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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>
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#include <string.h>
34

    
35
#include "avcodec.h"
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#include "ac3_parser.h"
37
#include "bitstream.h"
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#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
 */
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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.
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 * reference: Table 7.18 Mapping of bap to Quantizer
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 */
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static const uint8_t quantization_tab[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
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
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#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 },                                         },
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    { { 1, 0 }, { 0, 1 },                               },
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    { { 1, 0 }, { 3, 3 }, { 0, 1 },                     },
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    { { 1, 0 }, { 0, 1 }, { 4, 4 },                     },
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    { { 1, 0 }, { 3, 3 }, { 0, 1 }, { 5, 5 },           },
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    { { 1, 0 }, { 0, 1 }, { 4, 0 }, { 0, 4 },           },
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    { { 1, 0 }, { 3, 3 }, { 0, 1 }, { 4, 0 }, { 0, 4 }, },
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};
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 phase_flags[18];                    ///< phase flags
137
    int cpl_band_struct[18];                ///< coupling band structure
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
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    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
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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
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    int lfe_ch;                             ///< index of LFE channel
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    int output_mode;                        ///< output channel configuration
158
    int out_channels;                       ///< number of output channels
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160
    int center_mix_level;                   ///< Center mix level index
161
    int surround_mix_level;                 ///< Surround mix level index
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    float downmix_coeffs[AC3_MAX_CHANNELS][2];  ///< stereo downmix coefficients
163
    float dynamic_range[2];                 ///< dynamic range
164
    float cpl_coords[AC3_MAX_CHANNELS][18]; ///< coupling coordinates
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    int   num_cpl_bands;                    ///< number of coupling bands
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    int   num_cpl_subbands;                 ///< number of coupling sub bands
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    int   start_freq[AC3_MAX_CHANNELS];     ///< start frequency bin
168
    int   end_freq[AC3_MAX_CHANNELS];       ///< end frequency bin
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    AC3BitAllocParameters bit_alloc_params; ///< bit allocation parameters
170

    
171
    int8_t  dexps[AC3_MAX_CHANNELS][256];   ///< decoded exponents
172
    uint8_t bap[AC3_MAX_CHANNELS][256];     ///< bit allocation pointers
173
    int16_t psd[AC3_MAX_CHANNELS][256];     ///< scaled exponents
174
    int16_t band_psd[AC3_MAX_CHANNELS][50]; ///< interpolated exponents
175
    int16_t mask[AC3_MAX_CHANNELS][50];     ///< masking curve values
176

    
177
    DECLARE_ALIGNED_16(float, transform_coeffs[AC3_MAX_CHANNELS][256]);  ///< transform coefficients
178

    
179
    /* For IMDCT. */
180
    MDCTContext imdct_512;                  ///< for 512 sample IMDCT
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    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
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    DECLARE_ALIGNED_16(float, tmp_output[512]);                     ///< temporary storage for output before windowing
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    DECLARE_ALIGNED_16(float, window[256]);                         ///< window coefficients
192

    
193
    /* Miscellaneous. */
194
    GetBitContext gbc;                      ///< bitstream reader
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    AVRandomState dith_state;               ///< for dither generation
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    AVCodecContext *avctx;                  ///< parent context
197
} AC3DecodeContext;
198

    
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/**
200
 * Symmetrical Dequantization
201
 * reference: Section 7.3.3 Expansion of Mantissas for Symmetrical Quantization
202
 *            Tables 7.19 to 7.23
203
 */
204
static inline float
205
symmetric_dequant(int code, int levels)
206
{
207
    return (code - (levels >> 1)) * (2.0f / levels);
208
}
209

    
210
/*
211
 * Initialize tables at runtime.
212
 */
213
static void ac3_tables_init(void)
214
{
215
    int i;
216

    
217
    /* generate grouped mantissa tables
218
       reference: Section 7.3.5 Ungrouping of Mantissas */
219
    for(i=0; i<32; i++) {
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        /* bap=1 mantissas */
221
        b1_mantissas[i][0] = symmetric_dequant( i / 9     , 3);
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        b1_mantissas[i][1] = symmetric_dequant((i % 9) / 3, 3);
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        b1_mantissas[i][2] = symmetric_dequant((i % 9) % 3, 3);
224
    }
225
    for(i=0; i<128; i++) {
226
        /* bap=2 mantissas */
227
        b2_mantissas[i][0] = symmetric_dequant( i / 25     , 5);
228
        b2_mantissas[i][1] = symmetric_dequant((i % 25) / 5, 5);
229
        b2_mantissas[i][2] = symmetric_dequant((i % 25) % 5, 5);
230

    
231
        /* bap=4 mantissas */
232
        b4_mantissas[i][0] = symmetric_dequant(i / 11, 11);
233
        b4_mantissas[i][1] = symmetric_dequant(i % 11, 11);
234
    }
235
    /* generate ungrouped mantissa tables
236
       reference: Tables 7.21 and 7.23 */
237
    for(i=0; i<7; i++) {
238
        /* bap=3 mantissas */
239
        b3_mantissas[i] = symmetric_dequant(i, 7);
240
    }
241
    for(i=0; i<15; i++) {
242
        /* bap=5 mantissas */
243
        b5_mantissas[i] = symmetric_dequant(i, 15);
244
    }
245

    
246
    /* generate dynamic range table
247
       reference: Section 7.7.1 Dynamic Range Control */
248
    for(i=0; i<256; i++) {
249
        int v = (i >> 5) - ((i >> 7) << 3) - 5;
250
        dynamic_range_tab[i] = powf(2.0f, v) * ((i & 0x1F) | 0x20);
251
    }
252

    
253
    /* generate scale factors for exponents and asymmetrical dequantization
254
       reference: Section 7.3.2 Expansion of Mantissas for Asymmetric Quantization */
255
    for (i = 0; i < 25; i++)
256
        scale_factors[i] = pow(2.0, -i);
257

    
258
    /* generate exponent tables
259
       reference: Section 7.1.3 Exponent Decoding */
260
    for(i=0; i<128; i++) {
261
        exp_ungroup_tab[i][0] =  i / 25;
262
        exp_ungroup_tab[i][1] = (i % 25) / 5;
263
        exp_ungroup_tab[i][2] = (i % 25) % 5;
264
    }
265
}
266

    
267

    
268
/**
269
 * AVCodec initialization
270
 */
271
static int ac3_decode_init(AVCodecContext *avctx)
272
{
273
    AC3DecodeContext *s = avctx->priv_data;
274
    s->avctx = avctx;
275

    
276
    ac3_common_init();
277
    ac3_tables_init();
278
    ff_mdct_init(&s->imdct_256, 8, 1);
279
    ff_mdct_init(&s->imdct_512, 9, 1);
280
    ff_kbd_window_init(s->window);
281
    dsputil_init(&s->dsp, avctx);
282
    av_init_random(0, &s->dith_state);
283

    
284
    /* set bias values for float to int16 conversion */
285
    if(s->dsp.float_to_int16 == ff_float_to_int16_c) {
286
        s->add_bias = 385.0f;
287
        s->mul_bias = 1.0f;
288
    } else {
289
        s->add_bias = 0.0f;
290
        s->mul_bias = 32767.0f;
291
    }
292

    
293
    /* allow downmixing to stereo or mono */
294
    if (avctx->channels > 0 && avctx->request_channels > 0 &&
295
            avctx->request_channels < avctx->channels &&
296
            avctx->request_channels <= 2) {
297
        avctx->channels = avctx->request_channels;
298
    }
299

    
300
    return 0;
301
}
302

    
303
/**
304
 * Parse the 'sync info' and 'bit stream info' from the AC-3 bitstream.
305
 * GetBitContext within AC3DecodeContext must point to
306
 * start of the synchronized ac3 bitstream.
307
 */
308
static int ac3_parse_header(AC3DecodeContext *s)
309
{
310
    AC3HeaderInfo hdr;
311
    GetBitContext *gbc = &s->gbc;
312
    int err, i;
313

    
314
    err = ff_ac3_parse_header(gbc->buffer, &hdr);
315
    if(err)
316
        return err;
317

    
318
    if(hdr.bitstream_id > 10)
319
        return AC3_PARSE_ERROR_BSID;
320

    
321
    /* get decoding parameters from header info */
322
    s->bit_alloc_params.sr_code     = hdr.sr_code;
323
    s->channel_mode                 = hdr.channel_mode;
324
    s->lfe_on                       = hdr.lfe_on;
325
    s->bit_alloc_params.sr_shift    = hdr.sr_shift;
326
    s->sample_rate                  = hdr.sample_rate;
327
    s->bit_rate                     = hdr.bit_rate;
328
    s->channels                     = hdr.channels;
329
    s->fbw_channels                 = s->channels - s->lfe_on;
330
    s->lfe_ch                       = s->fbw_channels + 1;
331
    s->frame_size                   = hdr.frame_size;
332

    
333
    /* set default output to all source channels */
334
    s->out_channels = s->channels;
335
    s->output_mode = s->channel_mode;
336
    if(s->lfe_on)
337
        s->output_mode |= AC3_OUTPUT_LFEON;
338

    
339
    /* set default mix levels */
340
    s->center_mix_level   = 3;  // -4.5dB
341
    s->surround_mix_level = 4;  // -6.0dB
342

    
343
    /* skip over portion of header which has already been read */
344
    skip_bits(gbc, 16); // skip the sync_word
345
    skip_bits(gbc, 16); // skip crc1
346
    skip_bits(gbc, 8);  // skip fscod and frmsizecod
347
    skip_bits(gbc, 11); // skip bsid, bsmod, and acmod
348
    if(s->channel_mode == AC3_CHMODE_STEREO) {
349
        skip_bits(gbc, 2); // skip dsurmod
350
    } else {
351
        if((s->channel_mode & 1) && s->channel_mode != AC3_CHMODE_MONO)
352
            s->center_mix_level = center_levels[get_bits(gbc, 2)];
353
        if(s->channel_mode & 4)
354
            s->surround_mix_level = surround_levels[get_bits(gbc, 2)];
355
    }
356
    skip_bits1(gbc); // skip lfeon
357

    
358
    /* read the rest of the bsi. read twice for dual mono mode. */
359
    i = !(s->channel_mode);
360
    do {
361
        skip_bits(gbc, 5); // skip dialog normalization
362
        if (get_bits1(gbc))
363
            skip_bits(gbc, 8); //skip compression
364
        if (get_bits1(gbc))
365
            skip_bits(gbc, 8); //skip language code
366
        if (get_bits1(gbc))
367
            skip_bits(gbc, 7); //skip audio production information
368
    } while (i--);
369

    
370
    skip_bits(gbc, 2); //skip copyright bit and original bitstream bit
371

    
372
    /* skip the timecodes (or extra bitstream information for Alternate Syntax)
373
       TODO: read & use the xbsi1 downmix levels */
374
    if (get_bits1(gbc))
375
        skip_bits(gbc, 14); //skip timecode1 / xbsi1
376
    if (get_bits1(gbc))
377
        skip_bits(gbc, 14); //skip timecode2 / xbsi2
378

    
379
    /* skip additional bitstream info */
380
    if (get_bits1(gbc)) {
381
        i = get_bits(gbc, 6);
382
        do {
383
            skip_bits(gbc, 8);
384
        } while(i--);
385
    }
386

    
387
    return 0;
388
}
389

    
390
/**
391
 * Set stereo downmixing coefficients based on frame header info.
392
 * reference: Section 7.8.2 Downmixing Into Two Channels
393
 */
394
static void set_downmix_coeffs(AC3DecodeContext *s)
395
{
396
    int i;
397
    float cmix = gain_levels[s->center_mix_level];
398
    float smix = gain_levels[s->surround_mix_level];
399

    
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] = cmix;
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] = smix * 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] = smix;
414
    }
415
}
416

    
417
/**
418
 * Decode the grouped exponents according to exponent strategy.
419
 * reference: Section 7.1.3 Exponent Decoding
420
 */
421
static void decode_exponents(GetBitContext *gbc, int exp_strategy, int ngrps,
422
                             uint8_t absexp, int8_t *dexps)
423
{
424
    int i, j, grp, group_size;
425
    int dexp[256];
426
    int expacc, prevexp;
427

    
428
    /* unpack groups */
429
    group_size = exp_strategy + (exp_strategy == EXP_D45);
430
    for(grp=0,i=0; grp<ngrps; grp++) {
431
        expacc = get_bits(gbc, 7);
432
        dexp[i++] = exp_ungroup_tab[expacc][0];
433
        dexp[i++] = exp_ungroup_tab[expacc][1];
434
        dexp[i++] = exp_ungroup_tab[expacc][2];
435
    }
436

    
437
    /* convert to absolute exps and expand groups */
438
    prevexp = absexp;
439
    for(i=0; i<ngrps*3; i++) {
440
        prevexp = av_clip(prevexp + dexp[i]-2, 0, 24);
441
        for(j=0; j<group_size; j++) {
442
            dexps[(i*group_size)+j] = prevexp;
443
        }
444
    }
445
}
446

    
447
/**
448
 * Generate transform coefficients for each coupled channel in the coupling
449
 * range using the coupling coefficients and coupling coordinates.
450
 * reference: Section 7.4.3 Coupling Coordinate Format
451
 */
452
static void uncouple_channels(AC3DecodeContext *s)
453
{
454
    int i, j, ch, bnd, subbnd;
455

    
456
    subbnd = -1;
457
    i = s->start_freq[CPL_CH];
458
    for(bnd=0; bnd<s->num_cpl_bands; bnd++) {
459
        do {
460
            subbnd++;
461
            for(j=0; j<12; j++) {
462
                for(ch=1; ch<=s->fbw_channels; ch++) {
463
                    if(s->channel_in_cpl[ch]) {
464
                        s->transform_coeffs[ch][i] = s->transform_coeffs[CPL_CH][i] * s->cpl_coords[ch][bnd] * 8.0f;
465
                        if (ch == 2 && s->phase_flags[bnd])
466
                            s->transform_coeffs[ch][i] = -s->transform_coeffs[ch][i];
467
                    }
468
                }
469
                i++;
470
            }
471
        } while(s->cpl_band_struct[subbnd]);
472
    }
473
}
474

    
475
/**
476
 * Grouped mantissas for 3-level 5-level and 11-level quantization
477
 */
478
typedef struct {
479
    float b1_mant[3];
480
    float b2_mant[3];
481
    float b4_mant[2];
482
    int b1ptr;
483
    int b2ptr;
484
    int b4ptr;
485
} mant_groups;
486

    
487
/**
488
 * Get the transform coefficients for a particular channel
489
 * reference: Section 7.3 Quantization and Decoding of Mantissas
490
 */
491
static int get_transform_coeffs_ch(AC3DecodeContext *s, int ch_index, mant_groups *m)
492
{
493
    GetBitContext *gbc = &s->gbc;
494
    int i, gcode, tbap, start, end;
495
    uint8_t *exps;
496
    uint8_t *bap;
497
    float *coeffs;
498

    
499
    exps = s->dexps[ch_index];
500
    bap = s->bap[ch_index];
501
    coeffs = s->transform_coeffs[ch_index];
502
    start = s->start_freq[ch_index];
503
    end = s->end_freq[ch_index];
504

    
505
    for (i = start; i < end; i++) {
506
        tbap = bap[i];
507
        switch (tbap) {
508
            case 0:
509
                coeffs[i] = ((av_random(&s->dith_state) & 0xFFFF) / 65535.0f) - 0.5f;
510
                break;
511

    
512
            case 1:
513
                if(m->b1ptr > 2) {
514
                    gcode = get_bits(gbc, 5);
515
                    m->b1_mant[0] = b1_mantissas[gcode][0];
516
                    m->b1_mant[1] = b1_mantissas[gcode][1];
517
                    m->b1_mant[2] = b1_mantissas[gcode][2];
518
                    m->b1ptr = 0;
519
                }
520
                coeffs[i] = m->b1_mant[m->b1ptr++];
521
                break;
522

    
523
            case 2:
524
                if(m->b2ptr > 2) {
525
                    gcode = get_bits(gbc, 7);
526
                    m->b2_mant[0] = b2_mantissas[gcode][0];
527
                    m->b2_mant[1] = b2_mantissas[gcode][1];
528
                    m->b2_mant[2] = b2_mantissas[gcode][2];
529
                    m->b2ptr = 0;
530
                }
531
                coeffs[i] = m->b2_mant[m->b2ptr++];
532
                break;
533

    
534
            case 3:
535
                coeffs[i] = b3_mantissas[get_bits(gbc, 3)];
536
                break;
537

    
538
            case 4:
539
                if(m->b4ptr > 1) {
540
                    gcode = get_bits(gbc, 7);
541
                    m->b4_mant[0] = b4_mantissas[gcode][0];
542
                    m->b4_mant[1] = b4_mantissas[gcode][1];
543
                    m->b4ptr = 0;
544
                }
545
                coeffs[i] = m->b4_mant[m->b4ptr++];
546
                break;
547

    
548
            case 5:
549
                coeffs[i] = b5_mantissas[get_bits(gbc, 4)];
550
                break;
551

    
552
            default:
553
                /* asymmetric dequantization */
554
                coeffs[i] = get_sbits(gbc, quantization_tab[tbap]) * scale_factors[quantization_tab[tbap]-1];
555
                break;
556
        }
557
        coeffs[i] *= scale_factors[exps[i]];
558
    }
559

    
560
    return 0;
561
}
562

    
563
/**
564
 * Remove random dithering from coefficients with zero-bit mantissas
565
 * reference: Section 7.3.4 Dither for Zero Bit Mantissas (bap=0)
566
 */
567
static void remove_dithering(AC3DecodeContext *s) {
568
    int ch, i;
569
    int end=0;
570
    float *coeffs;
571
    uint8_t *bap;
572

    
573
    for(ch=1; ch<=s->fbw_channels; ch++) {
574
        if(!s->dither_flag[ch]) {
575
            coeffs = s->transform_coeffs[ch];
576
            bap = s->bap[ch];
577
            if(s->channel_in_cpl[ch])
578
                end = s->start_freq[CPL_CH];
579
            else
580
                end = s->end_freq[ch];
581
            for(i=0; i<end; i++) {
582
                if(!bap[i])
583
                    coeffs[i] = 0.0f;
584
            }
585
            if(s->channel_in_cpl[ch]) {
586
                bap = s->bap[CPL_CH];
587
                for(; i<s->end_freq[CPL_CH]; i++) {
588
                    if(!bap[i])
589
                        coeffs[i] = 0.0f;
590
                }
591
            }
592
        }
593
    }
594
}
595

    
596
/**
597
 * Get the transform coefficients.
598
 */
599
static int get_transform_coeffs(AC3DecodeContext *s)
600
{
601
    int ch, end;
602
    int got_cplchan = 0;
603
    mant_groups m;
604

    
605
    m.b1ptr = m.b2ptr = m.b4ptr = 3;
606

    
607
    for (ch = 1; ch <= s->channels; ch++) {
608
        /* transform coefficients for full-bandwidth channel */
609
        if (get_transform_coeffs_ch(s, ch, &m))
610
            return -1;
611
        /* tranform coefficients for coupling channel come right after the
612
           coefficients for the first coupled channel*/
613
        if (s->channel_in_cpl[ch])  {
614
            if (!got_cplchan) {
615
                if (get_transform_coeffs_ch(s, CPL_CH, &m)) {
616
                    av_log(s->avctx, AV_LOG_ERROR, "error in decoupling channels\n");
617
                    return -1;
618
                }
619
                uncouple_channels(s);
620
                got_cplchan = 1;
621
            }
622
            end = s->end_freq[CPL_CH];
623
        } else {
624
            end = s->end_freq[ch];
625
        }
626
        do
627
            s->transform_coeffs[ch][end] = 0;
628
        while(++end < 256);
629
    }
630

    
631
    /* if any channel doesn't use dithering, zero appropriate coefficients */
632
    if(!s->dither_all)
633
        remove_dithering(s);
634

    
635
    return 0;
636
}
637

    
638
/**
639
 * Stereo rematrixing.
640
 * reference: Section 7.5.4 Rematrixing : Decoding Technique
641
 */
642
static void do_rematrixing(AC3DecodeContext *s)
643
{
644
    int bnd, i;
645
    int end, bndend;
646
    float tmp0, tmp1;
647

    
648
    end = FFMIN(s->end_freq[1], s->end_freq[2]);
649

    
650
    for(bnd=0; bnd<s->num_rematrixing_bands; bnd++) {
651
        if(s->rematrixing_flags[bnd]) {
652
            bndend = FFMIN(end, rematrix_band_tab[bnd+1]);
653
            for(i=rematrix_band_tab[bnd]; i<bndend; i++) {
654
                tmp0 = s->transform_coeffs[1][i];
655
                tmp1 = s->transform_coeffs[2][i];
656
                s->transform_coeffs[1][i] = tmp0 + tmp1;
657
                s->transform_coeffs[2][i] = tmp0 - tmp1;
658
            }
659
        }
660
    }
661
}
662

    
663
/**
664
 * Perform the 256-point IMDCT
665
 */
666
static void do_imdct_256(AC3DecodeContext *s, int chindex)
667
{
668
    int i, k;
669
    DECLARE_ALIGNED_16(float, x[128]);
670
    FFTComplex z[2][64];
671
    float *o_ptr = s->tmp_output;
672

    
673
    for(i=0; i<2; i++) {
674
        /* de-interleave coefficients */
675
        for(k=0; k<128; k++) {
676
            x[k] = s->transform_coeffs[chindex][2*k+i];
677
        }
678

    
679
        /* run standard IMDCT */
680
        s->imdct_256.fft.imdct_calc(&s->imdct_256, o_ptr, x, s->tmp_imdct);
681

    
682
        /* reverse the post-rotation & reordering from standard IMDCT */
683
        for(k=0; k<32; k++) {
684
            z[i][32+k].re = -o_ptr[128+2*k];
685
            z[i][32+k].im = -o_ptr[2*k];
686
            z[i][31-k].re =  o_ptr[2*k+1];
687
            z[i][31-k].im =  o_ptr[128+2*k+1];
688
        }
689
    }
690

    
691
    /* apply AC-3 post-rotation & reordering */
692
    for(k=0; k<64; k++) {
693
        o_ptr[    2*k  ] = -z[0][   k].im;
694
        o_ptr[    2*k+1] =  z[0][63-k].re;
695
        o_ptr[128+2*k  ] = -z[0][   k].re;
696
        o_ptr[128+2*k+1] =  z[0][63-k].im;
697
        o_ptr[256+2*k  ] = -z[1][   k].re;
698
        o_ptr[256+2*k+1] =  z[1][63-k].im;
699
        o_ptr[384+2*k  ] =  z[1][   k].im;
700
        o_ptr[384+2*k+1] = -z[1][63-k].re;
701
    }
702
}
703

    
704
/**
705
 * Inverse MDCT Transform.
706
 * Convert frequency domain coefficients to time-domain audio samples.
707
 * reference: Section 7.9.4 Transformation Equations
708
 */
709
static inline void do_imdct(AC3DecodeContext *s)
710
{
711
    int ch;
712
    int channels;
713

    
714
    /* Don't perform the IMDCT on the LFE channel unless it's used in the output */
715
    channels = s->fbw_channels;
716
    if(s->output_mode & AC3_OUTPUT_LFEON)
717
        channels++;
718

    
719
    for (ch=1; ch<=channels; ch++) {
720
        if (s->block_switch[ch]) {
721
            do_imdct_256(s, ch);
722
        } else {
723
            s->imdct_512.fft.imdct_calc(&s->imdct_512, s->tmp_output,
724
                                        s->transform_coeffs[ch], s->tmp_imdct);
725
        }
726
        /* For the first half of the block, apply the window, add the delay
727
           from the previous block, and send to output */
728
        s->dsp.vector_fmul_add_add(s->output[ch-1], s->tmp_output,
729
                                     s->window, s->delay[ch-1], 0, 256, 1);
730
        /* For the second half of the block, apply the window and store the
731
           samples to delay, to be combined with the next block */
732
        s->dsp.vector_fmul_reverse(s->delay[ch-1], s->tmp_output+256,
733
                                   s->window, 256);
734
    }
735
}
736

    
737
/**
738
 * Downmix the output to mono or stereo.
739
 */
740
static void ac3_downmix(AC3DecodeContext *s)
741
{
742
    int i, j;
743
    float v0, v1, s0, s1;
744

    
745
    for(i=0; i<256; i++) {
746
        v0 = v1 = s0 = s1 = 0.0f;
747
        for(j=0; j<s->fbw_channels; j++) {
748
            v0 += s->output[j][i] * s->downmix_coeffs[j][0];
749
            v1 += s->output[j][i] * s->downmix_coeffs[j][1];
750
            s0 += s->downmix_coeffs[j][0];
751
            s1 += s->downmix_coeffs[j][1];
752
        }
753
        v0 /= s0;
754
        v1 /= s1;
755
        if(s->output_mode == AC3_CHMODE_MONO) {
756
            s->output[0][i] = (v0 + v1) * LEVEL_MINUS_3DB;
757
        } else if(s->output_mode == AC3_CHMODE_STEREO) {
758
            s->output[0][i] = v0;
759
            s->output[1][i] = v1;
760
        }
761
    }
762
}
763

    
764
/**
765
 * Parse an audio block from AC-3 bitstream.
766
 */
767
static int ac3_parse_audio_block(AC3DecodeContext *s, int blk)
768
{
769
    int fbw_channels = s->fbw_channels;
770
    int channel_mode = s->channel_mode;
771
    int i, bnd, seg, ch;
772
    GetBitContext *gbc = &s->gbc;
773
    uint8_t bit_alloc_stages[AC3_MAX_CHANNELS];
774

    
775
    memset(bit_alloc_stages, 0, AC3_MAX_CHANNELS);
776

    
777
    /* block switch flags */
778
    for (ch = 1; ch <= fbw_channels; ch++)
779
        s->block_switch[ch] = get_bits1(gbc);
780

    
781
    /* dithering flags */
782
    s->dither_all = 1;
783
    for (ch = 1; ch <= fbw_channels; ch++) {
784
        s->dither_flag[ch] = get_bits1(gbc);
785
        if(!s->dither_flag[ch])
786
            s->dither_all = 0;
787
    }
788

    
789
    /* dynamic range */
790
    i = !(s->channel_mode);
791
    do {
792
        if(get_bits1(gbc)) {
793
            s->dynamic_range[i] = ((dynamic_range_tab[get_bits(gbc, 8)]-1.0) *
794
                                  s->avctx->drc_scale)+1.0;
795
        } else if(blk == 0) {
796
            s->dynamic_range[i] = 1.0f;
797
        }
798
    } while(i--);
799

    
800
    /* coupling strategy */
801
    if (get_bits1(gbc)) {
802
        memset(bit_alloc_stages, 3, AC3_MAX_CHANNELS);
803
        s->cpl_in_use = get_bits1(gbc);
804
        if (s->cpl_in_use) {
805
            /* coupling in use */
806
            int cpl_begin_freq, cpl_end_freq;
807

    
808
            /* determine which channels are coupled */
809
            for (ch = 1; ch <= fbw_channels; ch++)
810
                s->channel_in_cpl[ch] = get_bits1(gbc);
811

    
812
            /* phase flags in use */
813
            if (channel_mode == AC3_CHMODE_STEREO)
814
                s->phase_flags_in_use = get_bits1(gbc);
815

    
816
            /* coupling frequency range and band structure */
817
            cpl_begin_freq = get_bits(gbc, 4);
818
            cpl_end_freq = get_bits(gbc, 4);
819
            if (3 + cpl_end_freq - cpl_begin_freq < 0) {
820
                av_log(s->avctx, AV_LOG_ERROR, "3+cplendf = %d < cplbegf = %d\n", 3+cpl_end_freq, cpl_begin_freq);
821
                return -1;
822
            }
823
            s->num_cpl_bands = s->num_cpl_subbands = 3 + cpl_end_freq - cpl_begin_freq;
824
            s->start_freq[CPL_CH] = cpl_begin_freq * 12 + 37;
825
            s->end_freq[CPL_CH] = cpl_end_freq * 12 + 73;
826
            for (bnd = 0; bnd < s->num_cpl_subbands - 1; bnd++) {
827
                if (get_bits1(gbc)) {
828
                    s->cpl_band_struct[bnd] = 1;
829
                    s->num_cpl_bands--;
830
                }
831
            }
832
            s->cpl_band_struct[s->num_cpl_subbands-1] = 0;
833
        } else {
834
            /* coupling not in use */
835
            for (ch = 1; ch <= fbw_channels; ch++)
836
                s->channel_in_cpl[ch] = 0;
837
        }
838
    }
839

    
840
    /* coupling coordinates */
841
    if (s->cpl_in_use) {
842
        int cpl_coords_exist = 0;
843

    
844
        for (ch = 1; ch <= fbw_channels; ch++) {
845
            if (s->channel_in_cpl[ch]) {
846
                if (get_bits1(gbc)) {
847
                    int master_cpl_coord, cpl_coord_exp, cpl_coord_mant;
848
                    cpl_coords_exist = 1;
849
                    master_cpl_coord = 3 * get_bits(gbc, 2);
850
                    for (bnd = 0; bnd < s->num_cpl_bands; bnd++) {
851
                        cpl_coord_exp = get_bits(gbc, 4);
852
                        cpl_coord_mant = get_bits(gbc, 4);
853
                        if (cpl_coord_exp == 15)
854
                            s->cpl_coords[ch][bnd] = cpl_coord_mant / 16.0f;
855
                        else
856
                            s->cpl_coords[ch][bnd] = (cpl_coord_mant + 16.0f) / 32.0f;
857
                        s->cpl_coords[ch][bnd] *= scale_factors[cpl_coord_exp + master_cpl_coord];
858
                    }
859
                }
860
            }
861
        }
862
        /* phase flags */
863
        if (channel_mode == AC3_CHMODE_STEREO && cpl_coords_exist) {
864
            for (bnd = 0; bnd < s->num_cpl_bands; bnd++) {
865
                s->phase_flags[bnd] = s->phase_flags_in_use? get_bits1(gbc) : 0;
866
            }
867
        }
868
    }
869

    
870
    /* stereo rematrixing strategy and band structure */
871
    if (channel_mode == AC3_CHMODE_STEREO) {
872
        if (get_bits1(gbc)) {
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 >= FF_ER_CAREFUL) {
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
    /* set downmixing coefficients if needed */
1133
    if(s->channels != s->out_channels && !((s->output_mode & AC3_OUTPUT_LFEON) &&
1134
            s->fbw_channels == s->out_channels)) {
1135
        set_downmix_coeffs(s);
1136
    }
1137

    
1138
    /* parse the audio blocks */
1139
    for (blk = 0; blk < NB_BLOCKS; blk++) {
1140
        if (ac3_parse_audio_block(s, blk)) {
1141
            av_log(avctx, AV_LOG_ERROR, "error parsing the audio block\n");
1142
            *data_size = 0;
1143
            return s->frame_size;
1144
        }
1145
        for (i = 0; i < 256; i++)
1146
            for (ch = 0; ch < s->out_channels; ch++)
1147
                *(out_samples++) = s->int_output[ch][i];
1148
    }
1149
    *data_size = NB_BLOCKS * 256 * avctx->channels * sizeof (int16_t);
1150
    return s->frame_size;
1151
}
1152

    
1153
/**
1154
 * Uninitialize the AC-3 decoder.
1155
 */
1156
static int ac3_decode_end(AVCodecContext *avctx)
1157
{
1158
    AC3DecodeContext *s = avctx->priv_data;
1159
    ff_mdct_end(&s->imdct_512);
1160
    ff_mdct_end(&s->imdct_256);
1161

    
1162
    return 0;
1163
}
1164

    
1165
AVCodec ac3_decoder = {
1166
    .name = "ac3",
1167
    .type = CODEC_TYPE_AUDIO,
1168
    .id = CODEC_ID_AC3,
1169
    .priv_data_size = sizeof (AC3DecodeContext),
1170
    .init = ac3_decode_init,
1171
    .close = ac3_decode_end,
1172
    .decode = ac3_decode_frame,
1173
};