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1
/*
2
 * ALAC (Apple Lossless Audio Codec) decoder
3
 * Copyright (c) 2005 David Hammerton
4
 *
5
 * This file is part of FFmpeg.
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 *
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 * FFmpeg is free software; you can redistribute it and/or
8
 * modify it under the terms of the GNU Lesser General Public
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 * License as published by the Free Software Foundation; either
10
 * version 2.1 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,
13
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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 * Lesser General Public License for more details.
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 *
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 * You should have received a copy of the GNU Lesser 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
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 */
21

    
22
/**
23
 * @file alac.c
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 * ALAC (Apple Lossless Audio Codec) decoder
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 * @author 2005 David Hammerton
26
 *
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 * For more information on the ALAC format, visit:
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 *  http://crazney.net/programs/itunes/alac.html
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 *
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 * Note: This decoder expects a 36- (0x24-)byte QuickTime atom to be
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 * passed through the extradata[_size] fields. This atom is tacked onto
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 * the end of an 'alac' stsd atom and has the following format:
33
 *  bytes 0-3   atom size (0x24), big-endian
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 *  bytes 4-7   atom type ('alac', not the 'alac' tag from start of stsd)
35
 *  bytes 8-35  data bytes needed by decoder
36
 *
37
 * Extradata:
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 * 32bit  size
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 * 32bit  tag (=alac)
40
 * 32bit  zero?
41
 * 32bit  max sample per frame
42
 *  8bit  ?? (zero?)
43
 *  8bit  sample size
44
 *  8bit  history mult
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 *  8bit  initial history
46
 *  8bit  kmodifier
47
 *  8bit  channels?
48
 * 16bit  ??
49
 * 32bit  max coded frame size
50
 * 32bit  bitrate?
51
 * 32bit  samplerate
52
 */
53

    
54

    
55
#include "avcodec.h"
56
#include "bitstream.h"
57
#include "bytestream.h"
58
#include "unary.h"
59

    
60
#define ALAC_EXTRADATA_SIZE 36
61
#define MAX_CHANNELS 2
62

    
63
typedef struct {
64

    
65
    AVCodecContext *avctx;
66
    GetBitContext gb;
67
    /* init to 0; first frame decode should initialize from extradata and
68
     * set this to 1 */
69
    int context_initialized;
70

    
71
    int numchannels;
72
    int bytespersample;
73

    
74
    /* buffers */
75
    int32_t *predicterror_buffer[MAX_CHANNELS];
76

    
77
    int32_t *outputsamples_buffer[MAX_CHANNELS];
78

    
79
    /* stuff from setinfo */
80
    uint32_t setinfo_max_samples_per_frame; /* 0x1000 = 4096 */    /* max samples per frame? */
81
    uint8_t setinfo_sample_size; /* 0x10 */
82
    uint8_t setinfo_rice_historymult; /* 0x28 */
83
    uint8_t setinfo_rice_initialhistory; /* 0x0a */
84
    uint8_t setinfo_rice_kmodifier; /* 0x0e */
85
    /* end setinfo stuff */
86

    
87
} ALACContext;
88

    
89
static void allocate_buffers(ALACContext *alac)
90
{
91
    int chan;
92
    for (chan = 0; chan < MAX_CHANNELS; chan++) {
93
        alac->predicterror_buffer[chan] =
94
            av_malloc(alac->setinfo_max_samples_per_frame * 4);
95

    
96
        alac->outputsamples_buffer[chan] =
97
            av_malloc(alac->setinfo_max_samples_per_frame * 4);
98
    }
99
}
100

    
101
static int alac_set_info(ALACContext *alac)
102
{
103
    const unsigned char *ptr = alac->avctx->extradata;
104

    
105
    ptr += 4; /* size */
106
    ptr += 4; /* alac */
107
    ptr += 4; /* 0 ? */
108

    
109
    if(AV_RB32(ptr) >= UINT_MAX/4){
110
        av_log(alac->avctx, AV_LOG_ERROR, "setinfo_max_samples_per_frame too large\n");
111
        return -1;
112
    }
113

    
114
    /* buffer size / 2 ? */
115
    alac->setinfo_max_samples_per_frame = bytestream_get_be32(&ptr);
116
    ptr++;                          /* ??? */
117
    alac->setinfo_sample_size           = *ptr++;
118
    alac->setinfo_rice_historymult      = *ptr++;
119
    alac->setinfo_rice_initialhistory   = *ptr++;
120
    alac->setinfo_rice_kmodifier        = *ptr++;
121
    ptr++;                         /* channels? */
122
    bytestream_get_be16(&ptr);      /* ??? */
123
    bytestream_get_be32(&ptr);      /* max coded frame size */
124
    bytestream_get_be32(&ptr);      /* bitrate ? */
125
    bytestream_get_be32(&ptr);      /* samplerate */
126

    
127
    allocate_buffers(alac);
128

    
129
    return 0;
130
}
131

    
132
static inline int decode_scalar(GetBitContext *gb, int k, int limit, int readsamplesize){
133
    /* read x - number of 1s before 0 represent the rice */
134
    int x = get_unary_0_9(gb);
135

    
136
    if (x > 8) { /* RICE THRESHOLD */
137
        /* use alternative encoding */
138
        x = get_bits(gb, readsamplesize);
139
    } else {
140
        if (k >= limit)
141
            k = limit;
142

    
143
        if (k != 1) {
144
            int extrabits = show_bits(gb, k);
145

    
146
            /* multiply x by 2^k - 1, as part of their strange algorithm */
147
            x = (x << k) - x;
148

    
149
            if (extrabits > 1) {
150
                x += extrabits - 1;
151
                skip_bits(gb, k);
152
            } else
153
                skip_bits(gb, k - 1);
154
        }
155
    }
156
    return x;
157
}
158

    
159
static void bastardized_rice_decompress(ALACContext *alac,
160
                                 int32_t *output_buffer,
161
                                 int output_size,
162
                                 int readsamplesize, /* arg_10 */
163
                                 int rice_initialhistory, /* arg424->b */
164
                                 int rice_kmodifier, /* arg424->d */
165
                                 int rice_historymult, /* arg424->c */
166
                                 int rice_kmodifier_mask /* arg424->e */
167
        )
168
{
169
    int output_count;
170
    unsigned int history = rice_initialhistory;
171
    int sign_modifier = 0;
172

    
173
    for (output_count = 0; output_count < output_size; output_count++) {
174
        int32_t x;
175
        int32_t x_modified;
176
        int32_t final_val;
177

    
178
        /* standard rice encoding */
179
        int k; /* size of extra bits */
180

    
181
        /* read k, that is bits as is */
182
        k = av_log2((history >> 9) + 3);
183
        x= decode_scalar(&alac->gb, k, rice_kmodifier, readsamplesize);
184

    
185
        x_modified = sign_modifier + x;
186
        final_val = (x_modified + 1) / 2;
187
        if (x_modified & 1) final_val *= -1;
188

    
189
        output_buffer[output_count] = final_val;
190

    
191
        sign_modifier = 0;
192

    
193
        /* now update the history */
194
        history += x_modified * rice_historymult
195
                   - ((history * rice_historymult) >> 9);
196

    
197
        if (x_modified > 0xffff)
198
            history = 0xffff;
199

    
200
        /* special case: there may be compressed blocks of 0 */
201
        if ((history < 128) && (output_count+1 < output_size)) {
202
            int k;
203
            unsigned int block_size;
204

    
205
            sign_modifier = 1;
206

    
207
            k = 7 - av_log2(history) + ((history + 16) >> 6 /* / 64 */);
208

    
209
            block_size= decode_scalar(&alac->gb, k, rice_kmodifier, 16);
210

    
211
            if (block_size > 0) {
212
                if(block_size >= output_size - output_count){
213
                    av_log(alac->avctx, AV_LOG_ERROR, "invalid zero block size of %d %d %d\n", block_size, output_size, output_count);
214
                    block_size= output_size - output_count - 1;
215
                }
216
                memset(&output_buffer[output_count+1], 0, block_size * 4);
217
                output_count += block_size;
218
            }
219

    
220
            if (block_size > 0xffff)
221
                sign_modifier = 0;
222

    
223
            history = 0;
224
        }
225
    }
226
}
227

    
228
static inline int32_t extend_sign32(int32_t val, int bits)
229
{
230
    return (val << (32 - bits)) >> (32 - bits);
231
}
232

    
233
static inline int sign_only(int v)
234
{
235
    return v ? FFSIGN(v) : 0;
236
}
237

    
238
static void predictor_decompress_fir_adapt(int32_t *error_buffer,
239
                                           int32_t *buffer_out,
240
                                           int output_size,
241
                                           int readsamplesize,
242
                                           int16_t *predictor_coef_table,
243
                                           int predictor_coef_num,
244
                                           int predictor_quantitization)
245
{
246
    int i;
247

    
248
    /* first sample always copies */
249
    *buffer_out = *error_buffer;
250

    
251
    if (!predictor_coef_num) {
252
        if (output_size <= 1)
253
            return;
254

    
255
        memcpy(buffer_out+1, error_buffer+1, (output_size-1) * 4);
256
        return;
257
    }
258

    
259
    if (predictor_coef_num == 0x1f) { /* 11111 - max value of predictor_coef_num */
260
      /* second-best case scenario for fir decompression,
261
       * error describes a small difference from the previous sample only
262
       */
263
        if (output_size <= 1)
264
            return;
265
        for (i = 0; i < output_size - 1; i++) {
266
            int32_t prev_value;
267
            int32_t error_value;
268

    
269
            prev_value = buffer_out[i];
270
            error_value = error_buffer[i+1];
271
            buffer_out[i+1] =
272
                extend_sign32((prev_value + error_value), readsamplesize);
273
        }
274
        return;
275
    }
276

    
277
    /* read warm-up samples */
278
    if (predictor_coef_num > 0)
279
        for (i = 0; i < predictor_coef_num; i++) {
280
            int32_t val;
281

    
282
            val = buffer_out[i] + error_buffer[i+1];
283
            val = extend_sign32(val, readsamplesize);
284
            buffer_out[i+1] = val;
285
        }
286

    
287
#if 0
288
    /* 4 and 8 are very common cases (the only ones i've seen). these
289
     * should be unrolled and optimized
290
     */
291
    if (predictor_coef_num == 4) {
292
        /* FIXME: optimized general case */
293
        return;
294
    }
295

296
    if (predictor_coef_table == 8) {
297
        /* FIXME: optimized general case */
298
        return;
299
    }
300
#endif
301

    
302
    /* general case */
303
    if (predictor_coef_num > 0) {
304
        for (i = predictor_coef_num + 1; i < output_size; i++) {
305
            int j;
306
            int sum = 0;
307
            int outval;
308
            int error_val = error_buffer[i];
309

    
310
            for (j = 0; j < predictor_coef_num; j++) {
311
                sum += (buffer_out[predictor_coef_num-j] - buffer_out[0]) *
312
                       predictor_coef_table[j];
313
            }
314

    
315
            outval = (1 << (predictor_quantitization-1)) + sum;
316
            outval = outval >> predictor_quantitization;
317
            outval = outval + buffer_out[0] + error_val;
318
            outval = extend_sign32(outval, readsamplesize);
319

    
320
            buffer_out[predictor_coef_num+1] = outval;
321

    
322
            if (error_val > 0) {
323
                int predictor_num = predictor_coef_num - 1;
324

    
325
                while (predictor_num >= 0 && error_val > 0) {
326
                    int val = buffer_out[0] - buffer_out[predictor_coef_num - predictor_num];
327
                    int sign = sign_only(val);
328

    
329
                    predictor_coef_table[predictor_num] -= sign;
330

    
331
                    val *= sign; /* absolute value */
332

    
333
                    error_val -= ((val >> predictor_quantitization) *
334
                                  (predictor_coef_num - predictor_num));
335

    
336
                    predictor_num--;
337
                }
338
            } else if (error_val < 0) {
339
                int predictor_num = predictor_coef_num - 1;
340

    
341
                while (predictor_num >= 0 && error_val < 0) {
342
                    int val = buffer_out[0] - buffer_out[predictor_coef_num - predictor_num];
343
                    int sign = - sign_only(val);
344

    
345
                    predictor_coef_table[predictor_num] -= sign;
346

    
347
                    val *= sign; /* neg value */
348

    
349
                    error_val -= ((val >> predictor_quantitization) *
350
                                  (predictor_coef_num - predictor_num));
351

    
352
                    predictor_num--;
353
                }
354
            }
355

    
356
            buffer_out++;
357
        }
358
    }
359
}
360

    
361
static void reconstruct_stereo_16(int32_t *buffer[MAX_CHANNELS],
362
                                  int16_t *buffer_out,
363
                                  int numchannels, int numsamples,
364
                                  uint8_t interlacing_shift,
365
                                  uint8_t interlacing_leftweight)
366
{
367
    int i;
368
    if (numsamples <= 0)
369
        return;
370

    
371
    /* weighted interlacing */
372
    if (interlacing_leftweight) {
373
        for (i = 0; i < numsamples; i++) {
374
            int32_t a, b;
375

    
376
            a = buffer[0][i];
377
            b = buffer[1][i];
378

    
379
            a -= (b * interlacing_leftweight) >> interlacing_shift;
380
            b += a;
381

    
382
            buffer_out[i*numchannels] = b;
383
            buffer_out[i*numchannels + 1] = a;
384
        }
385

    
386
        return;
387
    }
388

    
389
    /* otherwise basic interlacing took place */
390
    for (i = 0; i < numsamples; i++) {
391
        int16_t left, right;
392

    
393
        left = buffer[0][i];
394
        right = buffer[1][i];
395

    
396
        buffer_out[i*numchannels] = left;
397
        buffer_out[i*numchannels + 1] = right;
398
    }
399
}
400

    
401
static int alac_decode_frame(AVCodecContext *avctx,
402
                             void *outbuffer, int *outputsize,
403
                             const uint8_t *inbuffer, int input_buffer_size)
404
{
405
    ALACContext *alac = avctx->priv_data;
406

    
407
    int channels;
408
    unsigned int outputsamples;
409
    int hassize;
410
    int readsamplesize;
411
    int wasted_bytes;
412
    int isnotcompressed;
413
    uint8_t interlacing_shift;
414
    uint8_t interlacing_leftweight;
415

    
416
    /* short-circuit null buffers */
417
    if (!inbuffer || !input_buffer_size)
418
        return input_buffer_size;
419

    
420
    /* initialize from the extradata */
421
    if (!alac->context_initialized) {
422
        if (alac->avctx->extradata_size != ALAC_EXTRADATA_SIZE) {
423
            av_log(avctx, AV_LOG_ERROR, "alac: expected %d extradata bytes\n",
424
                ALAC_EXTRADATA_SIZE);
425
            return input_buffer_size;
426
        }
427
        if (alac_set_info(alac)) {
428
            av_log(avctx, AV_LOG_ERROR, "alac: set_info failed\n");
429
            return input_buffer_size;
430
        }
431
        alac->context_initialized = 1;
432
    }
433

    
434
    init_get_bits(&alac->gb, inbuffer, input_buffer_size * 8);
435

    
436
    channels = get_bits(&alac->gb, 3) + 1;
437
    if (channels > MAX_CHANNELS) {
438
        av_log(avctx, AV_LOG_ERROR, "channels > %d not supported\n",
439
               MAX_CHANNELS);
440
        return input_buffer_size;
441
    }
442

    
443
    /* 2^result = something to do with output waiting.
444
     * perhaps matters if we read > 1 frame in a pass?
445
     */
446
    skip_bits(&alac->gb, 4);
447

    
448
    skip_bits(&alac->gb, 12); /* unknown, skip 12 bits */
449

    
450
    /* the output sample size is stored soon */
451
    hassize = get_bits1(&alac->gb);
452

    
453
    wasted_bytes = get_bits(&alac->gb, 2); /* unknown ? */
454

    
455
    /* whether the frame is compressed */
456
    isnotcompressed = get_bits1(&alac->gb);
457

    
458
    if (hassize) {
459
        /* now read the number of samples as a 32bit integer */
460
        outputsamples = get_bits(&alac->gb, 32);
461
        if(outputsamples > alac->setinfo_max_samples_per_frame){
462
            av_log(avctx, AV_LOG_ERROR, "outputsamples %d > %d\n", outputsamples, alac->setinfo_max_samples_per_frame);
463
            return -1;
464
        }
465
    } else
466
        outputsamples = alac->setinfo_max_samples_per_frame;
467

    
468
    *outputsize = outputsamples * alac->bytespersample;
469
    readsamplesize = alac->setinfo_sample_size - (wasted_bytes * 8) + channels - 1;
470

    
471
    if (!isnotcompressed) {
472
        /* so it is compressed */
473
        int16_t predictor_coef_table[channels][32];
474
        int predictor_coef_num[channels];
475
        int prediction_type[channels];
476
        int prediction_quantitization[channels];
477
        int ricemodifier[channels];
478
        int i, chan;
479

    
480
        interlacing_shift = get_bits(&alac->gb, 8);
481
        interlacing_leftweight = get_bits(&alac->gb, 8);
482

    
483
        for (chan = 0; chan < channels; chan++) {
484
            prediction_type[chan] = get_bits(&alac->gb, 4);
485
            prediction_quantitization[chan] = get_bits(&alac->gb, 4);
486

    
487
            ricemodifier[chan] = get_bits(&alac->gb, 3);
488
            predictor_coef_num[chan] = get_bits(&alac->gb, 5);
489

    
490
            /* read the predictor table */
491
            for (i = 0; i < predictor_coef_num[chan]; i++)
492
                predictor_coef_table[chan][i] = (int16_t)get_bits(&alac->gb, 16);
493
        }
494

    
495
        if (wasted_bytes)
496
            av_log(avctx, AV_LOG_ERROR, "FIXME: unimplemented, unhandling of wasted_bytes\n");
497

    
498
        for (chan = 0; chan < channels; chan++) {
499
            bastardized_rice_decompress(alac,
500
                                        alac->predicterror_buffer[chan],
501
                                        outputsamples,
502
                                        readsamplesize,
503
                                        alac->setinfo_rice_initialhistory,
504
                                        alac->setinfo_rice_kmodifier,
505
                                        ricemodifier[chan] * alac->setinfo_rice_historymult / 4,
506
                                        (1 << alac->setinfo_rice_kmodifier) - 1);
507

    
508
            if (prediction_type[chan] == 0) {
509
                /* adaptive fir */
510
                predictor_decompress_fir_adapt(alac->predicterror_buffer[chan],
511
                                               alac->outputsamples_buffer[chan],
512
                                               outputsamples,
513
                                               readsamplesize,
514
                                               predictor_coef_table[chan],
515
                                               predictor_coef_num[chan],
516
                                               prediction_quantitization[chan]);
517
            } else {
518
                av_log(avctx, AV_LOG_ERROR, "FIXME: unhandled prediction type: %i\n", prediction_type[chan]);
519
                /* I think the only other prediction type (or perhaps this is
520
                 * just a boolean?) runs adaptive fir twice.. like:
521
                 * predictor_decompress_fir_adapt(predictor_error, tempout, ...)
522
                 * predictor_decompress_fir_adapt(predictor_error, outputsamples ...)
523
                 * little strange..
524
                 */
525
            }
526
        }
527
    } else {
528
        /* not compressed, easy case */
529
        if (alac->setinfo_sample_size <= 16) {
530
            int i, chan;
531
            for (chan = 0; chan < channels; chan++)
532
                for (i = 0; i < outputsamples; i++) {
533
                    int32_t audiobits;
534

    
535
                    audiobits = get_bits(&alac->gb, alac->setinfo_sample_size);
536
                    audiobits = extend_sign32(audiobits, readsamplesize);
537

    
538
                    alac->outputsamples_buffer[chan][i] = audiobits;
539
                }
540
        } else {
541
            int i, chan;
542
            for (chan = 0; chan < channels; chan++)
543
                for (i = 0; i < outputsamples; i++) {
544
                    int32_t audiobits;
545

    
546
                    audiobits = get_bits(&alac->gb, 16);
547
                    /* special case of sign extension..
548
                     * as we'll be ORing the low 16bits into this */
549
                    audiobits = audiobits << 16;
550
                    audiobits = audiobits >> (32 - alac->setinfo_sample_size);
551
                    audiobits |= get_bits(&alac->gb, alac->setinfo_sample_size - 16);
552

    
553
                    alac->outputsamples_buffer[chan][i] = audiobits;
554
                }
555
        }
556
        /* wasted_bytes = 0; */
557
        interlacing_shift = 0;
558
        interlacing_leftweight = 0;
559
    }
560
    if (get_bits(&alac->gb, 3) != 7)
561
        av_log(avctx, AV_LOG_ERROR, "Error : Wrong End Of Frame\n");
562

    
563
    switch(alac->setinfo_sample_size) {
564
    case 16:
565
        if (channels == 2) {
566
            reconstruct_stereo_16(alac->outputsamples_buffer,
567
                                  (int16_t*)outbuffer,
568
                                  alac->numchannels,
569
                                  outputsamples,
570
                                  interlacing_shift,
571
                                  interlacing_leftweight);
572
        } else {
573
            int i;
574
            for (i = 0; i < outputsamples; i++) {
575
                int16_t sample = alac->outputsamples_buffer[0][i];
576
                ((int16_t*)outbuffer)[i * alac->numchannels] = sample;
577
            }
578
        }
579
        break;
580
    case 20:
581
    case 24:
582
        // It is not clear if there exist any encoder that creates 24 bit ALAC
583
        // files. iTunes convert 24 bit raw files to 16 bit before encoding.
584
    case 32:
585
        av_log(avctx, AV_LOG_ERROR, "FIXME: unimplemented sample size %i\n", alac->setinfo_sample_size);
586
        break;
587
    default:
588
        break;
589
    }
590

    
591
    if (input_buffer_size * 8 - get_bits_count(&alac->gb) > 8)
592
        av_log(avctx, AV_LOG_ERROR, "Error : %d bits left\n", input_buffer_size * 8 - get_bits_count(&alac->gb));
593

    
594
    return input_buffer_size;
595
}
596

    
597
static av_cold int alac_decode_init(AVCodecContext * avctx)
598
{
599
    ALACContext *alac = avctx->priv_data;
600
    alac->avctx = avctx;
601
    alac->context_initialized = 0;
602

    
603
    alac->numchannels = alac->avctx->channels;
604
    alac->bytespersample = (avctx->bits_per_sample / 8) * alac->numchannels;
605

    
606
    return 0;
607
}
608

    
609
static av_cold int alac_decode_close(AVCodecContext *avctx)
610
{
611
    ALACContext *alac = avctx->priv_data;
612

    
613
    int chan;
614
    for (chan = 0; chan < MAX_CHANNELS; chan++) {
615
        av_free(alac->predicterror_buffer[chan]);
616
        av_free(alac->outputsamples_buffer[chan]);
617
    }
618

    
619
    return 0;
620
}
621

    
622
AVCodec alac_decoder = {
623
    "alac",
624
    CODEC_TYPE_AUDIO,
625
    CODEC_ID_ALAC,
626
    sizeof(ALACContext),
627
    alac_decode_init,
628
    NULL,
629
    alac_decode_close,
630
    alac_decode_frame,
631
    .long_name = "ALAC (Apple Lossless Audio Codec)",
632
};