Statistics
| Branch: | Revision:

ffmpeg / libavcodec / ac3dec.c @ 6d96d626

History | View | Annotate | Download (35.3 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 "dsputil.h"
39
#include "random.h"
40

    
41
/**
42
 * Table of bin locations for rematrixing bands
43
 * 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
48
 * 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] = {
68
    0, 3, 5, 7, 11, 15,
69
    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 cplcoe;
103
    int cplbndstrc[18];
104
    int rematstr;
105
    int nrematbnd;
106
    int rematflg[AC3_MAX_CHANNELS];
107
    int cplexpstr;
108
    int lfeexpstr;
109
    int chexpstr[5];
110
    int cplsnroffst;
111
    int cplfgain;
112
    int snroffst[5];
113
    int fgain[5];
114
    int lfesnroffst;
115
    int lfefgain;
116
    int cpldeltbae;
117
    int deltbae[5];
118
    int cpldeltnseg;
119
    uint8_t  cpldeltoffst[8];
120
    uint8_t  cpldeltlen[8];
121
    uint8_t  cpldeltba[8];
122
    int deltnseg[5];
123
    uint8_t  deltoffst[5][8];
124
    uint8_t  deltlen[5][8];
125
    uint8_t  deltba[5][8];
126

    
127
    /* Derived Attributes. */
128
    int      sampling_rate;
129
    int      bit_rate;
130
    int      frame_size;
131

    
132
    int      nchans;            //number of total channels
133
    int      nfchans;           //number of full-bandwidth channels
134
    int      lfeon;             //lfe channel in use
135
    int      output_mode;       ///< output channel configuration
136
    int      out_channels;      ///< number of output channels
137

    
138
    float    dynrng;            //dynamic range gain
139
    float    dynrng2;           //dynamic range gain for 1+1 mode
140
    float    cplco[5][18];      //coupling coordinates
141
    int      ncplbnd;           //number of coupling bands
142
    int      ncplsubnd;         //number of coupling sub bands
143
    int      cplstrtmant;       //coupling start mantissa
144
    int      cplendmant;        //coupling end mantissa
145
    int      endmant[5];        //channel end mantissas
146
    AC3BitAllocParameters bit_alloc_params; ///< bit allocation parameters
147

    
148
    int8_t   dcplexps[256];     //decoded coupling exponents
149
    int8_t   dexps[5][256];     //decoded fbw channel exponents
150
    int8_t   dlfeexps[256];     //decoded lfe channel exponents
151
    uint8_t  cplbap[256];       //coupling bit allocation pointers
152
    uint8_t  bap[5][256];       //fbw channel bit allocation pointers
153
    uint8_t  lfebap[256];       //lfe channel bit allocation pointers
154

    
155
    float transform_coeffs_cpl[256];
156
    DECLARE_ALIGNED_16(float, transform_coeffs[AC3_MAX_CHANNELS][256]);  //transform coefficients
157

    
158
    /* For IMDCT. */
159
    MDCTContext imdct_512;  //for 512 sample imdct transform
160
    MDCTContext imdct_256;  //for 256 sample imdct transform
161
    DSPContext  dsp;        //for optimization
162

    
163
    DECLARE_ALIGNED_16(float, output[AC3_MAX_CHANNELS][256]);   //output after imdct transform and windowing
164
    DECLARE_ALIGNED_16(float, delay[AC3_MAX_CHANNELS][256]);    //delay - added to the next block
165
    DECLARE_ALIGNED_16(float, tmp_imdct[256]);                  //temporary storage for imdct transform
166
    DECLARE_ALIGNED_16(float, tmp_output[512]);                 //temporary storage for output before windowing
167
    DECLARE_ALIGNED_16(float, window[256]);                     //window coefficients
168

    
169
    /* Miscellaneous. */
170
    GetBitContext gb;
171
    AVRandomState dith_state;   //for dither generation
172
} AC3DecodeContext;
173

    
174
/*********** BEGIN INIT HELPER FUNCTIONS ***********/
175
/**
176
 * Generate a Kaiser-Bessel Derived Window.
177
 */
178
static void ac3_window_init(float *window)
179
{
180
   int i, j;
181
   double sum = 0.0, bessel, tmp;
182
   double local_window[256];
183
   double alpha2 = (5.0 * M_PI / 256.0) * (5.0 * M_PI / 256.0);
184

    
185
   for (i = 0; i < 256; i++) {
186
       tmp = i * (256 - i) * alpha2;
187
       bessel = 1.0;
188
       for (j = 100; j > 0; j--) /* defaul to 100 iterations */
189
           bessel = bessel * tmp / (j * j) + 1;
190
       sum += bessel;
191
       local_window[i] = sum;
192
   }
193

    
194
   sum++;
195
   for (i = 0; i < 256; i++)
196
       window[i] = sqrt(local_window[i] / sum);
197
}
198

    
199
static inline float
200
symmetric_dequant(int code, int levels)
201
{
202
    return (code - (levels >> 1)) * (2.0f / levels);
203
}
204

    
205
/*
206
 * Initialize tables at runtime.
207
 */
208
static void ac3_tables_init(void)
209
{
210
    int i;
211

    
212
    /* generate grouped mantissa tables
213
       reference: Section 7.3.5 Ungrouping of Mantissas */
214
    for(i=0; i<32; i++) {
215
        /* bap=1 mantissas */
216
        b1_mantissas[i][0] = symmetric_dequant( i / 9     , 3);
217
        b1_mantissas[i][1] = symmetric_dequant((i % 9) / 3, 3);
218
        b1_mantissas[i][2] = symmetric_dequant((i % 9) % 3, 3);
219
    }
220
    for(i=0; i<128; i++) {
221
        /* bap=2 mantissas */
222
        b2_mantissas[i][0] = symmetric_dequant( i / 25     , 5);
223
        b2_mantissas[i][1] = symmetric_dequant((i % 25) / 5, 5);
224
        b2_mantissas[i][2] = symmetric_dequant((i % 25) % 5, 5);
225

    
226
        /* bap=4 mantissas */
227
        b4_mantissas[i][0] = symmetric_dequant(i / 11, 11);
228
        b4_mantissas[i][1] = symmetric_dequant(i % 11, 11);
229
    }
230
    /* generate ungrouped mantissa tables
231
       reference: Tables 7.21 and 7.23 */
232
    for(i=0; i<7; i++) {
233
        /* bap=3 mantissas */
234
        b3_mantissas[i] = symmetric_dequant(i, 7);
235
    }
236
    for(i=0; i<15; i++) {
237
        /* bap=5 mantissas */
238
        b5_mantissas[i] = symmetric_dequant(i, 15);
239
    }
240

    
241
    /* generate dynamic range table
242
       reference: Section 7.7.1 Dynamic Range Control */
243
    for(i=0; i<256; i++) {
244
        int v = (i >> 5) - ((i >> 7) << 3) - 5;
245
        dynrng_tbl[i] = powf(2.0f, v) * ((i & 0x1F) | 0x20);
246
    }
247

    
248
    //generate scale factors
249
    for (i = 0; i < 25; i++)
250
        scale_factors[i] = pow(2.0, -i);
251

    
252
    /* generate exponent tables
253
       reference: Section 7.1.3 Exponent Decoding */
254
    for(i=0; i<128; i++) {
255
        exp_ungroup_tbl[i][0] =  i / 25;
256
        exp_ungroup_tbl[i][1] = (i % 25) / 5;
257
        exp_ungroup_tbl[i][2] = (i % 25) % 5;
258
    }
259
}
260

    
261

    
262
static int ac3_decode_init(AVCodecContext *avctx)
263
{
264
    AC3DecodeContext *ctx = avctx->priv_data;
265

    
266
    ac3_common_init();
267
    ac3_tables_init();
268
    ff_mdct_init(&ctx->imdct_256, 8, 1);
269
    ff_mdct_init(&ctx->imdct_512, 9, 1);
270
    ac3_window_init(ctx->window);
271
    dsputil_init(&ctx->dsp, avctx);
272
    av_init_random(0, &ctx->dith_state);
273

    
274
    return 0;
275
}
276
/*********** END INIT FUNCTIONS ***********/
277

    
278
/**
279
 * Parses the 'sync info' and 'bit stream info' from the AC-3 bitstream.
280
 * GetBitContext within AC3DecodeContext must point to
281
 * start of the synchronized ac3 bitstream.
282
 */
283
static int ac3_parse_header(AC3DecodeContext *ctx)
284
{
285
    AC3HeaderInfo hdr;
286
    GetBitContext *gb = &ctx->gb;
287
    int err, i;
288

    
289
    err = ff_ac3_parse_header(gb->buffer, &hdr);
290
    if(err)
291
        return err;
292

    
293
    /* get decoding parameters from header info */
294
    ctx->bit_alloc_params.fscod       = hdr.fscod;
295
    ctx->acmod                        = hdr.acmod;
296
    ctx->cmixlev                      = hdr.cmixlev;
297
    ctx->surmixlev                    = hdr.surmixlev;
298
    ctx->dsurmod                      = hdr.dsurmod;
299
    ctx->lfeon                        = hdr.lfeon;
300
    ctx->bit_alloc_params.halfratecod = hdr.halfratecod;
301
    ctx->sampling_rate                = hdr.sample_rate;
302
    ctx->bit_rate                     = hdr.bit_rate;
303
    ctx->nchans                       = hdr.channels;
304
    ctx->nfchans                      = ctx->nchans - ctx->lfeon;
305
    ctx->frame_size                   = hdr.frame_size;
306

    
307
    /* set default output to all source channels */
308
    ctx->out_channels = ctx->nchans;
309
    ctx->output_mode = ctx->acmod;
310
    if(ctx->lfeon)
311
        ctx->output_mode |= AC3_OUTPUT_LFEON;
312

    
313
    /* skip over portion of header which has already been read */
314
    skip_bits(gb, 16); //skip the sync_word, sync_info->sync_word = get_bits(gb, 16);
315
    skip_bits(gb, 16); // skip crc1
316
    skip_bits(gb, 8);  // skip fscod and frmsizecod
317
    skip_bits(gb, 11); // skip bsid, bsmod, and acmod
318
    if(ctx->acmod == AC3_ACMOD_STEREO) {
319
        skip_bits(gb, 2); // skip dsurmod
320
    } else {
321
        if((ctx->acmod & 1) && ctx->acmod != AC3_ACMOD_MONO)
322
            skip_bits(gb, 2); // skip cmixlev
323
        if(ctx->acmod & 4)
324
            skip_bits(gb, 2); // skip surmixlev
325
    }
326
    skip_bits1(gb); // skip lfeon
327

    
328
    /* read the rest of the bsi. read twice for dual mono mode. */
329
    i = !(ctx->acmod);
330
    do {
331
        skip_bits(gb, 5); //skip dialog normalization
332
        if (get_bits1(gb))
333
            skip_bits(gb, 8); //skip compression
334
        if (get_bits1(gb))
335
            skip_bits(gb, 8); //skip language code
336
        if (get_bits1(gb))
337
            skip_bits(gb, 7); //skip audio production information
338
    } while (i--);
339

    
340
    skip_bits(gb, 2); //skip copyright bit and original bitstream bit
341

    
342
    /* FIXME: read & use the xbsi1 downmix levels */
343
    if (get_bits1(gb))
344
        skip_bits(gb, 14); //skip timecode1
345
    if (get_bits1(gb))
346
        skip_bits(gb, 14); //skip timecode2
347

    
348
    if (get_bits1(gb)) {
349
        i = get_bits(gb, 6); //additional bsi length
350
        do {
351
            skip_bits(gb, 8);
352
        } while(i--);
353
    }
354

    
355
    return 0;
356
}
357

    
358
/**
359
 * Decodes the grouped exponents.
360
 * This function decodes the coded exponents according to exponent strategy
361
 * and stores them in the decoded exponents buffer.
362
 *
363
 * @param[in]  gb      GetBitContext which points to start of coded exponents
364
 * @param[in]  expstr  Exponent coding strategy
365
 * @param[in]  ngrps   Number of grouped exponents
366
 * @param[in]  absexp  Absolute exponent or DC exponent
367
 * @param[out] dexps   Decoded exponents are stored in dexps
368
 */
369
static void decode_exponents(GetBitContext *gb, int expstr, int ngrps,
370
                             uint8_t absexp, int8_t *dexps)
371
{
372
    int i, j, grp, grpsize;
373
    int dexp[256];
374
    int expacc, prevexp;
375

    
376
    /* unpack groups */
377
    grpsize = expstr + (expstr == EXP_D45);
378
    for(grp=0,i=0; grp<ngrps; grp++) {
379
        expacc = get_bits(gb, 7);
380
        dexp[i++] = exp_ungroup_tbl[expacc][0];
381
        dexp[i++] = exp_ungroup_tbl[expacc][1];
382
        dexp[i++] = exp_ungroup_tbl[expacc][2];
383
    }
384

    
385
    /* convert to absolute exps and expand groups */
386
    prevexp = absexp;
387
    for(i=0; i<ngrps*3; i++) {
388
        prevexp = av_clip(prevexp + dexp[i]-2, 0, 24);
389
        for(j=0; j<grpsize; j++) {
390
            dexps[(i*grpsize)+j] = prevexp;
391
        }
392
    }
393
}
394

    
395
/**
396
 * Generates transform coefficients for each coupled channel in the coupling
397
 * range using the coupling coefficients and coupling coordinates.
398
 * reference: Section 7.4.3 Coupling Coordinate Format
399
 */
400
static void uncouple_channels(AC3DecodeContext *ctx)
401
{
402
    int i, j, ch, bnd, subbnd;
403

    
404
    subbnd = -1;
405
    i = ctx->cplstrtmant;
406
    for(bnd=0; bnd<ctx->ncplbnd; bnd++) {
407
        do {
408
            subbnd++;
409
            for(j=0; j<12; j++) {
410
                for(ch=1; ch<=ctx->nfchans; ch++) {
411
                    if(ctx->chincpl[ch-1])
412
                        ctx->transform_coeffs[ch][i] = ctx->transform_coeffs_cpl[i] * ctx->cplco[ch-1][bnd] * 8.0f;
413
                }
414
                i++;
415
            }
416
        } while(ctx->cplbndstrc[subbnd]);
417
    }
418
}
419

    
420
typedef struct { /* grouped mantissas for 3-level 5-leve and 11-level quantization */
421
    float b1_mant[3];
422
    float b2_mant[3];
423
    float b4_mant[2];
424
    int b1ptr;
425
    int b2ptr;
426
    int b4ptr;
427
} mant_groups;
428

    
429
/* Get the transform coefficients for particular channel */
430
static int get_transform_coeffs_ch(AC3DecodeContext *ctx, int ch_index, mant_groups *m)
431
{
432
    GetBitContext *gb = &ctx->gb;
433
    int i, gcode, tbap, start, end;
434
    uint8_t *exps;
435
    uint8_t *bap;
436
    float *coeffs;
437

    
438
    if (ch_index >= 0) { /* fbw channels */
439
        exps = ctx->dexps[ch_index];
440
        bap = ctx->bap[ch_index];
441
        coeffs = ctx->transform_coeffs[ch_index + 1];
442
        start = 0;
443
        end = ctx->endmant[ch_index];
444
    } else if (ch_index == -1) {
445
        exps = ctx->dlfeexps;
446
        bap = ctx->lfebap;
447
        coeffs = ctx->transform_coeffs[0];
448
        start = 0;
449
        end = 7;
450
    } else {
451
        exps = ctx->dcplexps;
452
        bap = ctx->cplbap;
453
        coeffs = ctx->transform_coeffs_cpl;
454
        start = ctx->cplstrtmant;
455
        end = ctx->cplendmant;
456
    }
457

    
458

    
459
    for (i = start; i < end; i++) {
460
        tbap = bap[i];
461
        switch (tbap) {
462
            case 0:
463
                coeffs[i] = ((av_random(&ctx->dith_state) & 0xFFFF) * LEVEL_MINUS_3DB) / 32768.0f;
464
                break;
465

    
466
            case 1:
467
                if(m->b1ptr > 2) {
468
                    gcode = get_bits(gb, 5);
469
                    m->b1_mant[0] = b1_mantissas[gcode][0];
470
                    m->b1_mant[1] = b1_mantissas[gcode][1];
471
                    m->b1_mant[2] = b1_mantissas[gcode][2];
472
                    m->b1ptr = 0;
473
                }
474
                coeffs[i] = m->b1_mant[m->b1ptr++];
475
                break;
476

    
477
            case 2:
478
                if(m->b2ptr > 2) {
479
                    gcode = get_bits(gb, 7);
480
                    m->b2_mant[0] = b2_mantissas[gcode][0];
481
                    m->b2_mant[1] = b2_mantissas[gcode][1];
482
                    m->b2_mant[2] = b2_mantissas[gcode][2];
483
                    m->b2ptr = 0;
484
                }
485
                coeffs[i] = m->b2_mant[m->b2ptr++];
486
                break;
487

    
488
            case 3:
489
                coeffs[i] = b3_mantissas[get_bits(gb, 3)];
490
                break;
491

    
492
            case 4:
493
                if(m->b4ptr > 1) {
494
                    gcode = get_bits(gb, 7);
495
                    m->b4_mant[0] = b4_mantissas[gcode][0];
496
                    m->b4_mant[1] = b4_mantissas[gcode][1];
497
                    m->b4ptr = 0;
498
                }
499
                coeffs[i] = m->b4_mant[m->b4ptr++];
500
                break;
501

    
502
            case 5:
503
                coeffs[i] = b5_mantissas[get_bits(gb, 4)];
504
                break;
505

    
506
            default:
507
                coeffs[i] = get_sbits(gb, qntztab[tbap]) * scale_factors[qntztab[tbap]-1];
508
                break;
509
        }
510
        coeffs[i] *= scale_factors[exps[i]];
511
    }
512

    
513
    return 0;
514
}
515

    
516
/**
517
 * Removes random dithering from coefficients with zero-bit mantissas
518
 * reference: Section 7.3.4 Dither for Zero Bit Mantissas (bap=0)
519
 */
520
static void remove_dithering(AC3DecodeContext *ctx) {
521
    int ch, i;
522
    int end=0;
523
    float *coeffs;
524
    uint8_t *bap;
525

    
526
    for(ch=1; ch<=ctx->nfchans; ch++) {
527
        if(!ctx->dithflag[ch-1]) {
528
            coeffs = ctx->transform_coeffs[ch];
529
            bap = ctx->bap[ch-1];
530
            if(ctx->chincpl[ch-1])
531
                end = ctx->cplstrtmant;
532
            else
533
                end = ctx->endmant[ch-1];
534
            for(i=0; i<end; i++) {
535
                if(bap[i] == 0)
536
                    coeffs[i] = 0.0f;
537
            }
538
            if(ctx->chincpl[ch-1]) {
539
                bap = ctx->cplbap;
540
                for(; i<ctx->cplendmant; i++) {
541
                    if(bap[i] == 0)
542
                        coeffs[i] = 0.0f;
543
                }
544
            }
545
        }
546
    }
547
}
548

    
549
/* Get the transform coefficients.
550
 * This function extracts the tranform coefficients form the ac3 bitstream.
551
 * This function is called after bit allocation is performed.
552
 */
553
static int get_transform_coeffs(AC3DecodeContext * ctx)
554
{
555
    int i, end;
556
    int got_cplchan = 0;
557
    mant_groups m;
558

    
559
    m.b1ptr = m.b2ptr = m.b4ptr = 3;
560

    
561
    for (i = 0; i < ctx->nfchans; i++) {
562
        /* transform coefficients for individual channel */
563
        if (get_transform_coeffs_ch(ctx, i, &m))
564
            return -1;
565
        /* tranform coefficients for coupling channels */
566
        if (ctx->chincpl[i])  {
567
            if (!got_cplchan) {
568
                if (get_transform_coeffs_ch(ctx, -2, &m)) {
569
                    av_log(NULL, AV_LOG_ERROR, "error in decoupling channels\n");
570
                    return -1;
571
                }
572
                uncouple_channels(ctx);
573
                got_cplchan = 1;
574
            }
575
            end = ctx->cplendmant;
576
        } else
577
            end = ctx->endmant[i];
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
        } else {
759
            for (i = 0; i < nfchans; i++)
760
                ctx->chincpl[i] = 0;
761
        }
762
    }
763

    
764
    if (ctx->cplinu) {
765
        ctx->cplcoe = 0;
766

    
767
        for (i = 0; i < nfchans; i++)
768
            if (ctx->chincpl[i])
769
                if (get_bits1(gb)) { /* coupling co-ordinates */
770
                    ctx->cplcoe |= 1 << i;
771
                    mstrcplco = 3 * get_bits(gb, 2);
772
                    for (bnd = 0; bnd < ctx->ncplbnd; bnd++) {
773
                        cplcoexp = get_bits(gb, 4);
774
                        cplcomant = get_bits(gb, 4);
775
                        if (cplcoexp == 15)
776
                            ctx->cplco[i][bnd] = cplcomant / 16.0f;
777
                        else
778
                            ctx->cplco[i][bnd] = (cplcomant + 16.0f) / 32.0f;
779
                        ctx->cplco[i][bnd] *= scale_factors[cplcoexp + mstrcplco];
780
                    }
781
                }
782

    
783
        if (acmod == AC3_ACMOD_STEREO && ctx->phsflginu && (ctx->cplcoe & 1 || ctx->cplcoe & 2))
784
            for (bnd = 0; bnd < ctx->ncplbnd; bnd++)
785
                if (get_bits1(gb))
786
                    ctx->cplco[1][bnd] = -ctx->cplco[1][bnd];
787
    }
788

    
789
    if (acmod == AC3_ACMOD_STEREO) {/* rematrixing */
790
        ctx->rematstr = get_bits1(gb);
791
        if (ctx->rematstr) {
792
            ctx->nrematbnd = 4;
793
            if(ctx->cplinu && ctx->cplstrtmant <= 61)
794
                ctx->nrematbnd -= 1 + (ctx->cplstrtmant == 37);
795
            for(bnd=0; bnd<ctx->nrematbnd; bnd++)
796
                ctx->rematflg[bnd] = get_bits1(gb);
797
        }
798
    }
799

    
800
    ctx->cplexpstr = EXP_REUSE;
801
    ctx->lfeexpstr = EXP_REUSE;
802
    if (ctx->cplinu) /* coupling exponent strategy */
803
        ctx->cplexpstr = get_bits(gb, 2);
804
    for (i = 0; i < nfchans; i++)  /* channel exponent strategy */
805
        ctx->chexpstr[i] = get_bits(gb, 2);
806
    if (ctx->lfeon)  /* lfe exponent strategy */
807
        ctx->lfeexpstr = get_bits1(gb);
808

    
809
    for (i = 0; i < nfchans; i++) /* channel bandwidth code */
810
        if (ctx->chexpstr[i] != EXP_REUSE) {
811
            if (ctx->chincpl[i])
812
                ctx->endmant[i] = ctx->cplstrtmant;
813
            else {
814
                chbwcod = get_bits(gb, 6);
815
                if (chbwcod > 60) {
816
                    av_log(NULL, AV_LOG_ERROR, "chbwcod = %d > 60", chbwcod);
817
                    return -1;
818
                }
819
                ctx->endmant[i] = chbwcod * 3 + 73;
820
            }
821
        }
822

    
823
    if (ctx->cplexpstr != EXP_REUSE) {/* coupling exponents */
824
        bit_alloc_flags = 64;
825
        cplabsexp = get_bits(gb, 4) << 1;
826
        ngrps = (ctx->cplendmant - ctx->cplstrtmant) / (3 << (ctx->cplexpstr - 1));
827
        decode_exponents(gb, ctx->cplexpstr, ngrps, cplabsexp, ctx->dcplexps + ctx->cplstrtmant);
828
    }
829

    
830
    for (i = 0; i < nfchans; i++) /* fbw channel exponents */
831
        if (ctx->chexpstr[i] != EXP_REUSE) {
832
            bit_alloc_flags |= 1 << i;
833
            grpsize = 3 << (ctx->chexpstr[i] - 1);
834
            ngrps = (ctx->endmant[i] + grpsize - 4) / grpsize;
835
            dexps = ctx->dexps[i];
836
            dexps[0] = get_bits(gb, 4);
837
            decode_exponents(gb, ctx->chexpstr[i], ngrps, dexps[0], dexps + 1);
838
            skip_bits(gb, 2); /* skip gainrng */
839
        }
840

    
841
    if (ctx->lfeexpstr != EXP_REUSE) { /* lfe exponents */
842
        bit_alloc_flags |= 32;
843
        ctx->dlfeexps[0] = get_bits(gb, 4);
844
        decode_exponents(gb, ctx->lfeexpstr, 2, ctx->dlfeexps[0], ctx->dlfeexps + 1);
845
    }
846

    
847
    if (get_bits1(gb)) { /* bit allocation information */
848
        bit_alloc_flags = 127;
849
        ctx->bit_alloc_params.sdecay = ff_sdecaytab[get_bits(gb, 2)];
850
        ctx->bit_alloc_params.fdecay = ff_fdecaytab[get_bits(gb, 2)];
851
        ctx->bit_alloc_params.sgain  = ff_sgaintab[get_bits(gb, 2)];
852
        ctx->bit_alloc_params.dbknee = ff_dbkneetab[get_bits(gb, 2)];
853
        ctx->bit_alloc_params.floor  = ff_floortab[get_bits(gb, 3)];
854
    }
855

    
856
    if (get_bits1(gb)) { /* snroffset */
857
        int csnr;
858
        bit_alloc_flags = 127;
859
        csnr = (get_bits(gb, 6) - 15) << 4;
860
        if (ctx->cplinu) { /* coupling fine snr offset and fast gain code */
861
            ctx->cplsnroffst = (csnr + get_bits(gb, 4)) << 2;
862
            ctx->cplfgain = ff_fgaintab[get_bits(gb, 3)];
863
        }
864
        for (i = 0; i < nfchans; i++) { /* channel fine snr offset and fast gain code */
865
            ctx->snroffst[i] = (csnr + get_bits(gb, 4)) << 2;
866
            ctx->fgain[i] = ff_fgaintab[get_bits(gb, 3)];
867
        }
868
        if (ctx->lfeon) { /* lfe fine snr offset and fast gain code */
869
            ctx->lfesnroffst = (csnr + get_bits(gb, 4)) << 2;
870
            ctx->lfefgain = ff_fgaintab[get_bits(gb, 3)];
871
        }
872
    }
873

    
874
    if (ctx->cplinu && get_bits1(gb)) { /* coupling leak information */
875
        bit_alloc_flags |= 64;
876
        ctx->bit_alloc_params.cplfleak = get_bits(gb, 3);
877
        ctx->bit_alloc_params.cplsleak = get_bits(gb, 3);
878
    }
879

    
880
    if (get_bits1(gb)) { /* delta bit allocation information */
881
        bit_alloc_flags = 127;
882

    
883
        if (ctx->cplinu) {
884
            ctx->cpldeltbae = get_bits(gb, 2);
885
            if (ctx->cpldeltbae == DBA_RESERVED) {
886
                av_log(NULL, AV_LOG_ERROR, "coupling delta bit allocation strategy reserved\n");
887
                return -1;
888
            }
889
        }
890

    
891
        for (i = 0; i < nfchans; i++) {
892
            ctx->deltbae[i] = get_bits(gb, 2);
893
            if (ctx->deltbae[i] == DBA_RESERVED) {
894
                av_log(NULL, AV_LOG_ERROR, "delta bit allocation strategy reserved\n");
895
                return -1;
896
            }
897
        }
898

    
899
        if (ctx->cplinu)
900
            if (ctx->cpldeltbae == DBA_NEW) { /*coupling delta offset, len and bit allocation */
901
                ctx->cpldeltnseg = get_bits(gb, 3);
902
                for (seg = 0; seg <= ctx->cpldeltnseg; seg++) {
903
                    ctx->cpldeltoffst[seg] = get_bits(gb, 5);
904
                    ctx->cpldeltlen[seg] = get_bits(gb, 4);
905
                    ctx->cpldeltba[seg] = get_bits(gb, 3);
906
                }
907
            }
908

    
909
        for (i = 0; i < nfchans; i++)
910
            if (ctx->deltbae[i] == DBA_NEW) {/*channel delta offset, len and bit allocation */
911
                ctx->deltnseg[i] = get_bits(gb, 3);
912
                for (seg = 0; seg <= ctx->deltnseg[i]; seg++) {
913
                    ctx->deltoffst[i][seg] = get_bits(gb, 5);
914
                    ctx->deltlen[i][seg] = get_bits(gb, 4);
915
                    ctx->deltba[i][seg] = get_bits(gb, 3);
916
                }
917
            }
918
    } else if(blk == 0) {
919
        if(ctx->cplinu)
920
            ctx->cpldeltbae = DBA_NONE;
921
        for(i=0; i<nfchans; i++) {
922
            ctx->deltbae[i] = DBA_NONE;
923
        }
924
    }
925

    
926
    if (bit_alloc_flags) {
927
        if (ctx->cplinu && (bit_alloc_flags & 64))
928
            ac3_parametric_bit_allocation(&ctx->bit_alloc_params, ctx->cplbap,
929
                                          ctx->dcplexps, ctx->cplstrtmant,
930
                                          ctx->cplendmant, ctx->cplsnroffst,
931
                                          ctx->cplfgain, 0,
932
                                          ctx->cpldeltbae, ctx->cpldeltnseg,
933
                                          ctx->cpldeltoffst, ctx->cpldeltlen,
934
                                          ctx->cpldeltba);
935
        for (i = 0; i < nfchans; i++)
936
            if ((bit_alloc_flags >> i) & 1)
937
                ac3_parametric_bit_allocation(&ctx->bit_alloc_params,
938
                                              ctx->bap[i], ctx->dexps[i], 0,
939
                                              ctx->endmant[i], ctx->snroffst[i],
940
                                              ctx->fgain[i], 0, ctx->deltbae[i],
941
                                              ctx->deltnseg[i], ctx->deltoffst[i],
942
                                              ctx->deltlen[i], ctx->deltba[i]);
943
        if (ctx->lfeon && (bit_alloc_flags & 32))
944
            ac3_parametric_bit_allocation(&ctx->bit_alloc_params, ctx->lfebap,
945
                                          ctx->dlfeexps, 0, 7, ctx->lfesnroffst,
946
                                          ctx->lfefgain, 1,
947
                                          DBA_NONE, 0, NULL, NULL, NULL);
948
    }
949

    
950
    if (get_bits1(gb)) { /* unused dummy data */
951
        skipl = get_bits(gb, 9);
952
        while(skipl--)
953
            skip_bits(gb, 8);
954
    }
955
    /* unpack the transform coefficients
956
     * * this also uncouples channels if coupling is in use.
957
     */
958
    if (get_transform_coeffs(ctx)) {
959
        av_log(NULL, AV_LOG_ERROR, "Error in routine get_transform_coeffs\n");
960
        return -1;
961
    }
962

    
963
    /* recover coefficients if rematrixing is in use */
964
    if(ctx->acmod == AC3_ACMOD_STEREO)
965
        do_rematrixing(ctx);
966

    
967
    /* apply scaling to coefficients (headroom, dynrng) */
968
    if(ctx->lfeon) {
969
        for(i=0; i<7; i++) {
970
            ctx->transform_coeffs[0][i] *= 2.0f * ctx->dynrng;
971
        }
972
    }
973
    for(ch=1; ch<=ctx->nfchans; ch++) {
974
        float gain = 2.0f;
975
        if(ctx->acmod == AC3_ACMOD_DUALMONO && ch == 2) {
976
            gain *= ctx->dynrng2;
977
        } else {
978
            gain *= ctx->dynrng;
979
        }
980
        for(i=0; i<ctx->endmant[ch-1]; i++) {
981
            ctx->transform_coeffs[ch][i] *= gain;
982
        }
983
    }
984

    
985
    do_imdct(ctx);
986

    
987
    return 0;
988
}
989

    
990
static inline int16_t convert(int32_t i)
991
{
992
    if (i > 0x43c07fff)
993
        return 32767;
994
    else if (i <= 0x43bf8000)
995
        return -32768;
996
    else
997
        return (i - 0x43c00000);
998
}
999

    
1000
/* Decode ac3 frame.
1001
 *
1002
 * @param avctx Pointer to AVCodecContext
1003
 * @param data Pointer to pcm smaples
1004
 * @param data_size Set to number of pcm samples produced by decoding
1005
 * @param buf Data to be decoded
1006
 * @param buf_size Size of the buffer
1007
 */
1008
static int ac3_decode_frame(AVCodecContext * avctx, void *data, int *data_size, uint8_t *buf, int buf_size)
1009
{
1010
    AC3DecodeContext *ctx = (AC3DecodeContext *)avctx->priv_data;
1011
    int16_t *out_samples = (int16_t *)data;
1012
    int i, j, k, start;
1013
    int32_t *int_ptr[6];
1014

    
1015
    for (i = 0; i < 6; i++)
1016
        int_ptr[i] = (int32_t *)(&ctx->output[i]);
1017

    
1018
    //Initialize the GetBitContext with the start of valid AC3 Frame.
1019
    init_get_bits(&ctx->gb, buf, buf_size * 8);
1020

    
1021
    //Parse the syncinfo.
1022
    if (ac3_parse_header(ctx)) {
1023
        av_log(avctx, AV_LOG_ERROR, "\n");
1024
        *data_size = 0;
1025
        return buf_size;
1026
    }
1027

    
1028
    avctx->sample_rate = ctx->sampling_rate;
1029
    avctx->bit_rate = ctx->bit_rate;
1030

    
1031
    /* channel config */
1032
    if (avctx->channels == 0) {
1033
        avctx->channels = ctx->out_channels;
1034
    }
1035
    if(avctx->channels != ctx->out_channels) {
1036
        av_log(avctx, AV_LOG_ERROR, "Cannot mix AC3 to %d channels.\n",
1037
               avctx->channels);
1038
        return -1;
1039
    }
1040

    
1041
    //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);
1042

    
1043
    //Parse the Audio Blocks.
1044
    for (i = 0; i < NB_BLOCKS; i++) {
1045
        if (ac3_parse_audio_block(ctx, i)) {
1046
            av_log(avctx, AV_LOG_ERROR, "error parsing the audio block\n");
1047
            *data_size = 0;
1048
            return ctx->frame_size;
1049
        }
1050
        start = (ctx->output_mode & AC3_OUTPUT_LFEON) ? 0 : 1;
1051
        for (k = 0; k < 256; k++)
1052
            for (j = start; j <= ctx->nfchans; j++)
1053
                *(out_samples++) = convert(int_ptr[j][k]);
1054
    }
1055
    *data_size = NB_BLOCKS * 256 * avctx->channels * sizeof (int16_t);
1056
    return ctx->frame_size;
1057
}
1058

    
1059
/* Uninitialize ac3 decoder.
1060
 */
1061
static int ac3_decode_end(AVCodecContext *avctx)
1062
{
1063
    AC3DecodeContext *ctx = (AC3DecodeContext *)avctx->priv_data;
1064
    ff_mdct_end(&ctx->imdct_512);
1065
    ff_mdct_end(&ctx->imdct_256);
1066

    
1067
    return 0;
1068
}
1069

    
1070
AVCodec ac3_decoder = {
1071
    .name = "ac3",
1072
    .type = CODEC_TYPE_AUDIO,
1073
    .id = CODEC_ID_AC3,
1074
    .priv_data_size = sizeof (AC3DecodeContext),
1075
    .init = ac3_decode_init,
1076
    .close = ac3_decode_end,
1077
    .decode = ac3_decode_frame,
1078
};
1079