1138
av_log(avctx, AV_LOG_ERROR, "invalid sample rate\n");
1140
case AC3_PARSE_ERROR_FRAME_SIZE:
1141
av_log(avctx, AV_LOG_ERROR, "invalid frame size\n");
1143
case AC3_PARSE_ERROR_FRAME_TYPE:
1144
av_log(avctx, AV_LOG_ERROR, "invalid frame type\n");
1147
av_log(avctx, AV_LOG_ERROR, "invalid header\n");
1153
/* check that reported frame size fits in input buffer */
1154
if(s->frame_size > buf_size) {
1155
av_log(avctx, AV_LOG_ERROR, "incomplete frame\n");
1159
/* check for crc mismatch */
1160
if(avctx->error_resilience >= FF_ER_CAREFUL) {
1161
if(av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0, &buf[2], s->frame_size-2)) {
1162
av_log(avctx, AV_LOG_ERROR, "frame CRC mismatch\n");
1165
/* TODO: error concealment */
1168
avctx->sample_rate = s->sample_rate;
1169
avctx->bit_rate = s->bit_rate;
1171
/* channel config */
1172
s->out_channels = s->channels;
1173
if (avctx->request_channels > 0 && avctx->request_channels <= 2 &&
1174
avctx->request_channels < s->channels) {
1175
s->out_channels = avctx->request_channels;
1176
s->output_mode = avctx->request_channels == 1 ? AC3_CHMODE_MONO : AC3_CHMODE_STEREO;
1178
avctx->channels = s->out_channels;
1180
/* set downmixing coefficients if needed */
1181
if(s->channels != s->out_channels && !((s->output_mode & AC3_OUTPUT_LFEON) &&
1182
s->fbw_channels == s->out_channels)) {
1183
set_downmix_coeffs(s);
1186
/* parse the audio blocks */
1187
for (blk = 0; blk < NB_BLOCKS; blk++) {
1188
if (ac3_parse_audio_block(s, blk)) {
1189
av_log(avctx, AV_LOG_ERROR, "error parsing the audio block\n");
1191
return s->frame_size;
1193
for (i = 0; i < 256; i++)
1194
for (ch = 0; ch < s->out_channels; ch++)
1195
*(out_samples++) = s->int_output[ch][i];
1197
*data_size = NB_BLOCKS * 256 * avctx->channels * sizeof (int16_t);
1198
return s->frame_size;
1202
* Uninitialize the AC-3 decoder.
1204
static av_cold int ac3_decode_end(AVCodecContext *avctx)
1206
AC3DecodeContext *s = avctx->priv_data;
1207
ff_mdct_end(&s->imdct_512);
1208
ff_mdct_end(&s->imdct_256);
1210
av_freep(&s->input_buffer);
1215
AVCodec ac3_decoder = {
1217
.type = CODEC_TYPE_AUDIO,
1219
.priv_data_size = sizeof (AC3DecodeContext),
1220
.init = ac3_decode_init,
1221
.close = ac3_decode_end,
1222
.decode = ac3_decode_frame,
1223
.long_name = "ATSC A/52 / AC-3",
added
removed
ffmpeg/libavcodec/ac3dec.c
