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1
/*
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 * 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>
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#include <math.h>
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#include <string.h>
34

    
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#include "libavutil/crc.h"
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#include "libavutil/random.h"
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#include "avcodec.h"
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#include "ac3_parser.h"
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#include "bitstream.h"
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#include "dsputil.h"
41

    
42
/** Maximum possible frame size when the specification limit is ignored */
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#define AC3_MAX_FRAME_SIZE 21695
44

    
45
/**
46
 * Table of bin locations for rematrixing bands
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 * reference: Section 7.5.2 Rematrixing : Frequency Band Definitions
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 */
49
static const uint8_t rematrix_band_tab[5] = { 13, 25, 37, 61, 253 };
50

    
51
/** table for grouping exponents */
52
static uint8_t exp_ungroup_tab[128][3];
53

    
54

    
55
/** tables for ungrouping mantissas */
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static int b1_mantissas[32][3];
57
static int b2_mantissas[128][3];
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static int b3_mantissas[8];
59
static int b4_mantissas[128][2];
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static int b5_mantissas[16];
61

    
62
/**
63
 * Quantization table: levels for symmetric. bits for asymmetric.
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 * reference: Table 7.18 Mapping of bap to Quantizer
65
 */
66
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
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};
70

    
71
/** dynamic range table. converts codes to scale factors. */
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static float dynamic_range_tab[256];
73

    
74
/** Adjustments in dB gain */
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#define LEVEL_MINUS_3DB         0.7071067811865476
76
#define LEVEL_MINUS_4POINT5DB   0.5946035575013605
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#define LEVEL_MINUS_6DB         0.5000000000000000
78
#define LEVEL_MINUS_9DB         0.3535533905932738
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#define LEVEL_ZERO              0.0000000000000000
80
#define LEVEL_ONE               1.0000000000000000
81

    
82
static const float gain_levels[6] = {
83
    LEVEL_ZERO,
84
    LEVEL_ONE,
85
    LEVEL_MINUS_3DB,
86
    LEVEL_MINUS_4POINT5DB,
87
    LEVEL_MINUS_6DB,
88
    LEVEL_MINUS_9DB
89
};
90

    
91
/**
92
 * Table for default stereo downmixing coefficients
93
 * reference: Section 7.8.2 Downmixing Into Two Channels
94
 */
95
static const uint8_t ac3_default_coeffs[8][5][2] = {
96
    { { 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 }, },
104
};
105

    
106
/* override ac3.h to include coupling channel */
107
#undef AC3_MAX_CHANNELS
108
#define AC3_MAX_CHANNELS 7
109
#define CPL_CH 0
110

    
111
#define AC3_OUTPUT_LFEON  8
112

    
113
typedef struct {
114
    int num_blocks;                         ///< number of audio blocks
115
    int channel_mode;                       ///< channel mode (acmod)
116
    int block_switch[AC3_MAX_CHANNELS];     ///< block switch flags
117
    int dither_flag[AC3_MAX_CHANNELS];      ///< dither flags
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    int dither_all;                         ///< true if all channels are dithered
119
    int cpl_in_use;                         ///< coupling in use
120
    int channel_in_cpl[AC3_MAX_CHANNELS];   ///< channel in coupling
121
    int phase_flags_in_use;                 ///< phase flags in use
122
    int phase_flags[18];                    ///< phase flags
123
    int cpl_band_struct[18];                ///< coupling band structure
124
    int num_rematrixing_bands;              ///< number of rematrixing bands
125
    int rematrixing_flags[4];               ///< rematrixing flags
126
    int exp_strategy[AC3_MAX_CHANNELS];     ///< exponent strategies
127
    int snr_offset[AC3_MAX_CHANNELS];       ///< signal-to-noise ratio offsets
128
    int fast_gain[AC3_MAX_CHANNELS];        ///< fast gain values (signal-to-mask ratio)
129
    int dba_mode[AC3_MAX_CHANNELS];         ///< delta bit allocation mode
130
    int dba_nsegs[AC3_MAX_CHANNELS];        ///< number of delta segments
131
    uint8_t dba_offsets[AC3_MAX_CHANNELS][8]; ///< delta segment offsets
132
    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
134

    
135
    int sample_rate;                        ///< sample frequency, in Hz
136
    int bit_rate;                           ///< stream bit rate, in bits-per-second
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    int frame_type;                         ///< frame type (strmtyp)
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    int substreamid;                        ///< substream identification
139
    int frame_size;                         ///< current frame size, in bytes
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141
    int channels;                           ///< number of total channels
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    int fbw_channels;                       ///< number of full-bandwidth channels
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    int lfe_on;                             ///< lfe channel in use
144
    int lfe_ch;                             ///< index of LFE channel
145
    int output_mode;                        ///< output channel configuration
146
    int out_channels;                       ///< number of output channels
147

    
148
    int center_mix_level;                   ///< Center mix level index
149
    int surround_mix_level;                 ///< Surround mix level index
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    float downmix_coeffs[AC3_MAX_CHANNELS][2];  ///< stereo downmix coefficients
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    float downmix_coeff_adjust[2];          ///< adjustment needed for each output channel when downmixing
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    float dynamic_range[2];                 ///< dynamic range
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    int   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
157
    int   end_freq[AC3_MAX_CHANNELS];       ///< end frequency bin
158
    AC3BitAllocParameters bit_alloc_params; ///< bit allocation parameters
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160
    int num_exp_groups[AC3_MAX_CHANNELS];   ///< Number of exponent groups
161
    int8_t  dexps[AC3_MAX_CHANNELS][256];   ///< decoded exponents
162
    uint8_t bap[AC3_MAX_CHANNELS][256];     ///< bit allocation pointers
163
    int16_t psd[AC3_MAX_CHANNELS][256];     ///< scaled exponents
164
    int16_t band_psd[AC3_MAX_CHANNELS][50]; ///< interpolated exponents
165
    int16_t mask[AC3_MAX_CHANNELS][50];     ///< masking curve values
166

    
167
    int fixed_coeffs[AC3_MAX_CHANNELS][256];    ///> fixed-point transform coefficients
168
    DECLARE_ALIGNED_16(float, transform_coeffs[AC3_MAX_CHANNELS][256]);  ///< transform coefficients
169
    int downmixed;                              ///< indicates if coeffs are currently downmixed
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    /* For IMDCT. */
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    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][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][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
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    /* Miscellaneous. */
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    GetBitContext gbc;                      ///< bitstream reader
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    AVRandomState dith_state;               ///< for dither generation
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    AVCodecContext *avctx;                  ///< parent context
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    uint8_t *input_buffer;                  ///< temp buffer to prevent overread
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} AC3DecodeContext;
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/**
193
 * Symmetrical Dequantization
194
 * reference: Section 7.3.3 Expansion of Mantissas for Symmetrical Quantization
195
 *            Tables 7.19 to 7.23
196
 */
197
static inline int
198
symmetric_dequant(int code, int levels)
199
{
200
    return ((code - (levels >> 1)) << 24) / levels;
201
}
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203
/*
204
 * Initialize tables at runtime.
205
 */
206
static av_cold void ac3_tables_init(void)
207
{
208
    int i;
209

    
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    /* generate grouped mantissa tables
211
       reference: Section 7.3.5 Ungrouping of Mantissas */
212
    for(i=0; i<32; i++) {
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        /* bap=1 mantissas */
214
        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);
217
    }
218
    for(i=0; i<128; i++) {
219
        /* bap=2 mantissas */
220
        b2_mantissas[i][0] = symmetric_dequant( i / 25     , 5);
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        b2_mantissas[i][1] = symmetric_dequant((i % 25) / 5, 5);
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        b2_mantissas[i][2] = symmetric_dequant((i % 25) % 5, 5);
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224
        /* bap=4 mantissas */
225
        b4_mantissas[i][0] = symmetric_dequant(i / 11, 11);
226
        b4_mantissas[i][1] = symmetric_dequant(i % 11, 11);
227
    }
228
    /* generate ungrouped mantissa tables
229
       reference: Tables 7.21 and 7.23 */
230
    for(i=0; i<7; i++) {
231
        /* bap=3 mantissas */
232
        b3_mantissas[i] = symmetric_dequant(i, 7);
233
    }
234
    for(i=0; i<15; i++) {
235
        /* bap=5 mantissas */
236
        b5_mantissas[i] = symmetric_dequant(i, 15);
237
    }
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239
    /* generate dynamic range table
240
       reference: Section 7.7.1 Dynamic Range Control */
241
    for(i=0; i<256; i++) {
242
        int v = (i >> 5) - ((i >> 7) << 3) - 5;
243
        dynamic_range_tab[i] = powf(2.0f, v) * ((i & 0x1F) | 0x20);
244
    }
245

    
246
    /* generate exponent tables
247
       reference: Section 7.1.3 Exponent Decoding */
248
    for(i=0; i<128; i++) {
249
        exp_ungroup_tab[i][0] =  i / 25;
250
        exp_ungroup_tab[i][1] = (i % 25) / 5;
251
        exp_ungroup_tab[i][2] = (i % 25) % 5;
252
    }
253
}
254

    
255

    
256
/**
257
 * AVCodec initialization
258
 */
259
static av_cold int ac3_decode_init(AVCodecContext *avctx)
260
{
261
    AC3DecodeContext *s = avctx->priv_data;
262
    s->avctx = avctx;
263

    
264
    ac3_common_init();
265
    ac3_tables_init();
266
    ff_mdct_init(&s->imdct_256, 8, 1);
267
    ff_mdct_init(&s->imdct_512, 9, 1);
268
    ff_kbd_window_init(s->window, 5.0, 256);
269
    dsputil_init(&s->dsp, avctx);
270
    av_init_random(0, &s->dith_state);
271

    
272
    /* set bias values for float to int16 conversion */
273
    if(s->dsp.float_to_int16 == ff_float_to_int16_c) {
274
        s->add_bias = 385.0f;
275
        s->mul_bias = 1.0f;
276
    } else {
277
        s->add_bias = 0.0f;
278
        s->mul_bias = 32767.0f;
279
    }
280

    
281
    /* allow downmixing to stereo or mono */
282
    if (avctx->channels > 0 && avctx->request_channels > 0 &&
283
            avctx->request_channels < avctx->channels &&
284
            avctx->request_channels <= 2) {
285
        avctx->channels = avctx->request_channels;
286
    }
287
    s->downmixed = 1;
288

    
289
    /* allocate context input buffer */
290
    if (avctx->error_resilience >= FF_ER_CAREFUL) {
291
        s->input_buffer = av_mallocz(AC3_MAX_FRAME_SIZE + FF_INPUT_BUFFER_PADDING_SIZE);
292
        if (!s->input_buffer)
293
            return AVERROR_NOMEM;
294
    }
295

    
296
    return 0;
297
}
298

    
299
/**
300
 * Parse the 'sync info' and 'bit stream info' from the AC-3 bitstream.
301
 * GetBitContext within AC3DecodeContext must point to
302
 * start of the synchronized ac3 bitstream.
303
 */
304
static int ac3_parse_header(AC3DecodeContext *s)
305
{
306
    AC3HeaderInfo hdr;
307
    GetBitContext *gbc = &s->gbc;
308
    int err, i;
309

    
310
    err = ff_ac3_parse_header(gbc, &hdr);
311
    if(err)
312
        return err;
313

    
314
    if(hdr.bitstream_id > 10)
315
        return AC3_PARSE_ERROR_BSID;
316

    
317
    /* get decoding parameters from header info */
318
    s->bit_alloc_params.sr_code     = hdr.sr_code;
319
    s->channel_mode                 = hdr.channel_mode;
320
    s->lfe_on                       = hdr.lfe_on;
321
    s->bit_alloc_params.sr_shift    = hdr.sr_shift;
322
    s->sample_rate                  = hdr.sample_rate;
323
    s->bit_rate                     = hdr.bit_rate;
324
    s->channels                     = hdr.channels;
325
    s->fbw_channels                 = s->channels - s->lfe_on;
326
    s->lfe_ch                       = s->fbw_channels + 1;
327
    s->frame_size                   = hdr.frame_size;
328
    s->center_mix_level             = hdr.center_mix_level;
329
    s->surround_mix_level           = hdr.surround_mix_level;
330
    s->num_blocks                   = hdr.num_blocks;
331
    s->frame_type                   = hdr.frame_type;
332
    s->substreamid                  = hdr.substreamid;
333

    
334
    if(s->lfe_on) {
335
        s->start_freq[s->lfe_ch] = 0;
336
        s->end_freq[s->lfe_ch] = 7;
337
        s->num_exp_groups[s->lfe_ch] = 2;
338
        s->channel_in_cpl[s->lfe_ch] = 0;
339
    }
340

    
341
    /* read the rest of the bsi. read twice for dual mono mode. */
342
    i = !(s->channel_mode);
343
    do {
344
        skip_bits(gbc, 5); // skip dialog normalization
345
        if (get_bits1(gbc))
346
            skip_bits(gbc, 8); //skip compression
347
        if (get_bits1(gbc))
348
            skip_bits(gbc, 8); //skip language code
349
        if (get_bits1(gbc))
350
            skip_bits(gbc, 7); //skip audio production information
351
    } while (i--);
352

    
353
    skip_bits(gbc, 2); //skip copyright bit and original bitstream bit
354

    
355
    /* skip the timecodes (or extra bitstream information for Alternate Syntax)
356
       TODO: read & use the xbsi1 downmix levels */
357
    if (get_bits1(gbc))
358
        skip_bits(gbc, 14); //skip timecode1 / xbsi1
359
    if (get_bits1(gbc))
360
        skip_bits(gbc, 14); //skip timecode2 / xbsi2
361

    
362
    /* skip additional bitstream info */
363
    if (get_bits1(gbc)) {
364
        i = get_bits(gbc, 6);
365
        do {
366
            skip_bits(gbc, 8);
367
        } while(i--);
368
    }
369

    
370
    return 0;
371
}
372

    
373
/**
374
 * Set stereo downmixing coefficients based on frame header info.
375
 * reference: Section 7.8.2 Downmixing Into Two Channels
376
 */
377
static void set_downmix_coeffs(AC3DecodeContext *s)
378
{
379
    int i;
380
    float cmix = gain_levels[s->center_mix_level];
381
    float smix = gain_levels[s->surround_mix_level];
382

    
383
    for(i=0; i<s->fbw_channels; i++) {
384
        s->downmix_coeffs[i][0] = gain_levels[ac3_default_coeffs[s->channel_mode][i][0]];
385
        s->downmix_coeffs[i][1] = gain_levels[ac3_default_coeffs[s->channel_mode][i][1]];
386
    }
387
    if(s->channel_mode > 1 && s->channel_mode & 1) {
388
        s->downmix_coeffs[1][0] = s->downmix_coeffs[1][1] = cmix;
389
    }
390
    if(s->channel_mode == AC3_CHMODE_2F1R || s->channel_mode == AC3_CHMODE_3F1R) {
391
        int nf = s->channel_mode - 2;
392
        s->downmix_coeffs[nf][0] = s->downmix_coeffs[nf][1] = smix * LEVEL_MINUS_3DB;
393
    }
394
    if(s->channel_mode == AC3_CHMODE_2F2R || s->channel_mode == AC3_CHMODE_3F2R) {
395
        int nf = s->channel_mode - 4;
396
        s->downmix_coeffs[nf][0] = s->downmix_coeffs[nf+1][1] = smix;
397
    }
398

    
399
    /* calculate adjustment needed for each channel to avoid clipping */
400
    s->downmix_coeff_adjust[0] = s->downmix_coeff_adjust[1] = 0.0f;
401
    for(i=0; i<s->fbw_channels; i++) {
402
        s->downmix_coeff_adjust[0] += s->downmix_coeffs[i][0];
403
        s->downmix_coeff_adjust[1] += s->downmix_coeffs[i][1];
404
    }
405
    s->downmix_coeff_adjust[0] = 1.0f / s->downmix_coeff_adjust[0];
406
    s->downmix_coeff_adjust[1] = 1.0f / s->downmix_coeff_adjust[1];
407
}
408

    
409
/**
410
 * Decode the grouped exponents according to exponent strategy.
411
 * reference: Section 7.1.3 Exponent Decoding
412
 */
413
static void decode_exponents(GetBitContext *gbc, int exp_strategy, int ngrps,
414
                             uint8_t absexp, int8_t *dexps)
415
{
416
    int i, j, grp, group_size;
417
    int dexp[256];
418
    int expacc, prevexp;
419

    
420
    /* unpack groups */
421
    group_size = exp_strategy + (exp_strategy == EXP_D45);
422
    for(grp=0,i=0; grp<ngrps; grp++) {
423
        expacc = get_bits(gbc, 7);
424
        dexp[i++] = exp_ungroup_tab[expacc][0];
425
        dexp[i++] = exp_ungroup_tab[expacc][1];
426
        dexp[i++] = exp_ungroup_tab[expacc][2];
427
    }
428

    
429
    /* convert to absolute exps and expand groups */
430
    prevexp = absexp;
431
    for(i=0; i<ngrps*3; i++) {
432
        prevexp = av_clip(prevexp + dexp[i]-2, 0, 24);
433
        for(j=0; j<group_size; j++) {
434
            dexps[(i*group_size)+j] = prevexp;
435
        }
436
    }
437
}
438

    
439
/**
440
 * Generate transform coefficients for each coupled channel in the coupling
441
 * range using the coupling coefficients and coupling coordinates.
442
 * reference: Section 7.4.3 Coupling Coordinate Format
443
 */
444
static void uncouple_channels(AC3DecodeContext *s)
445
{
446
    int i, j, ch, bnd, subbnd;
447

    
448
    subbnd = -1;
449
    i = s->start_freq[CPL_CH];
450
    for(bnd=0; bnd<s->num_cpl_bands; bnd++) {
451
        do {
452
            subbnd++;
453
            for(j=0; j<12; j++) {
454
                for(ch=1; ch<=s->fbw_channels; ch++) {
455
                    if(s->channel_in_cpl[ch]) {
456
                        s->fixed_coeffs[ch][i] = ((int64_t)s->fixed_coeffs[CPL_CH][i] * (int64_t)s->cpl_coords[ch][bnd]) >> 23;
457
                        if (ch == 2 && s->phase_flags[bnd])
458
                            s->fixed_coeffs[ch][i] = -s->fixed_coeffs[ch][i];
459
                    }
460
                }
461
                i++;
462
            }
463
        } while(s->cpl_band_struct[subbnd]);
464
    }
465
}
466

    
467
/**
468
 * Grouped mantissas for 3-level 5-level and 11-level quantization
469
 */
470
typedef struct {
471
    int b1_mant[3];
472
    int b2_mant[3];
473
    int b4_mant[2];
474
    int b1ptr;
475
    int b2ptr;
476
    int b4ptr;
477
} mant_groups;
478

    
479
/**
480
 * Get the transform coefficients for a particular channel
481
 * reference: Section 7.3 Quantization and Decoding of Mantissas
482
 */
483
static void get_transform_coeffs_ch(AC3DecodeContext *s, int ch_index, mant_groups *m)
484
{
485
    GetBitContext *gbc = &s->gbc;
486
    int i, gcode, tbap, start, end;
487
    uint8_t *exps;
488
    uint8_t *bap;
489
    int *coeffs;
490

    
491
    exps = s->dexps[ch_index];
492
    bap = s->bap[ch_index];
493
    coeffs = s->fixed_coeffs[ch_index];
494
    start = s->start_freq[ch_index];
495
    end = s->end_freq[ch_index];
496

    
497
    for (i = start; i < end; i++) {
498
        tbap = bap[i];
499
        switch (tbap) {
500
            case 0:
501
                coeffs[i] = (av_random(&s->dith_state) & 0x7FFFFF) - 4194304;
502
                break;
503

    
504
            case 1:
505
                if(m->b1ptr > 2) {
506
                    gcode = get_bits(gbc, 5);
507
                    m->b1_mant[0] = b1_mantissas[gcode][0];
508
                    m->b1_mant[1] = b1_mantissas[gcode][1];
509
                    m->b1_mant[2] = b1_mantissas[gcode][2];
510
                    m->b1ptr = 0;
511
                }
512
                coeffs[i] = m->b1_mant[m->b1ptr++];
513
                break;
514

    
515
            case 2:
516
                if(m->b2ptr > 2) {
517
                    gcode = get_bits(gbc, 7);
518
                    m->b2_mant[0] = b2_mantissas[gcode][0];
519
                    m->b2_mant[1] = b2_mantissas[gcode][1];
520
                    m->b2_mant[2] = b2_mantissas[gcode][2];
521
                    m->b2ptr = 0;
522
                }
523
                coeffs[i] = m->b2_mant[m->b2ptr++];
524
                break;
525

    
526
            case 3:
527
                coeffs[i] = b3_mantissas[get_bits(gbc, 3)];
528
                break;
529

    
530
            case 4:
531
                if(m->b4ptr > 1) {
532
                    gcode = get_bits(gbc, 7);
533
                    m->b4_mant[0] = b4_mantissas[gcode][0];
534
                    m->b4_mant[1] = b4_mantissas[gcode][1];
535
                    m->b4ptr = 0;
536
                }
537
                coeffs[i] = m->b4_mant[m->b4ptr++];
538
                break;
539

    
540
            case 5:
541
                coeffs[i] = b5_mantissas[get_bits(gbc, 4)];
542
                break;
543

    
544
            default: {
545
                /* asymmetric dequantization */
546
                int qlevel = quantization_tab[tbap];
547
                coeffs[i] = get_sbits(gbc, qlevel) << (24 - qlevel);
548
                break;
549
            }
550
        }
551
        coeffs[i] >>= exps[i];
552
    }
553
}
554

    
555
/**
556
 * Remove random dithering from coefficients with zero-bit mantissas
557
 * reference: Section 7.3.4 Dither for Zero Bit Mantissas (bap=0)
558
 */
559
static void remove_dithering(AC3DecodeContext *s) {
560
    int ch, i;
561
    int end=0;
562
    int *coeffs;
563
    uint8_t *bap;
564

    
565
    for(ch=1; ch<=s->fbw_channels; ch++) {
566
        if(!s->dither_flag[ch]) {
567
            coeffs = s->fixed_coeffs[ch];
568
            bap = s->bap[ch];
569
            if(s->channel_in_cpl[ch])
570
                end = s->start_freq[CPL_CH];
571
            else
572
                end = s->end_freq[ch];
573
            for(i=0; i<end; i++) {
574
                if(!bap[i])
575
                    coeffs[i] = 0;
576
            }
577
            if(s->channel_in_cpl[ch]) {
578
                bap = s->bap[CPL_CH];
579
                for(; i<s->end_freq[CPL_CH]; i++) {
580
                    if(!bap[i])
581
                        coeffs[i] = 0;
582
                }
583
            }
584
        }
585
    }
586
}
587

    
588
/**
589
 * Get the transform coefficients.
590
 */
591
static void get_transform_coeffs(AC3DecodeContext *s)
592
{
593
    int ch, end;
594
    int got_cplchan = 0;
595
    mant_groups m;
596

    
597
    m.b1ptr = m.b2ptr = m.b4ptr = 3;
598

    
599
    for (ch = 1; ch <= s->channels; ch++) {
600
        /* transform coefficients for full-bandwidth channel */
601
        get_transform_coeffs_ch(s, ch, &m);
602
        /* tranform coefficients for coupling channel come right after the
603
           coefficients for the first coupled channel*/
604
        if (s->channel_in_cpl[ch])  {
605
            if (!got_cplchan) {
606
                get_transform_coeffs_ch(s, CPL_CH, &m);
607
                uncouple_channels(s);
608
                got_cplchan = 1;
609
            }
610
            end = s->end_freq[CPL_CH];
611
        } else {
612
            end = s->end_freq[ch];
613
        }
614
        do
615
            s->fixed_coeffs[ch][end] = 0;
616
        while(++end < 256);
617
    }
618

    
619
    /* if any channel doesn't use dithering, zero appropriate coefficients */
620
    if(!s->dither_all)
621
        remove_dithering(s);
622
}
623

    
624
/**
625
 * Stereo rematrixing.
626
 * reference: Section 7.5.4 Rematrixing : Decoding Technique
627
 */
628
static void do_rematrixing(AC3DecodeContext *s)
629
{
630
    int bnd, i;
631
    int end, bndend;
632
    int tmp0, tmp1;
633

    
634
    end = FFMIN(s->end_freq[1], s->end_freq[2]);
635

    
636
    for(bnd=0; bnd<s->num_rematrixing_bands; bnd++) {
637
        if(s->rematrixing_flags[bnd]) {
638
            bndend = FFMIN(end, rematrix_band_tab[bnd+1]);
639
            for(i=rematrix_band_tab[bnd]; i<bndend; i++) {
640
                tmp0 = s->fixed_coeffs[1][i];
641
                tmp1 = s->fixed_coeffs[2][i];
642
                s->fixed_coeffs[1][i] = tmp0 + tmp1;
643
                s->fixed_coeffs[2][i] = tmp0 - tmp1;
644
            }
645
        }
646
    }
647
}
648

    
649
/**
650
 * Perform the 256-point IMDCT
651
 */
652
static void do_imdct_256(AC3DecodeContext *s, int chindex)
653
{
654
    int i, k;
655
    DECLARE_ALIGNED_16(float, x[128]);
656
    FFTComplex z[2][64];
657
    float *o_ptr = s->tmp_output;
658

    
659
    for(i=0; i<2; i++) {
660
        /* de-interleave coefficients */
661
        for(k=0; k<128; k++) {
662
            x[k] = s->transform_coeffs[chindex][2*k+i];
663
        }
664

    
665
        /* run standard IMDCT */
666
        s->imdct_256.fft.imdct_calc(&s->imdct_256, o_ptr, x, s->tmp_imdct);
667

    
668
        /* reverse the post-rotation & reordering from standard IMDCT */
669
        for(k=0; k<32; k++) {
670
            z[i][32+k].re = -o_ptr[128+2*k];
671
            z[i][32+k].im = -o_ptr[2*k];
672
            z[i][31-k].re =  o_ptr[2*k+1];
673
            z[i][31-k].im =  o_ptr[128+2*k+1];
674
        }
675
    }
676

    
677
    /* apply AC-3 post-rotation & reordering */
678
    for(k=0; k<64; k++) {
679
        o_ptr[    2*k  ] = -z[0][   k].im;
680
        o_ptr[    2*k+1] =  z[0][63-k].re;
681
        o_ptr[128+2*k  ] = -z[0][   k].re;
682
        o_ptr[128+2*k+1] =  z[0][63-k].im;
683
        o_ptr[256+2*k  ] = -z[1][   k].re;
684
        o_ptr[256+2*k+1] =  z[1][63-k].im;
685
        o_ptr[384+2*k  ] =  z[1][   k].im;
686
        o_ptr[384+2*k+1] = -z[1][63-k].re;
687
    }
688
}
689

    
690
/**
691
 * Inverse MDCT Transform.
692
 * Convert frequency domain coefficients to time-domain audio samples.
693
 * reference: Section 7.9.4 Transformation Equations
694
 */
695
static inline void do_imdct(AC3DecodeContext *s, int channels)
696
{
697
    int ch;
698

    
699
    for (ch=1; ch<=channels; ch++) {
700
        if (s->block_switch[ch]) {
701
            do_imdct_256(s, ch);
702
        } else {
703
            s->imdct_512.fft.imdct_calc(&s->imdct_512, s->tmp_output,
704
                                        s->transform_coeffs[ch], s->tmp_imdct);
705
        }
706
        /* For the first half of the block, apply the window, add the delay
707
           from the previous block, and send to output */
708
        s->dsp.vector_fmul_add_add(s->output[ch-1], s->tmp_output,
709
                                     s->window, s->delay[ch-1], 0, 256, 1);
710
        /* For the second half of the block, apply the window and store the
711
           samples to delay, to be combined with the next block */
712
        s->dsp.vector_fmul_reverse(s->delay[ch-1], s->tmp_output+256,
713
                                   s->window, 256);
714
    }
715
}
716

    
717
/**
718
 * Downmix the output to mono or stereo.
719
 */
720
static void ac3_downmix(AC3DecodeContext *s,
721
                        float samples[AC3_MAX_CHANNELS][256], int ch_offset)
722
{
723
    int i, j;
724
    float v0, v1;
725

    
726
    for(i=0; i<256; i++) {
727
        v0 = v1 = 0.0f;
728
        for(j=0; j<s->fbw_channels; j++) {
729
            v0 += samples[j+ch_offset][i] * s->downmix_coeffs[j][0];
730
            v1 += samples[j+ch_offset][i] * s->downmix_coeffs[j][1];
731
        }
732
        v0 *= s->downmix_coeff_adjust[0];
733
        v1 *= s->downmix_coeff_adjust[1];
734
        if(s->output_mode == AC3_CHMODE_MONO) {
735
            samples[ch_offset][i] = (v0 + v1) * LEVEL_MINUS_3DB;
736
        } else if(s->output_mode == AC3_CHMODE_STEREO) {
737
            samples[  ch_offset][i] = v0;
738
            samples[1+ch_offset][i] = v1;
739
        }
740
    }
741
}
742

    
743
/**
744
 * Upmix delay samples from stereo to original channel layout.
745
 */
746
static void ac3_upmix_delay(AC3DecodeContext *s)
747
{
748
    int channel_data_size = sizeof(s->delay[0]);
749
    switch(s->channel_mode) {
750
        case AC3_CHMODE_DUALMONO:
751
        case AC3_CHMODE_STEREO:
752
            /* upmix mono to stereo */
753
            memcpy(s->delay[1], s->delay[0], channel_data_size);
754
            break;
755
        case AC3_CHMODE_2F2R:
756
            memset(s->delay[3], 0, channel_data_size);
757
        case AC3_CHMODE_2F1R:
758
            memset(s->delay[2], 0, channel_data_size);
759
            break;
760
        case AC3_CHMODE_3F2R:
761
            memset(s->delay[4], 0, channel_data_size);
762
        case AC3_CHMODE_3F1R:
763
            memset(s->delay[3], 0, channel_data_size);
764
        case AC3_CHMODE_3F:
765
            memcpy(s->delay[2], s->delay[1], channel_data_size);
766
            memset(s->delay[1], 0, channel_data_size);
767
            break;
768
    }
769
}
770

    
771
/**
772
 * Parse an audio block from AC-3 bitstream.
773
 */
774
static int ac3_parse_audio_block(AC3DecodeContext *s, int blk)
775
{
776
    int fbw_channels = s->fbw_channels;
777
    int channel_mode = s->channel_mode;
778
    int i, bnd, seg, ch;
779
    int different_transforms;
780
    int downmix_output;
781
    GetBitContext *gbc = &s->gbc;
782
    uint8_t bit_alloc_stages[AC3_MAX_CHANNELS];
783

    
784
    memset(bit_alloc_stages, 0, AC3_MAX_CHANNELS);
785

    
786
    /* block switch flags */
787
    different_transforms = 0;
788
    for (ch = 1; ch <= fbw_channels; ch++) {
789
        s->block_switch[ch] = get_bits1(gbc);
790
        if(ch > 1 && s->block_switch[ch] != s->block_switch[1])
791
            different_transforms = 1;
792
    }
793

    
794
    /* dithering flags */
795
    s->dither_all = 1;
796
    for (ch = 1; ch <= fbw_channels; ch++) {
797
        s->dither_flag[ch] = get_bits1(gbc);
798
        if(!s->dither_flag[ch])
799
            s->dither_all = 0;
800
    }
801

    
802
    /* dynamic range */
803
    i = !(s->channel_mode);
804
    do {
805
        if(get_bits1(gbc)) {
806
            s->dynamic_range[i] = ((dynamic_range_tab[get_bits(gbc, 8)]-1.0) *
807
                                  s->avctx->drc_scale)+1.0;
808
        } else if(blk == 0) {
809
            s->dynamic_range[i] = 1.0f;
810
        }
811
    } while(i--);
812

    
813
    /* coupling strategy */
814
    if (get_bits1(gbc)) {
815
        memset(bit_alloc_stages, 3, AC3_MAX_CHANNELS);
816
        s->cpl_in_use = get_bits1(gbc);
817
        if (s->cpl_in_use) {
818
            /* coupling in use */
819
            int cpl_begin_freq, cpl_end_freq;
820

    
821
            if (channel_mode < AC3_CHMODE_STEREO) {
822
                av_log(s->avctx, AV_LOG_ERROR, "coupling not allowed in mono or dual-mono\n");
823
                return -1;
824
            }
825

    
826
            /* determine which channels are coupled */
827
            for (ch = 1; ch <= fbw_channels; ch++)
828
                s->channel_in_cpl[ch] = get_bits1(gbc);
829

    
830
            /* phase flags in use */
831
            if (channel_mode == AC3_CHMODE_STEREO)
832
                s->phase_flags_in_use = get_bits1(gbc);
833

    
834
            /* coupling frequency range and band structure */
835
            cpl_begin_freq = get_bits(gbc, 4);
836
            cpl_end_freq = get_bits(gbc, 4);
837
            if (3 + cpl_end_freq - cpl_begin_freq < 0) {
838
                av_log(s->avctx, AV_LOG_ERROR, "3+cplendf = %d < cplbegf = %d\n", 3+cpl_end_freq, cpl_begin_freq);
839
                return -1;
840
            }
841
            s->num_cpl_bands = s->num_cpl_subbands = 3 + cpl_end_freq - cpl_begin_freq;
842
            s->start_freq[CPL_CH] = cpl_begin_freq * 12 + 37;
843
            s->end_freq[CPL_CH] = cpl_end_freq * 12 + 73;
844
            for (bnd = 0; bnd < s->num_cpl_subbands - 1; bnd++) {
845
                if (get_bits1(gbc)) {
846
                    s->cpl_band_struct[bnd] = 1;
847
                    s->num_cpl_bands--;
848
                }
849
            }
850
            s->cpl_band_struct[s->num_cpl_subbands-1] = 0;
851
        } else {
852
            /* coupling not in use */
853
            for (ch = 1; ch <= fbw_channels; ch++)
854
                s->channel_in_cpl[ch] = 0;
855
        }
856
    } else if (!blk) {
857
        av_log(s->avctx, AV_LOG_ERROR, "new coupling strategy must be present in block 0\n");
858
        return -1;
859
    }
860

    
861
    /* coupling coordinates */
862
    if (s->cpl_in_use) {
863
        int cpl_coords_exist = 0;
864

    
865
        for (ch = 1; ch <= fbw_channels; ch++) {
866
            if (s->channel_in_cpl[ch]) {
867
                if (get_bits1(gbc)) {
868
                    int master_cpl_coord, cpl_coord_exp, cpl_coord_mant;
869
                    cpl_coords_exist = 1;
870
                    master_cpl_coord = 3 * get_bits(gbc, 2);
871
                    for (bnd = 0; bnd < s->num_cpl_bands; bnd++) {
872
                        cpl_coord_exp = get_bits(gbc, 4);
873
                        cpl_coord_mant = get_bits(gbc, 4);
874
                        if (cpl_coord_exp == 15)
875
                            s->cpl_coords[ch][bnd] = cpl_coord_mant << 22;
876
                        else
877
                            s->cpl_coords[ch][bnd] = (cpl_coord_mant + 16) << 21;
878
                        s->cpl_coords[ch][bnd] >>= (cpl_coord_exp + master_cpl_coord);
879
                    }
880
                } else if (!blk) {
881
                    av_log(s->avctx, AV_LOG_ERROR, "new coupling coordinates must be present in block 0\n");
882
                    return -1;
883
                }
884
            }
885
        }
886
        /* phase flags */
887
        if (channel_mode == AC3_CHMODE_STEREO && cpl_coords_exist) {
888
            for (bnd = 0; bnd < s->num_cpl_bands; bnd++) {
889
                s->phase_flags[bnd] = s->phase_flags_in_use? get_bits1(gbc) : 0;
890
            }
891
        }
892
    }
893

    
894
    /* stereo rematrixing strategy and band structure */
895
    if (channel_mode == AC3_CHMODE_STEREO) {
896
        if (get_bits1(gbc)) {
897
            s->num_rematrixing_bands = 4;
898
            if(s->cpl_in_use && s->start_freq[CPL_CH] <= 61)
899
                s->num_rematrixing_bands -= 1 + (s->start_freq[CPL_CH] == 37);
900
            for(bnd=0; bnd<s->num_rematrixing_bands; bnd++)
901
                s->rematrixing_flags[bnd] = get_bits1(gbc);
902
        } else if (!blk) {
903
            av_log(s->avctx, AV_LOG_ERROR, "new rematrixing strategy must be present in block 0\n");
904
            return -1;
905
        }
906
    }
907

    
908
    /* exponent strategies for each channel */
909
    s->exp_strategy[CPL_CH] = EXP_REUSE;
910
    s->exp_strategy[s->lfe_ch] = EXP_REUSE;
911
    for (ch = !s->cpl_in_use; ch <= s->channels; ch++) {
912
        s->exp_strategy[ch] = get_bits(gbc, 2 - (ch == s->lfe_ch));
913
        if(s->exp_strategy[ch] != EXP_REUSE)
914
            bit_alloc_stages[ch] = 3;
915
    }
916

    
917
    /* channel bandwidth */
918
    for (ch = 1; ch <= fbw_channels; ch++) {
919
        s->start_freq[ch] = 0;
920
        if (s->exp_strategy[ch] != EXP_REUSE) {
921
            int group_size;
922
            int prev = s->end_freq[ch];
923
            if (s->channel_in_cpl[ch])
924
                s->end_freq[ch] = s->start_freq[CPL_CH];
925
            else {
926
                int bandwidth_code = get_bits(gbc, 6);
927
                if (bandwidth_code > 60) {
928
                    av_log(s->avctx, AV_LOG_ERROR, "bandwidth code = %d > 60", bandwidth_code);
929
                    return -1;
930
                }
931
                s->end_freq[ch] = bandwidth_code * 3 + 73;
932
            }
933
            group_size = 3 << (s->exp_strategy[ch] - 1);
934
            s->num_exp_groups[ch] = (s->end_freq[ch]+group_size-4) / group_size;
935
            if(blk > 0 && s->end_freq[ch] != prev)
936
                memset(bit_alloc_stages, 3, AC3_MAX_CHANNELS);
937
        }
938
    }
939
    if (s->cpl_in_use && s->exp_strategy[CPL_CH] != EXP_REUSE) {
940
        s->num_exp_groups[CPL_CH] = (s->end_freq[CPL_CH] - s->start_freq[CPL_CH]) /
941
                                    (3 << (s->exp_strategy[CPL_CH] - 1));
942
    }
943

    
944
    /* decode exponents for each channel */
945
    for (ch = !s->cpl_in_use; ch <= s->channels; ch++) {
946
        if (s->exp_strategy[ch] != EXP_REUSE) {
947
            s->dexps[ch][0] = get_bits(gbc, 4) << !ch;
948
            decode_exponents(gbc, s->exp_strategy[ch],
949
                             s->num_exp_groups[ch], s->dexps[ch][0],
950
                             &s->dexps[ch][s->start_freq[ch]+!!ch]);
951
            if(ch != CPL_CH && ch != s->lfe_ch)
952
                skip_bits(gbc, 2); /* skip gainrng */
953
        }
954
    }
955

    
956
    /* bit allocation information */
957
    if (get_bits1(gbc)) {
958
        s->bit_alloc_params.slow_decay = ff_ac3_slow_decay_tab[get_bits(gbc, 2)] >> s->bit_alloc_params.sr_shift;
959
        s->bit_alloc_params.fast_decay = ff_ac3_fast_decay_tab[get_bits(gbc, 2)] >> s->bit_alloc_params.sr_shift;
960
        s->bit_alloc_params.slow_gain  = ff_ac3_slow_gain_tab[get_bits(gbc, 2)];
961
        s->bit_alloc_params.db_per_bit = ff_ac3_db_per_bit_tab[get_bits(gbc, 2)];
962
        s->bit_alloc_params.floor  = ff_ac3_floor_tab[get_bits(gbc, 3)];
963
        for(ch=!s->cpl_in_use; ch<=s->channels; ch++)
964
            bit_alloc_stages[ch] = FFMAX(bit_alloc_stages[ch], 2);
965
    } else if (!blk) {
966
        av_log(s->avctx, AV_LOG_ERROR, "new bit allocation info must be present in block 0\n");
967
        return -1;
968
    }
969

    
970
    /* signal-to-noise ratio offsets and fast gains (signal-to-mask ratios) */
971
    if (get_bits1(gbc)) {
972
        int csnr;
973
        csnr = (get_bits(gbc, 6) - 15) << 4;
974
        for (ch = !s->cpl_in_use; ch <= s->channels; ch++) { /* snr offset and fast gain */
975
            s->snr_offset[ch] = (csnr + get_bits(gbc, 4)) << 2;
976
            s->fast_gain[ch] = ff_ac3_fast_gain_tab[get_bits(gbc, 3)];
977
        }
978
        memset(bit_alloc_stages, 3, AC3_MAX_CHANNELS);
979
    } else if (!blk) {
980
        av_log(s->avctx, AV_LOG_ERROR, "new snr offsets must be present in block 0\n");
981
        return -1;
982
    }
983

    
984
    /* coupling leak information */
985
    if (s->cpl_in_use) {
986
        if (get_bits1(gbc)) {
987
            s->bit_alloc_params.cpl_fast_leak = get_bits(gbc, 3);
988
            s->bit_alloc_params.cpl_slow_leak = get_bits(gbc, 3);
989
            bit_alloc_stages[CPL_CH] = FFMAX(bit_alloc_stages[CPL_CH], 2);
990
        } else if (!blk) {
991
            av_log(s->avctx, AV_LOG_ERROR, "new coupling leak info must be present in block 0\n");
992
            return -1;
993
        }
994
    }
995

    
996
    /* delta bit allocation information */
997
    if (get_bits1(gbc)) {
998
        /* delta bit allocation exists (strategy) */
999
        for (ch = !s->cpl_in_use; ch <= fbw_channels; ch++) {
1000
            s->dba_mode[ch] = get_bits(gbc, 2);
1001
            if (s->dba_mode[ch] == DBA_RESERVED) {
1002
                av_log(s->avctx, AV_LOG_ERROR, "delta bit allocation strategy reserved\n");
1003
                return -1;
1004
            }
1005
            bit_alloc_stages[ch] = FFMAX(bit_alloc_stages[ch], 2);
1006
        }
1007
        /* channel delta offset, len and bit allocation */
1008
        for (ch = !s->cpl_in_use; ch <= fbw_channels; ch++) {
1009
            if (s->dba_mode[ch] == DBA_NEW) {
1010
                s->dba_nsegs[ch] = get_bits(gbc, 3);
1011
                for (seg = 0; seg <= s->dba_nsegs[ch]; seg++) {
1012
                    s->dba_offsets[ch][seg] = get_bits(gbc, 5);
1013
                    s->dba_lengths[ch][seg] = get_bits(gbc, 4);
1014
                    s->dba_values[ch][seg] = get_bits(gbc, 3);
1015
                }
1016
                /* run last 2 bit allocation stages if new dba values */
1017
                bit_alloc_stages[ch] = FFMAX(bit_alloc_stages[ch], 2);
1018
            }
1019
        }
1020
    } else if(blk == 0) {
1021
        for(ch=0; ch<=s->channels; ch++) {
1022
            s->dba_mode[ch] = DBA_NONE;
1023
        }
1024
    }
1025

    
1026
    /* Bit allocation */
1027
    for(ch=!s->cpl_in_use; ch<=s->channels; ch++) {
1028
        if(bit_alloc_stages[ch] > 2) {
1029
            /* Exponent mapping into PSD and PSD integration */
1030
            ff_ac3_bit_alloc_calc_psd(s->dexps[ch],
1031
                                      s->start_freq[ch], s->end_freq[ch],
1032
                                      s->psd[ch], s->band_psd[ch]);
1033
        }
1034
        if(bit_alloc_stages[ch] > 1) {
1035
            /* Compute excitation function, Compute masking curve, and
1036
               Apply delta bit allocation */
1037
            ff_ac3_bit_alloc_calc_mask(&s->bit_alloc_params, s->band_psd[ch],
1038
                                       s->start_freq[ch], s->end_freq[ch],
1039
                                       s->fast_gain[ch], (ch == s->lfe_ch),
1040
                                       s->dba_mode[ch], s->dba_nsegs[ch],
1041
                                       s->dba_offsets[ch], s->dba_lengths[ch],
1042
                                       s->dba_values[ch], s->mask[ch]);
1043
        }
1044
        if(bit_alloc_stages[ch] > 0) {
1045
            /* Compute bit allocation */
1046
            ff_ac3_bit_alloc_calc_bap(s->mask[ch], s->psd[ch],
1047
                                      s->start_freq[ch], s->end_freq[ch],
1048
                                      s->snr_offset[ch],
1049
                                      s->bit_alloc_params.floor,
1050
                                      ff_ac3_bap_tab, s->bap[ch]);
1051
        }
1052
    }
1053

    
1054
    /* unused dummy data */
1055
    if (get_bits1(gbc)) {
1056
        int skipl = get_bits(gbc, 9);
1057
        while(skipl--)
1058
            skip_bits(gbc, 8);
1059
    }
1060

    
1061
    /* unpack the transform coefficients
1062
       this also uncouples channels if coupling is in use. */
1063
    get_transform_coeffs(s);
1064

    
1065
    /* recover coefficients if rematrixing is in use */
1066
    if(s->channel_mode == AC3_CHMODE_STEREO)
1067
        do_rematrixing(s);
1068

    
1069
    /* apply scaling to coefficients (headroom, dynrng) */
1070
    for(ch=1; ch<=s->channels; ch++) {
1071
        float gain = s->mul_bias / 4194304.0f;
1072
        if(s->channel_mode == AC3_CHMODE_DUALMONO) {
1073
            gain *= s->dynamic_range[ch-1];
1074
        } else {
1075
            gain *= s->dynamic_range[0];
1076
        }
1077
        for(i=0; i<256; i++) {
1078
            s->transform_coeffs[ch][i] = s->fixed_coeffs[ch][i] * gain;
1079
        }
1080
    }
1081

    
1082
    /* downmix and MDCT. order depends on whether block switching is used for
1083
       any channel in this block. this is because coefficients for the long
1084
       and short transforms cannot be mixed. */
1085
    downmix_output = s->channels != s->out_channels &&
1086
                     !((s->output_mode & AC3_OUTPUT_LFEON) &&
1087
                     s->fbw_channels == s->out_channels);
1088
    if(different_transforms) {
1089
        /* the delay samples have already been downmixed, so we upmix the delay
1090
           samples in order to reconstruct all channels before downmixing. */
1091
        if(s->downmixed) {
1092
            s->downmixed = 0;
1093
            ac3_upmix_delay(s);
1094
        }
1095

    
1096
        do_imdct(s, s->channels);
1097

    
1098
        if(downmix_output) {
1099
            ac3_downmix(s, s->output, 0);
1100
        }
1101
    } else {
1102
        if(downmix_output) {
1103
            ac3_downmix(s, s->transform_coeffs, 1);
1104
        }
1105

    
1106
        if(!s->downmixed) {
1107
            s->downmixed = 1;
1108
            ac3_downmix(s, s->delay, 0);
1109
        }
1110

    
1111
        do_imdct(s, s->out_channels);
1112
    }
1113

    
1114
    /* convert float to 16-bit integer */
1115
    for(ch=0; ch<s->out_channels; ch++) {
1116
        for(i=0; i<256; i++) {
1117
            s->output[ch][i] += s->add_bias;
1118
        }
1119
        s->dsp.float_to_int16(s->int_output[ch], s->output[ch], 256);
1120
    }
1121

    
1122
    return 0;
1123
}
1124

    
1125
/**
1126
 * Decode a single AC-3 frame.
1127
 */
1128
static int ac3_decode_frame(AVCodecContext * avctx, void *data, int *data_size,
1129
                            const uint8_t *buf, int buf_size)
1130
{
1131
    AC3DecodeContext *s = avctx->priv_data;
1132
    int16_t *out_samples = (int16_t *)data;
1133
    int i, blk, ch, err;
1134

    
1135
    /* initialize the GetBitContext with the start of valid AC-3 Frame */
1136
    if (s->input_buffer) {
1137
        /* copy input buffer to decoder context to avoid reading past the end
1138
           of the buffer, which can be caused by a damaged input stream. */
1139
        memcpy(s->input_buffer, buf, FFMIN(buf_size, AC3_MAX_FRAME_SIZE));
1140
        init_get_bits(&s->gbc, s->input_buffer, buf_size * 8);
1141
    } else {
1142
        init_get_bits(&s->gbc, buf, buf_size * 8);
1143
    }
1144

    
1145
    /* parse the syncinfo */
1146
    *data_size = 0;
1147
    err = ac3_parse_header(s);
1148

    
1149
    /* check that reported frame size fits in input buffer */
1150
    if(s->frame_size > buf_size) {
1151
        av_log(avctx, AV_LOG_ERROR, "incomplete frame\n");
1152
        err = AC3_PARSE_ERROR_FRAME_SIZE;
1153
    }
1154

    
1155
    /* check for crc mismatch */
1156
    if(err != AC3_PARSE_ERROR_FRAME_SIZE && avctx->error_resilience >= FF_ER_CAREFUL) {
1157
        if(av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0, &buf[2], s->frame_size-2)) {
1158
            av_log(avctx, AV_LOG_ERROR, "frame CRC mismatch\n");
1159
            err = AC3_PARSE_ERROR_CRC;
1160
        }
1161
    }
1162

    
1163
    if(err && err != AC3_PARSE_ERROR_CRC) {
1164
        switch(err) {
1165
            case AC3_PARSE_ERROR_SYNC:
1166
                av_log(avctx, AV_LOG_ERROR, "frame sync error\n");
1167
                return -1;
1168
            case AC3_PARSE_ERROR_BSID:
1169
                av_log(avctx, AV_LOG_ERROR, "invalid bitstream id\n");
1170
                break;
1171
            case AC3_PARSE_ERROR_SAMPLE_RATE:
1172
                av_log(avctx, AV_LOG_ERROR, "invalid sample rate\n");
1173
                break;
1174
            case AC3_PARSE_ERROR_FRAME_SIZE:
1175
                av_log(avctx, AV_LOG_ERROR, "invalid frame size\n");
1176
                break;
1177
            case AC3_PARSE_ERROR_FRAME_TYPE:
1178
                /* skip frame if CRC is ok. otherwise use error concealment. */
1179
                /* TODO: add support for substreams and dependent frames */
1180
                if(s->frame_type == EAC3_FRAME_TYPE_DEPENDENT || s->substreamid) {
1181
                    av_log(avctx, AV_LOG_ERROR, "unsupported frame type : skipping frame\n");
1182
                    return s->frame_size;
1183
                } else {
1184
                    av_log(avctx, AV_LOG_ERROR, "invalid frame type\n");
1185
                }
1186
                break;
1187
            default:
1188
                av_log(avctx, AV_LOG_ERROR, "invalid header\n");
1189
                break;
1190
        }
1191
    }
1192

    
1193
    /* if frame is ok, set audio parameters */
1194
    if (!err) {
1195
        avctx->sample_rate = s->sample_rate;
1196
        avctx->bit_rate = s->bit_rate;
1197

    
1198
        /* channel config */
1199
        s->out_channels = s->channels;
1200
        s->output_mode = s->channel_mode;
1201
        if(s->lfe_on)
1202
            s->output_mode |= AC3_OUTPUT_LFEON;
1203
        if (avctx->request_channels > 0 && avctx->request_channels <= 2 &&
1204
                avctx->request_channels < s->channels) {
1205
            s->out_channels = avctx->request_channels;
1206
            s->output_mode  = avctx->request_channels == 1 ? AC3_CHMODE_MONO : AC3_CHMODE_STEREO;
1207
        }
1208
        avctx->channels = s->out_channels;
1209

    
1210
        /* set downmixing coefficients if needed */
1211
        if(s->channels != s->out_channels && !((s->output_mode & AC3_OUTPUT_LFEON) &&
1212
                s->fbw_channels == s->out_channels)) {
1213
            set_downmix_coeffs(s);
1214
        }
1215
    } else if (!s->out_channels) {
1216
        s->out_channels = avctx->channels;
1217
        if(s->out_channels < s->channels)
1218
            s->output_mode  = s->out_channels == 1 ? AC3_CHMODE_MONO : AC3_CHMODE_STEREO;
1219
    }
1220

    
1221
    /* parse the audio blocks */
1222
    for (blk = 0; blk < s->num_blocks; blk++) {
1223
        if (!err && ac3_parse_audio_block(s, blk)) {
1224
            av_log(avctx, AV_LOG_ERROR, "error parsing the audio block\n");
1225
        }
1226

    
1227
        /* interleave output samples */
1228
        for (i = 0; i < 256; i++)
1229
            for (ch = 0; ch < s->out_channels; ch++)
1230
                *(out_samples++) = s->int_output[ch][i];
1231
    }
1232
    *data_size = s->num_blocks * 256 * avctx->channels * sizeof (int16_t);
1233
    return s->frame_size;
1234
}
1235

    
1236
/**
1237
 * Uninitialize the AC-3 decoder.
1238
 */
1239
static av_cold int ac3_decode_end(AVCodecContext *avctx)
1240
{
1241
    AC3DecodeContext *s = avctx->priv_data;
1242
    ff_mdct_end(&s->imdct_512);
1243
    ff_mdct_end(&s->imdct_256);
1244

    
1245
    av_freep(&s->input_buffer);
1246

    
1247
    return 0;
1248
}
1249

    
1250
AVCodec ac3_decoder = {
1251
    .name = "ac3",
1252
    .type = CODEC_TYPE_AUDIO,
1253
    .id = CODEC_ID_AC3,
1254
    .priv_data_size = sizeof (AC3DecodeContext),
1255
    .init = ac3_decode_init,
1256
    .close = ac3_decode_end,
1257
    .decode = ac3_decode_frame,
1258
    .long_name = "ATSC A/52 / AC-3",
1259
};