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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).
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 * Copyright (c) 2007 Justin Ruggles
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 *
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 * 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>
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 * Copyright (C) 1999-2000 Aaron Holtzman <aholtzma@ess.engr.uvic.ca>
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 *
13
 * This file is part of FFmpeg.
14
 *
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 * FFmpeg is free software; you can redistribute it and/or
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 * modify it under the terms of the GNU General Public
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 * License as published by the Free Software Foundation; either
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 * version 2 of the License, or (at your option) any later version.
19
 *
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 * 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
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 * General Public License for more details.
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 *
25
 * You should have received a copy of the GNU General Public
26
 * License along with FFmpeg; if not, write to the Free Software
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 * 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"
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#include "ac3_parser.h"
37
#include "bitstream.h"
38
#include "dsputil.h"
39
#include "random.h"
40

    
41
/**
42
 * Table of bin locations for rematrixing bands
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 * reference: Section 7.5.2 Rematrixing : Frequency Band Definitions
44
 */
45
static const uint8_t rematrix_band_tbl[5] = { 13, 25, 37, 61, 253 };
46

    
47
/* table for exponent to scale_factor mapping
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 * scale_factor[i] = 2 ^ -(i + 15)
49
 */
50
static float scale_factors[25];
51

    
52
/** table for grouping exponents */
53
static uint8_t exp_ungroup_tbl[128][3];
54

    
55

    
56
/** tables for ungrouping mantissas */
57
static float b1_mantissas[32][3];
58
static float b2_mantissas[128][3];
59
static float b3_mantissas[8];
60
static float b4_mantissas[128][2];
61
static float b5_mantissas[16];
62

    
63
/**
64
 * Quantization table: levels for symmetric. bits for asymmetric.
65
 * reference: Table 7.18 Mapping of bap to Quantizer
66
 */
67
static const uint8_t qntztab[16] = {
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    0, 3, 5, 7, 11, 15,
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    5, 6, 7, 8, 9, 10, 11, 12, 14, 16
70
};
71

    
72
/** dynamic range table. converts codes to scale factors. */
73
static float dynrng_tbl[256];
74

    
75
/* Adjustmens in dB gain */
76
#define LEVEL_MINUS_3DB         0.7071067811865476
77
#define LEVEL_MINUS_4POINT5DB   0.5946035575013605
78
#define LEVEL_MINUS_6DB         0.5000000000000000
79
#define LEVEL_PLUS_3DB          1.4142135623730951
80
#define LEVEL_PLUS_6DB          2.0000000000000000
81
#define LEVEL_ZERO              0.0000000000000000
82

    
83
static const float clevs[4] = { LEVEL_MINUS_3DB, LEVEL_MINUS_4POINT5DB,
84
    LEVEL_MINUS_6DB, LEVEL_MINUS_4POINT5DB };
85

    
86
static const float slevs[4] = { LEVEL_MINUS_3DB, LEVEL_MINUS_6DB, LEVEL_ZERO, LEVEL_MINUS_6DB };
87

    
88
#define AC3_OUTPUT_LFEON  8
89

    
90
typedef struct {
91
    int acmod;
92
    int cmixlev;
93
    int surmixlev;
94
    int dsurmod;
95

    
96
    int blksw[AC3_MAX_CHANNELS];
97
    int dithflag[AC3_MAX_CHANNELS];
98
    int dither_all;
99
    int cplinu;
100
    int chincpl[AC3_MAX_CHANNELS];
101
    int phsflginu;
102
    int cplbndstrc[18];
103
    int rematstr;
104
    int nrematbnd;
105
    int rematflg[AC3_MAX_CHANNELS];
106
    int cplexpstr;
107
    int lfeexpstr;
108
    int chexpstr[5];
109
    int cplsnroffst;
110
    int cplfgain;
111
    int snroffst[5];
112
    int fgain[5];
113
    int lfesnroffst;
114
    int lfefgain;
115
    int cpldeltbae;
116
    int deltbae[5];
117
    int cpldeltnseg;
118
    uint8_t  cpldeltoffst[8];
119
    uint8_t  cpldeltlen[8];
120
    uint8_t  cpldeltba[8];
121
    int deltnseg[5];
122
    uint8_t  deltoffst[5][8];
123
    uint8_t  deltlen[5][8];
124
    uint8_t  deltba[5][8];
125

    
126
    /* Derived Attributes. */
127
    int      sampling_rate;
128
    int      bit_rate;
129
    int      frame_size;
130

    
131
    int      nchans;            //number of total channels
132
    int      nfchans;           //number of full-bandwidth channels
133
    int      lfeon;             //lfe channel in use
134
    int      output_mode;       ///< output channel configuration
135
    int      out_channels;      ///< number of output channels
136

    
137
    float    dynrng;            //dynamic range gain
138
    float    dynrng2;           //dynamic range gain for 1+1 mode
139
    float    cplco[5][18];      //coupling coordinates
140
    int      ncplbnd;           //number of coupling bands
141
    int      ncplsubnd;         //number of coupling sub bands
142
    int      cplstrtmant;       //coupling start mantissa
143
    int      cplendmant;        //coupling end mantissa
144
    int      endmant[5];        //channel end mantissas
145
    AC3BitAllocParameters bit_alloc_params; ///< bit allocation parameters
146

    
147
    int8_t   dcplexps[256];     //decoded coupling exponents
148
    int8_t   dexps[5][256];     //decoded fbw channel exponents
149
    int8_t   dlfeexps[256];     //decoded lfe channel exponents
150
    uint8_t  cplbap[256];       //coupling bit allocation pointers
151
    uint8_t  bap[5][256];       //fbw channel bit allocation pointers
152
    uint8_t  lfebap[256];       //lfe channel bit allocation pointers
153

    
154
    float transform_coeffs_cpl[256];
155
    DECLARE_ALIGNED_16(float, transform_coeffs[AC3_MAX_CHANNELS][256]);  //transform coefficients
156

    
157
    /* For IMDCT. */
158
    MDCTContext imdct_512;  //for 512 sample imdct transform
159
    MDCTContext imdct_256;  //for 256 sample imdct transform
160
    DSPContext  dsp;        //for optimization
161

    
162
    DECLARE_ALIGNED_16(float, output[AC3_MAX_CHANNELS][256]);   //output after imdct transform and windowing
163
    DECLARE_ALIGNED_16(float, delay[AC3_MAX_CHANNELS][256]);    //delay - added to the next block
164
    DECLARE_ALIGNED_16(float, tmp_imdct[256]);                  //temporary storage for imdct transform
165
    DECLARE_ALIGNED_16(float, tmp_output[512]);                 //temporary storage for output before windowing
166
    DECLARE_ALIGNED_16(float, window[256]);                     //window coefficients
167

    
168
    /* Miscellaneous. */
169
    GetBitContext gb;
170
    AVRandomState dith_state;   //for dither generation
171
} AC3DecodeContext;
172

    
173
/*********** BEGIN INIT HELPER FUNCTIONS ***********/
174
/**
175
 * Generate a Kaiser-Bessel Derived Window.
176
 */
177
static void ac3_window_init(float *window)
178
{
179
   int i, j;
180
   double sum = 0.0, bessel, tmp;
181
   double local_window[256];
182
   double alpha2 = (5.0 * M_PI / 256.0) * (5.0 * M_PI / 256.0);
183

    
184
   for (i = 0; i < 256; i++) {
185
       tmp = i * (256 - i) * alpha2;
186
       bessel = 1.0;
187
       for (j = 100; j > 0; j--) /* defaul to 100 iterations */
188
           bessel = bessel * tmp / (j * j) + 1;
189
       sum += bessel;
190
       local_window[i] = sum;
191
   }
192

    
193
   sum++;
194
   for (i = 0; i < 256; i++)
195
       window[i] = sqrt(local_window[i] / sum);
196
}
197

    
198
static inline float
199
symmetric_dequant(int code, int levels)
200
{
201
    return (code - (levels >> 1)) * (2.0f / levels);
202
}
203

    
204
/*
205
 * Initialize tables at runtime.
206
 */
207
static void ac3_tables_init(void)
208
{
209
    int i;
210

    
211
    /* generate grouped mantissa tables
212
       reference: Section 7.3.5 Ungrouping of Mantissas */
213
    for(i=0; i<32; i++) {
214
        /* bap=1 mantissas */
215
        b1_mantissas[i][0] = symmetric_dequant( i / 9     , 3);
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        b1_mantissas[i][1] = symmetric_dequant((i % 9) / 3, 3);
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        b1_mantissas[i][2] = symmetric_dequant((i % 9) % 3, 3);
218
    }
219
    for(i=0; i<128; i++) {
220
        /* bap=2 mantissas */
221
        b2_mantissas[i][0] = symmetric_dequant( i / 25     , 5);
222
        b2_mantissas[i][1] = symmetric_dequant((i % 25) / 5, 5);
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        b2_mantissas[i][2] = symmetric_dequant((i % 25) % 5, 5);
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225
        /* bap=4 mantissas */
226
        b4_mantissas[i][0] = symmetric_dequant(i / 11, 11);
227
        b4_mantissas[i][1] = symmetric_dequant(i % 11, 11);
228
    }
229
    /* generate ungrouped mantissa tables
230
       reference: Tables 7.21 and 7.23 */
231
    for(i=0; i<7; i++) {
232
        /* bap=3 mantissas */
233
        b3_mantissas[i] = symmetric_dequant(i, 7);
234
    }
235
    for(i=0; i<15; i++) {
236
        /* bap=5 mantissas */
237
        b5_mantissas[i] = symmetric_dequant(i, 15);
238
    }
239

    
240
    /* generate dynamic range table
241
       reference: Section 7.7.1 Dynamic Range Control */
242
    for(i=0; i<256; i++) {
243
        int v = (i >> 5) - ((i >> 7) << 3) - 5;
244
        dynrng_tbl[i] = powf(2.0f, v) * ((i & 0x1F) | 0x20);
245
    }
246

    
247
    //generate scale factors
248
    for (i = 0; i < 25; i++)
249
        scale_factors[i] = pow(2.0, -i);
250

    
251
    /* generate exponent tables
252
       reference: Section 7.1.3 Exponent Decoding */
253
    for(i=0; i<128; i++) {
254
        exp_ungroup_tbl[i][0] =  i / 25;
255
        exp_ungroup_tbl[i][1] = (i % 25) / 5;
256
        exp_ungroup_tbl[i][2] = (i % 25) % 5;
257
    }
258
}
259

    
260

    
261
static int ac3_decode_init(AVCodecContext *avctx)
262
{
263
    AC3DecodeContext *ctx = avctx->priv_data;
264

    
265
    ac3_common_init();
266
    ac3_tables_init();
267
    ff_mdct_init(&ctx->imdct_256, 8, 1);
268
    ff_mdct_init(&ctx->imdct_512, 9, 1);
269
    ac3_window_init(ctx->window);
270
    dsputil_init(&ctx->dsp, avctx);
271
    av_init_random(0, &ctx->dith_state);
272

    
273
    return 0;
274
}
275
/*********** END INIT FUNCTIONS ***********/
276

    
277
/**
278
 * Parses the 'sync info' and 'bit stream info' from the AC-3 bitstream.
279
 * GetBitContext within AC3DecodeContext must point to
280
 * start of the synchronized ac3 bitstream.
281
 */
282
static int ac3_parse_header(AC3DecodeContext *ctx)
283
{
284
    AC3HeaderInfo hdr;
285
    GetBitContext *gb = &ctx->gb;
286
    int err, i;
287

    
288
    err = ff_ac3_parse_header(gb->buffer, &hdr);
289
    if(err)
290
        return err;
291

    
292
    /* get decoding parameters from header info */
293
    ctx->bit_alloc_params.fscod       = hdr.fscod;
294
    ctx->acmod                        = hdr.acmod;
295
    ctx->cmixlev                      = hdr.cmixlev;
296
    ctx->surmixlev                    = hdr.surmixlev;
297
    ctx->dsurmod                      = hdr.dsurmod;
298
    ctx->lfeon                        = hdr.lfeon;
299
    ctx->bit_alloc_params.halfratecod = hdr.halfratecod;
300
    ctx->sampling_rate                = hdr.sample_rate;
301
    ctx->bit_rate                     = hdr.bit_rate;
302
    ctx->nchans                       = hdr.channels;
303
    ctx->nfchans                      = ctx->nchans - ctx->lfeon;
304
    ctx->frame_size                   = hdr.frame_size;
305

    
306
    /* set default output to all source channels */
307
    ctx->out_channels = ctx->nchans;
308
    ctx->output_mode = ctx->acmod;
309
    if(ctx->lfeon)
310
        ctx->output_mode |= AC3_OUTPUT_LFEON;
311

    
312
    /* skip over portion of header which has already been read */
313
    skip_bits(gb, 16); //skip the sync_word, sync_info->sync_word = get_bits(gb, 16);
314
    skip_bits(gb, 16); // skip crc1
315
    skip_bits(gb, 8);  // skip fscod and frmsizecod
316
    skip_bits(gb, 11); // skip bsid, bsmod, and acmod
317
    if(ctx->acmod == AC3_ACMOD_STEREO) {
318
        skip_bits(gb, 2); // skip dsurmod
319
    } else {
320
        if((ctx->acmod & 1) && ctx->acmod != AC3_ACMOD_MONO)
321
            skip_bits(gb, 2); // skip cmixlev
322
        if(ctx->acmod & 4)
323
            skip_bits(gb, 2); // skip surmixlev
324
    }
325
    skip_bits1(gb); // skip lfeon
326

    
327
    /* read the rest of the bsi. read twice for dual mono mode. */
328
    i = !(ctx->acmod);
329
    do {
330
        skip_bits(gb, 5); //skip dialog normalization
331
        if (get_bits1(gb))
332
            skip_bits(gb, 8); //skip compression
333
        if (get_bits1(gb))
334
            skip_bits(gb, 8); //skip language code
335
        if (get_bits1(gb))
336
            skip_bits(gb, 7); //skip audio production information
337
    } while (i--);
338

    
339
    skip_bits(gb, 2); //skip copyright bit and original bitstream bit
340

    
341
    /* FIXME: read & use the xbsi1 downmix levels */
342
    if (get_bits1(gb))
343
        skip_bits(gb, 14); //skip timecode1
344
    if (get_bits1(gb))
345
        skip_bits(gb, 14); //skip timecode2
346

    
347
    if (get_bits1(gb)) {
348
        i = get_bits(gb, 6); //additional bsi length
349
        do {
350
            skip_bits(gb, 8);
351
        } while(i--);
352
    }
353

    
354
    return 0;
355
}
356

    
357
/**
358
 * Decodes the grouped exponents.
359
 * This function decodes the coded exponents according to exponent strategy
360
 * and stores them in the decoded exponents buffer.
361
 *
362
 * @param[in]  gb      GetBitContext which points to start of coded exponents
363
 * @param[in]  expstr  Exponent coding strategy
364
 * @param[in]  ngrps   Number of grouped exponents
365
 * @param[in]  absexp  Absolute exponent or DC exponent
366
 * @param[out] dexps   Decoded exponents are stored in dexps
367
 */
368
static void decode_exponents(GetBitContext *gb, int expstr, int ngrps,
369
                             uint8_t absexp, int8_t *dexps)
370
{
371
    int i, j, grp, grpsize;
372
    int dexp[256];
373
    int expacc, prevexp;
374

    
375
    /* unpack groups */
376
    grpsize = expstr + (expstr == EXP_D45);
377
    for(grp=0,i=0; grp<ngrps; grp++) {
378
        expacc = get_bits(gb, 7);
379
        dexp[i++] = exp_ungroup_tbl[expacc][0];
380
        dexp[i++] = exp_ungroup_tbl[expacc][1];
381
        dexp[i++] = exp_ungroup_tbl[expacc][2];
382
    }
383

    
384
    /* convert to absolute exps and expand groups */
385
    prevexp = absexp;
386
    for(i=0; i<ngrps*3; i++) {
387
        prevexp = av_clip(prevexp + dexp[i]-2, 0, 24);
388
        for(j=0; j<grpsize; j++) {
389
            dexps[(i*grpsize)+j] = prevexp;
390
        }
391
    }
392
}
393

    
394
/**
395
 * Generates transform coefficients for each coupled channel in the coupling
396
 * range using the coupling coefficients and coupling coordinates.
397
 * reference: Section 7.4.3 Coupling Coordinate Format
398
 */
399
static void uncouple_channels(AC3DecodeContext *ctx)
400
{
401
    int i, j, ch, bnd, subbnd;
402

    
403
    subbnd = -1;
404
    i = ctx->cplstrtmant;
405
    for(bnd=0; bnd<ctx->ncplbnd; bnd++) {
406
        do {
407
            subbnd++;
408
            for(j=0; j<12; j++) {
409
                for(ch=1; ch<=ctx->nfchans; ch++) {
410
                    if(ctx->chincpl[ch-1])
411
                        ctx->transform_coeffs[ch][i] = ctx->transform_coeffs_cpl[i] * ctx->cplco[ch-1][bnd] * 8.0f;
412
                }
413
                i++;
414
            }
415
        } while(ctx->cplbndstrc[subbnd]);
416
    }
417
}
418

    
419
typedef struct { /* grouped mantissas for 3-level 5-leve and 11-level quantization */
420
    float b1_mant[3];
421
    float b2_mant[3];
422
    float b4_mant[2];
423
    int b1ptr;
424
    int b2ptr;
425
    int b4ptr;
426
} mant_groups;
427

    
428
/* Get the transform coefficients for particular channel */
429
static int get_transform_coeffs_ch(AC3DecodeContext *ctx, int ch_index, mant_groups *m)
430
{
431
    GetBitContext *gb = &ctx->gb;
432
    int i, gcode, tbap, start, end;
433
    uint8_t *exps;
434
    uint8_t *bap;
435
    float *coeffs;
436

    
437
    if (ch_index >= 0) { /* fbw channels */
438
        exps = ctx->dexps[ch_index];
439
        bap = ctx->bap[ch_index];
440
        coeffs = ctx->transform_coeffs[ch_index + 1];
441
        start = 0;
442
        end = ctx->endmant[ch_index];
443
    } else if (ch_index == -1) {
444
        exps = ctx->dlfeexps;
445
        bap = ctx->lfebap;
446
        coeffs = ctx->transform_coeffs[0];
447
        start = 0;
448
        end = 7;
449
    } else {
450
        exps = ctx->dcplexps;
451
        bap = ctx->cplbap;
452
        coeffs = ctx->transform_coeffs_cpl;
453
        start = ctx->cplstrtmant;
454
        end = ctx->cplendmant;
455
    }
456

    
457

    
458
    for (i = start; i < end; i++) {
459
        tbap = bap[i];
460
        switch (tbap) {
461
            case 0:
462
                coeffs[i] = ((av_random(&ctx->dith_state) & 0xFFFF) * LEVEL_MINUS_3DB) / 32768.0f;
463
                break;
464

    
465
            case 1:
466
                if(m->b1ptr > 2) {
467
                    gcode = get_bits(gb, 5);
468
                    m->b1_mant[0] = b1_mantissas[gcode][0];
469
                    m->b1_mant[1] = b1_mantissas[gcode][1];
470
                    m->b1_mant[2] = b1_mantissas[gcode][2];
471
                    m->b1ptr = 0;
472
                }
473
                coeffs[i] = m->b1_mant[m->b1ptr++];
474
                break;
475

    
476
            case 2:
477
                if(m->b2ptr > 2) {
478
                    gcode = get_bits(gb, 7);
479
                    m->b2_mant[0] = b2_mantissas[gcode][0];
480
                    m->b2_mant[1] = b2_mantissas[gcode][1];
481
                    m->b2_mant[2] = b2_mantissas[gcode][2];
482
                    m->b2ptr = 0;
483
                }
484
                coeffs[i] = m->b2_mant[m->b2ptr++];
485
                break;
486

    
487
            case 3:
488
                coeffs[i] = b3_mantissas[get_bits(gb, 3)];
489
                break;
490

    
491
            case 4:
492
                if(m->b4ptr > 1) {
493
                    gcode = get_bits(gb, 7);
494
                    m->b4_mant[0] = b4_mantissas[gcode][0];
495
                    m->b4_mant[1] = b4_mantissas[gcode][1];
496
                    m->b4ptr = 0;
497
                }
498
                coeffs[i] = m->b4_mant[m->b4ptr++];
499
                break;
500

    
501
            case 5:
502
                coeffs[i] = b5_mantissas[get_bits(gb, 4)];
503
                break;
504

    
505
            default:
506
                coeffs[i] = get_sbits(gb, qntztab[tbap]) * scale_factors[qntztab[tbap]-1];
507
                break;
508
        }
509
        coeffs[i] *= scale_factors[exps[i]];
510
    }
511

    
512
    return 0;
513
}
514

    
515
/**
516
 * Removes random dithering from coefficients with zero-bit mantissas
517
 * reference: Section 7.3.4 Dither for Zero Bit Mantissas (bap=0)
518
 */
519
static void remove_dithering(AC3DecodeContext *ctx) {
520
    int ch, i;
521
    int end=0;
522
    float *coeffs;
523
    uint8_t *bap;
524

    
525
    for(ch=1; ch<=ctx->nfchans; ch++) {
526
        if(!ctx->dithflag[ch-1]) {
527
            coeffs = ctx->transform_coeffs[ch];
528
            bap = ctx->bap[ch-1];
529
            if(ctx->chincpl[ch-1])
530
                end = ctx->cplstrtmant;
531
            else
532
                end = ctx->endmant[ch-1];
533
            for(i=0; i<end; i++) {
534
                if(bap[i] == 0)
535
                    coeffs[i] = 0.0f;
536
            }
537
            if(ctx->chincpl[ch-1]) {
538
                bap = ctx->cplbap;
539
                for(; i<ctx->cplendmant; i++) {
540
                    if(bap[i] == 0)
541
                        coeffs[i] = 0.0f;
542
                }
543
            }
544
        }
545
    }
546
}
547

    
548
/* Get the transform coefficients.
549
 * This function extracts the tranform coefficients form the ac3 bitstream.
550
 * This function is called after bit allocation is performed.
551
 */
552
static int get_transform_coeffs(AC3DecodeContext * ctx)
553
{
554
    int i, end;
555
    int got_cplchan = 0;
556
    mant_groups m;
557

    
558
    m.b1ptr = m.b2ptr = m.b4ptr = 3;
559

    
560
    for (i = 0; i < ctx->nfchans; i++) {
561
        /* transform coefficients for individual channel */
562
        if (get_transform_coeffs_ch(ctx, i, &m))
563
            return -1;
564
        /* tranform coefficients for coupling channels */
565
        if (ctx->chincpl[i])  {
566
            if (!got_cplchan) {
567
                if (get_transform_coeffs_ch(ctx, -2, &m)) {
568
                    av_log(NULL, AV_LOG_ERROR, "error in decoupling channels\n");
569
                    return -1;
570
                }
571
                uncouple_channels(ctx);
572
                got_cplchan = 1;
573
            }
574
            end = ctx->cplendmant;
575
        } else {
576
            end = ctx->endmant[i];
577
        }
578
        do
579
            ctx->transform_coeffs[i + 1][end] = 0;
580
        while(++end < 256);
581
    }
582
    if (ctx->lfeon) {
583
        if (get_transform_coeffs_ch(ctx, -1, &m))
584
                return -1;
585
        for (i = 7; i < 256; i++) {
586
            ctx->transform_coeffs[0][i] = 0;
587
        }
588
    }
589

    
590
    /* if any channel doesn't use dithering, zero appropriate coefficients */
591
    if(!ctx->dither_all)
592
        remove_dithering(ctx);
593

    
594
    return 0;
595
}
596

    
597
/**
598
 * Performs stereo rematrixing.
599
 * reference: Section 7.5.4 Rematrixing : Decoding Technique
600
 */
601
static void do_rematrixing(AC3DecodeContext *ctx)
602
{
603
    int bnd, i;
604
    int end, bndend;
605
    float tmp0, tmp1;
606

    
607
    end = FFMIN(ctx->endmant[0], ctx->endmant[1]);
608

    
609
    for(bnd=0; bnd<ctx->nrematbnd; bnd++) {
610
        if(ctx->rematflg[bnd]) {
611
            bndend = FFMIN(end, rematrix_band_tbl[bnd+1]);
612
            for(i=rematrix_band_tbl[bnd]; i<bndend; i++) {
613
                tmp0 = ctx->transform_coeffs[1][i];
614
                tmp1 = ctx->transform_coeffs[2][i];
615
                ctx->transform_coeffs[1][i] = tmp0 + tmp1;
616
                ctx->transform_coeffs[2][i] = tmp0 - tmp1;
617
            }
618
        }
619
    }
620
}
621

    
622
/* This function performs the imdct on 256 sample transform
623
 * coefficients.
624
 */
625
static void do_imdct_256(AC3DecodeContext *ctx, int chindex)
626
{
627
    int i, k;
628
    DECLARE_ALIGNED_16(float, x[128]);
629
    FFTComplex z[2][64];
630
    float *o_ptr = ctx->tmp_output;
631

    
632
    for(i=0; i<2; i++) {
633
        /* de-interleave coefficients */
634
        for(k=0; k<128; k++) {
635
            x[k] = ctx->transform_coeffs[chindex][2*k+i];
636
        }
637

    
638
        /* run standard IMDCT */
639
        ctx->imdct_256.fft.imdct_calc(&ctx->imdct_256, o_ptr, x, ctx->tmp_imdct);
640

    
641
        /* reverse the post-rotation & reordering from standard IMDCT */
642
        for(k=0; k<32; k++) {
643
            z[i][32+k].re = -o_ptr[128+2*k];
644
            z[i][32+k].im = -o_ptr[2*k];
645
            z[i][31-k].re =  o_ptr[2*k+1];
646
            z[i][31-k].im =  o_ptr[128+2*k+1];
647
        }
648
    }
649

    
650
    /* apply AC-3 post-rotation & reordering */
651
    for(k=0; k<64; k++) {
652
        o_ptr[    2*k  ] = -z[0][   k].im;
653
        o_ptr[    2*k+1] =  z[0][63-k].re;
654
        o_ptr[128+2*k  ] = -z[0][   k].re;
655
        o_ptr[128+2*k+1] =  z[0][63-k].im;
656
        o_ptr[256+2*k  ] = -z[1][   k].re;
657
        o_ptr[256+2*k+1] =  z[1][63-k].im;
658
        o_ptr[384+2*k  ] =  z[1][   k].im;
659
        o_ptr[384+2*k+1] = -z[1][63-k].re;
660
    }
661
}
662

    
663
/* IMDCT Transform. */
664
static inline void do_imdct(AC3DecodeContext *ctx)
665
{
666
    int ch;
667

    
668
    if (ctx->output_mode & AC3_OUTPUT_LFEON) {
669
        ctx->imdct_512.fft.imdct_calc(&ctx->imdct_512, ctx->tmp_output,
670
                                      ctx->transform_coeffs[0], ctx->tmp_imdct);
671
        ctx->dsp.vector_fmul_add_add(ctx->output[0], ctx->tmp_output,
672
                                     ctx->window, ctx->delay[0], 384, 256, 1);
673
        ctx->dsp.vector_fmul_reverse(ctx->delay[0], ctx->tmp_output+256,
674
                                     ctx->window, 256);
675
    }
676
    for (ch=1; ch<=ctx->nfchans; ch++) {
677
        if (ctx->blksw[ch-1]) {
678
            do_imdct_256(ctx, ch);
679
        } else {
680
            ctx->imdct_512.fft.imdct_calc(&ctx->imdct_512, ctx->tmp_output,
681
                                          ctx->transform_coeffs[ch],
682
                                          ctx->tmp_imdct);
683
        }
684
        ctx->dsp.vector_fmul_add_add(ctx->output[ch], ctx->tmp_output,
685
                                     ctx->window, ctx->delay[ch], 384, 256, 1);
686
        ctx->dsp.vector_fmul_reverse(ctx->delay[ch], ctx->tmp_output+256,
687
                                     ctx->window, 256);
688
    }
689
}
690

    
691
/* Parse the audio block from ac3 bitstream.
692
 * This function extract the audio block from the ac3 bitstream
693
 * and produces the output for the block. This function must
694
 * be called for each of the six audio block in the ac3 bitstream.
695
 */
696
static int ac3_parse_audio_block(AC3DecodeContext *ctx, int blk)
697
{
698
    int nfchans = ctx->nfchans;
699
    int acmod = ctx->acmod;
700
    int i, bnd, seg, grpsize, ch;
701
    GetBitContext *gb = &ctx->gb;
702
    int bit_alloc_flags = 0;
703
    int8_t *dexps;
704
    int mstrcplco, cplcoexp, cplcomant;
705
    int chbwcod, ngrps, cplabsexp, skipl;
706

    
707
    for (i = 0; i < nfchans; i++) /*block switch flag */
708
        ctx->blksw[i] = get_bits1(gb);
709

    
710
    ctx->dither_all = 1;
711
    for (i = 0; i < nfchans; i++) { /* dithering flag */
712
        ctx->dithflag[i] = get_bits1(gb);
713
        if(!ctx->dithflag[i])
714
            ctx->dither_all = 0;
715
    }
716

    
717
    if (get_bits1(gb)) { /* dynamic range */
718
        ctx->dynrng = dynrng_tbl[get_bits(gb, 8)];
719
    } else if(blk == 0) {
720
        ctx->dynrng = 1.0;
721
    }
722

    
723
    if(acmod == AC3_ACMOD_DUALMONO) { /* dynamic range 1+1 mode */
724
        if(get_bits1(gb)) {
725
            ctx->dynrng2 = dynrng_tbl[get_bits(gb, 8)];
726
        } else if(blk == 0) {
727
            ctx->dynrng2 = 1.0;
728
        }
729
    }
730

    
731
    if (get_bits1(gb)) { /* coupling strategy */
732
        ctx->cplinu = get_bits1(gb);
733
        if (ctx->cplinu) { /* coupling in use */
734
            int cplbegf, cplendf;
735

    
736
            for (i = 0; i < nfchans; i++)
737
                ctx->chincpl[i] = get_bits1(gb);
738

    
739
            if (acmod == AC3_ACMOD_STEREO)
740
                ctx->phsflginu = get_bits1(gb); //phase flag in use
741

    
742
            cplbegf = get_bits(gb, 4);
743
            cplendf = get_bits(gb, 4);
744

    
745
            if (3 + cplendf - cplbegf < 0) {
746
                av_log(NULL, AV_LOG_ERROR, "cplendf = %d < cplbegf = %d\n", cplendf, cplbegf);
747
                return -1;
748
            }
749

    
750
            ctx->ncplbnd = ctx->ncplsubnd = 3 + cplendf - cplbegf;
751
            ctx->cplstrtmant = cplbegf * 12 + 37;
752
            ctx->cplendmant = cplendf * 12 + 73;
753
            for (i = 0; i < ctx->ncplsubnd - 1; i++) { /* coupling band structure */
754
                if (get_bits1(gb)) {
755
                    ctx->cplbndstrc[i] = 1;
756
                    ctx->ncplbnd--;
757
                }
758
            }
759
        } else {
760
            for (i = 0; i < nfchans; i++)
761
                ctx->chincpl[i] = 0;
762
        }
763
    }
764

    
765
    if (ctx->cplinu) {
766
        int cplcoe = 0;
767

    
768
        for (i = 0; i < nfchans; i++) {
769
            if (ctx->chincpl[i]) {
770
                if (get_bits1(gb)) { /* coupling co-ordinates */
771
                    cplcoe = 1;
772
                    mstrcplco = 3 * get_bits(gb, 2);
773
                    for (bnd = 0; bnd < ctx->ncplbnd; bnd++) {
774
                        cplcoexp = get_bits(gb, 4);
775
                        cplcomant = get_bits(gb, 4);
776
                        if (cplcoexp == 15)
777
                            ctx->cplco[i][bnd] = cplcomant / 16.0f;
778
                        else
779
                            ctx->cplco[i][bnd] = (cplcomant + 16.0f) / 32.0f;
780
                        ctx->cplco[i][bnd] *= scale_factors[cplcoexp + mstrcplco];
781
                    }
782
                }
783
            }
784
        }
785

    
786
        if (acmod == AC3_ACMOD_STEREO && ctx->phsflginu && cplcoe) {
787
            for (bnd = 0; bnd < ctx->ncplbnd; bnd++) {
788
                if (get_bits1(gb))
789
                    ctx->cplco[1][bnd] = -ctx->cplco[1][bnd];
790
            }
791
        }
792
    }
793

    
794
    if (acmod == AC3_ACMOD_STEREO) {/* rematrixing */
795
        ctx->rematstr = get_bits1(gb);
796
        if (ctx->rematstr) {
797
            ctx->nrematbnd = 4;
798
            if(ctx->cplinu && ctx->cplstrtmant <= 61)
799
                ctx->nrematbnd -= 1 + (ctx->cplstrtmant == 37);
800
            for(bnd=0; bnd<ctx->nrematbnd; bnd++)
801
                ctx->rematflg[bnd] = get_bits1(gb);
802
        }
803
    }
804

    
805
    ctx->cplexpstr = EXP_REUSE;
806
    ctx->lfeexpstr = EXP_REUSE;
807
    if (ctx->cplinu) /* coupling exponent strategy */
808
        ctx->cplexpstr = get_bits(gb, 2);
809
    for (i = 0; i < nfchans; i++)  /* channel exponent strategy */
810
        ctx->chexpstr[i] = get_bits(gb, 2);
811
    if (ctx->lfeon)  /* lfe exponent strategy */
812
        ctx->lfeexpstr = get_bits1(gb);
813

    
814
    for (i = 0; i < nfchans; i++) { /* channel bandwidth code */
815
        if (ctx->chexpstr[i] != EXP_REUSE) {
816
            if (ctx->chincpl[i])
817
                ctx->endmant[i] = ctx->cplstrtmant;
818
            else {
819
                chbwcod = get_bits(gb, 6);
820
                if (chbwcod > 60) {
821
                    av_log(NULL, AV_LOG_ERROR, "chbwcod = %d > 60", chbwcod);
822
                    return -1;
823
                }
824
                ctx->endmant[i] = chbwcod * 3 + 73;
825
            }
826
        }
827
    }
828

    
829
    if (ctx->cplexpstr != EXP_REUSE) {/* coupling exponents */
830
        bit_alloc_flags = 64;
831
        cplabsexp = get_bits(gb, 4) << 1;
832
        ngrps = (ctx->cplendmant - ctx->cplstrtmant) / (3 << (ctx->cplexpstr - 1));
833
        decode_exponents(gb, ctx->cplexpstr, ngrps, cplabsexp, ctx->dcplexps + ctx->cplstrtmant);
834
    }
835

    
836
    for (i = 0; i < nfchans; i++) { /* fbw channel exponents */
837
        if (ctx->chexpstr[i] != EXP_REUSE) {
838
            bit_alloc_flags |= 1 << i;
839
            grpsize = 3 << (ctx->chexpstr[i] - 1);
840
            ngrps = (ctx->endmant[i] + grpsize - 4) / grpsize;
841
            dexps = ctx->dexps[i];
842
            dexps[0] = get_bits(gb, 4);
843
            decode_exponents(gb, ctx->chexpstr[i], ngrps, dexps[0], dexps + 1);
844
            skip_bits(gb, 2); /* skip gainrng */
845
        }
846
    }
847

    
848
    if (ctx->lfeexpstr != EXP_REUSE) { /* lfe exponents */
849
        bit_alloc_flags |= 32;
850
        ctx->dlfeexps[0] = get_bits(gb, 4);
851
        decode_exponents(gb, ctx->lfeexpstr, 2, ctx->dlfeexps[0], ctx->dlfeexps + 1);
852
    }
853

    
854
    if (get_bits1(gb)) { /* bit allocation information */
855
        bit_alloc_flags = 127;
856
        ctx->bit_alloc_params.sdecay = ff_sdecaytab[get_bits(gb, 2)];
857
        ctx->bit_alloc_params.fdecay = ff_fdecaytab[get_bits(gb, 2)];
858
        ctx->bit_alloc_params.sgain  = ff_sgaintab[get_bits(gb, 2)];
859
        ctx->bit_alloc_params.dbknee = ff_dbkneetab[get_bits(gb, 2)];
860
        ctx->bit_alloc_params.floor  = ff_floortab[get_bits(gb, 3)];
861
    }
862

    
863
    if (get_bits1(gb)) { /* snroffset */
864
        int csnr;
865
        bit_alloc_flags = 127;
866
        csnr = (get_bits(gb, 6) - 15) << 4;
867
        if (ctx->cplinu) { /* coupling fine snr offset and fast gain code */
868
            ctx->cplsnroffst = (csnr + get_bits(gb, 4)) << 2;
869
            ctx->cplfgain = ff_fgaintab[get_bits(gb, 3)];
870
        }
871
        for (i = 0; i < nfchans; i++) { /* channel fine snr offset and fast gain code */
872
            ctx->snroffst[i] = (csnr + get_bits(gb, 4)) << 2;
873
            ctx->fgain[i] = ff_fgaintab[get_bits(gb, 3)];
874
        }
875
        if (ctx->lfeon) { /* lfe fine snr offset and fast gain code */
876
            ctx->lfesnroffst = (csnr + get_bits(gb, 4)) << 2;
877
            ctx->lfefgain = ff_fgaintab[get_bits(gb, 3)];
878
        }
879
    }
880

    
881
    if (ctx->cplinu && get_bits1(gb)) { /* coupling leak information */
882
        bit_alloc_flags |= 64;
883
        ctx->bit_alloc_params.cplfleak = get_bits(gb, 3);
884
        ctx->bit_alloc_params.cplsleak = get_bits(gb, 3);
885
    }
886

    
887
    if (get_bits1(gb)) { /* delta bit allocation information */
888
        bit_alloc_flags = 127;
889

    
890
        if (ctx->cplinu) {
891
            ctx->cpldeltbae = get_bits(gb, 2);
892
            if (ctx->cpldeltbae == DBA_RESERVED) {
893
                av_log(NULL, AV_LOG_ERROR, "coupling delta bit allocation strategy reserved\n");
894
                return -1;
895
            }
896
        }
897

    
898
        for (i = 0; i < nfchans; i++) {
899
            ctx->deltbae[i] = get_bits(gb, 2);
900
            if (ctx->deltbae[i] == DBA_RESERVED) {
901
                av_log(NULL, AV_LOG_ERROR, "delta bit allocation strategy reserved\n");
902
                return -1;
903
            }
904
        }
905

    
906
        if (ctx->cplinu) {
907
            if (ctx->cpldeltbae == DBA_NEW) { /*coupling delta offset, len and bit allocation */
908
                ctx->cpldeltnseg = get_bits(gb, 3);
909
                for (seg = 0; seg <= ctx->cpldeltnseg; seg++) {
910
                    ctx->cpldeltoffst[seg] = get_bits(gb, 5);
911
                    ctx->cpldeltlen[seg] = get_bits(gb, 4);
912
                    ctx->cpldeltba[seg] = get_bits(gb, 3);
913
                }
914
            }
915
        }
916

    
917
        for (i = 0; i < nfchans; i++) {
918
            if (ctx->deltbae[i] == DBA_NEW) {/*channel delta offset, len and bit allocation */
919
                ctx->deltnseg[i] = get_bits(gb, 3);
920
                for (seg = 0; seg <= ctx->deltnseg[i]; seg++) {
921
                    ctx->deltoffst[i][seg] = get_bits(gb, 5);
922
                    ctx->deltlen[i][seg] = get_bits(gb, 4);
923
                    ctx->deltba[i][seg] = get_bits(gb, 3);
924
                }
925
            }
926
        }
927
    } else if(blk == 0) {
928
        if(ctx->cplinu)
929
            ctx->cpldeltbae = DBA_NONE;
930
        for(i=0; i<nfchans; i++) {
931
            ctx->deltbae[i] = DBA_NONE;
932
        }
933
    }
934

    
935
    if (bit_alloc_flags) {
936
        if (ctx->cplinu && (bit_alloc_flags & 64)) {
937
            ac3_parametric_bit_allocation(&ctx->bit_alloc_params, ctx->cplbap,
938
                                          ctx->dcplexps, ctx->cplstrtmant,
939
                                          ctx->cplendmant, ctx->cplsnroffst,
940
                                          ctx->cplfgain, 0,
941
                                          ctx->cpldeltbae, ctx->cpldeltnseg,
942
                                          ctx->cpldeltoffst, ctx->cpldeltlen,
943
                                          ctx->cpldeltba);
944
        }
945
        for (i = 0; i < nfchans; i++) {
946
            if ((bit_alloc_flags >> i) & 1) {
947
                ac3_parametric_bit_allocation(&ctx->bit_alloc_params,
948
                                              ctx->bap[i], ctx->dexps[i], 0,
949
                                              ctx->endmant[i], ctx->snroffst[i],
950
                                              ctx->fgain[i], 0, ctx->deltbae[i],
951
                                              ctx->deltnseg[i], ctx->deltoffst[i],
952
                                              ctx->deltlen[i], ctx->deltba[i]);
953
            }
954
        }
955
        if (ctx->lfeon && (bit_alloc_flags & 32)) {
956
            ac3_parametric_bit_allocation(&ctx->bit_alloc_params, ctx->lfebap,
957
                                          ctx->dlfeexps, 0, 7, ctx->lfesnroffst,
958
                                          ctx->lfefgain, 1,
959
                                          DBA_NONE, 0, NULL, NULL, NULL);
960
        }
961
    }
962

    
963
    if (get_bits1(gb)) { /* unused dummy data */
964
        skipl = get_bits(gb, 9);
965
        while(skipl--)
966
            skip_bits(gb, 8);
967
    }
968
    /* unpack the transform coefficients
969
     * * this also uncouples channels if coupling is in use.
970
     */
971
    if (get_transform_coeffs(ctx)) {
972
        av_log(NULL, AV_LOG_ERROR, "Error in routine get_transform_coeffs\n");
973
        return -1;
974
    }
975

    
976
    /* recover coefficients if rematrixing is in use */
977
    if(ctx->acmod == AC3_ACMOD_STEREO)
978
        do_rematrixing(ctx);
979

    
980
    /* apply scaling to coefficients (headroom, dynrng) */
981
    if(ctx->lfeon) {
982
        for(i=0; i<7; i++) {
983
            ctx->transform_coeffs[0][i] *= 2.0f * ctx->dynrng;
984
        }
985
    }
986
    for(ch=1; ch<=ctx->nfchans; ch++) {
987
        float gain = 2.0f;
988
        if(ctx->acmod == AC3_ACMOD_DUALMONO && ch == 2) {
989
            gain *= ctx->dynrng2;
990
        } else {
991
            gain *= ctx->dynrng;
992
        }
993
        for(i=0; i<ctx->endmant[ch-1]; i++) {
994
            ctx->transform_coeffs[ch][i] *= gain;
995
        }
996
    }
997

    
998
    do_imdct(ctx);
999

    
1000
    return 0;
1001
}
1002

    
1003
static inline int16_t convert(int32_t i)
1004
{
1005
    if (i > 0x43c07fff)
1006
        return 32767;
1007
    else if (i <= 0x43bf8000)
1008
        return -32768;
1009
    else
1010
        return (i - 0x43c00000);
1011
}
1012

    
1013
/* Decode ac3 frame.
1014
 *
1015
 * @param avctx Pointer to AVCodecContext
1016
 * @param data Pointer to pcm smaples
1017
 * @param data_size Set to number of pcm samples produced by decoding
1018
 * @param buf Data to be decoded
1019
 * @param buf_size Size of the buffer
1020
 */
1021
static int ac3_decode_frame(AVCodecContext * avctx, void *data, int *data_size, uint8_t *buf, int buf_size)
1022
{
1023
    AC3DecodeContext *ctx = (AC3DecodeContext *)avctx->priv_data;
1024
    int16_t *out_samples = (int16_t *)data;
1025
    int i, j, k, start;
1026
    int32_t *int_ptr[6];
1027

    
1028
    for (i = 0; i < 6; i++)
1029
        int_ptr[i] = (int32_t *)(&ctx->output[i]);
1030

    
1031
    //Initialize the GetBitContext with the start of valid AC3 Frame.
1032
    init_get_bits(&ctx->gb, buf, buf_size * 8);
1033

    
1034
    //Parse the syncinfo.
1035
    if (ac3_parse_header(ctx)) {
1036
        av_log(avctx, AV_LOG_ERROR, "\n");
1037
        *data_size = 0;
1038
        return buf_size;
1039
    }
1040

    
1041
    avctx->sample_rate = ctx->sampling_rate;
1042
    avctx->bit_rate = ctx->bit_rate;
1043

    
1044
    /* channel config */
1045
    if (avctx->channels == 0) {
1046
        avctx->channels = ctx->out_channels;
1047
    }
1048
    if(avctx->channels != ctx->out_channels) {
1049
        av_log(avctx, AV_LOG_ERROR, "Cannot mix AC3 to %d channels.\n",
1050
               avctx->channels);
1051
        return -1;
1052
    }
1053

    
1054
    //av_log(avctx, AV_LOG_INFO, "channels = %d \t bit rate = %d \t sampling rate = %d \n", avctx->channels, avctx->bit_rate * 1000, avctx->sample_rate);
1055

    
1056
    //Parse the Audio Blocks.
1057
    for (i = 0; i < NB_BLOCKS; i++) {
1058
        if (ac3_parse_audio_block(ctx, i)) {
1059
            av_log(avctx, AV_LOG_ERROR, "error parsing the audio block\n");
1060
            *data_size = 0;
1061
            return ctx->frame_size;
1062
        }
1063
        start = (ctx->output_mode & AC3_OUTPUT_LFEON) ? 0 : 1;
1064
        for (k = 0; k < 256; k++)
1065
            for (j = start; j <= ctx->nfchans; j++)
1066
                *(out_samples++) = convert(int_ptr[j][k]);
1067
    }
1068
    *data_size = NB_BLOCKS * 256 * avctx->channels * sizeof (int16_t);
1069
    return ctx->frame_size;
1070
}
1071

    
1072
/* Uninitialize ac3 decoder.
1073
 */
1074
static int ac3_decode_end(AVCodecContext *avctx)
1075
{
1076
    AC3DecodeContext *ctx = (AC3DecodeContext *)avctx->priv_data;
1077
    ff_mdct_end(&ctx->imdct_512);
1078
    ff_mdct_end(&ctx->imdct_256);
1079

    
1080
    return 0;
1081
}
1082

    
1083
AVCodec ac3_decoder = {
1084
    .name = "ac3",
1085
    .type = CODEC_TYPE_AUDIO,
1086
    .id = CODEC_ID_AC3,
1087
    .priv_data_size = sizeof (AC3DecodeContext),
1088
    .init = ac3_decode_init,
1089
    .close = ac3_decode_end,
1090
    .decode = ac3_decode_frame,
1091
};
1092