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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
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 * 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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 *
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 * This file is part of FFmpeg.
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 *
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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.
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 *
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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
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 * 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
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 * 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"
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#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];
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static float b5_mantissas[16];
62

    
63
/**
64
 * Quantization table: levels for symmetric. bits for asymmetric.
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 * 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. */
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static float dynrng_tbl[256];
74

    
75
/** dialogue normalization table */
76
static float dialnorm_tbl[32];
77

    
78
/* Adjustmens in dB gain */
79
#define LEVEL_MINUS_3DB         0.7071067811865476
80
#define LEVEL_MINUS_4POINT5DB   0.5946035575013605
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#define LEVEL_MINUS_6DB         0.5000000000000000
82
#define LEVEL_MINUS_9DB         0.3535533905932738
83
#define LEVEL_ZERO              0.0000000000000000
84
#define LEVEL_ONE               1.0000000000000000
85

    
86
static const float gain_levels[6] = {
87
    LEVEL_ZERO,
88
    LEVEL_ONE,
89
    LEVEL_MINUS_3DB,
90
    LEVEL_MINUS_4POINT5DB,
91
    LEVEL_MINUS_6DB,
92
    LEVEL_MINUS_9DB
93
};
94

    
95
/**
96
 * Table for center mix levels
97
 * reference: Section 5.4.2.4 cmixlev
98
 */
99
static const uint8_t clevs[4] = { 2, 3, 4, 3 };
100

    
101
/**
102
 * Table for surround mix levels
103
 * reference: Section 5.4.2.5 surmixlev
104
 */
105
static const uint8_t slevs[4] = { 2, 4, 0, 4 };
106

    
107
/**
108
 * Table for default stereo downmixing coefficients
109
 * reference: Section 7.8.2 Downmixing Into Two Channels
110
 */
111
static const uint8_t ac3_default_coeffs[8][5][2] = {
112
    { { 1, 0 }, { 0, 1 },                               },
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    { { 2, 2 },                                         },
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    { { 1, 0 }, { 0, 1 },                               },
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    { { 1, 0 }, { 3, 3 }, { 0, 1 },                     },
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    { { 1, 0 }, { 0, 1 }, { 4, 4 },                     },
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    { { 1, 0 }, { 3, 3 }, { 0, 1 }, { 5, 5 },           },
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    { { 1, 0 }, { 0, 1 }, { 4, 0 }, { 0, 4 },           },
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    { { 1, 0 }, { 3, 3 }, { 0, 1 }, { 4, 0 }, { 0, 4 }, },
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};
121

    
122
/* override ac3.h to include coupling channel */
123
#undef AC3_MAX_CHANNELS
124
#define AC3_MAX_CHANNELS 7
125
#define CPL_CH 0
126

    
127
#define AC3_OUTPUT_LFEON  8
128

    
129
typedef struct {
130
    int acmod;
131
    int dsurmod;
132

    
133
    int blksw[AC3_MAX_CHANNELS];
134
    int dithflag[AC3_MAX_CHANNELS];
135
    int dither_all;
136
    int cplinu;
137
    int chincpl[AC3_MAX_CHANNELS];
138
    int phsflginu;
139
    int cplbndstrc[18];
140
    int rematstr;
141
    int nrematbnd;
142
    int rematflg[4];
143
    int expstr[AC3_MAX_CHANNELS];
144
    int snroffst[AC3_MAX_CHANNELS];
145
    int fgain[AC3_MAX_CHANNELS];
146
    int deltbae[AC3_MAX_CHANNELS];
147
    int deltnseg[AC3_MAX_CHANNELS];
148
    uint8_t  deltoffst[AC3_MAX_CHANNELS][8];
149
    uint8_t  deltlen[AC3_MAX_CHANNELS][8];
150
    uint8_t  deltba[AC3_MAX_CHANNELS][8];
151

    
152
    /* Derived Attributes. */
153
    int      sampling_rate;
154
    int      bit_rate;
155
    int      frame_size;
156

    
157
    int      nchans;            //number of total channels
158
    int      nfchans;           //number of full-bandwidth channels
159
    int      lfeon;             //lfe channel in use
160
    int      lfe_ch;            ///< index of LFE channel
161
    int      output_mode;       ///< output channel configuration
162
    int      out_channels;      ///< number of output channels
163

    
164
    float    downmix_coeffs[AC3_MAX_CHANNELS][2];   ///< stereo downmix coefficients
165
    float    dialnorm[2];                       ///< dialogue normalization
166
    float    dynrng[2];                         ///< dynamic range
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    float    cplco[AC3_MAX_CHANNELS][18];   //coupling coordinates
168
    int      ncplbnd;           //number of coupling bands
169
    int      ncplsubnd;         //number of coupling sub bands
170
    int      startmant[AC3_MAX_CHANNELS];   ///< start frequency bin
171
    int      endmant[AC3_MAX_CHANNELS];     //channel end mantissas
172
    AC3BitAllocParameters bit_alloc_params; ///< bit allocation parameters
173

    
174
    int8_t   dexps[AC3_MAX_CHANNELS][256];  ///< decoded exponents
175
    uint8_t  bap[AC3_MAX_CHANNELS][256];    ///< bit allocation pointers
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    int16_t  psd[AC3_MAX_CHANNELS][256];    ///< scaled exponents
177
    int16_t  bndpsd[AC3_MAX_CHANNELS][50];  ///< interpolated exponents
178
    int16_t  mask[AC3_MAX_CHANNELS][50];    ///< masking curve values
179

    
180
    DECLARE_ALIGNED_16(float, transform_coeffs[AC3_MAX_CHANNELS][256]);  //transform coefficients
181

    
182
    /* For IMDCT. */
183
    MDCTContext imdct_512;  //for 512 sample imdct transform
184
    MDCTContext imdct_256;  //for 256 sample imdct transform
185
    DSPContext  dsp;        //for optimization
186
    float       add_bias;   ///< offset for float_to_int16 conversion
187
    float       mul_bias;   ///< scaling for float_to_int16 conversion
188

    
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    DECLARE_ALIGNED_16(float, output[AC3_MAX_CHANNELS-1][256]); //output after imdct transform and windowing
190
    DECLARE_ALIGNED_16(short, int_output[AC3_MAX_CHANNELS-1][256]); ///< final 16-bit integer output
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    DECLARE_ALIGNED_16(float, delay[AC3_MAX_CHANNELS-1][256]);  //delay - added to the next block
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    DECLARE_ALIGNED_16(float, tmp_imdct[256]);                  //temporary storage for imdct transform
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    DECLARE_ALIGNED_16(float, tmp_output[512]);                 //temporary storage for output before windowing
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    DECLARE_ALIGNED_16(float, window[256]);                     //window coefficients
195

    
196
    /* Miscellaneous. */
197
    GetBitContext gb;
198
    AVRandomState dith_state;   //for dither generation
199
} AC3DecodeContext;
200

    
201
/*********** BEGIN INIT HELPER FUNCTIONS ***********/
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/**
203
 * Generate a Kaiser-Bessel Derived Window.
204
 */
205
static void ac3_window_init(float *window)
206
{
207
   int i, j;
208
   double sum = 0.0, bessel, tmp;
209
   double local_window[256];
210
   double alpha2 = (5.0 * M_PI / 256.0) * (5.0 * M_PI / 256.0);
211

    
212
   for (i = 0; i < 256; i++) {
213
       tmp = i * (256 - i) * alpha2;
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       bessel = 1.0;
215
       for (j = 100; j > 0; j--) /* defaul to 100 iterations */
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           bessel = bessel * tmp / (j * j) + 1;
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       sum += bessel;
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       local_window[i] = sum;
219
   }
220

    
221
   sum++;
222
   for (i = 0; i < 256; i++)
223
       window[i] = sqrt(local_window[i] / sum);
224
}
225

    
226
static inline float
227
symmetric_dequant(int code, int levels)
228
{
229
    return (code - (levels >> 1)) * (2.0f / levels);
230
}
231

    
232
/*
233
 * Initialize tables at runtime.
234
 */
235
static void ac3_tables_init(void)
236
{
237
    int i;
238

    
239
    /* generate grouped mantissa tables
240
       reference: Section 7.3.5 Ungrouping of Mantissas */
241
    for(i=0; i<32; i++) {
242
        /* bap=1 mantissas */
243
        b1_mantissas[i][0] = symmetric_dequant( i / 9     , 3);
244
        b1_mantissas[i][1] = symmetric_dequant((i % 9) / 3, 3);
245
        b1_mantissas[i][2] = symmetric_dequant((i % 9) % 3, 3);
246
    }
247
    for(i=0; i<128; i++) {
248
        /* bap=2 mantissas */
249
        b2_mantissas[i][0] = symmetric_dequant( i / 25     , 5);
250
        b2_mantissas[i][1] = symmetric_dequant((i % 25) / 5, 5);
251
        b2_mantissas[i][2] = symmetric_dequant((i % 25) % 5, 5);
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253
        /* bap=4 mantissas */
254
        b4_mantissas[i][0] = symmetric_dequant(i / 11, 11);
255
        b4_mantissas[i][1] = symmetric_dequant(i % 11, 11);
256
    }
257
    /* generate ungrouped mantissa tables
258
       reference: Tables 7.21 and 7.23 */
259
    for(i=0; i<7; i++) {
260
        /* bap=3 mantissas */
261
        b3_mantissas[i] = symmetric_dequant(i, 7);
262
    }
263
    for(i=0; i<15; i++) {
264
        /* bap=5 mantissas */
265
        b5_mantissas[i] = symmetric_dequant(i, 15);
266
    }
267

    
268
    /* generate dynamic range table
269
       reference: Section 7.7.1 Dynamic Range Control */
270
    for(i=0; i<256; i++) {
271
        int v = (i >> 5) - ((i >> 7) << 3) - 5;
272
        dynrng_tbl[i] = powf(2.0f, v) * ((i & 0x1F) | 0x20);
273
    }
274

    
275
    /* generate dialogue normalization table
276
       references: Section 5.4.2.8 dialnorm
277
                   Section 7.6 Dialogue Normalization */
278
    for(i=1; i<32; i++) {
279
        dialnorm_tbl[i] = expf((i-31) * M_LN10 / 20.0f);
280
    }
281
    dialnorm_tbl[0] = dialnorm_tbl[31];
282

    
283
    //generate scale factors
284
    for (i = 0; i < 25; i++)
285
        scale_factors[i] = pow(2.0, -i);
286

    
287
    /* generate exponent tables
288
       reference: Section 7.1.3 Exponent Decoding */
289
    for(i=0; i<128; i++) {
290
        exp_ungroup_tbl[i][0] =  i / 25;
291
        exp_ungroup_tbl[i][1] = (i % 25) / 5;
292
        exp_ungroup_tbl[i][2] = (i % 25) % 5;
293
    }
294
}
295

    
296

    
297
static int ac3_decode_init(AVCodecContext *avctx)
298
{
299
    AC3DecodeContext *ctx = avctx->priv_data;
300

    
301
    ac3_common_init();
302
    ac3_tables_init();
303
    ff_mdct_init(&ctx->imdct_256, 8, 1);
304
    ff_mdct_init(&ctx->imdct_512, 9, 1);
305
    ac3_window_init(ctx->window);
306
    dsputil_init(&ctx->dsp, avctx);
307
    av_init_random(0, &ctx->dith_state);
308

    
309
    if(ctx->dsp.float_to_int16 == ff_float_to_int16_c) {
310
        ctx->add_bias = 385.0f;
311
        ctx->mul_bias = 1.0f;
312
    } else {
313
        ctx->add_bias = 0.0f;
314
        ctx->mul_bias = 32767.0f;
315
    }
316

    
317
    return 0;
318
}
319
/*********** END INIT FUNCTIONS ***********/
320

    
321
/**
322
 * Parses the 'sync info' and 'bit stream info' from the AC-3 bitstream.
323
 * GetBitContext within AC3DecodeContext must point to
324
 * start of the synchronized ac3 bitstream.
325
 */
326
static int ac3_parse_header(AC3DecodeContext *ctx)
327
{
328
    AC3HeaderInfo hdr;
329
    GetBitContext *gb = &ctx->gb;
330
    float cmixlev, surmixlev;
331
    int err, i;
332

    
333
    err = ff_ac3_parse_header(gb->buffer, &hdr);
334
    if(err)
335
        return err;
336

    
337
    /* get decoding parameters from header info */
338
    ctx->bit_alloc_params.fscod       = hdr.fscod;
339
    ctx->acmod                        = hdr.acmod;
340
    cmixlev                           = gain_levels[clevs[hdr.cmixlev]];
341
    surmixlev                         = gain_levels[slevs[hdr.surmixlev]];
342
    ctx->dsurmod                      = hdr.dsurmod;
343
    ctx->lfeon                        = hdr.lfeon;
344
    ctx->bit_alloc_params.halfratecod = hdr.halfratecod;
345
    ctx->sampling_rate                = hdr.sample_rate;
346
    ctx->bit_rate                     = hdr.bit_rate;
347
    ctx->nchans                       = hdr.channels;
348
    ctx->nfchans                      = ctx->nchans - ctx->lfeon;
349
    ctx->lfe_ch                       = ctx->nfchans + 1;
350
    ctx->frame_size                   = hdr.frame_size;
351

    
352
    /* set default output to all source channels */
353
    ctx->out_channels = ctx->nchans;
354
    ctx->output_mode = ctx->acmod;
355
    if(ctx->lfeon)
356
        ctx->output_mode |= AC3_OUTPUT_LFEON;
357

    
358
    /* skip over portion of header which has already been read */
359
    skip_bits(gb, 16); //skip the sync_word, sync_info->sync_word = get_bits(gb, 16);
360
    skip_bits(gb, 16); // skip crc1
361
    skip_bits(gb, 8);  // skip fscod and frmsizecod
362
    skip_bits(gb, 11); // skip bsid, bsmod, and acmod
363
    if(ctx->acmod == AC3_ACMOD_STEREO) {
364
        skip_bits(gb, 2); // skip dsurmod
365
    } else {
366
        if((ctx->acmod & 1) && ctx->acmod != AC3_ACMOD_MONO)
367
            skip_bits(gb, 2); // skip cmixlev
368
        if(ctx->acmod & 4)
369
            skip_bits(gb, 2); // skip surmixlev
370
    }
371
    skip_bits1(gb); // skip lfeon
372

    
373
    /* read the rest of the bsi. read twice for dual mono mode. */
374
    i = !(ctx->acmod);
375
    do {
376
        ctx->dialnorm[i] = dialnorm_tbl[get_bits(gb, 5)]; // dialogue normalization
377
        if (get_bits1(gb))
378
            skip_bits(gb, 8); //skip compression
379
        if (get_bits1(gb))
380
            skip_bits(gb, 8); //skip language code
381
        if (get_bits1(gb))
382
            skip_bits(gb, 7); //skip audio production information
383
    } while (i--);
384

    
385
    skip_bits(gb, 2); //skip copyright bit and original bitstream bit
386

    
387
    /* FIXME: read & use the xbsi1 downmix levels */
388
    if (get_bits1(gb))
389
        skip_bits(gb, 14); //skip timecode1
390
    if (get_bits1(gb))
391
        skip_bits(gb, 14); //skip timecode2
392

    
393
    if (get_bits1(gb)) {
394
        i = get_bits(gb, 6); //additional bsi length
395
        do {
396
            skip_bits(gb, 8);
397
        } while(i--);
398
    }
399

    
400
    /* set stereo downmixing coefficients
401
       reference: Section 7.8.2 Downmixing Into Two Channels */
402
    for(i=0; i<ctx->nfchans; i++) {
403
        ctx->downmix_coeffs[i][0] = gain_levels[ac3_default_coeffs[ctx->acmod][i][0]];
404
        ctx->downmix_coeffs[i][1] = gain_levels[ac3_default_coeffs[ctx->acmod][i][1]];
405
    }
406
    if(ctx->acmod > 1 && ctx->acmod & 1) {
407
        ctx->downmix_coeffs[1][0] = ctx->downmix_coeffs[1][1] = cmixlev;
408
    }
409
    if(ctx->acmod == AC3_ACMOD_2F1R || ctx->acmod == AC3_ACMOD_3F1R) {
410
        int nf = ctx->acmod - 2;
411
        ctx->downmix_coeffs[nf][0] = ctx->downmix_coeffs[nf][1] = surmixlev * LEVEL_MINUS_3DB;
412
    }
413
    if(ctx->acmod == AC3_ACMOD_2F2R || ctx->acmod == AC3_ACMOD_3F2R) {
414
        int nf = ctx->acmod - 4;
415
        ctx->downmix_coeffs[nf][0] = ctx->downmix_coeffs[nf+1][1] = surmixlev;
416
    }
417

    
418
    return 0;
419
}
420

    
421
/**
422
 * Decodes the grouped exponents.
423
 * This function decodes the coded exponents according to exponent strategy
424
 * and stores them in the decoded exponents buffer.
425
 *
426
 * @param[in]  gb      GetBitContext which points to start of coded exponents
427
 * @param[in]  expstr  Exponent coding strategy
428
 * @param[in]  ngrps   Number of grouped exponents
429
 * @param[in]  absexp  Absolute exponent or DC exponent
430
 * @param[out] dexps   Decoded exponents are stored in dexps
431
 */
432
static void decode_exponents(GetBitContext *gb, int expstr, int ngrps,
433
                             uint8_t absexp, int8_t *dexps)
434
{
435
    int i, j, grp, grpsize;
436
    int dexp[256];
437
    int expacc, prevexp;
438

    
439
    /* unpack groups */
440
    grpsize = expstr + (expstr == EXP_D45);
441
    for(grp=0,i=0; grp<ngrps; grp++) {
442
        expacc = get_bits(gb, 7);
443
        dexp[i++] = exp_ungroup_tbl[expacc][0];
444
        dexp[i++] = exp_ungroup_tbl[expacc][1];
445
        dexp[i++] = exp_ungroup_tbl[expacc][2];
446
    }
447

    
448
    /* convert to absolute exps and expand groups */
449
    prevexp = absexp;
450
    for(i=0; i<ngrps*3; i++) {
451
        prevexp = av_clip(prevexp + dexp[i]-2, 0, 24);
452
        for(j=0; j<grpsize; j++) {
453
            dexps[(i*grpsize)+j] = prevexp;
454
        }
455
    }
456
}
457

    
458
/**
459
 * Generates transform coefficients for each coupled channel in the coupling
460
 * range using the coupling coefficients and coupling coordinates.
461
 * reference: Section 7.4.3 Coupling Coordinate Format
462
 */
463
static void uncouple_channels(AC3DecodeContext *ctx)
464
{
465
    int i, j, ch, bnd, subbnd;
466

    
467
    subbnd = -1;
468
    i = ctx->startmant[CPL_CH];
469
    for(bnd=0; bnd<ctx->ncplbnd; bnd++) {
470
        do {
471
            subbnd++;
472
            for(j=0; j<12; j++) {
473
                for(ch=1; ch<=ctx->nfchans; ch++) {
474
                    if(ctx->chincpl[ch])
475
                        ctx->transform_coeffs[ch][i] = ctx->transform_coeffs[CPL_CH][i] * ctx->cplco[ch][bnd] * 8.0f;
476
                }
477
                i++;
478
            }
479
        } while(ctx->cplbndstrc[subbnd]);
480
    }
481
}
482

    
483
typedef struct { /* grouped mantissas for 3-level 5-leve and 11-level quantization */
484
    float b1_mant[3];
485
    float b2_mant[3];
486
    float b4_mant[2];
487
    int b1ptr;
488
    int b2ptr;
489
    int b4ptr;
490
} mant_groups;
491

    
492
/* Get the transform coefficients for particular channel */
493
static int get_transform_coeffs_ch(AC3DecodeContext *ctx, int ch_index, mant_groups *m)
494
{
495
    GetBitContext *gb = &ctx->gb;
496
    int i, gcode, tbap, start, end;
497
    uint8_t *exps;
498
    uint8_t *bap;
499
    float *coeffs;
500

    
501
    exps = ctx->dexps[ch_index];
502
    bap = ctx->bap[ch_index];
503
    coeffs = ctx->transform_coeffs[ch_index];
504
    start = ctx->startmant[ch_index];
505
    end = ctx->endmant[ch_index];
506

    
507

    
508
    for (i = start; i < end; i++) {
509
        tbap = bap[i];
510
        switch (tbap) {
511
            case 0:
512
                coeffs[i] = ((av_random(&ctx->dith_state) & 0xFFFF) * LEVEL_MINUS_3DB) / 32768.0f;
513
                break;
514

    
515
            case 1:
516
                if(m->b1ptr > 2) {
517
                    gcode = get_bits(gb, 5);
518
                    m->b1_mant[0] = b1_mantissas[gcode][0];
519
                    m->b1_mant[1] = b1_mantissas[gcode][1];
520
                    m->b1_mant[2] = b1_mantissas[gcode][2];
521
                    m->b1ptr = 0;
522
                }
523
                coeffs[i] = m->b1_mant[m->b1ptr++];
524
                break;
525

    
526
            case 2:
527
                if(m->b2ptr > 2) {
528
                    gcode = get_bits(gb, 7);
529
                    m->b2_mant[0] = b2_mantissas[gcode][0];
530
                    m->b2_mant[1] = b2_mantissas[gcode][1];
531
                    m->b2_mant[2] = b2_mantissas[gcode][2];
532
                    m->b2ptr = 0;
533
                }
534
                coeffs[i] = m->b2_mant[m->b2ptr++];
535
                break;
536

    
537
            case 3:
538
                coeffs[i] = b3_mantissas[get_bits(gb, 3)];
539
                break;
540

    
541
            case 4:
542
                if(m->b4ptr > 1) {
543
                    gcode = get_bits(gb, 7);
544
                    m->b4_mant[0] = b4_mantissas[gcode][0];
545
                    m->b4_mant[1] = b4_mantissas[gcode][1];
546
                    m->b4ptr = 0;
547
                }
548
                coeffs[i] = m->b4_mant[m->b4ptr++];
549
                break;
550

    
551
            case 5:
552
                coeffs[i] = b5_mantissas[get_bits(gb, 4)];
553
                break;
554

    
555
            default:
556
                coeffs[i] = get_sbits(gb, qntztab[tbap]) * scale_factors[qntztab[tbap]-1];
557
                break;
558
        }
559
        coeffs[i] *= scale_factors[exps[i]];
560
    }
561

    
562
    return 0;
563
}
564

    
565
/**
566
 * Removes random dithering from coefficients with zero-bit mantissas
567
 * reference: Section 7.3.4 Dither for Zero Bit Mantissas (bap=0)
568
 */
569
static void remove_dithering(AC3DecodeContext *ctx) {
570
    int ch, i;
571
    int end=0;
572
    float *coeffs;
573
    uint8_t *bap;
574

    
575
    for(ch=1; ch<=ctx->nfchans; ch++) {
576
        if(!ctx->dithflag[ch]) {
577
            coeffs = ctx->transform_coeffs[ch];
578
            bap = ctx->bap[ch];
579
            if(ctx->chincpl[ch])
580
                end = ctx->startmant[CPL_CH];
581
            else
582
                end = ctx->endmant[ch];
583
            for(i=0; i<end; i++) {
584
                if(bap[i] == 0)
585
                    coeffs[i] = 0.0f;
586
            }
587
            if(ctx->chincpl[ch]) {
588
                bap = ctx->bap[CPL_CH];
589
                for(; i<ctx->endmant[CPL_CH]; i++) {
590
                    if(bap[i] == 0)
591
                        coeffs[i] = 0.0f;
592
                }
593
            }
594
        }
595
    }
596
}
597

    
598
/* Get the transform coefficients.
599
 * This function extracts the tranform coefficients form the ac3 bitstream.
600
 * This function is called after bit allocation is performed.
601
 */
602
static int get_transform_coeffs(AC3DecodeContext * ctx)
603
{
604
    int ch, end;
605
    int got_cplchan = 0;
606
    mant_groups m;
607

    
608
    m.b1ptr = m.b2ptr = m.b4ptr = 3;
609

    
610
    for (ch = 1; ch <= ctx->nchans; ch++) {
611
        /* transform coefficients for individual channel */
612
        if (get_transform_coeffs_ch(ctx, ch, &m))
613
            return -1;
614
        /* tranform coefficients for coupling channels */
615
        if (ctx->chincpl[ch])  {
616
            if (!got_cplchan) {
617
                if (get_transform_coeffs_ch(ctx, CPL_CH, &m)) {
618
                    av_log(NULL, AV_LOG_ERROR, "error in decoupling channels\n");
619
                    return -1;
620
                }
621
                uncouple_channels(ctx);
622
                got_cplchan = 1;
623
            }
624
            end = ctx->endmant[CPL_CH];
625
        } else {
626
            end = ctx->endmant[ch];
627
        }
628
        do
629
            ctx->transform_coeffs[ch][end] = 0;
630
        while(++end < 256);
631
    }
632

    
633
    /* if any channel doesn't use dithering, zero appropriate coefficients */
634
    if(!ctx->dither_all)
635
        remove_dithering(ctx);
636

    
637
    return 0;
638
}
639

    
640
/**
641
 * Performs stereo rematrixing.
642
 * reference: Section 7.5.4 Rematrixing : Decoding Technique
643
 */
644
static void do_rematrixing(AC3DecodeContext *ctx)
645
{
646
    int bnd, i;
647
    int end, bndend;
648
    float tmp0, tmp1;
649

    
650
    end = FFMIN(ctx->endmant[1], ctx->endmant[2]);
651

    
652
    for(bnd=0; bnd<ctx->nrematbnd; bnd++) {
653
        if(ctx->rematflg[bnd]) {
654
            bndend = FFMIN(end, rematrix_band_tbl[bnd+1]);
655
            for(i=rematrix_band_tbl[bnd]; i<bndend; i++) {
656
                tmp0 = ctx->transform_coeffs[1][i];
657
                tmp1 = ctx->transform_coeffs[2][i];
658
                ctx->transform_coeffs[1][i] = tmp0 + tmp1;
659
                ctx->transform_coeffs[2][i] = tmp0 - tmp1;
660
            }
661
        }
662
    }
663
}
664

    
665
/* This function performs the imdct on 256 sample transform
666
 * coefficients.
667
 */
668
static void do_imdct_256(AC3DecodeContext *ctx, int chindex)
669
{
670
    int i, k;
671
    DECLARE_ALIGNED_16(float, x[128]);
672
    FFTComplex z[2][64];
673
    float *o_ptr = ctx->tmp_output;
674

    
675
    for(i=0; i<2; i++) {
676
        /* de-interleave coefficients */
677
        for(k=0; k<128; k++) {
678
            x[k] = ctx->transform_coeffs[chindex][2*k+i];
679
        }
680

    
681
        /* run standard IMDCT */
682
        ctx->imdct_256.fft.imdct_calc(&ctx->imdct_256, o_ptr, x, ctx->tmp_imdct);
683

    
684
        /* reverse the post-rotation & reordering from standard IMDCT */
685
        for(k=0; k<32; k++) {
686
            z[i][32+k].re = -o_ptr[128+2*k];
687
            z[i][32+k].im = -o_ptr[2*k];
688
            z[i][31-k].re =  o_ptr[2*k+1];
689
            z[i][31-k].im =  o_ptr[128+2*k+1];
690
        }
691
    }
692

    
693
    /* apply AC-3 post-rotation & reordering */
694
    for(k=0; k<64; k++) {
695
        o_ptr[    2*k  ] = -z[0][   k].im;
696
        o_ptr[    2*k+1] =  z[0][63-k].re;
697
        o_ptr[128+2*k  ] = -z[0][   k].re;
698
        o_ptr[128+2*k+1] =  z[0][63-k].im;
699
        o_ptr[256+2*k  ] = -z[1][   k].re;
700
        o_ptr[256+2*k+1] =  z[1][63-k].im;
701
        o_ptr[384+2*k  ] =  z[1][   k].im;
702
        o_ptr[384+2*k+1] = -z[1][63-k].re;
703
    }
704
}
705

    
706
/* IMDCT Transform. */
707
static inline void do_imdct(AC3DecodeContext *ctx)
708
{
709
    int ch;
710
    int nchans;
711

    
712
    nchans = ctx->nfchans;
713
    if(ctx->output_mode & AC3_OUTPUT_LFEON)
714
        nchans++;
715

    
716
    for (ch=1; ch<=nchans; ch++) {
717
        if (ctx->blksw[ch]) {
718
            do_imdct_256(ctx, ch);
719
        } else {
720
            ctx->imdct_512.fft.imdct_calc(&ctx->imdct_512, ctx->tmp_output,
721
                                          ctx->transform_coeffs[ch],
722
                                          ctx->tmp_imdct);
723
        }
724
        ctx->dsp.vector_fmul_add_add(ctx->output[ch-1], ctx->tmp_output,
725
                                     ctx->window, ctx->delay[ch-1], 0, 256, 1);
726
        ctx->dsp.vector_fmul_reverse(ctx->delay[ch-1], ctx->tmp_output+256,
727
                                     ctx->window, 256);
728
    }
729
}
730

    
731
/**
732
 * Downmixes the output to stereo.
733
 */
734
static void ac3_downmix(float samples[AC3_MAX_CHANNELS][256], int nfchans,
735
                        int output_mode, float coef[AC3_MAX_CHANNELS][2])
736
{
737
    int i, j;
738
    float v0, v1, s0, s1;
739

    
740
    for(i=0; i<256; i++) {
741
        v0 = v1 = s0 = s1 = 0.0f;
742
        for(j=0; j<nfchans; j++) {
743
            v0 += samples[j][i] * coef[j][0];
744
            v1 += samples[j][i] * coef[j][1];
745
            s0 += coef[j][0];
746
            s1 += coef[j][1];
747
        }
748
        v0 /= s0;
749
        v1 /= s1;
750
        if(output_mode == AC3_ACMOD_MONO) {
751
            samples[0][i] = (v0 + v1) * LEVEL_MINUS_3DB;
752
        } else if(output_mode == AC3_ACMOD_STEREO) {
753
            samples[0][i] = v0;
754
            samples[1][i] = v1;
755
        }
756
    }
757
}
758

    
759
/* Parse the audio block from ac3 bitstream.
760
 * This function extract the audio block from the ac3 bitstream
761
 * and produces the output for the block. This function must
762
 * be called for each of the six audio block in the ac3 bitstream.
763
 */
764
static int ac3_parse_audio_block(AC3DecodeContext *ctx, int blk)
765
{
766
    int nfchans = ctx->nfchans;
767
    int acmod = ctx->acmod;
768
    int i, bnd, seg, ch;
769
    GetBitContext *gb = &ctx->gb;
770
    uint8_t bit_alloc_stages[AC3_MAX_CHANNELS];
771

    
772
    memset(bit_alloc_stages, 0, AC3_MAX_CHANNELS);
773

    
774
    for (ch = 1; ch <= nfchans; ch++) /*block switch flag */
775
        ctx->blksw[ch] = get_bits1(gb);
776

    
777
    ctx->dither_all = 1;
778
    for (ch = 1; ch <= nfchans; ch++) { /* dithering flag */
779
        ctx->dithflag[ch] = get_bits1(gb);
780
        if(!ctx->dithflag[ch])
781
            ctx->dither_all = 0;
782
    }
783

    
784
    /* dynamic range */
785
    i = !(ctx->acmod);
786
    do {
787
        if(get_bits1(gb)) {
788
            ctx->dynrng[i] = dynrng_tbl[get_bits(gb, 8)];
789
        } else if(blk == 0) {
790
            ctx->dynrng[i] = 1.0f;
791
        }
792
    } while(i--);
793

    
794
    if (get_bits1(gb)) { /* coupling strategy */
795
        memset(bit_alloc_stages, 3, AC3_MAX_CHANNELS);
796
        ctx->cplinu = get_bits1(gb);
797
        if (ctx->cplinu) { /* coupling in use */
798
            int cplbegf, cplendf;
799

    
800
            for (ch = 1; ch <= nfchans; ch++)
801
                ctx->chincpl[ch] = get_bits1(gb);
802

    
803
            if (acmod == AC3_ACMOD_STEREO)
804
                ctx->phsflginu = get_bits1(gb); //phase flag in use
805

    
806
            cplbegf = get_bits(gb, 4);
807
            cplendf = get_bits(gb, 4);
808

    
809
            if (3 + cplendf - cplbegf < 0) {
810
                av_log(NULL, AV_LOG_ERROR, "cplendf = %d < cplbegf = %d\n", cplendf, cplbegf);
811
                return -1;
812
            }
813

    
814
            ctx->ncplbnd = ctx->ncplsubnd = 3 + cplendf - cplbegf;
815
            ctx->startmant[CPL_CH] = cplbegf * 12 + 37;
816
            ctx->endmant[CPL_CH] = cplendf * 12 + 73;
817
            for (bnd = 0; bnd < ctx->ncplsubnd - 1; bnd++) { /* coupling band structure */
818
                if (get_bits1(gb)) {
819
                    ctx->cplbndstrc[bnd] = 1;
820
                    ctx->ncplbnd--;
821
                }
822
            }
823
        } else {
824
            for (ch = 1; ch <= nfchans; ch++)
825
                ctx->chincpl[ch] = 0;
826
        }
827
    }
828

    
829
    if (ctx->cplinu) {
830
        int cplcoe = 0;
831

    
832
        for (ch = 1; ch <= nfchans; ch++) {
833
            if (ctx->chincpl[ch]) {
834
                if (get_bits1(gb)) { /* coupling co-ordinates */
835
                    int mstrcplco, cplcoexp, cplcomant;
836
                    cplcoe = 1;
837
                    mstrcplco = 3 * get_bits(gb, 2);
838
                    for (bnd = 0; bnd < ctx->ncplbnd; bnd++) {
839
                        cplcoexp = get_bits(gb, 4);
840
                        cplcomant = get_bits(gb, 4);
841
                        if (cplcoexp == 15)
842
                            ctx->cplco[ch][bnd] = cplcomant / 16.0f;
843
                        else
844
                            ctx->cplco[ch][bnd] = (cplcomant + 16.0f) / 32.0f;
845
                        ctx->cplco[ch][bnd] *= scale_factors[cplcoexp + mstrcplco];
846
                    }
847
                }
848
            }
849
        }
850

    
851
        if (acmod == AC3_ACMOD_STEREO && ctx->phsflginu && cplcoe) {
852
            for (bnd = 0; bnd < ctx->ncplbnd; bnd++) {
853
                if (get_bits1(gb))
854
                    ctx->cplco[2][bnd] = -ctx->cplco[2][bnd];
855
            }
856
        }
857
    }
858

    
859
    if (acmod == AC3_ACMOD_STEREO) {/* rematrixing */
860
        ctx->rematstr = get_bits1(gb);
861
        if (ctx->rematstr) {
862
            ctx->nrematbnd = 4;
863
            if(ctx->cplinu && ctx->startmant[CPL_CH] <= 61)
864
                ctx->nrematbnd -= 1 + (ctx->startmant[CPL_CH] == 37);
865
            for(bnd=0; bnd<ctx->nrematbnd; bnd++)
866
                ctx->rematflg[bnd] = get_bits1(gb);
867
        }
868
    }
869

    
870
    ctx->expstr[CPL_CH] = EXP_REUSE;
871
    ctx->expstr[ctx->lfe_ch] = EXP_REUSE;
872
    for (ch = !ctx->cplinu; ch <= ctx->nchans; ch++) {
873
        if(ch == ctx->lfe_ch)
874
            ctx->expstr[ch] = get_bits(gb, 1);
875
        else
876
            ctx->expstr[ch] = get_bits(gb, 2);
877
        if(ctx->expstr[ch] != EXP_REUSE)
878
            bit_alloc_stages[ch] = 3;
879
    }
880

    
881
    for (ch = 1; ch <= nfchans; ch++) { /* channel bandwidth code */
882
        ctx->startmant[ch] = 0;
883
        if (ctx->expstr[ch] != EXP_REUSE) {
884
            int prev = ctx->endmant[ch];
885
            if (ctx->chincpl[ch])
886
                ctx->endmant[ch] = ctx->startmant[CPL_CH];
887
            else {
888
                int chbwcod = get_bits(gb, 6);
889
                if (chbwcod > 60) {
890
                    av_log(NULL, AV_LOG_ERROR, "chbwcod = %d > 60", chbwcod);
891
                    return -1;
892
                }
893
                ctx->endmant[ch] = chbwcod * 3 + 73;
894
            }
895
            if(blk > 0 && ctx->endmant[ch] != prev)
896
                memset(bit_alloc_stages, 3, AC3_MAX_CHANNELS);
897
        }
898
    }
899
    ctx->startmant[ctx->lfe_ch] = 0;
900
    ctx->endmant[ctx->lfe_ch] = 7;
901

    
902
    for (ch = !ctx->cplinu; ch <= ctx->nchans; ch++) {
903
        if (ctx->expstr[ch] != EXP_REUSE) {
904
            int grpsize, ngrps;
905
            grpsize = 3 << (ctx->expstr[ch] - 1);
906
            if(ch == CPL_CH)
907
                ngrps = (ctx->endmant[ch] - ctx->startmant[ch]) / grpsize;
908
            else if(ch == ctx->lfe_ch)
909
                ngrps = 2;
910
            else
911
                ngrps = (ctx->endmant[ch] + grpsize - 4) / grpsize;
912
            ctx->dexps[ch][0] = get_bits(gb, 4) << !ch;
913
            decode_exponents(gb, ctx->expstr[ch], ngrps, ctx->dexps[ch][0],
914
                             &ctx->dexps[ch][ctx->startmant[ch]+!!ch]);
915
            if(ch != CPL_CH && ch != ctx->lfe_ch)
916
                skip_bits(gb, 2); /* skip gainrng */
917
        }
918
    }
919

    
920
    if (get_bits1(gb)) { /* bit allocation information */
921
        ctx->bit_alloc_params.sdecay = ff_sdecaytab[get_bits(gb, 2)];
922
        ctx->bit_alloc_params.fdecay = ff_fdecaytab[get_bits(gb, 2)];
923
        ctx->bit_alloc_params.sgain  = ff_sgaintab[get_bits(gb, 2)];
924
        ctx->bit_alloc_params.dbknee = ff_dbkneetab[get_bits(gb, 2)];
925
        ctx->bit_alloc_params.floor  = ff_floortab[get_bits(gb, 3)];
926
        for(ch=!ctx->cplinu; ch<=ctx->nchans; ch++) {
927
            bit_alloc_stages[ch] = FFMAX(bit_alloc_stages[ch], 2);
928
        }
929
    }
930

    
931
    if (get_bits1(gb)) { /* snroffset */
932
        int csnr;
933
        csnr = (get_bits(gb, 6) - 15) << 4;
934
        for (ch = !ctx->cplinu; ch <= ctx->nchans; ch++) { /* snr offset and fast gain */
935
            ctx->snroffst[ch] = (csnr + get_bits(gb, 4)) << 2;
936
            ctx->fgain[ch] = ff_fgaintab[get_bits(gb, 3)];
937
        }
938
        memset(bit_alloc_stages, 3, AC3_MAX_CHANNELS);
939
    }
940

    
941
    if (ctx->cplinu && get_bits1(gb)) { /* coupling leak information */
942
        ctx->bit_alloc_params.cplfleak = get_bits(gb, 3);
943
        ctx->bit_alloc_params.cplsleak = get_bits(gb, 3);
944
        bit_alloc_stages[CPL_CH] = FFMAX(bit_alloc_stages[CPL_CH], 2);
945
    }
946

    
947
    if (get_bits1(gb)) { /* delta bit allocation information */
948
        for (ch = !ctx->cplinu; ch <= nfchans; ch++) {
949
            ctx->deltbae[ch] = get_bits(gb, 2);
950
            if (ctx->deltbae[ch] == DBA_RESERVED) {
951
                av_log(NULL, AV_LOG_ERROR, "delta bit allocation strategy reserved\n");
952
                return -1;
953
            }
954
            bit_alloc_stages[ch] = FFMAX(bit_alloc_stages[ch], 2);
955
        }
956

    
957
        for (ch = !ctx->cplinu; ch <= nfchans; ch++) {
958
            if (ctx->deltbae[ch] == DBA_NEW) {/*channel delta offset, len and bit allocation */
959
                ctx->deltnseg[ch] = get_bits(gb, 3);
960
                for (seg = 0; seg <= ctx->deltnseg[ch]; seg++) {
961
                    ctx->deltoffst[ch][seg] = get_bits(gb, 5);
962
                    ctx->deltlen[ch][seg] = get_bits(gb, 4);
963
                    ctx->deltba[ch][seg] = get_bits(gb, 3);
964
                }
965
            }
966
        }
967
    } else if(blk == 0) {
968
        for(ch=0; ch<=ctx->nchans; ch++) {
969
            ctx->deltbae[ch] = DBA_NONE;
970
        }
971
    }
972

    
973
    for(ch=!ctx->cplinu; ch<=ctx->nchans; ch++) {
974
        if(bit_alloc_stages[ch] > 2) {
975
            /* Exponent mapping into PSD and PSD integration */
976
            ff_ac3_bit_alloc_calc_psd(ctx->dexps[ch],
977
                                      ctx->startmant[ch], ctx->endmant[ch],
978
                                      ctx->psd[ch], ctx->bndpsd[ch]);
979
        }
980
        if(bit_alloc_stages[ch] > 1) {
981
            /* Compute excitation function, Compute masking curve, and
982
               Apply delta bit allocation */
983
            ff_ac3_bit_alloc_calc_mask(&ctx->bit_alloc_params, ctx->bndpsd[ch],
984
                                       ctx->startmant[ch], ctx->endmant[ch],
985
                                       ctx->fgain[ch], (ch == ctx->lfe_ch),
986
                                       ctx->deltbae[ch], ctx->deltnseg[ch],
987
                                       ctx->deltoffst[ch], ctx->deltlen[ch],
988
                                       ctx->deltba[ch], ctx->mask[ch]);
989
        }
990
        if(bit_alloc_stages[ch] > 0) {
991
            /* Compute bit allocation */
992
            ff_ac3_bit_alloc_calc_bap(ctx->mask[ch], ctx->psd[ch],
993
                                      ctx->startmant[ch], ctx->endmant[ch],
994
                                      ctx->snroffst[ch],
995
                                      ctx->bit_alloc_params.floor,
996
                                      ctx->bap[ch]);
997
        }
998
    }
999

    
1000
    if (get_bits1(gb)) { /* unused dummy data */
1001
        int skipl = get_bits(gb, 9);
1002
        while(skipl--)
1003
            skip_bits(gb, 8);
1004
    }
1005
    /* unpack the transform coefficients
1006
     * * this also uncouples channels if coupling is in use.
1007
     */
1008
    if (get_transform_coeffs(ctx)) {
1009
        av_log(NULL, AV_LOG_ERROR, "Error in routine get_transform_coeffs\n");
1010
        return -1;
1011
    }
1012

    
1013
    /* recover coefficients if rematrixing is in use */
1014
    if(ctx->acmod == AC3_ACMOD_STEREO)
1015
        do_rematrixing(ctx);
1016

    
1017
    /* apply scaling to coefficients (headroom, dialnorm, dynrng) */
1018
    for(ch=1; ch<=ctx->nchans; ch++) {
1019
        float gain = 2.0f * ctx->mul_bias;
1020
        if(ctx->acmod == AC3_ACMOD_DUALMONO) {
1021
            gain *= ctx->dialnorm[ch-1] * ctx->dynrng[ch-1];
1022
        } else {
1023
            gain *= ctx->dialnorm[0] * ctx->dynrng[0];
1024
        }
1025
        for(i=0; i<ctx->endmant[ch]; i++) {
1026
            ctx->transform_coeffs[ch][i] *= gain;
1027
        }
1028
    }
1029

    
1030
    do_imdct(ctx);
1031

    
1032
    /* downmix output if needed */
1033
    if(ctx->nchans != ctx->out_channels && !((ctx->output_mode & AC3_OUTPUT_LFEON) &&
1034
            ctx->nfchans == ctx->out_channels)) {
1035
        ac3_downmix(ctx->output, ctx->nfchans, ctx->output_mode,
1036
                    ctx->downmix_coeffs);
1037
    }
1038

    
1039
    /* convert float to 16-bit integer */
1040
    for(ch=0; ch<ctx->out_channels; ch++) {
1041
        for(i=0; i<256; i++) {
1042
            ctx->output[ch][i] += ctx->add_bias;
1043
        }
1044
        ctx->dsp.float_to_int16(ctx->int_output[ch], ctx->output[ch], 256);
1045
    }
1046

    
1047
    return 0;
1048
}
1049

    
1050
/* Decode ac3 frame.
1051
 *
1052
 * @param avctx Pointer to AVCodecContext
1053
 * @param data Pointer to pcm smaples
1054
 * @param data_size Set to number of pcm samples produced by decoding
1055
 * @param buf Data to be decoded
1056
 * @param buf_size Size of the buffer
1057
 */
1058
static int ac3_decode_frame(AVCodecContext * avctx, void *data, int *data_size, uint8_t *buf, int buf_size)
1059
{
1060
    AC3DecodeContext *ctx = (AC3DecodeContext *)avctx->priv_data;
1061
    int16_t *out_samples = (int16_t *)data;
1062
    int i, blk, ch;
1063

    
1064
    //Initialize the GetBitContext with the start of valid AC3 Frame.
1065
    init_get_bits(&ctx->gb, buf, buf_size * 8);
1066

    
1067
    //Parse the syncinfo.
1068
    if (ac3_parse_header(ctx)) {
1069
        av_log(avctx, AV_LOG_ERROR, "\n");
1070
        *data_size = 0;
1071
        return buf_size;
1072
    }
1073

    
1074
    avctx->sample_rate = ctx->sampling_rate;
1075
    avctx->bit_rate = ctx->bit_rate;
1076

    
1077
    /* channel config */
1078
    ctx->out_channels = ctx->nchans;
1079
    if (avctx->channels == 0) {
1080
        avctx->channels = ctx->out_channels;
1081
    } else if(ctx->out_channels < avctx->channels) {
1082
        av_log(avctx, AV_LOG_ERROR, "Cannot upmix AC3 from %d to %d channels.\n",
1083
               ctx->out_channels, avctx->channels);
1084
        return -1;
1085
    }
1086
    if(avctx->channels == 2) {
1087
        ctx->output_mode = AC3_ACMOD_STEREO;
1088
    } else if(avctx->channels == 1) {
1089
        ctx->output_mode = AC3_ACMOD_MONO;
1090
    } else if(avctx->channels != ctx->out_channels) {
1091
        av_log(avctx, AV_LOG_ERROR, "Cannot downmix AC3 from %d to %d channels.\n",
1092
               ctx->out_channels, avctx->channels);
1093
        return -1;
1094
    }
1095
    ctx->out_channels = avctx->channels;
1096

    
1097
    //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);
1098

    
1099
    //Parse the Audio Blocks.
1100
    for (blk = 0; blk < NB_BLOCKS; blk++) {
1101
        if (ac3_parse_audio_block(ctx, blk)) {
1102
            av_log(avctx, AV_LOG_ERROR, "error parsing the audio block\n");
1103
            *data_size = 0;
1104
            return ctx->frame_size;
1105
        }
1106
        for (i = 0; i < 256; i++)
1107
            for (ch = 0; ch < ctx->out_channels; ch++)
1108
                *(out_samples++) = ctx->int_output[ch][i];
1109
    }
1110
    *data_size = NB_BLOCKS * 256 * avctx->channels * sizeof (int16_t);
1111
    return ctx->frame_size;
1112
}
1113

    
1114
/* Uninitialize ac3 decoder.
1115
 */
1116
static int ac3_decode_end(AVCodecContext *avctx)
1117
{
1118
    AC3DecodeContext *ctx = (AC3DecodeContext *)avctx->priv_data;
1119
    ff_mdct_end(&ctx->imdct_512);
1120
    ff_mdct_end(&ctx->imdct_256);
1121

    
1122
    return 0;
1123
}
1124

    
1125
AVCodec ac3_decoder = {
1126
    .name = "ac3",
1127
    .type = CODEC_TYPE_AUDIO,
1128
    .id = CODEC_ID_AC3,
1129
    .priv_data_size = sizeof (AC3DecodeContext),
1130
    .init = ac3_decode_init,
1131
    .close = ac3_decode_end,
1132
    .decode = ac3_decode_frame,
1133
};
1134