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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
7
 *
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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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 *
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 "crc.h"
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#include "dsputil.h"
40
#include "random.h"
41

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

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

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

    
57

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

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

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

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

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

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

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

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

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

    
126
#define AC3_OUTPUT_LFEON  8
127

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

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

    
153
    int channels;                           ///< number of total channels
154
    int fbw_channels;                       ///< number of full-bandwidth channels
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    int lfe_on;                             ///< lfe channel in use
156
    int lfe_ch;                             ///< index of LFE channel
157
    int output_mode;                        ///< output channel configuration
158
    int out_channels;                       ///< number of output channels
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160
    float downmix_coeffs[AC3_MAX_CHANNELS][2];  ///< stereo downmix coefficients
161
    float dynamic_range[2];                 ///< dynamic range
162
    float cpl_coords[AC3_MAX_CHANNELS][18]; ///< coupling coordinates
163
    int   num_cpl_bands;                    ///< number of coupling bands
164
    int   num_cpl_subbands;                 ///< number of coupling sub bands
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    int   start_freq[AC3_MAX_CHANNELS];     ///< start frequency bin
166
    int   end_freq[AC3_MAX_CHANNELS];       ///< end frequency bin
167
    AC3BitAllocParameters bit_alloc_params; ///< bit allocation parameters
168

    
169
    int8_t  dexps[AC3_MAX_CHANNELS][256];   ///< decoded exponents
170
    uint8_t bap[AC3_MAX_CHANNELS][256];     ///< bit allocation pointers
171
    int16_t psd[AC3_MAX_CHANNELS][256];     ///< scaled exponents
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    int16_t band_psd[AC3_MAX_CHANNELS][50]; ///< interpolated exponents
173
    int16_t mask[AC3_MAX_CHANNELS][50];     ///< masking curve values
174

    
175
    DECLARE_ALIGNED_16(float, transform_coeffs[AC3_MAX_CHANNELS][256]);  ///< transform coefficients
176

    
177
    /* For IMDCT. */
178
    MDCTContext imdct_512;                  ///< for 512 sample IMDCT
179
    MDCTContext imdct_256;                  ///< for 256 sample IMDCT
180
    DSPContext  dsp;                        ///< for optimization
181
    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
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    DECLARE_ALIGNED_16(float, tmp_output[512]);                     ///< temporary storage for output before windowing
189
    DECLARE_ALIGNED_16(float, window[256]);                         ///< window coefficients
190

    
191
    /* Miscellaneous. */
192
    GetBitContext gbc;                      ///< bitstream reader
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    AVRandomState dith_state;               ///< for dither generation
194
    AVCodecContext *avctx;                  ///< parent context
195
} AC3DecodeContext;
196

    
197
/**
198
 * Generate a Kaiser-Bessel Derived Window.
199
 */
200
static void ac3_window_init(float *window)
201
{
202
   int i, j;
203
   double sum = 0.0, bessel, tmp;
204
   double local_window[256];
205
   double alpha2 = (5.0 * M_PI / 256.0) * (5.0 * M_PI / 256.0);
206

    
207
   for (i = 0; i < 256; i++) {
208
       tmp = i * (256 - i) * alpha2;
209
       bessel = 1.0;
210
       for (j = 100; j > 0; j--) /* default to 100 iterations */
211
           bessel = bessel * tmp / (j * j) + 1;
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       sum += bessel;
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       local_window[i] = sum;
214
   }
215

    
216
   sum++;
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   for (i = 0; i < 256; i++)
218
       window[i] = sqrt(local_window[i] / sum);
219
}
220

    
221
/**
222
 * Symmetrical Dequantization
223
 * reference: Section 7.3.3 Expansion of Mantissas for Symmetrical Quantization
224
 *            Tables 7.19 to 7.23
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);
252

    
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
        dynamic_range_tab[i] = powf(2.0f, v) * ((i & 0x1F) | 0x20);
273
    }
274

    
275
    /* generate scale factors for exponents and asymmetrical dequantization
276
       reference: Section 7.3.2 Expansion of Mantissas for Asymmetric Quantization */
277
    for (i = 0; i < 25; i++)
278
        scale_factors[i] = pow(2.0, -i);
279

    
280
    /* generate exponent tables
281
       reference: Section 7.1.3 Exponent Decoding */
282
    for(i=0; i<128; i++) {
283
        exp_ungroup_tab[i][0] =  i / 25;
284
        exp_ungroup_tab[i][1] = (i % 25) / 5;
285
        exp_ungroup_tab[i][2] = (i % 25) % 5;
286
    }
287
}
288

    
289

    
290
/**
291
 * AVCodec initialization
292
 */
293
static int ac3_decode_init(AVCodecContext *avctx)
294
{
295
    AC3DecodeContext *s = avctx->priv_data;
296
    s->avctx = avctx;
297

    
298
    ac3_common_init();
299
    ac3_tables_init();
300
    ff_mdct_init(&s->imdct_256, 8, 1);
301
    ff_mdct_init(&s->imdct_512, 9, 1);
302
    ac3_window_init(s->window);
303
    dsputil_init(&s->dsp, avctx);
304
    av_init_random(0, &s->dith_state);
305

    
306
    /* set bias values for float to int16 conversion */
307
    if(s->dsp.float_to_int16 == ff_float_to_int16_c) {
308
        s->add_bias = 385.0f;
309
        s->mul_bias = 1.0f;
310
    } else {
311
        s->add_bias = 0.0f;
312
        s->mul_bias = 32767.0f;
313
    }
314

    
315
    return 0;
316
}
317

    
318
/**
319
 * Parse the 'sync info' and 'bit stream info' from the AC-3 bitstream.
320
 * GetBitContext within AC3DecodeContext must point to
321
 * start of the synchronized ac3 bitstream.
322
 */
323
static int ac3_parse_header(AC3DecodeContext *s)
324
{
325
    AC3HeaderInfo hdr;
326
    GetBitContext *gbc = &s->gbc;
327
    float center_mix_level, surround_mix_level;
328
    int err, i;
329

    
330
    err = ff_ac3_parse_header(gbc->buffer, &hdr);
331
    if(err)
332
        return err;
333

    
334
    /* get decoding parameters from header info */
335
    s->bit_alloc_params.sr_code     = hdr.sr_code;
336
    s->channel_mode                 = hdr.channel_mode;
337
    center_mix_level                = gain_levels[center_levels[hdr.center_mix_level]];
338
    surround_mix_level              = gain_levels[surround_levels[hdr.surround_mix_level]];
339
    s->lfe_on                       = hdr.lfe_on;
340
    s->bit_alloc_params.sr_shift    = hdr.sr_shift;
341
    s->sample_rate                  = hdr.sample_rate;
342
    s->bit_rate                     = hdr.bit_rate;
343
    s->channels                     = hdr.channels;
344
    s->fbw_channels                 = s->channels - s->lfe_on;
345
    s->lfe_ch                       = s->fbw_channels + 1;
346
    s->frame_size                   = hdr.frame_size;
347

    
348
    /* set default output to all source channels */
349
    s->out_channels = s->channels;
350
    s->output_mode = s->channel_mode;
351
    if(s->lfe_on)
352
        s->output_mode |= AC3_OUTPUT_LFEON;
353

    
354
    /* skip over portion of header which has already been read */
355
    skip_bits(gbc, 16); // skip the sync_word
356
    skip_bits(gbc, 16); // skip crc1
357
    skip_bits(gbc, 8);  // skip fscod and frmsizecod
358
    skip_bits(gbc, 11); // skip bsid, bsmod, and acmod
359
    if(s->channel_mode == AC3_CHMODE_STEREO) {
360
        skip_bits(gbc, 2); // skip dsurmod
361
    } else {
362
        if((s->channel_mode & 1) && s->channel_mode != AC3_CHMODE_MONO)
363
            skip_bits(gbc, 2); // skip cmixlev
364
        if(s->channel_mode & 4)
365
            skip_bits(gbc, 2); // skip surmixlev
366
    }
367
    skip_bits1(gbc); // skip lfeon
368

    
369
    /* read the rest of the bsi. read twice for dual mono mode. */
370
    i = !(s->channel_mode);
371
    do {
372
        skip_bits(gbc, 5); // skip dialog normalization
373
        if (get_bits1(gbc))
374
            skip_bits(gbc, 8); //skip compression
375
        if (get_bits1(gbc))
376
            skip_bits(gbc, 8); //skip language code
377
        if (get_bits1(gbc))
378
            skip_bits(gbc, 7); //skip audio production information
379
    } while (i--);
380

    
381
    skip_bits(gbc, 2); //skip copyright bit and original bitstream bit
382

    
383
    /* skip the timecodes (or extra bitstream information for Alternate Syntax)
384
       TODO: read & use the xbsi1 downmix levels */
385
    if (get_bits1(gbc))
386
        skip_bits(gbc, 14); //skip timecode1 / xbsi1
387
    if (get_bits1(gbc))
388
        skip_bits(gbc, 14); //skip timecode2 / xbsi2
389

    
390
    /* skip additional bitstream info */
391
    if (get_bits1(gbc)) {
392
        i = get_bits(gbc, 6);
393
        do {
394
            skip_bits(gbc, 8);
395
        } while(i--);
396
    }
397

    
398
    /* set stereo downmixing coefficients
399
       reference: Section 7.8.2 Downmixing Into Two Channels */
400
    for(i=0; i<s->fbw_channels; i++) {
401
        s->downmix_coeffs[i][0] = gain_levels[ac3_default_coeffs[s->channel_mode][i][0]];
402
        s->downmix_coeffs[i][1] = gain_levels[ac3_default_coeffs[s->channel_mode][i][1]];
403
    }
404
    if(s->channel_mode > 1 && s->channel_mode & 1) {
405
        s->downmix_coeffs[1][0] = s->downmix_coeffs[1][1] = center_mix_level;
406
    }
407
    if(s->channel_mode == AC3_CHMODE_2F1R || s->channel_mode == AC3_CHMODE_3F1R) {
408
        int nf = s->channel_mode - 2;
409
        s->downmix_coeffs[nf][0] = s->downmix_coeffs[nf][1] = surround_mix_level * LEVEL_MINUS_3DB;
410
    }
411
    if(s->channel_mode == AC3_CHMODE_2F2R || s->channel_mode == AC3_CHMODE_3F2R) {
412
        int nf = s->channel_mode - 4;
413
        s->downmix_coeffs[nf][0] = s->downmix_coeffs[nf+1][1] = surround_mix_level;
414
    }
415

    
416
    return 0;
417
}
418

    
419
/**
420
 * Decode the grouped exponents according to exponent strategy.
421
 * reference: Section 7.1.3 Exponent Decoding
422
 */
423
static void decode_exponents(GetBitContext *gbc, int exp_strategy, int ngrps,
424
                             uint8_t absexp, int8_t *dexps)
425
{
426
    int i, j, grp, group_size;
427
    int dexp[256];
428
    int expacc, prevexp;
429

    
430
    /* unpack groups */
431
    group_size = exp_strategy + (exp_strategy == EXP_D45);
432
    for(grp=0,i=0; grp<ngrps; grp++) {
433
        expacc = get_bits(gbc, 7);
434
        dexp[i++] = exp_ungroup_tab[expacc][0];
435
        dexp[i++] = exp_ungroup_tab[expacc][1];
436
        dexp[i++] = exp_ungroup_tab[expacc][2];
437
    }
438

    
439
    /* convert to absolute exps and expand groups */
440
    prevexp = absexp;
441
    for(i=0; i<ngrps*3; i++) {
442
        prevexp = av_clip(prevexp + dexp[i]-2, 0, 24);
443
        for(j=0; j<group_size; j++) {
444
            dexps[(i*group_size)+j] = prevexp;
445
        }
446
    }
447
}
448

    
449
/**
450
 * Generate transform coefficients for each coupled channel in the coupling
451
 * range using the coupling coefficients and coupling coordinates.
452
 * reference: Section 7.4.3 Coupling Coordinate Format
453
 */
454
static void uncouple_channels(AC3DecodeContext *s)
455
{
456
    int i, j, ch, bnd, subbnd;
457

    
458
    subbnd = -1;
459
    i = s->start_freq[CPL_CH];
460
    for(bnd=0; bnd<s->num_cpl_bands; bnd++) {
461
        do {
462
            subbnd++;
463
            for(j=0; j<12; j++) {
464
                for(ch=1; ch<=s->fbw_channels; ch++) {
465
                    if(s->channel_in_cpl[ch])
466
                        s->transform_coeffs[ch][i] = s->transform_coeffs[CPL_CH][i] * s->cpl_coords[ch][bnd] * 8.0f;
467
                }
468
                i++;
469
            }
470
        } while(s->cpl_band_struct[subbnd]);
471
    }
472
}
473

    
474
/**
475
 * Grouped mantissas for 3-level 5-level and 11-level quantization
476
 */
477
typedef struct {
478
    float b1_mant[3];
479
    float b2_mant[3];
480
    float b4_mant[2];
481
    int b1ptr;
482
    int b2ptr;
483
    int b4ptr;
484
} mant_groups;
485

    
486
/**
487
 * Get the transform coefficients for a particular channel
488
 * reference: Section 7.3 Quantization and Decoding of Mantissas
489
 */
490
static int get_transform_coeffs_ch(AC3DecodeContext *s, int ch_index, mant_groups *m)
491
{
492
    GetBitContext *gbc = &s->gbc;
493
    int i, gcode, tbap, start, end;
494
    uint8_t *exps;
495
    uint8_t *bap;
496
    float *coeffs;
497

    
498
    exps = s->dexps[ch_index];
499
    bap = s->bap[ch_index];
500
    coeffs = s->transform_coeffs[ch_index];
501
    start = s->start_freq[ch_index];
502
    end = s->end_freq[ch_index];
503

    
504
    for (i = start; i < end; i++) {
505
        tbap = bap[i];
506
        switch (tbap) {
507
            case 0:
508
                coeffs[i] = ((av_random(&s->dith_state) & 0xFFFF) / 65535.0f) - 0.5f;
509
                break;
510

    
511
            case 1:
512
                if(m->b1ptr > 2) {
513
                    gcode = get_bits(gbc, 5);
514
                    m->b1_mant[0] = b1_mantissas[gcode][0];
515
                    m->b1_mant[1] = b1_mantissas[gcode][1];
516
                    m->b1_mant[2] = b1_mantissas[gcode][2];
517
                    m->b1ptr = 0;
518
                }
519
                coeffs[i] = m->b1_mant[m->b1ptr++];
520
                break;
521

    
522
            case 2:
523
                if(m->b2ptr > 2) {
524
                    gcode = get_bits(gbc, 7);
525
                    m->b2_mant[0] = b2_mantissas[gcode][0];
526
                    m->b2_mant[1] = b2_mantissas[gcode][1];
527
                    m->b2_mant[2] = b2_mantissas[gcode][2];
528
                    m->b2ptr = 0;
529
                }
530
                coeffs[i] = m->b2_mant[m->b2ptr++];
531
                break;
532

    
533
            case 3:
534
                coeffs[i] = b3_mantissas[get_bits(gbc, 3)];
535
                break;
536

    
537
            case 4:
538
                if(m->b4ptr > 1) {
539
                    gcode = get_bits(gbc, 7);
540
                    m->b4_mant[0] = b4_mantissas[gcode][0];
541
                    m->b4_mant[1] = b4_mantissas[gcode][1];
542
                    m->b4ptr = 0;
543
                }
544
                coeffs[i] = m->b4_mant[m->b4ptr++];
545
                break;
546

    
547
            case 5:
548
                coeffs[i] = b5_mantissas[get_bits(gbc, 4)];
549
                break;
550

    
551
            default:
552
                /* asymmetric dequantization */
553
                coeffs[i] = get_sbits(gbc, quantization_tab[tbap]) * scale_factors[quantization_tab[tbap]-1];
554
                break;
555
        }
556
        coeffs[i] *= scale_factors[exps[i]];
557
    }
558

    
559
    return 0;
560
}
561

    
562
/**
563
 * Remove random dithering from coefficients with zero-bit mantissas
564
 * reference: Section 7.3.4 Dither for Zero Bit Mantissas (bap=0)
565
 */
566
static void remove_dithering(AC3DecodeContext *s) {
567
    int ch, i;
568
    int end=0;
569
    float *coeffs;
570
    uint8_t *bap;
571

    
572
    for(ch=1; ch<=s->fbw_channels; ch++) {
573
        if(!s->dither_flag[ch]) {
574
            coeffs = s->transform_coeffs[ch];
575
            bap = s->bap[ch];
576
            if(s->channel_in_cpl[ch])
577
                end = s->start_freq[CPL_CH];
578
            else
579
                end = s->end_freq[ch];
580
            for(i=0; i<end; i++) {
581
                if(!bap[i])
582
                    coeffs[i] = 0.0f;
583
            }
584
            if(s->channel_in_cpl[ch]) {
585
                bap = s->bap[CPL_CH];
586
                for(; i<s->end_freq[CPL_CH]; i++) {
587
                    if(!bap[i])
588
                        coeffs[i] = 0.0f;
589
                }
590
            }
591
        }
592
    }
593
}
594

    
595
/**
596
 * Get the transform coefficients.
597
 */
598
static int get_transform_coeffs(AC3DecodeContext *s)
599
{
600
    int ch, end;
601
    int got_cplchan = 0;
602
    mant_groups m;
603

    
604
    m.b1ptr = m.b2ptr = m.b4ptr = 3;
605

    
606
    for (ch = 1; ch <= s->channels; ch++) {
607
        /* transform coefficients for full-bandwidth channel */
608
        if (get_transform_coeffs_ch(s, ch, &m))
609
            return -1;
610
        /* tranform coefficients for coupling channel come right after the
611
           coefficients for the first coupled channel*/
612
        if (s->channel_in_cpl[ch])  {
613
            if (!got_cplchan) {
614
                if (get_transform_coeffs_ch(s, CPL_CH, &m)) {
615
                    av_log(s->avctx, AV_LOG_ERROR, "error in decoupling channels\n");
616
                    return -1;
617
                }
618
                uncouple_channels(s);
619
                got_cplchan = 1;
620
            }
621
            end = s->end_freq[CPL_CH];
622
        } else {
623
            end = s->end_freq[ch];
624
        }
625
        do
626
            s->transform_coeffs[ch][end] = 0;
627
        while(++end < 256);
628
    }
629

    
630
    /* if any channel doesn't use dithering, zero appropriate coefficients */
631
    if(!s->dither_all)
632
        remove_dithering(s);
633

    
634
    return 0;
635
}
636

    
637
/**
638
 * Stereo rematrixing.
639
 * reference: Section 7.5.4 Rematrixing : Decoding Technique
640
 */
641
static void do_rematrixing(AC3DecodeContext *s)
642
{
643
    int bnd, i;
644
    int end, bndend;
645
    float tmp0, tmp1;
646

    
647
    end = FFMIN(s->end_freq[1], s->end_freq[2]);
648

    
649
    for(bnd=0; bnd<s->num_rematrixing_bands; bnd++) {
650
        if(s->rematrixing_flags[bnd]) {
651
            bndend = FFMIN(end, rematrix_band_tab[bnd+1]);
652
            for(i=rematrix_band_tab[bnd]; i<bndend; i++) {
653
                tmp0 = s->transform_coeffs[1][i];
654
                tmp1 = s->transform_coeffs[2][i];
655
                s->transform_coeffs[1][i] = tmp0 + tmp1;
656
                s->transform_coeffs[2][i] = tmp0 - tmp1;
657
            }
658
        }
659
    }
660
}
661

    
662
/**
663
 * Perform the 256-point IMDCT
664
 */
665
static void do_imdct_256(AC3DecodeContext *s, int chindex)
666
{
667
    int i, k;
668
    DECLARE_ALIGNED_16(float, x[128]);
669
    FFTComplex z[2][64];
670
    float *o_ptr = s->tmp_output;
671

    
672
    for(i=0; i<2; i++) {
673
        /* de-interleave coefficients */
674
        for(k=0; k<128; k++) {
675
            x[k] = s->transform_coeffs[chindex][2*k+i];
676
        }
677

    
678
        /* run standard IMDCT */
679
        s->imdct_256.fft.imdct_calc(&s->imdct_256, o_ptr, x, s->tmp_imdct);
680

    
681
        /* reverse the post-rotation & reordering from standard IMDCT */
682
        for(k=0; k<32; k++) {
683
            z[i][32+k].re = -o_ptr[128+2*k];
684
            z[i][32+k].im = -o_ptr[2*k];
685
            z[i][31-k].re =  o_ptr[2*k+1];
686
            z[i][31-k].im =  o_ptr[128+2*k+1];
687
        }
688
    }
689

    
690
    /* apply AC-3 post-rotation & reordering */
691
    for(k=0; k<64; k++) {
692
        o_ptr[    2*k  ] = -z[0][   k].im;
693
        o_ptr[    2*k+1] =  z[0][63-k].re;
694
        o_ptr[128+2*k  ] = -z[0][   k].re;
695
        o_ptr[128+2*k+1] =  z[0][63-k].im;
696
        o_ptr[256+2*k  ] = -z[1][   k].re;
697
        o_ptr[256+2*k+1] =  z[1][63-k].im;
698
        o_ptr[384+2*k  ] =  z[1][   k].im;
699
        o_ptr[384+2*k+1] = -z[1][63-k].re;
700
    }
701
}
702

    
703
/**
704
 * Inverse MDCT Transform.
705
 * Convert frequency domain coefficients to time-domain audio samples.
706
 * reference: Section 7.9.4 Transformation Equations
707
 */
708
static inline void do_imdct(AC3DecodeContext *s)
709
{
710
    int ch;
711
    int channels;
712

    
713
    /* Don't perform the IMDCT on the LFE channel unless it's used in the output */
714
    channels = s->fbw_channels;
715
    if(s->output_mode & AC3_OUTPUT_LFEON)
716
        channels++;
717

    
718
    for (ch=1; ch<=channels; ch++) {
719
        if (s->block_switch[ch]) {
720
            do_imdct_256(s, ch);
721
        } else {
722
            s->imdct_512.fft.imdct_calc(&s->imdct_512, s->tmp_output,
723
                                        s->transform_coeffs[ch], s->tmp_imdct);
724
        }
725
        /* For the first half of the block, apply the window, add the delay
726
           from the previous block, and send to output */
727
        s->dsp.vector_fmul_add_add(s->output[ch-1], s->tmp_output,
728
                                     s->window, s->delay[ch-1], 0, 256, 1);
729
        /* For the second half of the block, apply the window and store the
730
           samples to delay, to be combined with the next block */
731
        s->dsp.vector_fmul_reverse(s->delay[ch-1], s->tmp_output+256,
732
                                   s->window, 256);
733
    }
734
}
735

    
736
/**
737
 * Downmix the output to mono or stereo.
738
 */
739
static void ac3_downmix(AC3DecodeContext *s)
740
{
741
    int i, j;
742
    float v0, v1, s0, s1;
743

    
744
    for(i=0; i<256; i++) {
745
        v0 = v1 = s0 = s1 = 0.0f;
746
        for(j=0; j<s->fbw_channels; j++) {
747
            v0 += s->output[j][i] * s->downmix_coeffs[j][0];
748
            v1 += s->output[j][i] * s->downmix_coeffs[j][1];
749
            s0 += s->downmix_coeffs[j][0];
750
            s1 += s->downmix_coeffs[j][1];
751
        }
752
        v0 /= s0;
753
        v1 /= s1;
754
        if(s->output_mode == AC3_CHMODE_MONO) {
755
            s->output[0][i] = (v0 + v1) * LEVEL_MINUS_3DB;
756
        } else if(s->output_mode == AC3_CHMODE_STEREO) {
757
            s->output[0][i] = v0;
758
            s->output[1][i] = v1;
759
        }
760
    }
761
}
762

    
763
/**
764
 * Parse an audio block from AC-3 bitstream.
765
 */
766
static int ac3_parse_audio_block(AC3DecodeContext *s, int blk)
767
{
768
    int fbw_channels = s->fbw_channels;
769
    int channel_mode = s->channel_mode;
770
    int i, bnd, seg, ch;
771
    GetBitContext *gbc = &s->gbc;
772
    uint8_t bit_alloc_stages[AC3_MAX_CHANNELS];
773

    
774
    memset(bit_alloc_stages, 0, AC3_MAX_CHANNELS);
775

    
776
    /* block switch flags */
777
    for (ch = 1; ch <= fbw_channels; ch++)
778
        s->block_switch[ch] = get_bits1(gbc);
779

    
780
    /* dithering flags */
781
    s->dither_all = 1;
782
    for (ch = 1; ch <= fbw_channels; ch++) {
783
        s->dither_flag[ch] = get_bits1(gbc);
784
        if(!s->dither_flag[ch])
785
            s->dither_all = 0;
786
    }
787

    
788
    /* dynamic range */
789
    i = !(s->channel_mode);
790
    do {
791
        if(get_bits1(gbc)) {
792
            s->dynamic_range[i] = ((dynamic_range_tab[get_bits(gbc, 8)]-1.0) *
793
                                  s->avctx->drc_scale)+1.0;
794
        } else if(blk == 0) {
795
            s->dynamic_range[i] = 1.0f;
796
        }
797
    } while(i--);
798

    
799
    /* coupling strategy */
800
    if (get_bits1(gbc)) {
801
        memset(bit_alloc_stages, 3, AC3_MAX_CHANNELS);
802
        s->cpl_in_use = get_bits1(gbc);
803
        if (s->cpl_in_use) {
804
            /* coupling in use */
805
            int cpl_begin_freq, cpl_end_freq;
806

    
807
            /* determine which channels are coupled */
808
            for (ch = 1; ch <= fbw_channels; ch++)
809
                s->channel_in_cpl[ch] = get_bits1(gbc);
810

    
811
            /* phase flags in use */
812
            if (channel_mode == AC3_CHMODE_STEREO)
813
                s->phase_flags_in_use = get_bits1(gbc);
814

    
815
            /* coupling frequency range and band structure */
816
            cpl_begin_freq = get_bits(gbc, 4);
817
            cpl_end_freq = get_bits(gbc, 4);
818
            if (3 + cpl_end_freq - cpl_begin_freq < 0) {
819
                av_log(s->avctx, AV_LOG_ERROR, "3+cplendf = %d < cplbegf = %d\n", 3+cpl_end_freq, cpl_begin_freq);
820
                return -1;
821
            }
822
            s->num_cpl_bands = s->num_cpl_subbands = 3 + cpl_end_freq - cpl_begin_freq;
823
            s->start_freq[CPL_CH] = cpl_begin_freq * 12 + 37;
824
            s->end_freq[CPL_CH] = cpl_end_freq * 12 + 73;
825
            for (bnd = 0; bnd < s->num_cpl_subbands - 1; bnd++) {
826
                if (get_bits1(gbc)) {
827
                    s->cpl_band_struct[bnd] = 1;
828
                    s->num_cpl_bands--;
829
                }
830
            }
831
        } else {
832
            /* coupling not in use */
833
            for (ch = 1; ch <= fbw_channels; ch++)
834
                s->channel_in_cpl[ch] = 0;
835
        }
836
    }
837

    
838
    /* coupling coordinates */
839
    if (s->cpl_in_use) {
840
        int cpl_coords_exist = 0;
841

    
842
        for (ch = 1; ch <= fbw_channels; ch++) {
843
            if (s->channel_in_cpl[ch]) {
844
                if (get_bits1(gbc)) {
845
                    int master_cpl_coord, cpl_coord_exp, cpl_coord_mant;
846
                    cpl_coords_exist = 1;
847
                    master_cpl_coord = 3 * get_bits(gbc, 2);
848
                    for (bnd = 0; bnd < s->num_cpl_bands; bnd++) {
849
                        cpl_coord_exp = get_bits(gbc, 4);
850
                        cpl_coord_mant = get_bits(gbc, 4);
851
                        if (cpl_coord_exp == 15)
852
                            s->cpl_coords[ch][bnd] = cpl_coord_mant / 16.0f;
853
                        else
854
                            s->cpl_coords[ch][bnd] = (cpl_coord_mant + 16.0f) / 32.0f;
855
                        s->cpl_coords[ch][bnd] *= scale_factors[cpl_coord_exp + master_cpl_coord];
856
                    }
857
                }
858
            }
859
        }
860
        /* phase flags */
861
        if (channel_mode == AC3_CHMODE_STEREO && s->phase_flags_in_use && cpl_coords_exist) {
862
            for (bnd = 0; bnd < s->num_cpl_bands; bnd++) {
863
                if (get_bits1(gbc))
864
                    s->cpl_coords[2][bnd] = -s->cpl_coords[2][bnd];
865
            }
866
        }
867
    }
868

    
869
    /* stereo rematrixing strategy and band structure */
870
    if (channel_mode == AC3_CHMODE_STEREO) {
871
        s->rematrixing_strategy = get_bits1(gbc);
872
        if (s->rematrixing_strategy) {
873
            s->num_rematrixing_bands = 4;
874
            if(s->cpl_in_use && s->start_freq[CPL_CH] <= 61)
875
                s->num_rematrixing_bands -= 1 + (s->start_freq[CPL_CH] == 37);
876
            for(bnd=0; bnd<s->num_rematrixing_bands; bnd++)
877
                s->rematrixing_flags[bnd] = get_bits1(gbc);
878
        }
879
    }
880

    
881
    /* exponent strategies for each channel */
882
    s->exp_strategy[CPL_CH] = EXP_REUSE;
883
    s->exp_strategy[s->lfe_ch] = EXP_REUSE;
884
    for (ch = !s->cpl_in_use; ch <= s->channels; ch++) {
885
        if(ch == s->lfe_ch)
886
            s->exp_strategy[ch] = get_bits(gbc, 1);
887
        else
888
            s->exp_strategy[ch] = get_bits(gbc, 2);
889
        if(s->exp_strategy[ch] != EXP_REUSE)
890
            bit_alloc_stages[ch] = 3;
891
    }
892

    
893
    /* channel bandwidth */
894
    for (ch = 1; ch <= fbw_channels; ch++) {
895
        s->start_freq[ch] = 0;
896
        if (s->exp_strategy[ch] != EXP_REUSE) {
897
            int prev = s->end_freq[ch];
898
            if (s->channel_in_cpl[ch])
899
                s->end_freq[ch] = s->start_freq[CPL_CH];
900
            else {
901
                int bandwidth_code = get_bits(gbc, 6);
902
                if (bandwidth_code > 60) {
903
                    av_log(s->avctx, AV_LOG_ERROR, "bandwidth code = %d > 60", bandwidth_code);
904
                    return -1;
905
                }
906
                s->end_freq[ch] = bandwidth_code * 3 + 73;
907
            }
908
            if(blk > 0 && s->end_freq[ch] != prev)
909
                memset(bit_alloc_stages, 3, AC3_MAX_CHANNELS);
910
        }
911
    }
912
    s->start_freq[s->lfe_ch] = 0;
913
    s->end_freq[s->lfe_ch] = 7;
914

    
915
    /* decode exponents for each channel */
916
    for (ch = !s->cpl_in_use; ch <= s->channels; ch++) {
917
        if (s->exp_strategy[ch] != EXP_REUSE) {
918
            int group_size, num_groups;
919
            group_size = 3 << (s->exp_strategy[ch] - 1);
920
            if(ch == CPL_CH)
921
                num_groups = (s->end_freq[ch] - s->start_freq[ch]) / group_size;
922
            else if(ch == s->lfe_ch)
923
                num_groups = 2;
924
            else
925
                num_groups = (s->end_freq[ch] + group_size - 4) / group_size;
926
            s->dexps[ch][0] = get_bits(gbc, 4) << !ch;
927
            decode_exponents(gbc, s->exp_strategy[ch], num_groups, s->dexps[ch][0],
928
                             &s->dexps[ch][s->start_freq[ch]+!!ch]);
929
            if(ch != CPL_CH && ch != s->lfe_ch)
930
                skip_bits(gbc, 2); /* skip gainrng */
931
        }
932
    }
933

    
934
    /* bit allocation information */
935
    if (get_bits1(gbc)) {
936
        s->bit_alloc_params.slow_decay = ff_ac3_slow_decay_tab[get_bits(gbc, 2)] >> s->bit_alloc_params.sr_shift;
937
        s->bit_alloc_params.fast_decay = ff_ac3_fast_decay_tab[get_bits(gbc, 2)] >> s->bit_alloc_params.sr_shift;
938
        s->bit_alloc_params.slow_gain  = ff_ac3_slow_gain_tab[get_bits(gbc, 2)];
939
        s->bit_alloc_params.db_per_bit = ff_ac3_db_per_bit_tab[get_bits(gbc, 2)];
940
        s->bit_alloc_params.floor  = ff_ac3_floor_tab[get_bits(gbc, 3)];
941
        for(ch=!s->cpl_in_use; ch<=s->channels; ch++) {
942
            bit_alloc_stages[ch] = FFMAX(bit_alloc_stages[ch], 2);
943
        }
944
    }
945

    
946
    /* signal-to-noise ratio offsets and fast gains (signal-to-mask ratios) */
947
    if (get_bits1(gbc)) {
948
        int csnr;
949
        csnr = (get_bits(gbc, 6) - 15) << 4;
950
        for (ch = !s->cpl_in_use; ch <= s->channels; ch++) { /* snr offset and fast gain */
951
            s->snr_offset[ch] = (csnr + get_bits(gbc, 4)) << 2;
952
            s->fast_gain[ch] = ff_ac3_fast_gain_tab[get_bits(gbc, 3)];
953
        }
954
        memset(bit_alloc_stages, 3, AC3_MAX_CHANNELS);
955
    }
956

    
957
    /* coupling leak information */
958
    if (s->cpl_in_use && get_bits1(gbc)) {
959
        s->bit_alloc_params.cpl_fast_leak = get_bits(gbc, 3);
960
        s->bit_alloc_params.cpl_slow_leak = get_bits(gbc, 3);
961
        bit_alloc_stages[CPL_CH] = FFMAX(bit_alloc_stages[CPL_CH], 2);
962
    }
963

    
964
    /* delta bit allocation information */
965
    if (get_bits1(gbc)) {
966
        /* delta bit allocation exists (strategy) */
967
        for (ch = !s->cpl_in_use; ch <= fbw_channels; ch++) {
968
            s->dba_mode[ch] = get_bits(gbc, 2);
969
            if (s->dba_mode[ch] == DBA_RESERVED) {
970
                av_log(s->avctx, AV_LOG_ERROR, "delta bit allocation strategy reserved\n");
971
                return -1;
972
            }
973
            bit_alloc_stages[ch] = FFMAX(bit_alloc_stages[ch], 2);
974
        }
975
        /* channel delta offset, len and bit allocation */
976
        for (ch = !s->cpl_in_use; ch <= fbw_channels; ch++) {
977
            if (s->dba_mode[ch] == DBA_NEW) {
978
                s->dba_nsegs[ch] = get_bits(gbc, 3);
979
                for (seg = 0; seg <= s->dba_nsegs[ch]; seg++) {
980
                    s->dba_offsets[ch][seg] = get_bits(gbc, 5);
981
                    s->dba_lengths[ch][seg] = get_bits(gbc, 4);
982
                    s->dba_values[ch][seg] = get_bits(gbc, 3);
983
                }
984
            }
985
        }
986
    } else if(blk == 0) {
987
        for(ch=0; ch<=s->channels; ch++) {
988
            s->dba_mode[ch] = DBA_NONE;
989
        }
990
    }
991

    
992
    /* Bit allocation */
993
    for(ch=!s->cpl_in_use; ch<=s->channels; ch++) {
994
        if(bit_alloc_stages[ch] > 2) {
995
            /* Exponent mapping into PSD and PSD integration */
996
            ff_ac3_bit_alloc_calc_psd(s->dexps[ch],
997
                                      s->start_freq[ch], s->end_freq[ch],
998
                                      s->psd[ch], s->band_psd[ch]);
999
        }
1000
        if(bit_alloc_stages[ch] > 1) {
1001
            /* Compute excitation function, Compute masking curve, and
1002
               Apply delta bit allocation */
1003
            ff_ac3_bit_alloc_calc_mask(&s->bit_alloc_params, s->band_psd[ch],
1004
                                       s->start_freq[ch], s->end_freq[ch],
1005
                                       s->fast_gain[ch], (ch == s->lfe_ch),
1006
                                       s->dba_mode[ch], s->dba_nsegs[ch],
1007
                                       s->dba_offsets[ch], s->dba_lengths[ch],
1008
                                       s->dba_values[ch], s->mask[ch]);
1009
        }
1010
        if(bit_alloc_stages[ch] > 0) {
1011
            /* Compute bit allocation */
1012
            ff_ac3_bit_alloc_calc_bap(s->mask[ch], s->psd[ch],
1013
                                      s->start_freq[ch], s->end_freq[ch],
1014
                                      s->snr_offset[ch],
1015
                                      s->bit_alloc_params.floor,
1016
                                      s->bap[ch]);
1017
        }
1018
    }
1019

    
1020
    /* unused dummy data */
1021
    if (get_bits1(gbc)) {
1022
        int skipl = get_bits(gbc, 9);
1023
        while(skipl--)
1024
            skip_bits(gbc, 8);
1025
    }
1026

    
1027
    /* unpack the transform coefficients
1028
       this also uncouples channels if coupling is in use. */
1029
    if (get_transform_coeffs(s)) {
1030
        av_log(s->avctx, AV_LOG_ERROR, "Error in routine get_transform_coeffs\n");
1031
        return -1;
1032
    }
1033

    
1034
    /* recover coefficients if rematrixing is in use */
1035
    if(s->channel_mode == AC3_CHMODE_STEREO)
1036
        do_rematrixing(s);
1037

    
1038
    /* apply scaling to coefficients (headroom, dynrng) */
1039
    for(ch=1; ch<=s->channels; ch++) {
1040
        float gain = 2.0f * s->mul_bias;
1041
        if(s->channel_mode == AC3_CHMODE_DUALMONO) {
1042
            gain *= s->dynamic_range[ch-1];
1043
        } else {
1044
            gain *= s->dynamic_range[0];
1045
        }
1046
        for(i=0; i<s->end_freq[ch]; i++) {
1047
            s->transform_coeffs[ch][i] *= gain;
1048
        }
1049
    }
1050

    
1051
    do_imdct(s);
1052

    
1053
    /* downmix output if needed */
1054
    if(s->channels != s->out_channels && !((s->output_mode & AC3_OUTPUT_LFEON) &&
1055
            s->fbw_channels == s->out_channels)) {
1056
        ac3_downmix(s);
1057
    }
1058

    
1059
    /* convert float to 16-bit integer */
1060
    for(ch=0; ch<s->out_channels; ch++) {
1061
        for(i=0; i<256; i++) {
1062
            s->output[ch][i] += s->add_bias;
1063
        }
1064
        s->dsp.float_to_int16(s->int_output[ch], s->output[ch], 256);
1065
    }
1066

    
1067
    return 0;
1068
}
1069

    
1070
/**
1071
 * Decode a single AC-3 frame.
1072
 */
1073
static int ac3_decode_frame(AVCodecContext * avctx, void *data, int *data_size, uint8_t *buf, int buf_size)
1074
{
1075
    AC3DecodeContext *s = avctx->priv_data;
1076
    int16_t *out_samples = (int16_t *)data;
1077
    int i, blk, ch, err;
1078

    
1079
    /* initialize the GetBitContext with the start of valid AC-3 Frame */
1080
    init_get_bits(&s->gbc, buf, buf_size * 8);
1081

    
1082
    /* parse the syncinfo */
1083
    err = ac3_parse_header(s);
1084
    if(err) {
1085
        switch(err) {
1086
            case AC3_PARSE_ERROR_SYNC:
1087
                av_log(avctx, AV_LOG_ERROR, "frame sync error\n");
1088
                break;
1089
            case AC3_PARSE_ERROR_BSID:
1090
                av_log(avctx, AV_LOG_ERROR, "invalid bitstream id\n");
1091
                break;
1092
            case AC3_PARSE_ERROR_SAMPLE_RATE:
1093
                av_log(avctx, AV_LOG_ERROR, "invalid sample rate\n");
1094
                break;
1095
            case AC3_PARSE_ERROR_FRAME_SIZE:
1096
                av_log(avctx, AV_LOG_ERROR, "invalid frame size\n");
1097
                break;
1098
            default:
1099
                av_log(avctx, AV_LOG_ERROR, "invalid header\n");
1100
                break;
1101
        }
1102
        return -1;
1103
    }
1104

    
1105
    /* check that reported frame size fits in input buffer */
1106
    if(s->frame_size > buf_size) {
1107
        av_log(avctx, AV_LOG_ERROR, "incomplete frame\n");
1108
        return -1;
1109
    }
1110

    
1111
    /* check for crc mismatch */
1112
    if(avctx->error_resilience > 0) {
1113
        if(av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0, &buf[2], s->frame_size-2)) {
1114
            av_log(avctx, AV_LOG_ERROR, "frame CRC mismatch\n");
1115
            return -1;
1116
        }
1117
        /* TODO: error concealment */
1118
    }
1119

    
1120
    avctx->sample_rate = s->sample_rate;
1121
    avctx->bit_rate = s->bit_rate;
1122

    
1123
    /* channel config */
1124
    s->out_channels = s->channels;
1125
    if (avctx->request_channels > 0 && avctx->request_channels <= 2 &&
1126
        avctx->request_channels < s->channels) {
1127
        s->out_channels = avctx->request_channels;
1128
        s->output_mode  = avctx->request_channels == 1 ? AC3_CHMODE_MONO : AC3_CHMODE_STEREO;
1129
    }
1130
    avctx->channels = s->out_channels;
1131

    
1132
    /* parse the audio blocks */
1133
    for (blk = 0; blk < NB_BLOCKS; blk++) {
1134
        if (ac3_parse_audio_block(s, blk)) {
1135
            av_log(avctx, AV_LOG_ERROR, "error parsing the audio block\n");
1136
            *data_size = 0;
1137
            return s->frame_size;
1138
        }
1139
        for (i = 0; i < 256; i++)
1140
            for (ch = 0; ch < s->out_channels; ch++)
1141
                *(out_samples++) = s->int_output[ch][i];
1142
    }
1143
    *data_size = NB_BLOCKS * 256 * avctx->channels * sizeof (int16_t);
1144
    return s->frame_size;
1145
}
1146

    
1147
/**
1148
 * Uninitialize the AC-3 decoder.
1149
 */
1150
static int ac3_decode_end(AVCodecContext *avctx)
1151
{
1152
    AC3DecodeContext *s = avctx->priv_data;
1153
    ff_mdct_end(&s->imdct_512);
1154
    ff_mdct_end(&s->imdct_256);
1155

    
1156
    return 0;
1157
}
1158

    
1159
AVCodec ac3_decoder = {
1160
    .name = "ac3",
1161
    .type = CODEC_TYPE_AUDIO,
1162
    .id = CODEC_ID_AC3,
1163
    .priv_data_size = sizeof (AC3DecodeContext),
1164
    .init = ac3_decode_init,
1165
    .close = ac3_decode_end,
1166
    .decode = ac3_decode_frame,
1167
};