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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,
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 * 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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 *
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 * 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"
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#include "bitstream.h"
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#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
/**
48
 * table for exponent to scale_factor mapping
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 * scale_factors[i] = 2 ^ -i
50
 */
51
static float scale_factors[25];
52

    
53
/** table for grouping exponents */
54
static uint8_t exp_ungroup_tbl[128][3];
55

    
56

    
57
/** tables for ungrouping mantissas */
58
static float b1_mantissas[32][3];
59
static float b2_mantissas[128][3];
60
static float b3_mantissas[8];
61
static float b4_mantissas[128][2];
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static float b5_mantissas[16];
63

    
64
/**
65
 * Quantization table: levels for symmetric. bits for asymmetric.
66
 * reference: Table 7.18 Mapping of bap to Quantizer
67
 */
68
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
71
};
72

    
73
/** dynamic range table. converts codes to scale factors. */
74
static float dynrng_tbl[256];
75

    
76
/** dialogue normalization table */
77
static float dialnorm_tbl[32];
78

    
79
/** Adjustments in dB gain */
80
#define LEVEL_MINUS_3DB         0.7071067811865476
81
#define LEVEL_MINUS_4POINT5DB   0.5946035575013605
82
#define LEVEL_MINUS_6DB         0.5000000000000000
83
#define LEVEL_MINUS_9DB         0.3535533905932738
84
#define LEVEL_ZERO              0.0000000000000000
85
#define LEVEL_ONE               1.0000000000000000
86

    
87
static const float gain_levels[6] = {
88
    LEVEL_ZERO,
89
    LEVEL_ONE,
90
    LEVEL_MINUS_3DB,
91
    LEVEL_MINUS_4POINT5DB,
92
    LEVEL_MINUS_6DB,
93
    LEVEL_MINUS_9DB
94
};
95

    
96
/**
97
 * Table for center mix levels
98
 * reference: Section 5.4.2.4 cmixlev
99
 */
100
static const uint8_t clevs[4] = { 2, 3, 4, 3 };
101

    
102
/**
103
 * Table for surround mix levels
104
 * reference: Section 5.4.2.5 surmixlev
105
 */
106
static const uint8_t slevs[4] = { 2, 4, 0, 4 };
107

    
108
/**
109
 * Table for default stereo downmixing coefficients
110
 * reference: Section 7.8.2 Downmixing Into Two Channels
111
 */
112
static const uint8_t ac3_default_coeffs[8][5][2] = {
113
    { { 1, 0 }, { 0, 1 },                               },
114
    { { 2, 2 },                                         },
115
    { { 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 }, },
121
};
122

    
123
/* override ac3.h to include coupling channel */
124
#undef AC3_MAX_CHANNELS
125
#define AC3_MAX_CHANNELS 7
126
#define CPL_CH 0
127

    
128
#define AC3_OUTPUT_LFEON  8
129

    
130
typedef struct {
131
    int acmod;                              ///< audio coding mode
132
    int dsurmod;                            ///< dolby surround mode
133
    int blksw[AC3_MAX_CHANNELS];            ///< block switch flags
134
    int dithflag[AC3_MAX_CHANNELS];         ///< dither flags
135
    int dither_all;                         ///< true if all channels are dithered
136
    int cplinu;                             ///< coupling in use
137
    int chincpl[AC3_MAX_CHANNELS];          ///< channel in coupling
138
    int phsflginu;                          ///< phase flags in use
139
    int cplbndstrc[18];                     ///< coupling band structure
140
    int rematstr;                           ///< rematrixing strategy
141
    int nrematbnd;                          ///< number of rematrixing bands
142
    int rematflg[4];                        ///< rematrixing flags
143
    int expstr[AC3_MAX_CHANNELS];           ///< exponent strategies
144
    int snroffst[AC3_MAX_CHANNELS];         ///< signal-to-noise ratio offsets
145
    int fgain[AC3_MAX_CHANNELS];            ///< fast gain values (signal-to-mask ratio)
146
    int deltbae[AC3_MAX_CHANNELS];          ///< delta bit allocation exists
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    int deltnseg[AC3_MAX_CHANNELS];         ///< number of delta segments
148
    uint8_t deltoffst[AC3_MAX_CHANNELS][8]; ///< delta segment offsets
149
    uint8_t deltlen[AC3_MAX_CHANNELS][8];   ///< delta segment lengths
150
    uint8_t deltba[AC3_MAX_CHANNELS][8];    ///< delta values for each segment
151

    
152
    int sampling_rate;                      ///< sample frequency, in Hz
153
    int bit_rate;                           ///< stream bit rate, in bits-per-second
154
    int frame_size;                         ///< current frame size, in bytes
155

    
156
    int nchans;                             ///< number of total channels
157
    int nfchans;                            ///< number of full-bandwidth channels
158
    int lfeon;                              ///< lfe channel in use
159
    int      lfe_ch;            ///< index of LFE channel
160
    int      output_mode;       ///< output channel configuration
161
    int      out_channels;      ///< number of output channels
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163
    float    downmix_coeffs[AC3_MAX_CHANNELS][2];   ///< stereo downmix coefficients
164
    float    dialnorm[2];                       ///< dialogue normalization
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    float    dynrng[2];                         ///< dynamic range
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    float cplco[AC3_MAX_CHANNELS][18];      ///< coupling coordinates
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    int ncplbnd;                            ///< number of coupling bands
168
    int ncplsubnd;                          ///< number of coupling sub bands
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    int      startmant[AC3_MAX_CHANNELS];   ///< start frequency bin
170
    int endmant[AC3_MAX_CHANNELS];          ///< end frequency bin
171
    AC3BitAllocParameters bit_alloc_params; ///< bit allocation parameters
172

    
173
    int8_t   dexps[AC3_MAX_CHANNELS][256];  ///< decoded exponents
174
    uint8_t  bap[AC3_MAX_CHANNELS][256];    ///< bit allocation pointers
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    int16_t  psd[AC3_MAX_CHANNELS][256];    ///< scaled exponents
176
    int16_t  bndpsd[AC3_MAX_CHANNELS][50];  ///< interpolated exponents
177
    int16_t  mask[AC3_MAX_CHANNELS][50];    ///< masking curve values
178

    
179
    DECLARE_ALIGNED_16(float, transform_coeffs[AC3_MAX_CHANNELS][256]);  ///< transform coefficients
180

    
181
    /* For IMDCT. */
182
    MDCTContext imdct_512;                  ///< for 512 sample IMDCT
183
    MDCTContext imdct_256;                  ///< for 256 sample IMDCT
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    DSPContext  dsp;                        ///< for optimization
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    float       add_bias;   ///< offset for float_to_int16 conversion
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    float       mul_bias;   ///< scaling for float_to_int16 conversion
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    DECLARE_ALIGNED_16(float, output[AC3_MAX_CHANNELS-1][256]);     ///< output after imdct transform and windowing
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    DECLARE_ALIGNED_16(short, int_output[AC3_MAX_CHANNELS-1][256]); ///< final 16-bit integer output
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    DECLARE_ALIGNED_16(float, delay[AC3_MAX_CHANNELS-1][256]);      ///< delay - added to the next block
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    DECLARE_ALIGNED_16(float, tmp_imdct[256]);                      ///< temporary storage for imdct transform
192
    DECLARE_ALIGNED_16(float, tmp_output[512]);                     ///< temporary storage for output before windowing
193
    DECLARE_ALIGNED_16(float, window[256]);                         ///< window coefficients
194

    
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    /* Miscellaneous. */
196
    GetBitContext gb;                       ///< bitstream reader
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    AVRandomState dith_state;               ///< for dither generation
198
    AVCodecContext *avctx;      ///< parent context
199
} AC3DecodeContext;
200

    
201
/**
202
 * Generate a Kaiser-Bessel Derived Window.
203
 */
204
static void ac3_window_init(float *window)
205
{
206
   int i, j;
207
   double sum = 0.0, bessel, tmp;
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   double local_window[256];
209
   double alpha2 = (5.0 * M_PI / 256.0) * (5.0 * M_PI / 256.0);
210

    
211
   for (i = 0; i < 256; i++) {
212
       tmp = i * (256 - i) * alpha2;
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       bessel = 1.0;
214
       for (j = 100; j > 0; j--) /* default 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;
218
   }
219

    
220
   sum++;
221
   for (i = 0; i < 256; i++)
222
       window[i] = sqrt(local_window[i] / sum);
223
}
224

    
225
/**
226
 * Symmetrical Dequantization
227
 * reference: Section 7.3.3 Expansion of Mantissas for Symmetrical Quantization
228
 *            Tables 7.19 to 7.23
229
 */
230
static inline float
231
symmetric_dequant(int code, int levels)
232
{
233
    return (code - (levels >> 1)) * (2.0f / levels);
234
}
235

    
236
/*
237
 * Initialize tables at runtime.
238
 */
239
static void ac3_tables_init(void)
240
{
241
    int i;
242

    
243
    /* generate grouped mantissa tables
244
       reference: Section 7.3.5 Ungrouping of Mantissas */
245
    for(i=0; i<32; i++) {
246
        /* bap=1 mantissas */
247
        b1_mantissas[i][0] = symmetric_dequant( i / 9     , 3);
248
        b1_mantissas[i][1] = symmetric_dequant((i % 9) / 3, 3);
249
        b1_mantissas[i][2] = symmetric_dequant((i % 9) % 3, 3);
250
    }
251
    for(i=0; i<128; i++) {
252
        /* bap=2 mantissas */
253
        b2_mantissas[i][0] = symmetric_dequant( i / 25     , 5);
254
        b2_mantissas[i][1] = symmetric_dequant((i % 25) / 5, 5);
255
        b2_mantissas[i][2] = symmetric_dequant((i % 25) % 5, 5);
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257
        /* bap=4 mantissas */
258
        b4_mantissas[i][0] = symmetric_dequant(i / 11, 11);
259
        b4_mantissas[i][1] = symmetric_dequant(i % 11, 11);
260
    }
261
    /* generate ungrouped mantissa tables
262
       reference: Tables 7.21 and 7.23 */
263
    for(i=0; i<7; i++) {
264
        /* bap=3 mantissas */
265
        b3_mantissas[i] = symmetric_dequant(i, 7);
266
    }
267
    for(i=0; i<15; i++) {
268
        /* bap=5 mantissas */
269
        b5_mantissas[i] = symmetric_dequant(i, 15);
270
    }
271

    
272
    /* generate dynamic range table
273
       reference: Section 7.7.1 Dynamic Range Control */
274
    for(i=0; i<256; i++) {
275
        int v = (i >> 5) - ((i >> 7) << 3) - 5;
276
        dynrng_tbl[i] = powf(2.0f, v) * ((i & 0x1F) | 0x20);
277
    }
278

    
279
    /* generate dialogue normalization table
280
       references: Section 5.4.2.8 dialnorm
281
                   Section 7.6 Dialogue Normalization */
282
    for(i=1; i<32; i++) {
283
        dialnorm_tbl[i] = expf((i-31) * M_LN10 / 20.0f);
284
    }
285
    dialnorm_tbl[0] = dialnorm_tbl[31];
286

    
287
    /* generate scale factors for exponents and asymmetrical dequantization
288
       reference: Section 7.3.2 Expansion of Mantissas for Asymmetric Quantization */
289
    for (i = 0; i < 25; i++)
290
        scale_factors[i] = pow(2.0, -i);
291

    
292
    /* generate exponent tables
293
       reference: Section 7.1.3 Exponent Decoding */
294
    for(i=0; i<128; i++) {
295
        exp_ungroup_tbl[i][0] =  i / 25;
296
        exp_ungroup_tbl[i][1] = (i % 25) / 5;
297
        exp_ungroup_tbl[i][2] = (i % 25) % 5;
298
    }
299
}
300

    
301

    
302
/**
303
 * AVCodec initialization
304
 */
305
static int ac3_decode_init(AVCodecContext *avctx)
306
{
307
    AC3DecodeContext *ctx = avctx->priv_data;
308
    ctx->avctx = avctx;
309

    
310
    ac3_common_init();
311
    ac3_tables_init();
312
    ff_mdct_init(&ctx->imdct_256, 8, 1);
313
    ff_mdct_init(&ctx->imdct_512, 9, 1);
314
    ac3_window_init(ctx->window);
315
    dsputil_init(&ctx->dsp, avctx);
316
    av_init_random(0, &ctx->dith_state);
317

    
318
    /* set bias values for float to int16 conversion */
319
    if(ctx->dsp.float_to_int16 == ff_float_to_int16_c) {
320
        ctx->add_bias = 385.0f;
321
        ctx->mul_bias = 1.0f;
322
    } else {
323
        ctx->add_bias = 0.0f;
324
        ctx->mul_bias = 32767.0f;
325
    }
326

    
327
    return 0;
328
}
329

    
330
/**
331
 * Parse the 'sync info' and 'bit stream info' from the AC-3 bitstream.
332
 * GetBitContext within AC3DecodeContext must point to
333
 * start of the synchronized ac3 bitstream.
334
 */
335
static int ac3_parse_header(AC3DecodeContext *ctx)
336
{
337
    AC3HeaderInfo hdr;
338
    GetBitContext *gb = &ctx->gb;
339
    float cmixlev, surmixlev;
340
    int err, i;
341

    
342
    err = ff_ac3_parse_header(gb->buffer, &hdr);
343
    if(err)
344
        return err;
345

    
346
    /* get decoding parameters from header info */
347
    ctx->bit_alloc_params.fscod       = hdr.fscod;
348
    ctx->acmod                        = hdr.acmod;
349
    cmixlev                           = gain_levels[clevs[hdr.cmixlev]];
350
    surmixlev                         = gain_levels[slevs[hdr.surmixlev]];
351
    ctx->dsurmod                      = hdr.dsurmod;
352
    ctx->lfeon                        = hdr.lfeon;
353
    ctx->bit_alloc_params.halfratecod = hdr.halfratecod;
354
    ctx->sampling_rate                = hdr.sample_rate;
355
    ctx->bit_rate                     = hdr.bit_rate;
356
    ctx->nchans                       = hdr.channels;
357
    ctx->nfchans                      = ctx->nchans - ctx->lfeon;
358
    ctx->lfe_ch                       = ctx->nfchans + 1;
359
    ctx->frame_size                   = hdr.frame_size;
360

    
361
    /* set default output to all source channels */
362
    ctx->out_channels = ctx->nchans;
363
    ctx->output_mode = ctx->acmod;
364
    if(ctx->lfeon)
365
        ctx->output_mode |= AC3_OUTPUT_LFEON;
366

    
367
    /* skip over portion of header which has already been read */
368
    skip_bits(gb, 16); // skip the sync_word
369
    skip_bits(gb, 16); // skip crc1
370
    skip_bits(gb, 8);  // skip fscod and frmsizecod
371
    skip_bits(gb, 11); // skip bsid, bsmod, and acmod
372
    if(ctx->acmod == AC3_ACMOD_STEREO) {
373
        skip_bits(gb, 2); // skip dsurmod
374
    } else {
375
        if((ctx->acmod & 1) && ctx->acmod != AC3_ACMOD_MONO)
376
            skip_bits(gb, 2); // skip cmixlev
377
        if(ctx->acmod & 4)
378
            skip_bits(gb, 2); // skip surmixlev
379
    }
380
    skip_bits1(gb); // skip lfeon
381

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

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

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

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

    
411
    /* set stereo downmixing coefficients
412
       reference: Section 7.8.2 Downmixing Into Two Channels */
413
    for(i=0; i<ctx->nfchans; i++) {
414
        ctx->downmix_coeffs[i][0] = gain_levels[ac3_default_coeffs[ctx->acmod][i][0]];
415
        ctx->downmix_coeffs[i][1] = gain_levels[ac3_default_coeffs[ctx->acmod][i][1]];
416
    }
417
    if(ctx->acmod > 1 && ctx->acmod & 1) {
418
        ctx->downmix_coeffs[1][0] = ctx->downmix_coeffs[1][1] = cmixlev;
419
    }
420
    if(ctx->acmod == AC3_ACMOD_2F1R || ctx->acmod == AC3_ACMOD_3F1R) {
421
        int nf = ctx->acmod - 2;
422
        ctx->downmix_coeffs[nf][0] = ctx->downmix_coeffs[nf][1] = surmixlev * LEVEL_MINUS_3DB;
423
    }
424
    if(ctx->acmod == AC3_ACMOD_2F2R || ctx->acmod == AC3_ACMOD_3F2R) {
425
        int nf = ctx->acmod - 4;
426
        ctx->downmix_coeffs[nf][0] = ctx->downmix_coeffs[nf+1][1] = surmixlev;
427
    }
428

    
429
    return 0;
430
}
431

    
432
/**
433
 * Decode the grouped exponents according to exponent strategy.
434
 * reference: Section 7.1.3 Exponent Decoding
435
 */
436
static void decode_exponents(GetBitContext *gb, int expstr, int ngrps,
437
                             uint8_t absexp, int8_t *dexps)
438
{
439
    int i, j, grp, grpsize;
440
    int dexp[256];
441
    int expacc, prevexp;
442

    
443
    /* unpack groups */
444
    grpsize = expstr + (expstr == EXP_D45);
445
    for(grp=0,i=0; grp<ngrps; grp++) {
446
        expacc = get_bits(gb, 7);
447
        dexp[i++] = exp_ungroup_tbl[expacc][0];
448
        dexp[i++] = exp_ungroup_tbl[expacc][1];
449
        dexp[i++] = exp_ungroup_tbl[expacc][2];
450
    }
451

    
452
    /* convert to absolute exps and expand groups */
453
    prevexp = absexp;
454
    for(i=0; i<ngrps*3; i++) {
455
        prevexp = av_clip(prevexp + dexp[i]-2, 0, 24);
456
        for(j=0; j<grpsize; j++) {
457
            dexps[(i*grpsize)+j] = prevexp;
458
        }
459
    }
460
}
461

    
462
/**
463
 * Generate transform coefficients for each coupled channel in the coupling
464
 * range using the coupling coefficients and coupling coordinates.
465
 * reference: Section 7.4.3 Coupling Coordinate Format
466
 */
467
static void uncouple_channels(AC3DecodeContext *ctx)
468
{
469
    int i, j, ch, bnd, subbnd;
470

    
471
    subbnd = -1;
472
    i = ctx->startmant[CPL_CH];
473
    for(bnd=0; bnd<ctx->ncplbnd; bnd++) {
474
        do {
475
            subbnd++;
476
            for(j=0; j<12; j++) {
477
                for(ch=1; ch<=ctx->nfchans; ch++) {
478
                    if(ctx->chincpl[ch])
479
                        ctx->transform_coeffs[ch][i] = ctx->transform_coeffs[CPL_CH][i] * ctx->cplco[ch][bnd] * 8.0f;
480
                }
481
                i++;
482
            }
483
        } while(ctx->cplbndstrc[subbnd]);
484
    }
485
}
486

    
487
/**
488
 * Grouped mantissas for 3-level 5-level and 11-level quantization
489
 */
490
typedef struct {
491
    float b1_mant[3];
492
    float b2_mant[3];
493
    float b4_mant[2];
494
    int b1ptr;
495
    int b2ptr;
496
    int b4ptr;
497
} mant_groups;
498

    
499
/**
500
 * Get the transform coefficients for a particular channel
501
 * reference: Section 7.3 Quantization and Decoding of Mantissas
502
 */
503
static int get_transform_coeffs_ch(AC3DecodeContext *ctx, int ch_index, mant_groups *m)
504
{
505
    GetBitContext *gb = &ctx->gb;
506
    int i, gcode, tbap, start, end;
507
    uint8_t *exps;
508
    uint8_t *bap;
509
    float *coeffs;
510

    
511
    exps = ctx->dexps[ch_index];
512
    bap = ctx->bap[ch_index];
513
    coeffs = ctx->transform_coeffs[ch_index];
514
    start = ctx->startmant[ch_index];
515
    end = ctx->endmant[ch_index];
516

    
517
    for (i = start; i < end; i++) {
518
        tbap = bap[i];
519
        switch (tbap) {
520
            case 0:
521
                coeffs[i] = ((av_random(&ctx->dith_state) & 0xFFFF) * LEVEL_MINUS_3DB) / 32768.0f;
522
                break;
523

    
524
            case 1:
525
                if(m->b1ptr > 2) {
526
                    gcode = get_bits(gb, 5);
527
                    m->b1_mant[0] = b1_mantissas[gcode][0];
528
                    m->b1_mant[1] = b1_mantissas[gcode][1];
529
                    m->b1_mant[2] = b1_mantissas[gcode][2];
530
                    m->b1ptr = 0;
531
                }
532
                coeffs[i] = m->b1_mant[m->b1ptr++];
533
                break;
534

    
535
            case 2:
536
                if(m->b2ptr > 2) {
537
                    gcode = get_bits(gb, 7);
538
                    m->b2_mant[0] = b2_mantissas[gcode][0];
539
                    m->b2_mant[1] = b2_mantissas[gcode][1];
540
                    m->b2_mant[2] = b2_mantissas[gcode][2];
541
                    m->b2ptr = 0;
542
                }
543
                coeffs[i] = m->b2_mant[m->b2ptr++];
544
                break;
545

    
546
            case 3:
547
                coeffs[i] = b3_mantissas[get_bits(gb, 3)];
548
                break;
549

    
550
            case 4:
551
                if(m->b4ptr > 1) {
552
                    gcode = get_bits(gb, 7);
553
                    m->b4_mant[0] = b4_mantissas[gcode][0];
554
                    m->b4_mant[1] = b4_mantissas[gcode][1];
555
                    m->b4ptr = 0;
556
                }
557
                coeffs[i] = m->b4_mant[m->b4ptr++];
558
                break;
559

    
560
            case 5:
561
                coeffs[i] = b5_mantissas[get_bits(gb, 4)];
562
                break;
563

    
564
            default:
565
                /* asymmetric dequantization */
566
                coeffs[i] = get_sbits(gb, qntztab[tbap]) * scale_factors[qntztab[tbap]-1];
567
                break;
568
        }
569
        coeffs[i] *= scale_factors[exps[i]];
570
    }
571

    
572
    return 0;
573
}
574

    
575
/**
576
 * Remove random dithering from coefficients with zero-bit mantissas
577
 * reference: Section 7.3.4 Dither for Zero Bit Mantissas (bap=0)
578
 */
579
static void remove_dithering(AC3DecodeContext *ctx) {
580
    int ch, i;
581
    int end=0;
582
    float *coeffs;
583
    uint8_t *bap;
584

    
585
    for(ch=1; ch<=ctx->nfchans; ch++) {
586
        if(!ctx->dithflag[ch]) {
587
            coeffs = ctx->transform_coeffs[ch];
588
            bap = ctx->bap[ch];
589
            if(ctx->chincpl[ch])
590
                end = ctx->startmant[CPL_CH];
591
            else
592
                end = ctx->endmant[ch];
593
            for(i=0; i<end; i++) {
594
                if(bap[i] == 0)
595
                    coeffs[i] = 0.0f;
596
            }
597
            if(ctx->chincpl[ch]) {
598
                bap = ctx->bap[CPL_CH];
599
                for(; i<ctx->endmant[CPL_CH]; i++) {
600
                    if(bap[i] == 0)
601
                        coeffs[i] = 0.0f;
602
                }
603
            }
604
        }
605
    }
606
}
607

    
608
/**
609
 * Get the transform coefficients.
610
 */
611
static int get_transform_coeffs(AC3DecodeContext * ctx)
612
{
613
    int ch, end;
614
    int got_cplchan = 0;
615
    mant_groups m;
616

    
617
    m.b1ptr = m.b2ptr = m.b4ptr = 3;
618

    
619
    for (ch = 1; ch <= ctx->nchans; ch++) {
620
        /* transform coefficients for full-bandwidth channel */
621
        if (get_transform_coeffs_ch(ctx, ch, &m))
622
            return -1;
623
        /* tranform coefficients for coupling channel come right after the
624
           coefficients for the first coupled channel*/
625
        if (ctx->chincpl[ch])  {
626
            if (!got_cplchan) {
627
                if (get_transform_coeffs_ch(ctx, CPL_CH, &m)) {
628
                    av_log(ctx->avctx, AV_LOG_ERROR, "error in decoupling channels\n");
629
                    return -1;
630
                }
631
                uncouple_channels(ctx);
632
                got_cplchan = 1;
633
            }
634
            end = ctx->endmant[CPL_CH];
635
        } else {
636
            end = ctx->endmant[ch];
637
        }
638
        do
639
            ctx->transform_coeffs[ch][end] = 0;
640
        while(++end < 256);
641
    }
642

    
643
    /* if any channel doesn't use dithering, zero appropriate coefficients */
644
    if(!ctx->dither_all)
645
        remove_dithering(ctx);
646

    
647
    return 0;
648
}
649

    
650
/**
651
 * Stereo rematrixing.
652
 * reference: Section 7.5.4 Rematrixing : Decoding Technique
653
 */
654
static void do_rematrixing(AC3DecodeContext *ctx)
655
{
656
    int bnd, i;
657
    int end, bndend;
658
    float tmp0, tmp1;
659

    
660
    end = FFMIN(ctx->endmant[1], ctx->endmant[2]);
661

    
662
    for(bnd=0; bnd<ctx->nrematbnd; bnd++) {
663
        if(ctx->rematflg[bnd]) {
664
            bndend = FFMIN(end, rematrix_band_tbl[bnd+1]);
665
            for(i=rematrix_band_tbl[bnd]; i<bndend; i++) {
666
                tmp0 = ctx->transform_coeffs[1][i];
667
                tmp1 = ctx->transform_coeffs[2][i];
668
                ctx->transform_coeffs[1][i] = tmp0 + tmp1;
669
                ctx->transform_coeffs[2][i] = tmp0 - tmp1;
670
            }
671
        }
672
    }
673
}
674

    
675
/**
676
 * Perform the 256-point IMDCT
677
 */
678
static void do_imdct_256(AC3DecodeContext *ctx, int chindex)
679
{
680
    int i, k;
681
    DECLARE_ALIGNED_16(float, x[128]);
682
    FFTComplex z[2][64];
683
    float *o_ptr = ctx->tmp_output;
684

    
685
    for(i=0; i<2; i++) {
686
        /* de-interleave coefficients */
687
        for(k=0; k<128; k++) {
688
            x[k] = ctx->transform_coeffs[chindex][2*k+i];
689
        }
690

    
691
        /* run standard IMDCT */
692
        ctx->imdct_256.fft.imdct_calc(&ctx->imdct_256, o_ptr, x, ctx->tmp_imdct);
693

    
694
        /* reverse the post-rotation & reordering from standard IMDCT */
695
        for(k=0; k<32; k++) {
696
            z[i][32+k].re = -o_ptr[128+2*k];
697
            z[i][32+k].im = -o_ptr[2*k];
698
            z[i][31-k].re =  o_ptr[2*k+1];
699
            z[i][31-k].im =  o_ptr[128+2*k+1];
700
        }
701
    }
702

    
703
    /* apply AC-3 post-rotation & reordering */
704
    for(k=0; k<64; k++) {
705
        o_ptr[    2*k  ] = -z[0][   k].im;
706
        o_ptr[    2*k+1] =  z[0][63-k].re;
707
        o_ptr[128+2*k  ] = -z[0][   k].re;
708
        o_ptr[128+2*k+1] =  z[0][63-k].im;
709
        o_ptr[256+2*k  ] = -z[1][   k].re;
710
        o_ptr[256+2*k+1] =  z[1][63-k].im;
711
        o_ptr[384+2*k  ] =  z[1][   k].im;
712
        o_ptr[384+2*k+1] = -z[1][63-k].re;
713
    }
714
}
715

    
716
/**
717
 * Inverse MDCT Transform.
718
 * Convert frequency domain coefficients to time-domain audio samples.
719
 * reference: Section 7.9.4 Transformation Equations
720
 */
721
static inline void do_imdct(AC3DecodeContext *ctx)
722
{
723
    int ch;
724
    int nchans;
725

    
726
    /* Don't perform the IMDCT on the LFE channel unless it's used in the output */
727
    nchans = ctx->nfchans;
728
    if(ctx->output_mode & AC3_OUTPUT_LFEON)
729
        nchans++;
730

    
731
    for (ch=1; ch<=nchans; ch++) {
732
        if (ctx->blksw[ch]) {
733
            do_imdct_256(ctx, ch);
734
        } else {
735
            ctx->imdct_512.fft.imdct_calc(&ctx->imdct_512, ctx->tmp_output,
736
                                          ctx->transform_coeffs[ch],
737
                                          ctx->tmp_imdct);
738
        }
739
        /* For the first half of the block, apply the window, add the delay
740
           from the previous block, and send to output */
741
        ctx->dsp.vector_fmul_add_add(ctx->output[ch-1], ctx->tmp_output,
742
                                     ctx->window, ctx->delay[ch-1], 0, 256, 1);
743
        /* For the second half of the block, apply the window and store the
744
           samples to delay, to be combined with the next block */
745
        ctx->dsp.vector_fmul_reverse(ctx->delay[ch-1], ctx->tmp_output+256,
746
                                     ctx->window, 256);
747
    }
748
}
749

    
750
/**
751
 * Downmix the output to mono or stereo.
752
 */
753
static void ac3_downmix(float samples[AC3_MAX_CHANNELS][256], int nfchans,
754
                        int output_mode, float coef[AC3_MAX_CHANNELS][2])
755
{
756
    int i, j;
757
    float v0, v1, s0, s1;
758

    
759
    for(i=0; i<256; i++) {
760
        v0 = v1 = s0 = s1 = 0.0f;
761
        for(j=0; j<nfchans; j++) {
762
            v0 += samples[j][i] * coef[j][0];
763
            v1 += samples[j][i] * coef[j][1];
764
            s0 += coef[j][0];
765
            s1 += coef[j][1];
766
        }
767
        v0 /= s0;
768
        v1 /= s1;
769
        if(output_mode == AC3_ACMOD_MONO) {
770
            samples[0][i] = (v0 + v1) * LEVEL_MINUS_3DB;
771
        } else if(output_mode == AC3_ACMOD_STEREO) {
772
            samples[0][i] = v0;
773
            samples[1][i] = v1;
774
        }
775
    }
776
}
777

    
778
/**
779
 * Parse an audio block from AC-3 bitstream.
780
 */
781
static int ac3_parse_audio_block(AC3DecodeContext *ctx, int blk)
782
{
783
    int nfchans = ctx->nfchans;
784
    int acmod = ctx->acmod;
785
    int i, bnd, seg, ch;
786
    GetBitContext *gb = &ctx->gb;
787
    uint8_t bit_alloc_stages[AC3_MAX_CHANNELS];
788

    
789
    memset(bit_alloc_stages, 0, AC3_MAX_CHANNELS);
790

    
791
    /* block switch flags */
792
    for (ch = 1; ch <= nfchans; ch++)
793
        ctx->blksw[ch] = get_bits1(gb);
794

    
795
    /* dithering flags */
796
    ctx->dither_all = 1;
797
    for (ch = 1; ch <= nfchans; ch++) {
798
        ctx->dithflag[ch] = get_bits1(gb);
799
        if(!ctx->dithflag[ch])
800
            ctx->dither_all = 0;
801
    }
802

    
803
    /* dynamic range */
804
    i = !(ctx->acmod);
805
    do {
806
        if(get_bits1(gb)) {
807
            ctx->dynrng[i] = dynrng_tbl[get_bits(gb, 8)];
808
        } else if(blk == 0) {
809
            ctx->dynrng[i] = 1.0f;
810
        }
811
    } while(i--);
812

    
813
    /* coupling strategy */
814
    if (get_bits1(gb)) {
815
        memset(bit_alloc_stages, 3, AC3_MAX_CHANNELS);
816
        ctx->cplinu = get_bits1(gb);
817
        if (ctx->cplinu) {
818
            /* coupling in use */
819
            int cplbegf, cplendf;
820

    
821
            /* determine which channels are coupled */
822
            for (ch = 1; ch <= nfchans; ch++)
823
                ctx->chincpl[ch] = get_bits1(gb);
824

    
825
            /* phase flags in use */
826
            if (acmod == AC3_ACMOD_STEREO)
827
                ctx->phsflginu = get_bits1(gb);
828

    
829
            /* coupling frequency range and band structure */
830
            cplbegf = get_bits(gb, 4);
831
            cplendf = get_bits(gb, 4);
832
            if (3 + cplendf - cplbegf < 0) {
833
                av_log(ctx->avctx, AV_LOG_ERROR, "cplendf = %d < cplbegf = %d\n", cplendf, cplbegf);
834
                return -1;
835
            }
836
            ctx->ncplbnd = ctx->ncplsubnd = 3 + cplendf - cplbegf;
837
            ctx->startmant[CPL_CH] = cplbegf * 12 + 37;
838
            ctx->endmant[CPL_CH] = cplendf * 12 + 73;
839
            for (bnd = 0; bnd < ctx->ncplsubnd - 1; bnd++) {
840
                if (get_bits1(gb)) {
841
                    ctx->cplbndstrc[bnd] = 1;
842
                    ctx->ncplbnd--;
843
                }
844
            }
845
        } else {
846
            /* coupling not in use */
847
            for (ch = 1; ch <= nfchans; ch++)
848
                ctx->chincpl[ch] = 0;
849
        }
850
    }
851

    
852
    /* coupling coordinates */
853
    if (ctx->cplinu) {
854
        int cplcoe = 0;
855

    
856
        for (ch = 1; ch <= nfchans; ch++) {
857
            if (ctx->chincpl[ch]) {
858
                if (get_bits1(gb)) {
859
                    int mstrcplco, cplcoexp, cplcomant;
860
                    cplcoe = 1;
861
                    mstrcplco = 3 * get_bits(gb, 2);
862
                    for (bnd = 0; bnd < ctx->ncplbnd; bnd++) {
863
                        cplcoexp = get_bits(gb, 4);
864
                        cplcomant = get_bits(gb, 4);
865
                        if (cplcoexp == 15)
866
                            ctx->cplco[ch][bnd] = cplcomant / 16.0f;
867
                        else
868
                            ctx->cplco[ch][bnd] = (cplcomant + 16.0f) / 32.0f;
869
                        ctx->cplco[ch][bnd] *= scale_factors[cplcoexp + mstrcplco];
870
                    }
871
                }
872
            }
873
        }
874
        /* phase flags */
875
        if (acmod == AC3_ACMOD_STEREO && ctx->phsflginu && cplcoe) {
876
            for (bnd = 0; bnd < ctx->ncplbnd; bnd++) {
877
                if (get_bits1(gb))
878
                    ctx->cplco[2][bnd] = -ctx->cplco[2][bnd];
879
            }
880
        }
881
    }
882

    
883
    /* stereo rematrixing strategy and band structure */
884
    if (acmod == AC3_ACMOD_STEREO) {
885
        ctx->rematstr = get_bits1(gb);
886
        if (ctx->rematstr) {
887
            ctx->nrematbnd = 4;
888
            if(ctx->cplinu && ctx->startmant[CPL_CH] <= 61)
889
                ctx->nrematbnd -= 1 + (ctx->startmant[CPL_CH] == 37);
890
            for(bnd=0; bnd<ctx->nrematbnd; bnd++)
891
                ctx->rematflg[bnd] = get_bits1(gb);
892
        }
893
    }
894

    
895
    /* exponent strategies for each channel */
896
    ctx->expstr[CPL_CH] = EXP_REUSE;
897
    ctx->expstr[ctx->lfe_ch] = EXP_REUSE;
898
    for (ch = !ctx->cplinu; ch <= ctx->nchans; ch++) {
899
        if(ch == ctx->lfe_ch)
900
            ctx->expstr[ch] = get_bits(gb, 1);
901
        else
902
            ctx->expstr[ch] = get_bits(gb, 2);
903
        if(ctx->expstr[ch] != EXP_REUSE)
904
            bit_alloc_stages[ch] = 3;
905
    }
906

    
907
    /* channel bandwidth */
908
    for (ch = 1; ch <= nfchans; ch++) {
909
        ctx->startmant[ch] = 0;
910
        if (ctx->expstr[ch] != EXP_REUSE) {
911
            int prev = ctx->endmant[ch];
912
            if (ctx->chincpl[ch])
913
                ctx->endmant[ch] = ctx->startmant[CPL_CH];
914
            else {
915
                int chbwcod = get_bits(gb, 6);
916
                if (chbwcod > 60) {
917
                    av_log(ctx->avctx, AV_LOG_ERROR, "chbwcod = %d > 60", chbwcod);
918
                    return -1;
919
                }
920
                ctx->endmant[ch] = chbwcod * 3 + 73;
921
            }
922
            if(blk > 0 && ctx->endmant[ch] != prev)
923
                memset(bit_alloc_stages, 3, AC3_MAX_CHANNELS);
924
        }
925
    }
926
    ctx->startmant[ctx->lfe_ch] = 0;
927
    ctx->endmant[ctx->lfe_ch] = 7;
928

    
929
    /* decode exponents for each channel */
930
    for (ch = !ctx->cplinu; ch <= ctx->nchans; ch++) {
931
        if (ctx->expstr[ch] != EXP_REUSE) {
932
            int grpsize, ngrps;
933
            grpsize = 3 << (ctx->expstr[ch] - 1);
934
            if(ch == CPL_CH)
935
                ngrps = (ctx->endmant[ch] - ctx->startmant[ch]) / grpsize;
936
            else if(ch == ctx->lfe_ch)
937
                ngrps = 2;
938
            else
939
                ngrps = (ctx->endmant[ch] + grpsize - 4) / grpsize;
940
            ctx->dexps[ch][0] = get_bits(gb, 4) << !ch;
941
            decode_exponents(gb, ctx->expstr[ch], ngrps, ctx->dexps[ch][0],
942
                             &ctx->dexps[ch][ctx->startmant[ch]+!!ch]);
943
            if(ch != CPL_CH && ch != ctx->lfe_ch)
944
                skip_bits(gb, 2); /* skip gainrng */
945
        }
946
    }
947

    
948
    /* bit allocation information */
949
    if (get_bits1(gb)) {
950
        ctx->bit_alloc_params.sdecay = ff_sdecaytab[get_bits(gb, 2)];
951
        ctx->bit_alloc_params.fdecay = ff_fdecaytab[get_bits(gb, 2)];
952
        ctx->bit_alloc_params.sgain  = ff_sgaintab[get_bits(gb, 2)];
953
        ctx->bit_alloc_params.dbknee = ff_dbkneetab[get_bits(gb, 2)];
954
        ctx->bit_alloc_params.floor  = ff_floortab[get_bits(gb, 3)];
955
        for(ch=!ctx->cplinu; ch<=ctx->nchans; ch++) {
956
            bit_alloc_stages[ch] = FFMAX(bit_alloc_stages[ch], 2);
957
        }
958
    }
959

    
960
    /* signal-to-noise ratio offsets and fast gains (signal-to-mask ratios) */
961
    if (get_bits1(gb)) {
962
        int csnr;
963
        csnr = (get_bits(gb, 6) - 15) << 4;
964
        for (ch = !ctx->cplinu; ch <= ctx->nchans; ch++) { /* snr offset and fast gain */
965
            ctx->snroffst[ch] = (csnr + get_bits(gb, 4)) << 2;
966
            ctx->fgain[ch] = ff_fgaintab[get_bits(gb, 3)];
967
        }
968
        memset(bit_alloc_stages, 3, AC3_MAX_CHANNELS);
969
    }
970

    
971
    /* coupling leak information */
972
    if (ctx->cplinu && get_bits1(gb)) {
973
        ctx->bit_alloc_params.cplfleak = get_bits(gb, 3);
974
        ctx->bit_alloc_params.cplsleak = get_bits(gb, 3);
975
        bit_alloc_stages[CPL_CH] = FFMAX(bit_alloc_stages[CPL_CH], 2);
976
    }
977

    
978
    /* delta bit allocation information */
979
    if (get_bits1(gb)) {
980
        /* delta bit allocation exists (strategy) */
981
        for (ch = !ctx->cplinu; ch <= nfchans; ch++) {
982
            ctx->deltbae[ch] = get_bits(gb, 2);
983
            if (ctx->deltbae[ch] == DBA_RESERVED) {
984
                av_log(ctx->avctx, AV_LOG_ERROR, "delta bit allocation strategy reserved\n");
985
                return -1;
986
            }
987
            bit_alloc_stages[ch] = FFMAX(bit_alloc_stages[ch], 2);
988
        }
989
        /* channel delta offset, len and bit allocation */
990
        for (ch = !ctx->cplinu; ch <= nfchans; ch++) {
991
            if (ctx->deltbae[ch] == DBA_NEW) {
992
                ctx->deltnseg[ch] = get_bits(gb, 3);
993
                for (seg = 0; seg <= ctx->deltnseg[ch]; seg++) {
994
                    ctx->deltoffst[ch][seg] = get_bits(gb, 5);
995
                    ctx->deltlen[ch][seg] = get_bits(gb, 4);
996
                    ctx->deltba[ch][seg] = get_bits(gb, 3);
997
                }
998
            }
999
        }
1000
    } else if(blk == 0) {
1001
        for(ch=0; ch<=ctx->nchans; ch++) {
1002
            ctx->deltbae[ch] = DBA_NONE;
1003
        }
1004
    }
1005

    
1006
    /* Bit allocation */
1007
    for(ch=!ctx->cplinu; ch<=ctx->nchans; ch++) {
1008
        if(bit_alloc_stages[ch] > 2) {
1009
            /* Exponent mapping into PSD and PSD integration */
1010
            ff_ac3_bit_alloc_calc_psd(ctx->dexps[ch],
1011
                                      ctx->startmant[ch], ctx->endmant[ch],
1012
                                      ctx->psd[ch], ctx->bndpsd[ch]);
1013
        }
1014
        if(bit_alloc_stages[ch] > 1) {
1015
            /* Compute excitation function, Compute masking curve, and
1016
               Apply delta bit allocation */
1017
            ff_ac3_bit_alloc_calc_mask(&ctx->bit_alloc_params, ctx->bndpsd[ch],
1018
                                       ctx->startmant[ch], ctx->endmant[ch],
1019
                                       ctx->fgain[ch], (ch == ctx->lfe_ch),
1020
                                       ctx->deltbae[ch], ctx->deltnseg[ch],
1021
                                       ctx->deltoffst[ch], ctx->deltlen[ch],
1022
                                       ctx->deltba[ch], ctx->mask[ch]);
1023
        }
1024
        if(bit_alloc_stages[ch] > 0) {
1025
            /* Compute bit allocation */
1026
            ff_ac3_bit_alloc_calc_bap(ctx->mask[ch], ctx->psd[ch],
1027
                                      ctx->startmant[ch], ctx->endmant[ch],
1028
                                      ctx->snroffst[ch],
1029
                                      ctx->bit_alloc_params.floor,
1030
                                      ctx->bap[ch]);
1031
        }
1032
    }
1033

    
1034
    /* unused dummy data */
1035
    if (get_bits1(gb)) {
1036
        int skipl = get_bits(gb, 9);
1037
        while(skipl--)
1038
            skip_bits(gb, 8);
1039
    }
1040

    
1041
    /* unpack the transform coefficients
1042
       this also uncouples channels if coupling is in use. */
1043
    if (get_transform_coeffs(ctx)) {
1044
        av_log(ctx->avctx, AV_LOG_ERROR, "Error in routine get_transform_coeffs\n");
1045
        return -1;
1046
    }
1047

    
1048
    /* recover coefficients if rematrixing is in use */
1049
    if(ctx->acmod == AC3_ACMOD_STEREO)
1050
        do_rematrixing(ctx);
1051

    
1052
    /* apply scaling to coefficients (headroom, dialnorm, dynrng) */
1053
    for(ch=1; ch<=ctx->nchans; ch++) {
1054
        float gain = 2.0f * ctx->mul_bias;
1055
        if(ctx->acmod == AC3_ACMOD_DUALMONO) {
1056
            gain *= ctx->dialnorm[ch-1] * ctx->dynrng[ch-1];
1057
        } else {
1058
            gain *= ctx->dialnorm[0] * ctx->dynrng[0];
1059
        }
1060
        for(i=0; i<ctx->endmant[ch]; i++) {
1061
            ctx->transform_coeffs[ch][i] *= gain;
1062
        }
1063
    }
1064

    
1065
    do_imdct(ctx);
1066

    
1067
    /* downmix output if needed */
1068
    if(ctx->nchans != ctx->out_channels && !((ctx->output_mode & AC3_OUTPUT_LFEON) &&
1069
            ctx->nfchans == ctx->out_channels)) {
1070
        ac3_downmix(ctx->output, ctx->nfchans, ctx->output_mode,
1071
                    ctx->downmix_coeffs);
1072
    }
1073

    
1074
    /* convert float to 16-bit integer */
1075
    for(ch=0; ch<ctx->out_channels; ch++) {
1076
        for(i=0; i<256; i++) {
1077
            ctx->output[ch][i] += ctx->add_bias;
1078
        }
1079
        ctx->dsp.float_to_int16(ctx->int_output[ch], ctx->output[ch], 256);
1080
    }
1081

    
1082
    return 0;
1083
}
1084

    
1085
/**
1086
 * Decode a single AC-3 frame.
1087
 */
1088
static int ac3_decode_frame(AVCodecContext * avctx, void *data, int *data_size, uint8_t *buf, int buf_size)
1089
{
1090
    AC3DecodeContext *ctx = (AC3DecodeContext *)avctx->priv_data;
1091
    int16_t *out_samples = (int16_t *)data;
1092
    int i, blk, ch;
1093

    
1094
    /* initialize the GetBitContext with the start of valid AC-3 Frame */
1095
    init_get_bits(&ctx->gb, buf, buf_size * 8);
1096

    
1097
    /* parse the syncinfo */
1098
    if (ac3_parse_header(ctx)) {
1099
        av_log(avctx, AV_LOG_ERROR, "\n");
1100
        *data_size = 0;
1101
        return buf_size;
1102
    }
1103

    
1104
    avctx->sample_rate = ctx->sampling_rate;
1105
    avctx->bit_rate = ctx->bit_rate;
1106

    
1107
    /* channel config */
1108
    ctx->out_channels = ctx->nchans;
1109
    if (avctx->channels == 0) {
1110
        avctx->channels = ctx->out_channels;
1111
    } else if(ctx->out_channels < avctx->channels) {
1112
        av_log(avctx, AV_LOG_ERROR, "Cannot upmix AC3 from %d to %d channels.\n",
1113
               ctx->out_channels, avctx->channels);
1114
        return -1;
1115
    }
1116
    if(avctx->channels == 2) {
1117
        ctx->output_mode = AC3_ACMOD_STEREO;
1118
    } else if(avctx->channels == 1) {
1119
        ctx->output_mode = AC3_ACMOD_MONO;
1120
    } else if(avctx->channels != ctx->out_channels) {
1121
        av_log(avctx, AV_LOG_ERROR, "Cannot downmix AC3 from %d to %d channels.\n",
1122
               ctx->out_channels, avctx->channels);
1123
        return -1;
1124
    }
1125
    ctx->out_channels = avctx->channels;
1126

    
1127
    /* parse the audio blocks */
1128
    for (blk = 0; blk < NB_BLOCKS; blk++) {
1129
        if (ac3_parse_audio_block(ctx, blk)) {
1130
            av_log(avctx, AV_LOG_ERROR, "error parsing the audio block\n");
1131
            *data_size = 0;
1132
            return ctx->frame_size;
1133
        }
1134
        for (i = 0; i < 256; i++)
1135
            for (ch = 0; ch < ctx->out_channels; ch++)
1136
                *(out_samples++) = ctx->int_output[ch][i];
1137
    }
1138
    *data_size = NB_BLOCKS * 256 * avctx->channels * sizeof (int16_t);
1139
    return ctx->frame_size;
1140
}
1141

    
1142
/**
1143
 * Uninitialize the AC-3 decoder.
1144
 */
1145
static int ac3_decode_end(AVCodecContext *avctx)
1146
{
1147
    AC3DecodeContext *ctx = (AC3DecodeContext *)avctx->priv_data;
1148
    ff_mdct_end(&ctx->imdct_512);
1149
    ff_mdct_end(&ctx->imdct_256);
1150

    
1151
    return 0;
1152
}
1153

    
1154
AVCodec ac3_decoder = {
1155
    .name = "ac3",
1156
    .type = CODEC_TYPE_AUDIO,
1157
    .id = CODEC_ID_AC3,
1158
    .priv_data_size = sizeof (AC3DecodeContext),
1159
    .init = ac3_decode_init,
1160
    .close = ac3_decode_end,
1161
    .decode = ac3_decode_frame,
1162
};