Statistics
| Branch: | Revision:

ffmpeg / libavcodec / ac3dec.c @ f0b3a7ba

History | View | Annotate | Download (40.7 KB)

1
/*
2
 * AC-3 Audio Decoder
3
 * This code is developed as part of Google Summer of Code 2006 Program.
4
 *
5
 * Copyright (c) 2006 Kartikey Mahendra BHATT (bhattkm at gmail dot com).
6
 * Copyright (c) 2007 Justin Ruggles
7
 *
8
 * Portions of this code are derived from liba52
9
 * http://liba52.sourceforge.net
10
 * Copyright (C) 2000-2003 Michel Lespinasse <walken@zoy.org>
11
 * Copyright (C) 1999-2000 Aaron Holtzman <aholtzma@ess.engr.uvic.ca>
12
 *
13
 * This file is part of FFmpeg.
14
 *
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.
19
 *
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.
24
 *
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
28
 */
29

    
30
#include <stdio.h>
31
#include <stddef.h>
32
#include <math.h>
33
#include <string.h>
34

    
35
#include "avcodec.h"
36
#include "ac3_parser.h"
37
#include "bitstream.h"
38
#include "crc.h"
39
#include "dsputil.h"
40
#include "random.h"
41

    
42
/**
43
 * Table of bin locations for rematrixing bands
44
 * reference: Section 7.5.2 Rematrixing : Frequency Band Definitions
45
 */
46
static const uint8_t rematrix_band_tab[5] = { 13, 25, 37, 61, 253 };
47

    
48
/**
49
 * table for exponent to scale_factor mapping
50
 * scale_factors[i] = 2 ^ -i
51
 */
52
static float scale_factors[25];
53

    
54
/** table for grouping exponents */
55
static uint8_t exp_ungroup_tab[128][3];
56

    
57

    
58
/** tables for ungrouping mantissas */
59
static float b1_mantissas[32][3];
60
static float b2_mantissas[128][3];
61
static float b3_mantissas[8];
62
static float b4_mantissas[128][2];
63
static float b5_mantissas[16];
64

    
65
/**
66
 * Quantization table: levels for symmetric. bits for asymmetric.
67
 * reference: Table 7.18 Mapping of bap to Quantizer
68
 */
69
static const uint8_t quantization_tab[16] = {
70
    0, 3, 5, 7, 11, 15,
71
    5, 6, 7, 8, 9, 10, 11, 12, 14, 16
72
};
73

    
74
/** dynamic range table. converts codes to scale factors. */
75
static float dynamic_range_tab[256];
76

    
77
/** Adjustments in dB gain */
78
#define LEVEL_MINUS_3DB         0.7071067811865476
79
#define LEVEL_MINUS_4POINT5DB   0.5946035575013605
80
#define LEVEL_MINUS_6DB         0.5000000000000000
81
#define LEVEL_MINUS_9DB         0.3535533905932738
82
#define LEVEL_ZERO              0.0000000000000000
83
#define LEVEL_ONE               1.0000000000000000
84

    
85
static const float gain_levels[6] = {
86
    LEVEL_ZERO,
87
    LEVEL_ONE,
88
    LEVEL_MINUS_3DB,
89
    LEVEL_MINUS_4POINT5DB,
90
    LEVEL_MINUS_6DB,
91
    LEVEL_MINUS_9DB
92
};
93

    
94
/**
95
 * Table for center mix levels
96
 * reference: Section 5.4.2.4 cmixlev
97
 */
98
static const uint8_t center_levels[4] = { 2, 3, 4, 3 };
99

    
100
/**
101
 * Table for surround mix levels
102
 * reference: Section 5.4.2.5 surmixlev
103
 */
104
static const uint8_t surround_levels[4] = { 2, 4, 0, 4 };
105

    
106
/**
107
 * Table for default stereo downmixing coefficients
108
 * reference: Section 7.8.2 Downmixing Into Two Channels
109
 */
110
static const uint8_t ac3_default_coeffs[8][5][2] = {
111
    { { 1, 0 }, { 0, 1 },                               },
112
    { { 2, 2 },                                         },
113
    { { 1, 0 }, { 0, 1 },                               },
114
    { { 1, 0 }, { 3, 3 }, { 0, 1 },                     },
115
    { { 1, 0 }, { 0, 1 }, { 4, 4 },                     },
116
    { { 1, 0 }, { 3, 3 }, { 0, 1 }, { 5, 5 },           },
117
    { { 1, 0 }, { 0, 1 }, { 4, 0 }, { 0, 4 },           },
118
    { { 1, 0 }, { 3, 3 }, { 0, 1 }, { 4, 0 }, { 0, 4 }, },
119
};
120

    
121
/* override ac3.h to include coupling channel */
122
#undef AC3_MAX_CHANNELS
123
#define AC3_MAX_CHANNELS 7
124
#define CPL_CH 0
125

    
126
#define AC3_OUTPUT_LFEON  8
127

    
128
typedef struct {
129
    int channel_mode;                       ///< channel mode (acmod)
130
    int block_switch[AC3_MAX_CHANNELS];     ///< block switch flags
131
    int dither_flag[AC3_MAX_CHANNELS];      ///< dither flags
132
    int dither_all;                         ///< true if all channels are dithered
133
    int cpl_in_use;                         ///< coupling in use
134
    int channel_in_cpl[AC3_MAX_CHANNELS];   ///< channel in coupling
135
    int phase_flags_in_use;                 ///< phase flags in use
136
    int phase_flags[18];                    ///< phase flags
137
    int cpl_band_struct[18];                ///< coupling band structure
138
    int num_rematrixing_bands;              ///< number of rematrixing bands
139
    int rematrixing_flags[4];               ///< rematrixing flags
140
    int exp_strategy[AC3_MAX_CHANNELS];     ///< exponent strategies
141
    int snr_offset[AC3_MAX_CHANNELS];       ///< signal-to-noise ratio offsets
142
    int fast_gain[AC3_MAX_CHANNELS];        ///< fast gain values (signal-to-mask ratio)
143
    int dba_mode[AC3_MAX_CHANNELS];         ///< delta bit allocation mode
144
    int dba_nsegs[AC3_MAX_CHANNELS];        ///< number of delta segments
145
    uint8_t dba_offsets[AC3_MAX_CHANNELS][8]; ///< delta segment offsets
146
    uint8_t dba_lengths[AC3_MAX_CHANNELS][8]; ///< delta segment lengths
147
    uint8_t dba_values[AC3_MAX_CHANNELS][8];  ///< delta values for each segment
148

    
149
    int sample_rate;                        ///< sample frequency, in Hz
150
    int bit_rate;                           ///< stream bit rate, in bits-per-second
151
    int frame_size;                         ///< current frame size, in bytes
152

    
153
    int channels;                           ///< number of total channels
154
    int fbw_channels;                       ///< number of full-bandwidth channels
155
    int lfe_on;                             ///< lfe channel in use
156
    int lfe_ch;                             ///< index of LFE channel
157
    int output_mode;                        ///< output channel configuration
158
    int out_channels;                       ///< number of output channels
159

    
160
    int center_mix_level;                   ///< Center mix level index
161
    int surround_mix_level;                 ///< Surround mix level index
162
    float downmix_coeffs[AC3_MAX_CHANNELS][2];  ///< stereo downmix coefficients
163
    float dynamic_range[2];                 ///< dynamic range
164
    float cpl_coords[AC3_MAX_CHANNELS][18]; ///< coupling coordinates
165
    int   num_cpl_bands;                    ///< number of coupling bands
166
    int   num_cpl_subbands;                 ///< number of coupling sub bands
167
    int   start_freq[AC3_MAX_CHANNELS];     ///< start frequency bin
168
    int   end_freq[AC3_MAX_CHANNELS];       ///< end frequency bin
169
    AC3BitAllocParameters bit_alloc_params; ///< bit allocation parameters
170

    
171
    int8_t  dexps[AC3_MAX_CHANNELS][256];   ///< decoded exponents
172
    uint8_t bap[AC3_MAX_CHANNELS][256];     ///< bit allocation pointers
173
    int16_t psd[AC3_MAX_CHANNELS][256];     ///< scaled exponents
174
    int16_t band_psd[AC3_MAX_CHANNELS][50]; ///< interpolated exponents
175
    int16_t mask[AC3_MAX_CHANNELS][50];     ///< masking curve values
176

    
177
    DECLARE_ALIGNED_16(float, transform_coeffs[AC3_MAX_CHANNELS][256]);  ///< transform coefficients
178

    
179
    /* For IMDCT. */
180
    MDCTContext imdct_512;                  ///< for 512 sample IMDCT
181
    MDCTContext imdct_256;                  ///< for 256 sample IMDCT
182
    DSPContext  dsp;                        ///< for optimization
183
    float       add_bias;                   ///< offset for float_to_int16 conversion
184
    float       mul_bias;                   ///< scaling for float_to_int16 conversion
185

    
186
    DECLARE_ALIGNED_16(float, output[AC3_MAX_CHANNELS-1][256]);     ///< output after imdct transform and windowing
187
    DECLARE_ALIGNED_16(short, int_output[AC3_MAX_CHANNELS-1][256]); ///< final 16-bit integer output
188
    DECLARE_ALIGNED_16(float, delay[AC3_MAX_CHANNELS-1][256]);      ///< delay - added to the next block
189
    DECLARE_ALIGNED_16(float, tmp_imdct[256]);                      ///< temporary storage for imdct transform
190
    DECLARE_ALIGNED_16(float, tmp_output[512]);                     ///< temporary storage for output before windowing
191
    DECLARE_ALIGNED_16(float, window[256]);                         ///< window coefficients
192

    
193
    /* Miscellaneous. */
194
    GetBitContext gbc;                      ///< bitstream reader
195
    AVRandomState dith_state;               ///< for dither generation
196
    AVCodecContext *avctx;                  ///< parent context
197
} AC3DecodeContext;
198

    
199
/**
200
 * Generate a Kaiser-Bessel Derived Window.
201
 */
202
static void ac3_window_init(float *window)
203
{
204
   int i, j;
205
   double sum = 0.0, bessel, tmp;
206
   double local_window[256];
207
   double alpha2 = (5.0 * M_PI / 256.0) * (5.0 * M_PI / 256.0);
208

    
209
   for (i = 0; i < 256; i++) {
210
       tmp = i * (256 - i) * alpha2;
211
       bessel = 1.0;
212
       for (j = 100; j > 0; j--) /* default to 100 iterations */
213
           bessel = bessel * tmp / (j * j) + 1;
214
       sum += bessel;
215
       local_window[i] = sum;
216
   }
217

    
218
   sum++;
219
   for (i = 0; i < 256; i++)
220
       window[i] = sqrt(local_window[i] / sum);
221
}
222

    
223
/**
224
 * Symmetrical Dequantization
225
 * reference: Section 7.3.3 Expansion of Mantissas for Symmetrical Quantization
226
 *            Tables 7.19 to 7.23
227
 */
228
static inline float
229
symmetric_dequant(int code, int levels)
230
{
231
    return (code - (levels >> 1)) * (2.0f / levels);
232
}
233

    
234
/*
235
 * Initialize tables at runtime.
236
 */
237
static void ac3_tables_init(void)
238
{
239
    int i;
240

    
241
    /* generate grouped mantissa tables
242
       reference: Section 7.3.5 Ungrouping of Mantissas */
243
    for(i=0; i<32; i++) {
244
        /* bap=1 mantissas */
245
        b1_mantissas[i][0] = symmetric_dequant( i / 9     , 3);
246
        b1_mantissas[i][1] = symmetric_dequant((i % 9) / 3, 3);
247
        b1_mantissas[i][2] = symmetric_dequant((i % 9) % 3, 3);
248
    }
249
    for(i=0; i<128; i++) {
250
        /* bap=2 mantissas */
251
        b2_mantissas[i][0] = symmetric_dequant( i / 25     , 5);
252
        b2_mantissas[i][1] = symmetric_dequant((i % 25) / 5, 5);
253
        b2_mantissas[i][2] = symmetric_dequant((i % 25) % 5, 5);
254

    
255
        /* bap=4 mantissas */
256
        b4_mantissas[i][0] = symmetric_dequant(i / 11, 11);
257
        b4_mantissas[i][1] = symmetric_dequant(i % 11, 11);
258
    }
259
    /* generate ungrouped mantissa tables
260
       reference: Tables 7.21 and 7.23 */
261
    for(i=0; i<7; i++) {
262
        /* bap=3 mantissas */
263
        b3_mantissas[i] = symmetric_dequant(i, 7);
264
    }
265
    for(i=0; i<15; i++) {
266
        /* bap=5 mantissas */
267
        b5_mantissas[i] = symmetric_dequant(i, 15);
268
    }
269

    
270
    /* generate dynamic range table
271
       reference: Section 7.7.1 Dynamic Range Control */
272
    for(i=0; i<256; i++) {
273
        int v = (i >> 5) - ((i >> 7) << 3) - 5;
274
        dynamic_range_tab[i] = powf(2.0f, v) * ((i & 0x1F) | 0x20);
275
    }
276

    
277
    /* generate scale factors for exponents and asymmetrical dequantization
278
       reference: Section 7.3.2 Expansion of Mantissas for Asymmetric Quantization */
279
    for (i = 0; i < 25; i++)
280
        scale_factors[i] = pow(2.0, -i);
281

    
282
    /* generate exponent tables
283
       reference: Section 7.1.3 Exponent Decoding */
284
    for(i=0; i<128; i++) {
285
        exp_ungroup_tab[i][0] =  i / 25;
286
        exp_ungroup_tab[i][1] = (i % 25) / 5;
287
        exp_ungroup_tab[i][2] = (i % 25) % 5;
288
    }
289
}
290

    
291

    
292
/**
293
 * AVCodec initialization
294
 */
295
static int ac3_decode_init(AVCodecContext *avctx)
296
{
297
    AC3DecodeContext *s = avctx->priv_data;
298
    s->avctx = avctx;
299

    
300
    ac3_common_init();
301
    ac3_tables_init();
302
    ff_mdct_init(&s->imdct_256, 8, 1);
303
    ff_mdct_init(&s->imdct_512, 9, 1);
304
    ac3_window_init(s->window);
305
    dsputil_init(&s->dsp, avctx);
306
    av_init_random(0, &s->dith_state);
307

    
308
    /* set bias values for float to int16 conversion */
309
    if(s->dsp.float_to_int16 == ff_float_to_int16_c) {
310
        s->add_bias = 385.0f;
311
        s->mul_bias = 1.0f;
312
    } else {
313
        s->add_bias = 0.0f;
314
        s->mul_bias = 32767.0f;
315
    }
316

    
317
    /* allow downmixing to stereo or mono */
318
    if (avctx->channels > 0 && avctx->request_channels > 0 &&
319
            avctx->request_channels < avctx->channels &&
320
            avctx->request_channels <= 2) {
321
        avctx->channels = avctx->request_channels;
322
    }
323

    
324
    return 0;
325
}
326

    
327
/**
328
 * Parse the 'sync info' and 'bit stream info' from the AC-3 bitstream.
329
 * GetBitContext within AC3DecodeContext must point to
330
 * start of the synchronized ac3 bitstream.
331
 */
332
static int ac3_parse_header(AC3DecodeContext *s)
333
{
334
    AC3HeaderInfo hdr;
335
    GetBitContext *gbc = &s->gbc;
336
    int err, i;
337

    
338
    err = ff_ac3_parse_header(gbc->buffer, &hdr);
339
    if(err)
340
        return err;
341

    
342
    if(hdr.bitstream_id > 10)
343
        return AC3_PARSE_ERROR_BSID;
344

    
345
    /* get decoding parameters from header info */
346
    s->bit_alloc_params.sr_code     = hdr.sr_code;
347
    s->channel_mode                 = hdr.channel_mode;
348
    s->lfe_on                       = hdr.lfe_on;
349
    s->bit_alloc_params.sr_shift    = hdr.sr_shift;
350
    s->sample_rate                  = hdr.sample_rate;
351
    s->bit_rate                     = hdr.bit_rate;
352
    s->channels                     = hdr.channels;
353
    s->fbw_channels                 = s->channels - s->lfe_on;
354
    s->lfe_ch                       = s->fbw_channels + 1;
355
    s->frame_size                   = hdr.frame_size;
356

    
357
    /* set default output to all source channels */
358
    s->out_channels = s->channels;
359
    s->output_mode = s->channel_mode;
360
    if(s->lfe_on)
361
        s->output_mode |= AC3_OUTPUT_LFEON;
362

    
363
    /* set default mix levels */
364
    s->center_mix_level   = 3;  // -4.5dB
365
    s->surround_mix_level = 4;  // -6.0dB
366

    
367
    /* skip over portion of header which has already been read */
368
    skip_bits(gbc, 16); // skip the sync_word
369
    skip_bits(gbc, 16); // skip crc1
370
    skip_bits(gbc, 8);  // skip fscod and frmsizecod
371
    skip_bits(gbc, 11); // skip bsid, bsmod, and acmod
372
    if(s->channel_mode == AC3_CHMODE_STEREO) {
373
        skip_bits(gbc, 2); // skip dsurmod
374
    } else {
375
        if((s->channel_mode & 1) && s->channel_mode != AC3_CHMODE_MONO)
376
            s->center_mix_level = center_levels[get_bits(gbc, 2)];
377
        if(s->channel_mode & 4)
378
            s->surround_mix_level = surround_levels[get_bits(gbc, 2)];
379
    }
380
    skip_bits1(gbc); // skip lfeon
381

    
382
    /* read the rest of the bsi. read twice for dual mono mode. */
383
    i = !(s->channel_mode);
384
    do {
385
        skip_bits(gbc, 5); // skip dialog normalization
386
        if (get_bits1(gbc))
387
            skip_bits(gbc, 8); //skip compression
388
        if (get_bits1(gbc))
389
            skip_bits(gbc, 8); //skip language code
390
        if (get_bits1(gbc))
391
            skip_bits(gbc, 7); //skip audio production information
392
    } while (i--);
393

    
394
    skip_bits(gbc, 2); //skip copyright bit and original bitstream bit
395

    
396
    /* skip the timecodes (or extra bitstream information for Alternate Syntax)
397
       TODO: read & use the xbsi1 downmix levels */
398
    if (get_bits1(gbc))
399
        skip_bits(gbc, 14); //skip timecode1 / xbsi1
400
    if (get_bits1(gbc))
401
        skip_bits(gbc, 14); //skip timecode2 / xbsi2
402

    
403
    /* skip additional bitstream info */
404
    if (get_bits1(gbc)) {
405
        i = get_bits(gbc, 6);
406
        do {
407
            skip_bits(gbc, 8);
408
        } while(i--);
409
    }
410

    
411
    return 0;
412
}
413

    
414
/**
415
 * Set stereo downmixing coefficients based on frame header info.
416
 * reference: Section 7.8.2 Downmixing Into Two Channels
417
 */
418
static void set_downmix_coeffs(AC3DecodeContext *s)
419
{
420
    int i;
421
    float cmix = gain_levels[s->center_mix_level];
422
    float smix = gain_levels[s->surround_mix_level];
423

    
424
    for(i=0; i<s->fbw_channels; i++) {
425
        s->downmix_coeffs[i][0] = gain_levels[ac3_default_coeffs[s->channel_mode][i][0]];
426
        s->downmix_coeffs[i][1] = gain_levels[ac3_default_coeffs[s->channel_mode][i][1]];
427
    }
428
    if(s->channel_mode > 1 && s->channel_mode & 1) {
429
        s->downmix_coeffs[1][0] = s->downmix_coeffs[1][1] = cmix;
430
    }
431
    if(s->channel_mode == AC3_CHMODE_2F1R || s->channel_mode == AC3_CHMODE_3F1R) {
432
        int nf = s->channel_mode - 2;
433
        s->downmix_coeffs[nf][0] = s->downmix_coeffs[nf][1] = smix * LEVEL_MINUS_3DB;
434
    }
435
    if(s->channel_mode == AC3_CHMODE_2F2R || s->channel_mode == AC3_CHMODE_3F2R) {
436
        int nf = s->channel_mode - 4;
437
        s->downmix_coeffs[nf][0] = s->downmix_coeffs[nf+1][1] = smix;
438
    }
439
}
440

    
441
/**
442
 * Decode the grouped exponents according to exponent strategy.
443
 * reference: Section 7.1.3 Exponent Decoding
444
 */
445
static void decode_exponents(GetBitContext *gbc, int exp_strategy, int ngrps,
446
                             uint8_t absexp, int8_t *dexps)
447
{
448
    int i, j, grp, group_size;
449
    int dexp[256];
450
    int expacc, prevexp;
451

    
452
    /* unpack groups */
453
    group_size = exp_strategy + (exp_strategy == EXP_D45);
454
    for(grp=0,i=0; grp<ngrps; grp++) {
455
        expacc = get_bits(gbc, 7);
456
        dexp[i++] = exp_ungroup_tab[expacc][0];
457
        dexp[i++] = exp_ungroup_tab[expacc][1];
458
        dexp[i++] = exp_ungroup_tab[expacc][2];
459
    }
460

    
461
    /* convert to absolute exps and expand groups */
462
    prevexp = absexp;
463
    for(i=0; i<ngrps*3; i++) {
464
        prevexp = av_clip(prevexp + dexp[i]-2, 0, 24);
465
        for(j=0; j<group_size; j++) {
466
            dexps[(i*group_size)+j] = prevexp;
467
        }
468
    }
469
}
470

    
471
/**
472
 * Generate transform coefficients for each coupled channel in the coupling
473
 * range using the coupling coefficients and coupling coordinates.
474
 * reference: Section 7.4.3 Coupling Coordinate Format
475
 */
476
static void uncouple_channels(AC3DecodeContext *s)
477
{
478
    int i, j, ch, bnd, subbnd;
479

    
480
    subbnd = -1;
481
    i = s->start_freq[CPL_CH];
482
    for(bnd=0; bnd<s->num_cpl_bands; bnd++) {
483
        do {
484
            subbnd++;
485
            for(j=0; j<12; j++) {
486
                for(ch=1; ch<=s->fbw_channels; ch++) {
487
                    if(s->channel_in_cpl[ch]) {
488
                        s->transform_coeffs[ch][i] = s->transform_coeffs[CPL_CH][i] * s->cpl_coords[ch][bnd] * 8.0f;
489
                        if (ch == 2 && s->phase_flags[bnd])
490
                            s->transform_coeffs[ch][i] = -s->transform_coeffs[ch][i];
491
                    }
492
                }
493
                i++;
494
            }
495
        } while(s->cpl_band_struct[subbnd]);
496
    }
497
}
498

    
499
/**
500
 * Grouped mantissas for 3-level 5-level and 11-level quantization
501
 */
502
typedef struct {
503
    float b1_mant[3];
504
    float b2_mant[3];
505
    float b4_mant[2];
506
    int b1ptr;
507
    int b2ptr;
508
    int b4ptr;
509
} mant_groups;
510

    
511
/**
512
 * Get the transform coefficients for a particular channel
513
 * reference: Section 7.3 Quantization and Decoding of Mantissas
514
 */
515
static int get_transform_coeffs_ch(AC3DecodeContext *s, int ch_index, mant_groups *m)
516
{
517
    GetBitContext *gbc = &s->gbc;
518
    int i, gcode, tbap, start, end;
519
    uint8_t *exps;
520
    uint8_t *bap;
521
    float *coeffs;
522

    
523
    exps = s->dexps[ch_index];
524
    bap = s->bap[ch_index];
525
    coeffs = s->transform_coeffs[ch_index];
526
    start = s->start_freq[ch_index];
527
    end = s->end_freq[ch_index];
528

    
529
    for (i = start; i < end; i++) {
530
        tbap = bap[i];
531
        switch (tbap) {
532
            case 0:
533
                coeffs[i] = ((av_random(&s->dith_state) & 0xFFFF) / 65535.0f) - 0.5f;
534
                break;
535

    
536
            case 1:
537
                if(m->b1ptr > 2) {
538
                    gcode = get_bits(gbc, 5);
539
                    m->b1_mant[0] = b1_mantissas[gcode][0];
540
                    m->b1_mant[1] = b1_mantissas[gcode][1];
541
                    m->b1_mant[2] = b1_mantissas[gcode][2];
542
                    m->b1ptr = 0;
543
                }
544
                coeffs[i] = m->b1_mant[m->b1ptr++];
545
                break;
546

    
547
            case 2:
548
                if(m->b2ptr > 2) {
549
                    gcode = get_bits(gbc, 7);
550
                    m->b2_mant[0] = b2_mantissas[gcode][0];
551
                    m->b2_mant[1] = b2_mantissas[gcode][1];
552
                    m->b2_mant[2] = b2_mantissas[gcode][2];
553
                    m->b2ptr = 0;
554
                }
555
                coeffs[i] = m->b2_mant[m->b2ptr++];
556
                break;
557

    
558
            case 3:
559
                coeffs[i] = b3_mantissas[get_bits(gbc, 3)];
560
                break;
561

    
562
            case 4:
563
                if(m->b4ptr > 1) {
564
                    gcode = get_bits(gbc, 7);
565
                    m->b4_mant[0] = b4_mantissas[gcode][0];
566
                    m->b4_mant[1] = b4_mantissas[gcode][1];
567
                    m->b4ptr = 0;
568
                }
569
                coeffs[i] = m->b4_mant[m->b4ptr++];
570
                break;
571

    
572
            case 5:
573
                coeffs[i] = b5_mantissas[get_bits(gbc, 4)];
574
                break;
575

    
576
            default:
577
                /* asymmetric dequantization */
578
                coeffs[i] = get_sbits(gbc, quantization_tab[tbap]) * scale_factors[quantization_tab[tbap]-1];
579
                break;
580
        }
581
        coeffs[i] *= scale_factors[exps[i]];
582
    }
583

    
584
    return 0;
585
}
586

    
587
/**
588
 * Remove random dithering from coefficients with zero-bit mantissas
589
 * reference: Section 7.3.4 Dither for Zero Bit Mantissas (bap=0)
590
 */
591
static void remove_dithering(AC3DecodeContext *s) {
592
    int ch, i;
593
    int end=0;
594
    float *coeffs;
595
    uint8_t *bap;
596

    
597
    for(ch=1; ch<=s->fbw_channels; ch++) {
598
        if(!s->dither_flag[ch]) {
599
            coeffs = s->transform_coeffs[ch];
600
            bap = s->bap[ch];
601
            if(s->channel_in_cpl[ch])
602
                end = s->start_freq[CPL_CH];
603
            else
604
                end = s->end_freq[ch];
605
            for(i=0; i<end; i++) {
606
                if(!bap[i])
607
                    coeffs[i] = 0.0f;
608
            }
609
            if(s->channel_in_cpl[ch]) {
610
                bap = s->bap[CPL_CH];
611
                for(; i<s->end_freq[CPL_CH]; i++) {
612
                    if(!bap[i])
613
                        coeffs[i] = 0.0f;
614
                }
615
            }
616
        }
617
    }
618
}
619

    
620
/**
621
 * Get the transform coefficients.
622
 */
623
static int get_transform_coeffs(AC3DecodeContext *s)
624
{
625
    int ch, end;
626
    int got_cplchan = 0;
627
    mant_groups m;
628

    
629
    m.b1ptr = m.b2ptr = m.b4ptr = 3;
630

    
631
    for (ch = 1; ch <= s->channels; ch++) {
632
        /* transform coefficients for full-bandwidth channel */
633
        if (get_transform_coeffs_ch(s, ch, &m))
634
            return -1;
635
        /* tranform coefficients for coupling channel come right after the
636
           coefficients for the first coupled channel*/
637
        if (s->channel_in_cpl[ch])  {
638
            if (!got_cplchan) {
639
                if (get_transform_coeffs_ch(s, CPL_CH, &m)) {
640
                    av_log(s->avctx, AV_LOG_ERROR, "error in decoupling channels\n");
641
                    return -1;
642
                }
643
                uncouple_channels(s);
644
                got_cplchan = 1;
645
            }
646
            end = s->end_freq[CPL_CH];
647
        } else {
648
            end = s->end_freq[ch];
649
        }
650
        do
651
            s->transform_coeffs[ch][end] = 0;
652
        while(++end < 256);
653
    }
654

    
655
    /* if any channel doesn't use dithering, zero appropriate coefficients */
656
    if(!s->dither_all)
657
        remove_dithering(s);
658

    
659
    return 0;
660
}
661

    
662
/**
663
 * Stereo rematrixing.
664
 * reference: Section 7.5.4 Rematrixing : Decoding Technique
665
 */
666
static void do_rematrixing(AC3DecodeContext *s)
667
{
668
    int bnd, i;
669
    int end, bndend;
670
    float tmp0, tmp1;
671

    
672
    end = FFMIN(s->end_freq[1], s->end_freq[2]);
673

    
674
    for(bnd=0; bnd<s->num_rematrixing_bands; bnd++) {
675
        if(s->rematrixing_flags[bnd]) {
676
            bndend = FFMIN(end, rematrix_band_tab[bnd+1]);
677
            for(i=rematrix_band_tab[bnd]; i<bndend; i++) {
678
                tmp0 = s->transform_coeffs[1][i];
679
                tmp1 = s->transform_coeffs[2][i];
680
                s->transform_coeffs[1][i] = tmp0 + tmp1;
681
                s->transform_coeffs[2][i] = tmp0 - tmp1;
682
            }
683
        }
684
    }
685
}
686

    
687
/**
688
 * Perform the 256-point IMDCT
689
 */
690
static void do_imdct_256(AC3DecodeContext *s, int chindex)
691
{
692
    int i, k;
693
    DECLARE_ALIGNED_16(float, x[128]);
694
    FFTComplex z[2][64];
695
    float *o_ptr = s->tmp_output;
696

    
697
    for(i=0; i<2; i++) {
698
        /* de-interleave coefficients */
699
        for(k=0; k<128; k++) {
700
            x[k] = s->transform_coeffs[chindex][2*k+i];
701
        }
702

    
703
        /* run standard IMDCT */
704
        s->imdct_256.fft.imdct_calc(&s->imdct_256, o_ptr, x, s->tmp_imdct);
705

    
706
        /* reverse the post-rotation & reordering from standard IMDCT */
707
        for(k=0; k<32; k++) {
708
            z[i][32+k].re = -o_ptr[128+2*k];
709
            z[i][32+k].im = -o_ptr[2*k];
710
            z[i][31-k].re =  o_ptr[2*k+1];
711
            z[i][31-k].im =  o_ptr[128+2*k+1];
712
        }
713
    }
714

    
715
    /* apply AC-3 post-rotation & reordering */
716
    for(k=0; k<64; k++) {
717
        o_ptr[    2*k  ] = -z[0][   k].im;
718
        o_ptr[    2*k+1] =  z[0][63-k].re;
719
        o_ptr[128+2*k  ] = -z[0][   k].re;
720
        o_ptr[128+2*k+1] =  z[0][63-k].im;
721
        o_ptr[256+2*k  ] = -z[1][   k].re;
722
        o_ptr[256+2*k+1] =  z[1][63-k].im;
723
        o_ptr[384+2*k  ] =  z[1][   k].im;
724
        o_ptr[384+2*k+1] = -z[1][63-k].re;
725
    }
726
}
727

    
728
/**
729
 * Inverse MDCT Transform.
730
 * Convert frequency domain coefficients to time-domain audio samples.
731
 * reference: Section 7.9.4 Transformation Equations
732
 */
733
static inline void do_imdct(AC3DecodeContext *s)
734
{
735
    int ch;
736
    int channels;
737

    
738
    /* Don't perform the IMDCT on the LFE channel unless it's used in the output */
739
    channels = s->fbw_channels;
740
    if(s->output_mode & AC3_OUTPUT_LFEON)
741
        channels++;
742

    
743
    for (ch=1; ch<=channels; ch++) {
744
        if (s->block_switch[ch]) {
745
            do_imdct_256(s, ch);
746
        } else {
747
            s->imdct_512.fft.imdct_calc(&s->imdct_512, s->tmp_output,
748
                                        s->transform_coeffs[ch], s->tmp_imdct);
749
        }
750
        /* For the first half of the block, apply the window, add the delay
751
           from the previous block, and send to output */
752
        s->dsp.vector_fmul_add_add(s->output[ch-1], s->tmp_output,
753
                                     s->window, s->delay[ch-1], 0, 256, 1);
754
        /* For the second half of the block, apply the window and store the
755
           samples to delay, to be combined with the next block */
756
        s->dsp.vector_fmul_reverse(s->delay[ch-1], s->tmp_output+256,
757
                                   s->window, 256);
758
    }
759
}
760

    
761
/**
762
 * Downmix the output to mono or stereo.
763
 */
764
static void ac3_downmix(AC3DecodeContext *s)
765
{
766
    int i, j;
767
    float v0, v1, s0, s1;
768

    
769
    for(i=0; i<256; i++) {
770
        v0 = v1 = s0 = s1 = 0.0f;
771
        for(j=0; j<s->fbw_channels; j++) {
772
            v0 += s->output[j][i] * s->downmix_coeffs[j][0];
773
            v1 += s->output[j][i] * s->downmix_coeffs[j][1];
774
            s0 += s->downmix_coeffs[j][0];
775
            s1 += s->downmix_coeffs[j][1];
776
        }
777
        v0 /= s0;
778
        v1 /= s1;
779
        if(s->output_mode == AC3_CHMODE_MONO) {
780
            s->output[0][i] = (v0 + v1) * LEVEL_MINUS_3DB;
781
        } else if(s->output_mode == AC3_CHMODE_STEREO) {
782
            s->output[0][i] = v0;
783
            s->output[1][i] = v1;
784
        }
785
    }
786
}
787

    
788
/**
789
 * Parse an audio block from AC-3 bitstream.
790
 */
791
static int ac3_parse_audio_block(AC3DecodeContext *s, int blk)
792
{
793
    int fbw_channels = s->fbw_channels;
794
    int channel_mode = s->channel_mode;
795
    int i, bnd, seg, ch;
796
    GetBitContext *gbc = &s->gbc;
797
    uint8_t bit_alloc_stages[AC3_MAX_CHANNELS];
798

    
799
    memset(bit_alloc_stages, 0, AC3_MAX_CHANNELS);
800

    
801
    /* block switch flags */
802
    for (ch = 1; ch <= fbw_channels; ch++)
803
        s->block_switch[ch] = get_bits1(gbc);
804

    
805
    /* dithering flags */
806
    s->dither_all = 1;
807
    for (ch = 1; ch <= fbw_channels; ch++) {
808
        s->dither_flag[ch] = get_bits1(gbc);
809
        if(!s->dither_flag[ch])
810
            s->dither_all = 0;
811
    }
812

    
813
    /* dynamic range */
814
    i = !(s->channel_mode);
815
    do {
816
        if(get_bits1(gbc)) {
817
            s->dynamic_range[i] = ((dynamic_range_tab[get_bits(gbc, 8)]-1.0) *
818
                                  s->avctx->drc_scale)+1.0;
819
        } else if(blk == 0) {
820
            s->dynamic_range[i] = 1.0f;
821
        }
822
    } while(i--);
823

    
824
    /* coupling strategy */
825
    if (get_bits1(gbc)) {
826
        memset(bit_alloc_stages, 3, AC3_MAX_CHANNELS);
827
        s->cpl_in_use = get_bits1(gbc);
828
        if (s->cpl_in_use) {
829
            /* coupling in use */
830
            int cpl_begin_freq, cpl_end_freq;
831

    
832
            /* determine which channels are coupled */
833
            for (ch = 1; ch <= fbw_channels; ch++)
834
                s->channel_in_cpl[ch] = get_bits1(gbc);
835

    
836
            /* phase flags in use */
837
            if (channel_mode == AC3_CHMODE_STEREO)
838
                s->phase_flags_in_use = get_bits1(gbc);
839

    
840
            /* coupling frequency range and band structure */
841
            cpl_begin_freq = get_bits(gbc, 4);
842
            cpl_end_freq = get_bits(gbc, 4);
843
            if (3 + cpl_end_freq - cpl_begin_freq < 0) {
844
                av_log(s->avctx, AV_LOG_ERROR, "3+cplendf = %d < cplbegf = %d\n", 3+cpl_end_freq, cpl_begin_freq);
845
                return -1;
846
            }
847
            s->num_cpl_bands = s->num_cpl_subbands = 3 + cpl_end_freq - cpl_begin_freq;
848
            s->start_freq[CPL_CH] = cpl_begin_freq * 12 + 37;
849
            s->end_freq[CPL_CH] = cpl_end_freq * 12 + 73;
850
            for (bnd = 0; bnd < s->num_cpl_subbands - 1; bnd++) {
851
                if (get_bits1(gbc)) {
852
                    s->cpl_band_struct[bnd] = 1;
853
                    s->num_cpl_bands--;
854
                }
855
            }
856
            s->cpl_band_struct[s->num_cpl_subbands-1] = 0;
857
        } else {
858
            /* coupling not in use */
859
            for (ch = 1; ch <= fbw_channels; ch++)
860
                s->channel_in_cpl[ch] = 0;
861
        }
862
    }
863

    
864
    /* coupling coordinates */
865
    if (s->cpl_in_use) {
866
        int cpl_coords_exist = 0;
867

    
868
        for (ch = 1; ch <= fbw_channels; ch++) {
869
            if (s->channel_in_cpl[ch]) {
870
                if (get_bits1(gbc)) {
871
                    int master_cpl_coord, cpl_coord_exp, cpl_coord_mant;
872
                    cpl_coords_exist = 1;
873
                    master_cpl_coord = 3 * get_bits(gbc, 2);
874
                    for (bnd = 0; bnd < s->num_cpl_bands; bnd++) {
875
                        cpl_coord_exp = get_bits(gbc, 4);
876
                        cpl_coord_mant = get_bits(gbc, 4);
877
                        if (cpl_coord_exp == 15)
878
                            s->cpl_coords[ch][bnd] = cpl_coord_mant / 16.0f;
879
                        else
880
                            s->cpl_coords[ch][bnd] = (cpl_coord_mant + 16.0f) / 32.0f;
881
                        s->cpl_coords[ch][bnd] *= scale_factors[cpl_coord_exp + master_cpl_coord];
882
                    }
883
                }
884
            }
885
        }
886
        /* phase flags */
887
        if (channel_mode == AC3_CHMODE_STEREO && cpl_coords_exist) {
888
            for (bnd = 0; bnd < s->num_cpl_bands; bnd++) {
889
                s->phase_flags[bnd] = s->phase_flags_in_use? get_bits1(gbc) : 0;
890
            }
891
        }
892
    }
893

    
894
    /* stereo rematrixing strategy and band structure */
895
    if (channel_mode == AC3_CHMODE_STEREO) {
896
        if (get_bits1(gbc)) {
897
            s->num_rematrixing_bands = 4;
898
            if(s->cpl_in_use && s->start_freq[CPL_CH] <= 61)
899
                s->num_rematrixing_bands -= 1 + (s->start_freq[CPL_CH] == 37);
900
            for(bnd=0; bnd<s->num_rematrixing_bands; bnd++)
901
                s->rematrixing_flags[bnd] = get_bits1(gbc);
902
        }
903
    }
904

    
905
    /* exponent strategies for each channel */
906
    s->exp_strategy[CPL_CH] = EXP_REUSE;
907
    s->exp_strategy[s->lfe_ch] = EXP_REUSE;
908
    for (ch = !s->cpl_in_use; ch <= s->channels; ch++) {
909
        if(ch == s->lfe_ch)
910
            s->exp_strategy[ch] = get_bits(gbc, 1);
911
        else
912
            s->exp_strategy[ch] = get_bits(gbc, 2);
913
        if(s->exp_strategy[ch] != EXP_REUSE)
914
            bit_alloc_stages[ch] = 3;
915
    }
916

    
917
    /* channel bandwidth */
918
    for (ch = 1; ch <= fbw_channels; ch++) {
919
        s->start_freq[ch] = 0;
920
        if (s->exp_strategy[ch] != EXP_REUSE) {
921
            int prev = s->end_freq[ch];
922
            if (s->channel_in_cpl[ch])
923
                s->end_freq[ch] = s->start_freq[CPL_CH];
924
            else {
925
                int bandwidth_code = get_bits(gbc, 6);
926
                if (bandwidth_code > 60) {
927
                    av_log(s->avctx, AV_LOG_ERROR, "bandwidth code = %d > 60", bandwidth_code);
928
                    return -1;
929
                }
930
                s->end_freq[ch] = bandwidth_code * 3 + 73;
931
            }
932
            if(blk > 0 && s->end_freq[ch] != prev)
933
                memset(bit_alloc_stages, 3, AC3_MAX_CHANNELS);
934
        }
935
    }
936
    s->start_freq[s->lfe_ch] = 0;
937
    s->end_freq[s->lfe_ch] = 7;
938

    
939
    /* decode exponents for each channel */
940
    for (ch = !s->cpl_in_use; ch <= s->channels; ch++) {
941
        if (s->exp_strategy[ch] != EXP_REUSE) {
942
            int group_size, num_groups;
943
            group_size = 3 << (s->exp_strategy[ch] - 1);
944
            if(ch == CPL_CH)
945
                num_groups = (s->end_freq[ch] - s->start_freq[ch]) / group_size;
946
            else if(ch == s->lfe_ch)
947
                num_groups = 2;
948
            else
949
                num_groups = (s->end_freq[ch] + group_size - 4) / group_size;
950
            s->dexps[ch][0] = get_bits(gbc, 4) << !ch;
951
            decode_exponents(gbc, s->exp_strategy[ch], num_groups, s->dexps[ch][0],
952
                             &s->dexps[ch][s->start_freq[ch]+!!ch]);
953
            if(ch != CPL_CH && ch != s->lfe_ch)
954
                skip_bits(gbc, 2); /* skip gainrng */
955
        }
956
    }
957

    
958
    /* bit allocation information */
959
    if (get_bits1(gbc)) {
960
        s->bit_alloc_params.slow_decay = ff_ac3_slow_decay_tab[get_bits(gbc, 2)] >> s->bit_alloc_params.sr_shift;
961
        s->bit_alloc_params.fast_decay = ff_ac3_fast_decay_tab[get_bits(gbc, 2)] >> s->bit_alloc_params.sr_shift;
962
        s->bit_alloc_params.slow_gain  = ff_ac3_slow_gain_tab[get_bits(gbc, 2)];
963
        s->bit_alloc_params.db_per_bit = ff_ac3_db_per_bit_tab[get_bits(gbc, 2)];
964
        s->bit_alloc_params.floor  = ff_ac3_floor_tab[get_bits(gbc, 3)];
965
        for(ch=!s->cpl_in_use; ch<=s->channels; ch++) {
966
            bit_alloc_stages[ch] = FFMAX(bit_alloc_stages[ch], 2);
967
        }
968
    }
969

    
970
    /* signal-to-noise ratio offsets and fast gains (signal-to-mask ratios) */
971
    if (get_bits1(gbc)) {
972
        int csnr;
973
        csnr = (get_bits(gbc, 6) - 15) << 4;
974
        for (ch = !s->cpl_in_use; ch <= s->channels; ch++) { /* snr offset and fast gain */
975
            s->snr_offset[ch] = (csnr + get_bits(gbc, 4)) << 2;
976
            s->fast_gain[ch] = ff_ac3_fast_gain_tab[get_bits(gbc, 3)];
977
        }
978
        memset(bit_alloc_stages, 3, AC3_MAX_CHANNELS);
979
    }
980

    
981
    /* coupling leak information */
982
    if (s->cpl_in_use && get_bits1(gbc)) {
983
        s->bit_alloc_params.cpl_fast_leak = get_bits(gbc, 3);
984
        s->bit_alloc_params.cpl_slow_leak = get_bits(gbc, 3);
985
        bit_alloc_stages[CPL_CH] = FFMAX(bit_alloc_stages[CPL_CH], 2);
986
    }
987

    
988
    /* delta bit allocation information */
989
    if (get_bits1(gbc)) {
990
        /* delta bit allocation exists (strategy) */
991
        for (ch = !s->cpl_in_use; ch <= fbw_channels; ch++) {
992
            s->dba_mode[ch] = get_bits(gbc, 2);
993
            if (s->dba_mode[ch] == DBA_RESERVED) {
994
                av_log(s->avctx, AV_LOG_ERROR, "delta bit allocation strategy reserved\n");
995
                return -1;
996
            }
997
            bit_alloc_stages[ch] = FFMAX(bit_alloc_stages[ch], 2);
998
        }
999
        /* channel delta offset, len and bit allocation */
1000
        for (ch = !s->cpl_in_use; ch <= fbw_channels; ch++) {
1001
            if (s->dba_mode[ch] == DBA_NEW) {
1002
                s->dba_nsegs[ch] = get_bits(gbc, 3);
1003
                for (seg = 0; seg <= s->dba_nsegs[ch]; seg++) {
1004
                    s->dba_offsets[ch][seg] = get_bits(gbc, 5);
1005
                    s->dba_lengths[ch][seg] = get_bits(gbc, 4);
1006
                    s->dba_values[ch][seg] = get_bits(gbc, 3);
1007
                }
1008
            }
1009
        }
1010
    } else if(blk == 0) {
1011
        for(ch=0; ch<=s->channels; ch++) {
1012
            s->dba_mode[ch] = DBA_NONE;
1013
        }
1014
    }
1015

    
1016
    /* Bit allocation */
1017
    for(ch=!s->cpl_in_use; ch<=s->channels; ch++) {
1018
        if(bit_alloc_stages[ch] > 2) {
1019
            /* Exponent mapping into PSD and PSD integration */
1020
            ff_ac3_bit_alloc_calc_psd(s->dexps[ch],
1021
                                      s->start_freq[ch], s->end_freq[ch],
1022
                                      s->psd[ch], s->band_psd[ch]);
1023
        }
1024
        if(bit_alloc_stages[ch] > 1) {
1025
            /* Compute excitation function, Compute masking curve, and
1026
               Apply delta bit allocation */
1027
            ff_ac3_bit_alloc_calc_mask(&s->bit_alloc_params, s->band_psd[ch],
1028
                                       s->start_freq[ch], s->end_freq[ch],
1029
                                       s->fast_gain[ch], (ch == s->lfe_ch),
1030
                                       s->dba_mode[ch], s->dba_nsegs[ch],
1031
                                       s->dba_offsets[ch], s->dba_lengths[ch],
1032
                                       s->dba_values[ch], s->mask[ch]);
1033
        }
1034
        if(bit_alloc_stages[ch] > 0) {
1035
            /* Compute bit allocation */
1036
            ff_ac3_bit_alloc_calc_bap(s->mask[ch], s->psd[ch],
1037
                                      s->start_freq[ch], s->end_freq[ch],
1038
                                      s->snr_offset[ch],
1039
                                      s->bit_alloc_params.floor,
1040
                                      s->bap[ch]);
1041
        }
1042
    }
1043

    
1044
    /* unused dummy data */
1045
    if (get_bits1(gbc)) {
1046
        int skipl = get_bits(gbc, 9);
1047
        while(skipl--)
1048
            skip_bits(gbc, 8);
1049
    }
1050

    
1051
    /* unpack the transform coefficients
1052
       this also uncouples channels if coupling is in use. */
1053
    if (get_transform_coeffs(s)) {
1054
        av_log(s->avctx, AV_LOG_ERROR, "Error in routine get_transform_coeffs\n");
1055
        return -1;
1056
    }
1057

    
1058
    /* recover coefficients if rematrixing is in use */
1059
    if(s->channel_mode == AC3_CHMODE_STEREO)
1060
        do_rematrixing(s);
1061

    
1062
    /* apply scaling to coefficients (headroom, dynrng) */
1063
    for(ch=1; ch<=s->channels; ch++) {
1064
        float gain = 2.0f * s->mul_bias;
1065
        if(s->channel_mode == AC3_CHMODE_DUALMONO) {
1066
            gain *= s->dynamic_range[ch-1];
1067
        } else {
1068
            gain *= s->dynamic_range[0];
1069
        }
1070
        for(i=0; i<s->end_freq[ch]; i++) {
1071
            s->transform_coeffs[ch][i] *= gain;
1072
        }
1073
    }
1074

    
1075
    do_imdct(s);
1076

    
1077
    /* downmix output if needed */
1078
    if(s->channels != s->out_channels && !((s->output_mode & AC3_OUTPUT_LFEON) &&
1079
            s->fbw_channels == s->out_channels)) {
1080
        ac3_downmix(s);
1081
    }
1082

    
1083
    /* convert float to 16-bit integer */
1084
    for(ch=0; ch<s->out_channels; ch++) {
1085
        for(i=0; i<256; i++) {
1086
            s->output[ch][i] += s->add_bias;
1087
        }
1088
        s->dsp.float_to_int16(s->int_output[ch], s->output[ch], 256);
1089
    }
1090

    
1091
    return 0;
1092
}
1093

    
1094
/**
1095
 * Decode a single AC-3 frame.
1096
 */
1097
static int ac3_decode_frame(AVCodecContext * avctx, void *data, int *data_size, uint8_t *buf, int buf_size)
1098
{
1099
    AC3DecodeContext *s = avctx->priv_data;
1100
    int16_t *out_samples = (int16_t *)data;
1101
    int i, blk, ch, err;
1102

    
1103
    /* initialize the GetBitContext with the start of valid AC-3 Frame */
1104
    init_get_bits(&s->gbc, buf, buf_size * 8);
1105

    
1106
    /* parse the syncinfo */
1107
    err = ac3_parse_header(s);
1108
    if(err) {
1109
        switch(err) {
1110
            case AC3_PARSE_ERROR_SYNC:
1111
                av_log(avctx, AV_LOG_ERROR, "frame sync error\n");
1112
                break;
1113
            case AC3_PARSE_ERROR_BSID:
1114
                av_log(avctx, AV_LOG_ERROR, "invalid bitstream id\n");
1115
                break;
1116
            case AC3_PARSE_ERROR_SAMPLE_RATE:
1117
                av_log(avctx, AV_LOG_ERROR, "invalid sample rate\n");
1118
                break;
1119
            case AC3_PARSE_ERROR_FRAME_SIZE:
1120
                av_log(avctx, AV_LOG_ERROR, "invalid frame size\n");
1121
                break;
1122
            default:
1123
                av_log(avctx, AV_LOG_ERROR, "invalid header\n");
1124
                break;
1125
        }
1126
        return -1;
1127
    }
1128

    
1129
    /* check that reported frame size fits in input buffer */
1130
    if(s->frame_size > buf_size) {
1131
        av_log(avctx, AV_LOG_ERROR, "incomplete frame\n");
1132
        return -1;
1133
    }
1134

    
1135
    /* check for crc mismatch */
1136
    if(avctx->error_resilience > 0) {
1137
        if(av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0, &buf[2], s->frame_size-2)) {
1138
            av_log(avctx, AV_LOG_ERROR, "frame CRC mismatch\n");
1139
            return -1;
1140
        }
1141
        /* TODO: error concealment */
1142
    }
1143

    
1144
    avctx->sample_rate = s->sample_rate;
1145
    avctx->bit_rate = s->bit_rate;
1146

    
1147
    /* channel config */
1148
    s->out_channels = s->channels;
1149
    if (avctx->request_channels > 0 && avctx->request_channels <= 2 &&
1150
            avctx->request_channels < s->channels) {
1151
        s->out_channels = avctx->request_channels;
1152
        s->output_mode  = avctx->request_channels == 1 ? AC3_CHMODE_MONO : AC3_CHMODE_STEREO;
1153
    }
1154
    avctx->channels = s->out_channels;
1155

    
1156
    /* set downmixing coefficients if needed */
1157
    if(s->channels != s->out_channels && !((s->output_mode & AC3_OUTPUT_LFEON) &&
1158
            s->fbw_channels == s->out_channels)) {
1159
        set_downmix_coeffs(s);
1160
    }
1161

    
1162
    /* parse the audio blocks */
1163
    for (blk = 0; blk < NB_BLOCKS; blk++) {
1164
        if (ac3_parse_audio_block(s, blk)) {
1165
            av_log(avctx, AV_LOG_ERROR, "error parsing the audio block\n");
1166
            *data_size = 0;
1167
            return s->frame_size;
1168
        }
1169
        for (i = 0; i < 256; i++)
1170
            for (ch = 0; ch < s->out_channels; ch++)
1171
                *(out_samples++) = s->int_output[ch][i];
1172
    }
1173
    *data_size = NB_BLOCKS * 256 * avctx->channels * sizeof (int16_t);
1174
    return s->frame_size;
1175
}
1176

    
1177
/**
1178
 * Uninitialize the AC-3 decoder.
1179
 */
1180
static int ac3_decode_end(AVCodecContext *avctx)
1181
{
1182
    AC3DecodeContext *s = avctx->priv_data;
1183
    ff_mdct_end(&s->imdct_512);
1184
    ff_mdct_end(&s->imdct_256);
1185

    
1186
    return 0;
1187
}
1188

    
1189
AVCodec ac3_decoder = {
1190
    .name = "ac3",
1191
    .type = CODEC_TYPE_AUDIO,
1192
    .id = CODEC_ID_AC3,
1193
    .priv_data_size = sizeof (AC3DecodeContext),
1194
    .init = ac3_decode_init,
1195
    .close = ac3_decode_end,
1196
    .decode = ac3_decode_frame,
1197
};