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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
22
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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 * General Public License for more details.
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 *
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 * You should have received a copy of the GNU General Public
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 * License along with FFmpeg; if not, write to the Free Software
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 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
28
 */
29

    
30
#include <stdio.h>
31
#include <stddef.h>
32
#include <math.h>
33
#include <string.h>
34

    
35
#include "avcodec.h"
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#include "ac3_parser.h"
37
#include "bitstream.h"
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#include "dsputil.h"
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#include "random.h"
40

    
41
/**
42
 * Table of bin locations for rematrixing bands
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 * reference: Section 7.5.2 Rematrixing : Frequency Band Definitions
44
 */
45
static const uint8_t rematrix_band_tbl[5] = { 13, 25, 37, 61, 253 };
46

    
47
/* table for exponent to scale_factor mapping
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 * scale_factor[i] = 2 ^ -(i + 15)
49
 */
50
static float scale_factors[25];
51

    
52
/** table for grouping exponents */
53
static uint8_t exp_ungroup_tbl[128][3];
54

    
55

    
56
/** tables for ungrouping mantissas */
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static float b1_mantissas[32][3];
58
static float b2_mantissas[128][3];
59
static float b3_mantissas[8];
60
static float b4_mantissas[128][2];
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static float b5_mantissas[16];
62

    
63
/**
64
 * Quantization table: levels for symmetric. bits for asymmetric.
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 * reference: Table 7.18 Mapping of bap to Quantizer
66
 */
67
static const uint8_t qntztab[16] = {
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    0, 3, 5, 7, 11, 15,
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    5, 6, 7, 8, 9, 10, 11, 12, 14, 16
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};
71

    
72
/** dynamic range table. converts codes to scale factors. */
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static float dynrng_tbl[256];
74

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

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

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

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

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

    
107
/**
108
 * Table for default stereo downmixing coefficients
109
 * reference: Section 7.8.2 Downmixing Into Two Channels
110
 */
111
static const uint8_t ac3_default_coeffs[8][5][2] = {
112
    { { 1, 0 }, { 0, 1 },                               },
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    { { 2, 2 },                                         },
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    { { 1, 0 }, { 0, 1 },                               },
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    { { 1, 0 }, { 3, 3 }, { 0, 1 },                     },
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    { { 1, 0 }, { 0, 1 }, { 4, 4 },                     },
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    { { 1, 0 }, { 3, 3 }, { 0, 1 }, { 5, 5 },           },
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    { { 1, 0 }, { 0, 1 }, { 4, 0 }, { 0, 4 },           },
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    { { 1, 0 }, { 3, 3 }, { 0, 1 }, { 4, 0 }, { 0, 4 }, },
120
};
121

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

    
127
#define AC3_OUTPUT_LFEON  8
128

    
129
typedef struct {
130
    int acmod;
131
    int dsurmod;
132
    int blksw[AC3_MAX_CHANNELS];
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    int dithflag[AC3_MAX_CHANNELS];
134
    int dither_all;
135
    int cplinu;
136
    int chincpl[AC3_MAX_CHANNELS];
137
    int phsflginu;
138
    int cplbndstrc[18];
139
    int rematstr;
140
    int nrematbnd;
141
    int rematflg[4];
142
    int expstr[AC3_MAX_CHANNELS];
143
    int snroffst[AC3_MAX_CHANNELS];
144
    int fgain[AC3_MAX_CHANNELS];
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    int deltbae[AC3_MAX_CHANNELS];
146
    int deltnseg[AC3_MAX_CHANNELS];
147
    uint8_t  deltoffst[AC3_MAX_CHANNELS][8];
148
    uint8_t  deltlen[AC3_MAX_CHANNELS][8];
149
    uint8_t  deltba[AC3_MAX_CHANNELS][8];
150

    
151
    /* Derived Attributes. */
152
    int      sampling_rate;
153
    int      bit_rate;
154
    int      frame_size;
155

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

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

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

    
181
    /* For IMDCT. */
182
    MDCTContext imdct_512;  //for 512 sample imdct transform
183
    MDCTContext imdct_256;  //for 256 sample imdct transform
184
    DSPContext  dsp;        //for optimization
185
    float       add_bias;   ///< offset for float_to_int16 conversion
186
    float       mul_bias;   ///< scaling for float_to_int16 conversion
187

    
188
    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
194

    
195
    /* Miscellaneous. */
196
    GetBitContext gb;
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    AVRandomState dith_state;   //for dither generation
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    AVCodecContext *avctx;      ///< parent context
199
} AC3DecodeContext;
200

    
201
/**
202
 * Generate a Kaiser-Bessel Derived Window.
203
 */
204
static void ac3_window_init(float *window)
205
{
206
   int i, j;
207
   double sum = 0.0, bessel, tmp;
208
   double local_window[256];
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   double alpha2 = (5.0 * M_PI / 256.0) * (5.0 * M_PI / 256.0);
210

    
211
   for (i = 0; i < 256; i++) {
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       tmp = i * (256 - i) * alpha2;
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       bessel = 1.0;
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       for (j = 100; j > 0; j--) /* defaul to 100 iterations */
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           bessel = bessel * tmp / (j * j) + 1;
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       sum += bessel;
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       local_window[i] = sum;
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   }
219

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

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

    
231
/*
232
 * Initialize tables at runtime.
233
 */
234
static void ac3_tables_init(void)
235
{
236
    int i;
237

    
238
    /* generate grouped mantissa tables
239
       reference: Section 7.3.5 Ungrouping of Mantissas */
240
    for(i=0; i<32; i++) {
241
        /* bap=1 mantissas */
242
        b1_mantissas[i][0] = symmetric_dequant( i / 9     , 3);
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        b1_mantissas[i][1] = symmetric_dequant((i % 9) / 3, 3);
244
        b1_mantissas[i][2] = symmetric_dequant((i % 9) % 3, 3);
245
    }
246
    for(i=0; i<128; i++) {
247
        /* bap=2 mantissas */
248
        b2_mantissas[i][0] = symmetric_dequant( i / 25     , 5);
249
        b2_mantissas[i][1] = symmetric_dequant((i % 25) / 5, 5);
250
        b2_mantissas[i][2] = symmetric_dequant((i % 25) % 5, 5);
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252
        /* bap=4 mantissas */
253
        b4_mantissas[i][0] = symmetric_dequant(i / 11, 11);
254
        b4_mantissas[i][1] = symmetric_dequant(i % 11, 11);
255
    }
256
    /* generate ungrouped mantissa tables
257
       reference: Tables 7.21 and 7.23 */
258
    for(i=0; i<7; i++) {
259
        /* bap=3 mantissas */
260
        b3_mantissas[i] = symmetric_dequant(i, 7);
261
    }
262
    for(i=0; i<15; i++) {
263
        /* bap=5 mantissas */
264
        b5_mantissas[i] = symmetric_dequant(i, 15);
265
    }
266

    
267
    /* generate dynamic range table
268
       reference: Section 7.7.1 Dynamic Range Control */
269
    for(i=0; i<256; i++) {
270
        int v = (i >> 5) - ((i >> 7) << 3) - 5;
271
        dynrng_tbl[i] = powf(2.0f, v) * ((i & 0x1F) | 0x20);
272
    }
273

    
274
    /* generate dialogue normalization table
275
       references: Section 5.4.2.8 dialnorm
276
                   Section 7.6 Dialogue Normalization */
277
    for(i=1; i<32; i++) {
278
        dialnorm_tbl[i] = expf((i-31) * M_LN10 / 20.0f);
279
    }
280
    dialnorm_tbl[0] = dialnorm_tbl[31];
281

    
282
    //generate scale factors
283
    for (i = 0; i < 25; i++)
284
        scale_factors[i] = pow(2.0, -i);
285

    
286
    /* generate exponent tables
287
       reference: Section 7.1.3 Exponent Decoding */
288
    for(i=0; i<128; i++) {
289
        exp_ungroup_tbl[i][0] =  i / 25;
290
        exp_ungroup_tbl[i][1] = (i % 25) / 5;
291
        exp_ungroup_tbl[i][2] = (i % 25) % 5;
292
    }
293
}
294

    
295

    
296
static int ac3_decode_init(AVCodecContext *avctx)
297
{
298
    AC3DecodeContext *ctx = avctx->priv_data;
299
    ctx->avctx = avctx;
300

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

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

    
317
    return 0;
318
}
319

    
320
/**
321
 * Parses the 'sync info' and 'bit stream info' from the AC-3 bitstream.
322
 * GetBitContext within AC3DecodeContext must point to
323
 * start of the synchronized ac3 bitstream.
324
 */
325
static int ac3_parse_header(AC3DecodeContext *ctx)
326
{
327
    AC3HeaderInfo hdr;
328
    GetBitContext *gb = &ctx->gb;
329
    float cmixlev, surmixlev;
330
    int err, i;
331

    
332
    err = ff_ac3_parse_header(gb->buffer, &hdr);
333
    if(err)
334
        return err;
335

    
336
    /* get decoding parameters from header info */
337
    ctx->bit_alloc_params.fscod       = hdr.fscod;
338
    ctx->acmod                        = hdr.acmod;
339
    cmixlev                           = gain_levels[clevs[hdr.cmixlev]];
340
    surmixlev                         = gain_levels[slevs[hdr.surmixlev]];
341
    ctx->dsurmod                      = hdr.dsurmod;
342
    ctx->lfeon                        = hdr.lfeon;
343
    ctx->bit_alloc_params.halfratecod = hdr.halfratecod;
344
    ctx->sampling_rate                = hdr.sample_rate;
345
    ctx->bit_rate                     = hdr.bit_rate;
346
    ctx->nchans                       = hdr.channels;
347
    ctx->nfchans                      = ctx->nchans - ctx->lfeon;
348
    ctx->lfe_ch                       = ctx->nfchans + 1;
349
    ctx->frame_size                   = hdr.frame_size;
350

    
351
    /* set default output to all source channels */
352
    ctx->out_channels = ctx->nchans;
353
    ctx->output_mode = ctx->acmod;
354
    if(ctx->lfeon)
355
        ctx->output_mode |= AC3_OUTPUT_LFEON;
356

    
357
    /* skip over portion of header which has already been read */
358
    skip_bits(gb, 16); //skip the sync_word, sync_info->sync_word = get_bits(gb, 16);
359
    skip_bits(gb, 16); // skip crc1
360
    skip_bits(gb, 8);  // skip fscod and frmsizecod
361
    skip_bits(gb, 11); // skip bsid, bsmod, and acmod
362
    if(ctx->acmod == AC3_ACMOD_STEREO) {
363
        skip_bits(gb, 2); // skip dsurmod
364
    } else {
365
        if((ctx->acmod & 1) && ctx->acmod != AC3_ACMOD_MONO)
366
            skip_bits(gb, 2); // skip cmixlev
367
        if(ctx->acmod & 4)
368
            skip_bits(gb, 2); // skip surmixlev
369
    }
370
    skip_bits1(gb); // skip lfeon
371

    
372
    /* read the rest of the bsi. read twice for dual mono mode. */
373
    i = !(ctx->acmod);
374
    do {
375
        ctx->dialnorm[i] = dialnorm_tbl[get_bits(gb, 5)]; // dialogue normalization
376
        if (get_bits1(gb))
377
            skip_bits(gb, 8); //skip compression
378
        if (get_bits1(gb))
379
            skip_bits(gb, 8); //skip language code
380
        if (get_bits1(gb))
381
            skip_bits(gb, 7); //skip audio production information
382
    } while (i--);
383

    
384
    skip_bits(gb, 2); //skip copyright bit and original bitstream bit
385

    
386
    /* FIXME: read & use the xbsi1 downmix levels */
387
    if (get_bits1(gb))
388
        skip_bits(gb, 14); //skip timecode1
389
    if (get_bits1(gb))
390
        skip_bits(gb, 14); //skip timecode2
391

    
392
    if (get_bits1(gb)) {
393
        i = get_bits(gb, 6); //additional bsi length
394
        do {
395
            skip_bits(gb, 8);
396
        } while(i--);
397
    }
398

    
399
    /* set stereo downmixing coefficients
400
       reference: Section 7.8.2 Downmixing Into Two Channels */
401
    for(i=0; i<ctx->nfchans; i++) {
402
        ctx->downmix_coeffs[i][0] = gain_levels[ac3_default_coeffs[ctx->acmod][i][0]];
403
        ctx->downmix_coeffs[i][1] = gain_levels[ac3_default_coeffs[ctx->acmod][i][1]];
404
    }
405
    if(ctx->acmod > 1 && ctx->acmod & 1) {
406
        ctx->downmix_coeffs[1][0] = ctx->downmix_coeffs[1][1] = cmixlev;
407
    }
408
    if(ctx->acmod == AC3_ACMOD_2F1R || ctx->acmod == AC3_ACMOD_3F1R) {
409
        int nf = ctx->acmod - 2;
410
        ctx->downmix_coeffs[nf][0] = ctx->downmix_coeffs[nf][1] = surmixlev * LEVEL_MINUS_3DB;
411
    }
412
    if(ctx->acmod == AC3_ACMOD_2F2R || ctx->acmod == AC3_ACMOD_3F2R) {
413
        int nf = ctx->acmod - 4;
414
        ctx->downmix_coeffs[nf][0] = ctx->downmix_coeffs[nf+1][1] = surmixlev;
415
    }
416

    
417
    return 0;
418
}
419

    
420
/**
421
 * Decodes the grouped exponents.
422
 * This function decodes the coded exponents according to exponent strategy
423
 * and stores them in the decoded exponents buffer.
424
 *
425
 * @param[in]  gb      GetBitContext which points to start of coded exponents
426
 * @param[in]  expstr  Exponent coding strategy
427
 * @param[in]  ngrps   Number of grouped exponents
428
 * @param[in]  absexp  Absolute exponent or DC exponent
429
 * @param[out] dexps   Decoded exponents are stored in dexps
430
 */
431
static void decode_exponents(GetBitContext *gb, int expstr, int ngrps,
432
                             uint8_t absexp, int8_t *dexps)
433
{
434
    int i, j, grp, grpsize;
435
    int dexp[256];
436
    int expacc, prevexp;
437

    
438
    /* unpack groups */
439
    grpsize = expstr + (expstr == EXP_D45);
440
    for(grp=0,i=0; grp<ngrps; grp++) {
441
        expacc = get_bits(gb, 7);
442
        dexp[i++] = exp_ungroup_tbl[expacc][0];
443
        dexp[i++] = exp_ungroup_tbl[expacc][1];
444
        dexp[i++] = exp_ungroup_tbl[expacc][2];
445
    }
446

    
447
    /* convert to absolute exps and expand groups */
448
    prevexp = absexp;
449
    for(i=0; i<ngrps*3; i++) {
450
        prevexp = av_clip(prevexp + dexp[i]-2, 0, 24);
451
        for(j=0; j<grpsize; j++) {
452
            dexps[(i*grpsize)+j] = prevexp;
453
        }
454
    }
455
}
456

    
457
/**
458
 * Generates transform coefficients for each coupled channel in the coupling
459
 * range using the coupling coefficients and coupling coordinates.
460
 * reference: Section 7.4.3 Coupling Coordinate Format
461
 */
462
static void uncouple_channels(AC3DecodeContext *ctx)
463
{
464
    int i, j, ch, bnd, subbnd;
465

    
466
    subbnd = -1;
467
    i = ctx->startmant[CPL_CH];
468
    for(bnd=0; bnd<ctx->ncplbnd; bnd++) {
469
        do {
470
            subbnd++;
471
            for(j=0; j<12; j++) {
472
                for(ch=1; ch<=ctx->nfchans; ch++) {
473
                    if(ctx->chincpl[ch])
474
                        ctx->transform_coeffs[ch][i] = ctx->transform_coeffs[CPL_CH][i] * ctx->cplco[ch][bnd] * 8.0f;
475
                }
476
                i++;
477
            }
478
        } while(ctx->cplbndstrc[subbnd]);
479
    }
480
}
481

    
482
typedef struct { /* grouped mantissas for 3-level 5-leve and 11-level quantization */
483
    float b1_mant[3];
484
    float b2_mant[3];
485
    float b4_mant[2];
486
    int b1ptr;
487
    int b2ptr;
488
    int b4ptr;
489
} mant_groups;
490

    
491
/* Get the transform coefficients for particular channel */
492
static int get_transform_coeffs_ch(AC3DecodeContext *ctx, int ch_index, mant_groups *m)
493
{
494
    GetBitContext *gb = &ctx->gb;
495
    int i, gcode, tbap, start, end;
496
    uint8_t *exps;
497
    uint8_t *bap;
498
    float *coeffs;
499

    
500
    exps = ctx->dexps[ch_index];
501
    bap = ctx->bap[ch_index];
502
    coeffs = ctx->transform_coeffs[ch_index];
503
    start = ctx->startmant[ch_index];
504
    end = ctx->endmant[ch_index];
505

    
506
    for (i = start; i < end; i++) {
507
        tbap = bap[i];
508
        switch (tbap) {
509
            case 0:
510
                coeffs[i] = ((av_random(&ctx->dith_state) & 0xFFFF) * LEVEL_MINUS_3DB) / 32768.0f;
511
                break;
512

    
513
            case 1:
514
                if(m->b1ptr > 2) {
515
                    gcode = get_bits(gb, 5);
516
                    m->b1_mant[0] = b1_mantissas[gcode][0];
517
                    m->b1_mant[1] = b1_mantissas[gcode][1];
518
                    m->b1_mant[2] = b1_mantissas[gcode][2];
519
                    m->b1ptr = 0;
520
                }
521
                coeffs[i] = m->b1_mant[m->b1ptr++];
522
                break;
523

    
524
            case 2:
525
                if(m->b2ptr > 2) {
526
                    gcode = get_bits(gb, 7);
527
                    m->b2_mant[0] = b2_mantissas[gcode][0];
528
                    m->b2_mant[1] = b2_mantissas[gcode][1];
529
                    m->b2_mant[2] = b2_mantissas[gcode][2];
530
                    m->b2ptr = 0;
531
                }
532
                coeffs[i] = m->b2_mant[m->b2ptr++];
533
                break;
534

    
535
            case 3:
536
                coeffs[i] = b3_mantissas[get_bits(gb, 3)];
537
                break;
538

    
539
            case 4:
540
                if(m->b4ptr > 1) {
541
                    gcode = get_bits(gb, 7);
542
                    m->b4_mant[0] = b4_mantissas[gcode][0];
543
                    m->b4_mant[1] = b4_mantissas[gcode][1];
544
                    m->b4ptr = 0;
545
                }
546
                coeffs[i] = m->b4_mant[m->b4ptr++];
547
                break;
548

    
549
            case 5:
550
                coeffs[i] = b5_mantissas[get_bits(gb, 4)];
551
                break;
552

    
553
            default:
554
                coeffs[i] = get_sbits(gb, qntztab[tbap]) * scale_factors[qntztab[tbap]-1];
555
                break;
556
        }
557
        coeffs[i] *= scale_factors[exps[i]];
558
    }
559

    
560
    return 0;
561
}
562

    
563
/**
564
 * Removes 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 *ctx) {
568
    int ch, i;
569
    int end=0;
570
    float *coeffs;
571
    uint8_t *bap;
572

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

    
596
/* Get the transform coefficients.
597
 * This function extracts the tranform coefficients form the ac3 bitstream.
598
 * This function is called after bit allocation is performed.
599
 */
600
static int get_transform_coeffs(AC3DecodeContext * ctx)
601
{
602
    int ch, end;
603
    int got_cplchan = 0;
604
    mant_groups m;
605

    
606
    m.b1ptr = m.b2ptr = m.b4ptr = 3;
607

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

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

    
635
    return 0;
636
}
637

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

    
648
    end = FFMIN(ctx->endmant[1], ctx->endmant[2]);
649

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

    
663
/* This function performs the imdct on 256 sample transform
664
 * coefficients.
665
 */
666
static void do_imdct_256(AC3DecodeContext *ctx, int chindex)
667
{
668
    int i, k;
669
    DECLARE_ALIGNED_16(float, x[128]);
670
    FFTComplex z[2][64];
671
    float *o_ptr = ctx->tmp_output;
672

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

    
679
        /* run standard IMDCT */
680
        ctx->imdct_256.fft.imdct_calc(&ctx->imdct_256, o_ptr, x, ctx->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
/* IMDCT Transform. */
705
static inline void do_imdct(AC3DecodeContext *ctx)
706
{
707
    int ch;
708
    int nchans;
709

    
710
    nchans = ctx->nfchans;
711
    if(ctx->output_mode & AC3_OUTPUT_LFEON)
712
        nchans++;
713

    
714
    for (ch=1; ch<=nchans; ch++) {
715
        if (ctx->blksw[ch]) {
716
            do_imdct_256(ctx, ch);
717
        } else {
718
            ctx->imdct_512.fft.imdct_calc(&ctx->imdct_512, ctx->tmp_output,
719
                                          ctx->transform_coeffs[ch],
720
                                          ctx->tmp_imdct);
721
        }
722
        ctx->dsp.vector_fmul_add_add(ctx->output[ch-1], ctx->tmp_output,
723
                                     ctx->window, ctx->delay[ch-1], 0, 256, 1);
724
        ctx->dsp.vector_fmul_reverse(ctx->delay[ch-1], ctx->tmp_output+256,
725
                                     ctx->window, 256);
726
    }
727
}
728

    
729
/**
730
 * Downmixes the output to stereo.
731
 */
732
static void ac3_downmix(float samples[AC3_MAX_CHANNELS][256], int nfchans,
733
                        int output_mode, float coef[AC3_MAX_CHANNELS][2])
734
{
735
    int i, j;
736
    float v0, v1, s0, s1;
737

    
738
    for(i=0; i<256; i++) {
739
        v0 = v1 = s0 = s1 = 0.0f;
740
        for(j=0; j<nfchans; j++) {
741
            v0 += samples[j][i] * coef[j][0];
742
            v1 += samples[j][i] * coef[j][1];
743
            s0 += coef[j][0];
744
            s1 += coef[j][1];
745
        }
746
        v0 /= s0;
747
        v1 /= s1;
748
        if(output_mode == AC3_ACMOD_MONO) {
749
            samples[0][i] = (v0 + v1) * LEVEL_MINUS_3DB;
750
        } else if(output_mode == AC3_ACMOD_STEREO) {
751
            samples[0][i] = v0;
752
            samples[1][i] = v1;
753
        }
754
    }
755
}
756

    
757
/* Parse the audio block from ac3 bitstream.
758
 * This function extract the audio block from the ac3 bitstream
759
 * and produces the output for the block. This function must
760
 * be called for each of the six audio block in the ac3 bitstream.
761
 */
762
static int ac3_parse_audio_block(AC3DecodeContext *ctx, int blk)
763
{
764
    int nfchans = ctx->nfchans;
765
    int acmod = ctx->acmod;
766
    int i, bnd, seg, ch;
767
    GetBitContext *gb = &ctx->gb;
768
    uint8_t bit_alloc_stages[AC3_MAX_CHANNELS];
769

    
770
    memset(bit_alloc_stages, 0, AC3_MAX_CHANNELS);
771

    
772
    for (ch = 1; ch <= nfchans; ch++) /*block switch flag */
773
        ctx->blksw[ch] = get_bits1(gb);
774

    
775
    ctx->dither_all = 1;
776
    for (ch = 1; ch <= nfchans; ch++) { /* dithering flag */
777
        ctx->dithflag[ch] = get_bits1(gb);
778
        if(!ctx->dithflag[ch])
779
            ctx->dither_all = 0;
780
    }
781

    
782
    /* dynamic range */
783
    i = !(ctx->acmod);
784
    do {
785
        if(get_bits1(gb)) {
786
            ctx->dynrng[i] = dynrng_tbl[get_bits(gb, 8)];
787
        } else if(blk == 0) {
788
            ctx->dynrng[i] = 1.0f;
789
        }
790
    } while(i--);
791

    
792
    if (get_bits1(gb)) { /* coupling strategy */
793
        memset(bit_alloc_stages, 3, AC3_MAX_CHANNELS);
794
        ctx->cplinu = get_bits1(gb);
795
        if (ctx->cplinu) { /* coupling in use */
796
            int cplbegf, cplendf;
797

    
798
            for (ch = 1; ch <= nfchans; ch++)
799
                ctx->chincpl[ch] = get_bits1(gb);
800

    
801
            if (acmod == AC3_ACMOD_STEREO)
802
                ctx->phsflginu = get_bits1(gb); //phase flag in use
803

    
804
            cplbegf = get_bits(gb, 4);
805
            cplendf = get_bits(gb, 4);
806

    
807
            if (3 + cplendf - cplbegf < 0) {
808
                av_log(ctx->avctx, AV_LOG_ERROR, "cplendf = %d < cplbegf = %d\n", cplendf, cplbegf);
809
                return -1;
810
            }
811

    
812
            ctx->ncplbnd = ctx->ncplsubnd = 3 + cplendf - cplbegf;
813
            ctx->startmant[CPL_CH] = cplbegf * 12 + 37;
814
            ctx->endmant[CPL_CH] = cplendf * 12 + 73;
815
            for (bnd = 0; bnd < ctx->ncplsubnd - 1; bnd++) { /* coupling band structure */
816
                if (get_bits1(gb)) {
817
                    ctx->cplbndstrc[bnd] = 1;
818
                    ctx->ncplbnd--;
819
                }
820
            }
821
        } else {
822
            for (ch = 1; ch <= nfchans; ch++)
823
                ctx->chincpl[ch] = 0;
824
        }
825
    }
826

    
827
    if (ctx->cplinu) {
828
        int cplcoe = 0;
829

    
830
        for (ch = 1; ch <= nfchans; ch++) {
831
            if (ctx->chincpl[ch]) {
832
                if (get_bits1(gb)) { /* coupling co-ordinates */
833
                    int mstrcplco, cplcoexp, cplcomant;
834
                    cplcoe = 1;
835
                    mstrcplco = 3 * get_bits(gb, 2);
836
                    for (bnd = 0; bnd < ctx->ncplbnd; bnd++) {
837
                        cplcoexp = get_bits(gb, 4);
838
                        cplcomant = get_bits(gb, 4);
839
                        if (cplcoexp == 15)
840
                            ctx->cplco[ch][bnd] = cplcomant / 16.0f;
841
                        else
842
                            ctx->cplco[ch][bnd] = (cplcomant + 16.0f) / 32.0f;
843
                        ctx->cplco[ch][bnd] *= scale_factors[cplcoexp + mstrcplco];
844
                    }
845
                }
846
            }
847
        }
848

    
849
        if (acmod == AC3_ACMOD_STEREO && ctx->phsflginu && cplcoe) {
850
            for (bnd = 0; bnd < ctx->ncplbnd; bnd++) {
851
                if (get_bits1(gb))
852
                    ctx->cplco[2][bnd] = -ctx->cplco[2][bnd];
853
            }
854
        }
855
    }
856

    
857
    if (acmod == AC3_ACMOD_STEREO) {/* rematrixing */
858
        ctx->rematstr = get_bits1(gb);
859
        if (ctx->rematstr) {
860
            ctx->nrematbnd = 4;
861
            if(ctx->cplinu && ctx->startmant[CPL_CH] <= 61)
862
                ctx->nrematbnd -= 1 + (ctx->startmant[CPL_CH] == 37);
863
            for(bnd=0; bnd<ctx->nrematbnd; bnd++)
864
                ctx->rematflg[bnd] = get_bits1(gb);
865
        }
866
    }
867

    
868
    ctx->expstr[CPL_CH] = EXP_REUSE;
869
    ctx->expstr[ctx->lfe_ch] = EXP_REUSE;
870
    for (ch = !ctx->cplinu; ch <= ctx->nchans; ch++) {
871
        if(ch == ctx->lfe_ch)
872
            ctx->expstr[ch] = get_bits(gb, 1);
873
        else
874
            ctx->expstr[ch] = get_bits(gb, 2);
875
        if(ctx->expstr[ch] != EXP_REUSE)
876
            bit_alloc_stages[ch] = 3;
877
    }
878

    
879
    for (ch = 1; ch <= nfchans; ch++) { /* channel bandwidth code */
880
        ctx->startmant[ch] = 0;
881
        if (ctx->expstr[ch] != EXP_REUSE) {
882
            int prev = ctx->endmant[ch];
883
            if (ctx->chincpl[ch])
884
                ctx->endmant[ch] = ctx->startmant[CPL_CH];
885
            else {
886
                int chbwcod = get_bits(gb, 6);
887
                if (chbwcod > 60) {
888
                    av_log(ctx->avctx, AV_LOG_ERROR, "chbwcod = %d > 60", chbwcod);
889
                    return -1;
890
                }
891
                ctx->endmant[ch] = chbwcod * 3 + 73;
892
            }
893
            if(blk > 0 && ctx->endmant[ch] != prev)
894
                memset(bit_alloc_stages, 3, AC3_MAX_CHANNELS);
895
        }
896
    }
897
    ctx->startmant[ctx->lfe_ch] = 0;
898
    ctx->endmant[ctx->lfe_ch] = 7;
899

    
900
    for (ch = !ctx->cplinu; ch <= ctx->nchans; ch++) {
901
        if (ctx->expstr[ch] != EXP_REUSE) {
902
            int grpsize, ngrps;
903
            grpsize = 3 << (ctx->expstr[ch] - 1);
904
            if(ch == CPL_CH)
905
                ngrps = (ctx->endmant[ch] - ctx->startmant[ch]) / grpsize;
906
            else if(ch == ctx->lfe_ch)
907
                ngrps = 2;
908
            else
909
                ngrps = (ctx->endmant[ch] + grpsize - 4) / grpsize;
910
            ctx->dexps[ch][0] = get_bits(gb, 4) << !ch;
911
            decode_exponents(gb, ctx->expstr[ch], ngrps, ctx->dexps[ch][0],
912
                             &ctx->dexps[ch][ctx->startmant[ch]+!!ch]);
913
            if(ch != CPL_CH && ch != ctx->lfe_ch)
914
                skip_bits(gb, 2); /* skip gainrng */
915
        }
916
    }
917

    
918
    if (get_bits1(gb)) { /* bit allocation information */
919
        ctx->bit_alloc_params.sdecay = ff_sdecaytab[get_bits(gb, 2)];
920
        ctx->bit_alloc_params.fdecay = ff_fdecaytab[get_bits(gb, 2)];
921
        ctx->bit_alloc_params.sgain  = ff_sgaintab[get_bits(gb, 2)];
922
        ctx->bit_alloc_params.dbknee = ff_dbkneetab[get_bits(gb, 2)];
923
        ctx->bit_alloc_params.floor  = ff_floortab[get_bits(gb, 3)];
924
        for(ch=!ctx->cplinu; ch<=ctx->nchans; ch++) {
925
            bit_alloc_stages[ch] = FFMAX(bit_alloc_stages[ch], 2);
926
        }
927
    }
928

    
929
    if (get_bits1(gb)) { /* snroffset */
930
        int csnr;
931
        csnr = (get_bits(gb, 6) - 15) << 4;
932
        for (ch = !ctx->cplinu; ch <= ctx->nchans; ch++) { /* snr offset and fast gain */
933
            ctx->snroffst[ch] = (csnr + get_bits(gb, 4)) << 2;
934
            ctx->fgain[ch] = ff_fgaintab[get_bits(gb, 3)];
935
        }
936
        memset(bit_alloc_stages, 3, AC3_MAX_CHANNELS);
937
    }
938

    
939
    if (ctx->cplinu && get_bits1(gb)) { /* coupling leak information */
940
        ctx->bit_alloc_params.cplfleak = get_bits(gb, 3);
941
        ctx->bit_alloc_params.cplsleak = get_bits(gb, 3);
942
        bit_alloc_stages[CPL_CH] = FFMAX(bit_alloc_stages[CPL_CH], 2);
943
    }
944

    
945
    if (get_bits1(gb)) { /* delta bit allocation information */
946
        for (ch = !ctx->cplinu; ch <= nfchans; ch++) {
947
            ctx->deltbae[ch] = get_bits(gb, 2);
948
            if (ctx->deltbae[ch] == DBA_RESERVED) {
949
                av_log(ctx->avctx, AV_LOG_ERROR, "delta bit allocation strategy reserved\n");
950
                return -1;
951
            }
952
            bit_alloc_stages[ch] = FFMAX(bit_alloc_stages[ch], 2);
953
        }
954
        for (ch = !ctx->cplinu; ch <= nfchans; ch++) {
955
            if (ctx->deltbae[ch] == DBA_NEW) {/*channel delta offset, len and bit allocation */
956
                ctx->deltnseg[ch] = get_bits(gb, 3);
957
                for (seg = 0; seg <= ctx->deltnseg[ch]; seg++) {
958
                    ctx->deltoffst[ch][seg] = get_bits(gb, 5);
959
                    ctx->deltlen[ch][seg] = get_bits(gb, 4);
960
                    ctx->deltba[ch][seg] = get_bits(gb, 3);
961
                }
962
            }
963
        }
964
    } else if(blk == 0) {
965
        for(ch=0; ch<=ctx->nchans; ch++) {
966
            ctx->deltbae[ch] = DBA_NONE;
967
        }
968
    }
969

    
970
    for(ch=!ctx->cplinu; ch<=ctx->nchans; ch++) {
971
        if(bit_alloc_stages[ch] > 2) {
972
            /* Exponent mapping into PSD and PSD integration */
973
            ff_ac3_bit_alloc_calc_psd(ctx->dexps[ch],
974
                                      ctx->startmant[ch], ctx->endmant[ch],
975
                                      ctx->psd[ch], ctx->bndpsd[ch]);
976
        }
977
        if(bit_alloc_stages[ch] > 1) {
978
            /* Compute excitation function, Compute masking curve, and
979
               Apply delta bit allocation */
980
            ff_ac3_bit_alloc_calc_mask(&ctx->bit_alloc_params, ctx->bndpsd[ch],
981
                                       ctx->startmant[ch], ctx->endmant[ch],
982
                                       ctx->fgain[ch], (ch == ctx->lfe_ch),
983
                                       ctx->deltbae[ch], ctx->deltnseg[ch],
984
                                       ctx->deltoffst[ch], ctx->deltlen[ch],
985
                                       ctx->deltba[ch], ctx->mask[ch]);
986
        }
987
        if(bit_alloc_stages[ch] > 0) {
988
            /* Compute bit allocation */
989
            ff_ac3_bit_alloc_calc_bap(ctx->mask[ch], ctx->psd[ch],
990
                                      ctx->startmant[ch], ctx->endmant[ch],
991
                                      ctx->snroffst[ch],
992
                                      ctx->bit_alloc_params.floor,
993
                                      ctx->bap[ch]);
994
        }
995
    }
996

    
997
    if (get_bits1(gb)) { /* unused dummy data */
998
        int skipl = get_bits(gb, 9);
999
        while(skipl--)
1000
            skip_bits(gb, 8);
1001
    }
1002

    
1003
    /* unpack the transform coefficients
1004
     * * this also uncouples channels if coupling is in use.
1005
     */
1006
    if (get_transform_coeffs(ctx)) {
1007
        av_log(ctx->avctx, AV_LOG_ERROR, "Error in routine get_transform_coeffs\n");
1008
        return -1;
1009
    }
1010

    
1011
    /* recover coefficients if rematrixing is in use */
1012
    if(ctx->acmod == AC3_ACMOD_STEREO)
1013
        do_rematrixing(ctx);
1014

    
1015
    /* apply scaling to coefficients (headroom, dialnorm, dynrng) */
1016
    for(ch=1; ch<=ctx->nchans; ch++) {
1017
        float gain = 2.0f * ctx->mul_bias;
1018
        if(ctx->acmod == AC3_ACMOD_DUALMONO) {
1019
            gain *= ctx->dialnorm[ch-1] * ctx->dynrng[ch-1];
1020
        } else {
1021
            gain *= ctx->dialnorm[0] * ctx->dynrng[0];
1022
        }
1023
        for(i=0; i<ctx->endmant[ch]; i++) {
1024
            ctx->transform_coeffs[ch][i] *= gain;
1025
        }
1026
    }
1027

    
1028
    do_imdct(ctx);
1029

    
1030
    /* downmix output if needed */
1031
    if(ctx->nchans != ctx->out_channels && !((ctx->output_mode & AC3_OUTPUT_LFEON) &&
1032
            ctx->nfchans == ctx->out_channels)) {
1033
        ac3_downmix(ctx->output, ctx->nfchans, ctx->output_mode,
1034
                    ctx->downmix_coeffs);
1035
    }
1036

    
1037
    /* convert float to 16-bit integer */
1038
    for(ch=0; ch<ctx->out_channels; ch++) {
1039
        for(i=0; i<256; i++) {
1040
            ctx->output[ch][i] += ctx->add_bias;
1041
        }
1042
        ctx->dsp.float_to_int16(ctx->int_output[ch], ctx->output[ch], 256);
1043
    }
1044

    
1045
    return 0;
1046
}
1047

    
1048
/* Decode ac3 frame.
1049
 *
1050
 * @param avctx Pointer to AVCodecContext
1051
 * @param data Pointer to pcm smaples
1052
 * @param data_size Set to number of pcm samples produced by decoding
1053
 * @param buf Data to be decoded
1054
 * @param buf_size Size of the buffer
1055
 */
1056
static int ac3_decode_frame(AVCodecContext * avctx, void *data, int *data_size, uint8_t *buf, int buf_size)
1057
{
1058
    AC3DecodeContext *ctx = (AC3DecodeContext *)avctx->priv_data;
1059
    int16_t *out_samples = (int16_t *)data;
1060
    int i, blk, ch;
1061

    
1062
    //Initialize the GetBitContext with the start of valid AC3 Frame.
1063
    init_get_bits(&ctx->gb, buf, buf_size * 8);
1064

    
1065
    //Parse the syncinfo.
1066
    if (ac3_parse_header(ctx)) {
1067
        av_log(avctx, AV_LOG_ERROR, "\n");
1068
        *data_size = 0;
1069
        return buf_size;
1070
    }
1071

    
1072
    avctx->sample_rate = ctx->sampling_rate;
1073
    avctx->bit_rate = ctx->bit_rate;
1074

    
1075
    /* channel config */
1076
    ctx->out_channels = ctx->nchans;
1077
    if (avctx->channels == 0) {
1078
        avctx->channels = ctx->out_channels;
1079
    } else if(ctx->out_channels < avctx->channels) {
1080
        av_log(avctx, AV_LOG_ERROR, "Cannot upmix AC3 from %d to %d channels.\n",
1081
               ctx->out_channels, avctx->channels);
1082
        return -1;
1083
    }
1084
    if(avctx->channels == 2) {
1085
        ctx->output_mode = AC3_ACMOD_STEREO;
1086
    } else if(avctx->channels == 1) {
1087
        ctx->output_mode = AC3_ACMOD_MONO;
1088
    } else if(avctx->channels != ctx->out_channels) {
1089
        av_log(avctx, AV_LOG_ERROR, "Cannot downmix AC3 from %d to %d channels.\n",
1090
               ctx->out_channels, avctx->channels);
1091
        return -1;
1092
    }
1093
    ctx->out_channels = avctx->channels;
1094

    
1095
    //Parse the Audio Blocks.
1096
    for (blk = 0; blk < NB_BLOCKS; blk++) {
1097
        if (ac3_parse_audio_block(ctx, blk)) {
1098
            av_log(avctx, AV_LOG_ERROR, "error parsing the audio block\n");
1099
            *data_size = 0;
1100
            return ctx->frame_size;
1101
        }
1102
        for (i = 0; i < 256; i++)
1103
            for (ch = 0; ch < ctx->out_channels; ch++)
1104
                *(out_samples++) = ctx->int_output[ch][i];
1105
    }
1106
    *data_size = NB_BLOCKS * 256 * avctx->channels * sizeof (int16_t);
1107
    return ctx->frame_size;
1108
}
1109

    
1110
/* Uninitialize ac3 decoder.
1111
 */
1112
static int ac3_decode_end(AVCodecContext *avctx)
1113
{
1114
    AC3DecodeContext *ctx = (AC3DecodeContext *)avctx->priv_data;
1115
    ff_mdct_end(&ctx->imdct_512);
1116
    ff_mdct_end(&ctx->imdct_256);
1117

    
1118
    return 0;
1119
}
1120

    
1121
AVCodec ac3_decoder = {
1122
    .name = "ac3",
1123
    .type = CODEC_TYPE_AUDIO,
1124
    .id = CODEC_ID_AC3,
1125
    .priv_data_size = sizeof (AC3DecodeContext),
1126
    .init = ac3_decode_init,
1127
    .close = ac3_decode_end,
1128
    .decode = ac3_decode_frame,
1129
};