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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
 *
27
 * 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
32
 * the end of an 'alac' stsd atom and has the following format:
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 *  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
39
 * 32bit  tag (=alac)
40
 * 32bit  zero?
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 * 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

    
59
#define ALAC_EXTRADATA_SIZE 36
60
#define MAX_CHANNELS 2
61

    
62
typedef struct {
63

    
64
    AVCodecContext *avctx;
65
    GetBitContext gb;
66
    /* init to 0; first frame decode should initialize from extradata and
67
     * set this to 1 */
68
    int context_initialized;
69

    
70
    int samplesize;
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_7a; /* 0x00 */
82
    uint8_t setinfo_sample_size; /* 0x10 */
83
    uint8_t setinfo_rice_historymult; /* 0x28 */
84
    uint8_t setinfo_rice_initialhistory; /* 0x0a */
85
    uint8_t setinfo_rice_kmodifier; /* 0x0e */
86
    uint8_t setinfo_7f; /* 0x02 */
87
    uint16_t setinfo_80; /* 0x00ff */
88
    uint32_t setinfo_82; /* 0x000020e7 */ /* max sample size?? */
89
    uint32_t setinfo_86; /* 0x00069fe4 */ /* bit rate (average)?? */
90
    uint32_t setinfo_8a_rate; /* 0x0000ac44 */
91
    /* end setinfo stuff */
92

    
93
} ALACContext;
94

    
95
static void allocate_buffers(ALACContext *alac)
96
{
97
    int chan;
98
    for (chan = 0; chan < MAX_CHANNELS; chan++) {
99
        alac->predicterror_buffer[chan] =
100
            av_malloc(alac->setinfo_max_samples_per_frame * 4);
101

    
102
        alac->outputsamples_buffer[chan] =
103
            av_malloc(alac->setinfo_max_samples_per_frame * 4);
104
    }
105
}
106

    
107
static int alac_set_info(ALACContext *alac)
108
{
109
    unsigned char *ptr = alac->avctx->extradata;
110

    
111
    ptr += 4; /* size */
112
    ptr += 4; /* alac */
113
    ptr += 4; /* 0 ? */
114

    
115
    if(AV_RB32(ptr) >= UINT_MAX/4){
116
        av_log(alac->avctx, AV_LOG_ERROR, "setinfo_max_samples_per_frame too large\n");
117
        return -1;
118
    }
119

    
120
    /* buffer size / 2 ? */
121
    alac->setinfo_max_samples_per_frame = bytestream_get_be32(&ptr);
122
    alac->setinfo_7a                    = *ptr++;
123
    alac->setinfo_sample_size           = *ptr++;
124
    alac->setinfo_rice_historymult      = *ptr++;
125
    alac->setinfo_rice_initialhistory   = *ptr++;
126
    alac->setinfo_rice_kmodifier        = *ptr++;
127
    /* channels? */
128
    alac->setinfo_7f                    = *ptr++;
129
    alac->setinfo_80                    = bytestream_get_be16(&ptr);
130
    /* max coded frame size */
131
    alac->setinfo_82                    = bytestream_get_be32(&ptr);
132
    /* bitrate ? */
133
    alac->setinfo_86                    = bytestream_get_be32(&ptr);
134
    /* samplerate */
135
    alac->setinfo_8a_rate               = bytestream_get_be32(&ptr);
136

    
137
    allocate_buffers(alac);
138

    
139
    return 0;
140
}
141

    
142
/* hideously inefficient. could use a bitmask search,
143
 * alternatively bsr on x86,
144
 */
145
static int count_leading_zeros(int32_t input)
146
{
147
    int i = 0;
148
    while (!(0x80000000 & input) && i < 32) {
149
        i++;
150
        input = input << 1;
151
    }
152
    return i;
153
}
154

    
155
static void bastardized_rice_decompress(ALACContext *alac,
156
                                 int32_t *output_buffer,
157
                                 int output_size,
158
                                 int readsamplesize, /* arg_10 */
159
                                 int rice_initialhistory, /* arg424->b */
160
                                 int rice_kmodifier, /* arg424->d */
161
                                 int rice_historymult, /* arg424->c */
162
                                 int rice_kmodifier_mask /* arg424->e */
163
        )
164
{
165
    int output_count;
166
    unsigned int history = rice_initialhistory;
167
    int sign_modifier = 0;
168

    
169
    for (output_count = 0; output_count < output_size; output_count++) {
170
        int32_t x = 0;
171
        int32_t x_modified;
172
        int32_t final_val;
173

    
174
        /* read x - number of 1s before 0 represent the rice */
175
        while (x <= 8 && get_bits1(&alac->gb)) {
176
            x++;
177
        }
178

    
179

    
180
        if (x > 8) { /* RICE THRESHOLD */
181
          /* use alternative encoding */
182
            int32_t value;
183

    
184
            value = get_bits(&alac->gb, readsamplesize);
185

    
186
            /* mask value to readsamplesize size */
187
            if (readsamplesize != 32)
188
                value &= (0xffffffff >> (32 - readsamplesize));
189

    
190
            x = value;
191
        } else {
192
          /* standard rice encoding */
193
            int extrabits;
194
            int k; /* size of extra bits */
195

    
196
            /* read k, that is bits as is */
197
            k = 31 - rice_kmodifier - count_leading_zeros((history >> 9) + 3);
198

    
199
            if (k < 0)
200
                k += rice_kmodifier;
201
            else
202
                k = rice_kmodifier;
203

    
204
            if (k != 1) {
205
                extrabits = show_bits(&alac->gb, k);
206

    
207
                /* multiply x by 2^k - 1, as part of their strange algorithm */
208
                x = (x << k) - x;
209

    
210
                if (extrabits > 1) {
211
                    x += extrabits - 1;
212
                    get_bits(&alac->gb, k);
213
                } else {
214
                    get_bits(&alac->gb, k - 1);
215
                }
216
            }
217
        }
218

    
219
        x_modified = sign_modifier + x;
220
        final_val = (x_modified + 1) / 2;
221
        if (x_modified & 1) final_val *= -1;
222

    
223
        output_buffer[output_count] = final_val;
224

    
225
        sign_modifier = 0;
226

    
227
        /* now update the history */
228
        history += (x_modified * rice_historymult)
229
                 - ((history * rice_historymult) >> 9);
230

    
231
        if (x_modified > 0xffff)
232
            history = 0xffff;
233

    
234
        /* special case: there may be compressed blocks of 0 */
235
        if ((history < 128) && (output_count+1 < output_size)) {
236
            int block_size;
237

    
238
            sign_modifier = 1;
239

    
240
            x = 0;
241
            while (x <= 8 && get_bits1(&alac->gb)) {
242
                x++;
243
            }
244

    
245
            if (x > 8) {
246
                block_size = get_bits(&alac->gb, 16);
247
                block_size &= 0xffff;
248
            } else {
249
                int k;
250
                int extrabits;
251

    
252
                k = count_leading_zeros(history) + ((history + 16) >> 6 /* / 64 */) - 24;
253

    
254
                extrabits = show_bits(&alac->gb, k);
255

    
256
                block_size = (((1 << k) - 1) & rice_kmodifier_mask) * x
257
                           + extrabits - 1;
258

    
259
                if (extrabits < 2) {
260
                    x = 1 - extrabits;
261
                    block_size += x;
262
                    get_bits(&alac->gb, k - 1);
263
                } else {
264
                    get_bits(&alac->gb, k);
265
                }
266
            }
267

    
268
            if (block_size > 0) {
269
                memset(&output_buffer[output_count+1], 0, block_size * 4);
270
                output_count += block_size;
271

    
272
            }
273

    
274
            if (block_size > 0xffff)
275
                sign_modifier = 0;
276

    
277
            history = 0;
278
        }
279
    }
280
}
281

    
282
#define SIGN_EXTENDED32(val, bits) ((val << (32 - bits)) >> (32 - bits))
283

    
284
#define SIGN_ONLY(v) \
285
                     ((v < 0) ? (-1) : \
286
                                ((v > 0) ? (1) : \
287
                                           (0)))
288

    
289
static void predictor_decompress_fir_adapt(int32_t *error_buffer,
290
                                           int32_t *buffer_out,
291
                                           int output_size,
292
                                           int readsamplesize,
293
                                           int16_t *predictor_coef_table,
294
                                           int predictor_coef_num,
295
                                           int predictor_quantitization)
296
{
297
    int i;
298

    
299
    /* first sample always copies */
300
    *buffer_out = *error_buffer;
301

    
302
    if (!predictor_coef_num) {
303
        if (output_size <= 1) return;
304
        memcpy(buffer_out+1, error_buffer+1, (output_size-1) * 4);
305
        return;
306
    }
307

    
308
    if (predictor_coef_num == 0x1f) { /* 11111 - max value of predictor_coef_num */
309
      /* second-best case scenario for fir decompression,
310
       * error describes a small difference from the previous sample only
311
       */
312
        if (output_size <= 1) return;
313
        for (i = 0; i < output_size - 1; i++) {
314
            int32_t prev_value;
315
            int32_t error_value;
316

    
317
            prev_value = buffer_out[i];
318
            error_value = error_buffer[i+1];
319
            buffer_out[i+1] = SIGN_EXTENDED32((prev_value + error_value), readsamplesize);
320
        }
321
        return;
322
    }
323

    
324
    /* read warm-up samples */
325
    if (predictor_coef_num > 0) {
326
        int i;
327
        for (i = 0; i < predictor_coef_num; i++) {
328
            int32_t val;
329

    
330
            val = buffer_out[i] + error_buffer[i+1];
331

    
332
            val = SIGN_EXTENDED32(val, readsamplesize);
333

    
334
            buffer_out[i+1] = val;
335
        }
336
    }
337

    
338
#if 0
339
    /* 4 and 8 are very common cases (the only ones i've seen). these
340
     * should be unrolled and optimised
341
     */
342
    if (predictor_coef_num == 4) {
343
        /* FIXME: optimised general case */
344
        return;
345
    }
346

347
    if (predictor_coef_table == 8) {
348
        /* FIXME: optimised general case */
349
        return;
350
    }
351
#endif
352

    
353

    
354
    /* general case */
355
    if (predictor_coef_num > 0) {
356
        for (i = predictor_coef_num + 1;
357
             i < output_size;
358
             i++) {
359
            int j;
360
            int sum = 0;
361
            int outval;
362
            int error_val = error_buffer[i];
363

    
364
            for (j = 0; j < predictor_coef_num; j++) {
365
                sum += (buffer_out[predictor_coef_num-j] - buffer_out[0]) *
366
                       predictor_coef_table[j];
367
            }
368

    
369
            outval = (1 << (predictor_quantitization-1)) + sum;
370
            outval = outval >> predictor_quantitization;
371
            outval = outval + buffer_out[0] + error_val;
372
            outval = SIGN_EXTENDED32(outval, readsamplesize);
373

    
374
            buffer_out[predictor_coef_num+1] = outval;
375

    
376
            if (error_val > 0) {
377
                int predictor_num = predictor_coef_num - 1;
378

    
379
                while (predictor_num >= 0 && error_val > 0) {
380
                    int val = buffer_out[0] - buffer_out[predictor_coef_num - predictor_num];
381
                    int sign = SIGN_ONLY(val);
382

    
383
                    predictor_coef_table[predictor_num] -= sign;
384

    
385
                    val *= sign; /* absolute value */
386

    
387
                    error_val -= ((val >> predictor_quantitization) *
388
                                  (predictor_coef_num - predictor_num));
389

    
390
                    predictor_num--;
391
                }
392
            } else if (error_val < 0) {
393
                int predictor_num = predictor_coef_num - 1;
394

    
395
                while (predictor_num >= 0 && error_val < 0) {
396
                    int val = buffer_out[0] - buffer_out[predictor_coef_num - predictor_num];
397
                    int sign = - SIGN_ONLY(val);
398

    
399
                    predictor_coef_table[predictor_num] -= sign;
400

    
401
                    val *= sign; /* neg value */
402

    
403
                    error_val -= ((val >> predictor_quantitization) *
404
                                  (predictor_coef_num - predictor_num));
405

    
406
                    predictor_num--;
407
                }
408
            }
409

    
410
            buffer_out++;
411
        }
412
    }
413
}
414

    
415
static void deinterlace_16(int32_t *buffer_a, int32_t *buffer_b,
416
                    int16_t *buffer_out,
417
                    int numchannels, int numsamples,
418
                    uint8_t interlacing_shift,
419
                    uint8_t interlacing_leftweight)
420
{
421
    int i;
422
    if (numsamples <= 0) return;
423

    
424
    /* weighted interlacing */
425
    if (interlacing_leftweight) {
426
        for (i = 0; i < numsamples; i++) {
427
            int32_t difference, midright;
428
            int16_t left;
429
            int16_t right;
430

    
431
            midright = buffer_a[i];
432
            difference = buffer_b[i];
433

    
434

    
435
            right = midright - ((difference * interlacing_leftweight) >> interlacing_shift);
436
            left = (midright - ((difference * interlacing_leftweight) >> interlacing_shift))
437
                 + difference;
438

    
439
            buffer_out[i*numchannels] = left;
440
            buffer_out[i*numchannels + 1] = right;
441
        }
442

    
443
        return;
444
    }
445

    
446
    /* otherwise basic interlacing took place */
447
    for (i = 0; i < numsamples; i++) {
448
        int16_t left, right;
449

    
450
        left = buffer_a[i];
451
        right = buffer_b[i];
452

    
453
        buffer_out[i*numchannels] = left;
454
        buffer_out[i*numchannels + 1] = right;
455
    }
456
}
457

    
458
static int alac_decode_frame(AVCodecContext *avctx,
459
                             void *outbuffer, int *outputsize,
460
                             uint8_t *inbuffer, int input_buffer_size)
461
{
462
    ALACContext *alac = avctx->priv_data;
463

    
464
    int channels;
465
    int32_t outputsamples;
466
    int hassize;
467
    int readsamplesize;
468
    int wasted_bytes;
469
    int isnotcompressed;
470
    uint8_t interlacing_shift;
471
    uint8_t interlacing_leftweight;
472

    
473
    /* short-circuit null buffers */
474
    if (!inbuffer || !input_buffer_size)
475
        return input_buffer_size;
476

    
477
    /* initialize from the extradata */
478
    if (!alac->context_initialized) {
479
        if (alac->avctx->extradata_size != ALAC_EXTRADATA_SIZE) {
480
            av_log(avctx, AV_LOG_ERROR, "alac: expected %d extradata bytes\n",
481
                ALAC_EXTRADATA_SIZE);
482
            return input_buffer_size;
483
        }
484
        if (alac_set_info(alac)) {
485
            av_log(avctx, AV_LOG_ERROR, "alac: set_info failed\n");
486
            return input_buffer_size;
487
        }
488
        alac->context_initialized = 1;
489
    }
490

    
491
    init_get_bits(&alac->gb, inbuffer, input_buffer_size * 8);
492

    
493
    channels = get_bits(&alac->gb, 3) + 1;
494

    
495
        /* 2^result = something to do with output waiting.
496
         * perhaps matters if we read > 1 frame in a pass?
497
         */
498
        get_bits(&alac->gb, 4);
499

    
500
        get_bits(&alac->gb, 12); /* unknown, skip 12 bits */
501

    
502
        hassize = get_bits(&alac->gb, 1); /* the output sample size is stored soon */
503

    
504
        wasted_bytes = get_bits(&alac->gb, 2); /* unknown ? */
505

    
506
        isnotcompressed = get_bits(&alac->gb, 1); /* whether the frame is compressed */
507

    
508
        if (hassize) {
509
            /* now read the number of samples,
510
             * as a 32bit integer */
511
            outputsamples = get_bits(&alac->gb, 32);
512
        } else
513
            outputsamples = alac->setinfo_max_samples_per_frame;
514

    
515
        *outputsize = outputsamples * alac->bytespersample;
516
        readsamplesize = alac->setinfo_sample_size - (wasted_bytes * 8) + channels - 1;
517

    
518
        if (!isnotcompressed) {
519
         /* so it is compressed */
520
            int16_t predictor_coef_table[channels][32];
521
            int predictor_coef_num[channels];
522
            int prediction_type[channels];
523
            int prediction_quantitization[channels];
524
            int ricemodifier[channels];
525

    
526
            int i, chan;
527

    
528
            interlacing_shift = get_bits(&alac->gb, 8);
529
            interlacing_leftweight = get_bits(&alac->gb, 8);
530

    
531
          for (chan = 0; chan < channels; chan++) {
532
            prediction_type[chan] = get_bits(&alac->gb, 4);
533
            prediction_quantitization[chan] = get_bits(&alac->gb, 4);
534

    
535
            ricemodifier[chan] = get_bits(&alac->gb, 3);
536
            predictor_coef_num[chan] = get_bits(&alac->gb, 5);
537

    
538
            /* read the predictor table */
539
            for (i = 0; i < predictor_coef_num[chan]; i++) {
540
                predictor_coef_table[chan][i] = (int16_t)get_bits(&alac->gb, 16);
541
            }
542
          }
543

    
544
            if (wasted_bytes) {
545
                av_log(avctx, AV_LOG_ERROR, "FIXME: unimplemented, unhandling of wasted_bytes\n");
546
            }
547

    
548
          for (chan = 0; chan < channels; chan++) {
549
            bastardized_rice_decompress(alac,
550
                                        alac->predicterror_buffer[chan],
551
                                        outputsamples,
552
                                        readsamplesize,
553
                                        alac->setinfo_rice_initialhistory,
554
                                        alac->setinfo_rice_kmodifier,
555
                                        ricemodifier[chan] * alac->setinfo_rice_historymult / 4,
556
                                        (1 << alac->setinfo_rice_kmodifier) - 1);
557

    
558
            if (prediction_type[chan] == 0) {
559
              /* adaptive fir */
560
                predictor_decompress_fir_adapt(alac->predicterror_buffer[chan],
561
                                               alac->outputsamples_buffer[chan],
562
                                               outputsamples,
563
                                               readsamplesize,
564
                                               predictor_coef_table[chan],
565
                                               predictor_coef_num[chan],
566
                                               prediction_quantitization[chan]);
567
            } else {
568
                av_log(avctx, AV_LOG_ERROR, "FIXME: unhandled prediction type: %i\n", prediction_type[chan]);
569
                /* i think the only other prediction type (or perhaps this is just a
570
                 * boolean?) runs adaptive fir twice.. like:
571
                 * predictor_decompress_fir_adapt(predictor_error, tempout, ...)
572
                 * predictor_decompress_fir_adapt(predictor_error, outputsamples ...)
573
                 * little strange..
574
                 */
575
            }
576
          }
577
        } else {
578
         /* not compressed, easy case */
579
            if (alac->setinfo_sample_size <= 16) {
580
                int i, chan;
581
              for (chan = 0; chan < channels; chan++) {
582
                for (i = 0; i < outputsamples; i++) {
583
                    int32_t audiobits;
584

    
585
                    audiobits = get_bits(&alac->gb, alac->setinfo_sample_size);
586
                    audiobits = SIGN_EXTENDED32(audiobits, readsamplesize);
587

    
588
                    alac->outputsamples_buffer[chan][i] = audiobits;
589
                }
590
              }
591
            } else {
592
                int i, chan;
593
              for (chan = 0; chan < channels; chan++) {
594
                for (i = 0; i < outputsamples; i++) {
595
                    int32_t audiobits;
596

    
597
                    audiobits = get_bits(&alac->gb, 16);
598
                    /* special case of sign extension..
599
                     * as we'll be ORing the low 16bits into this */
600
                    audiobits = audiobits << 16;
601
                    audiobits = audiobits >> (32 - alac->setinfo_sample_size);
602
                    audiobits |= get_bits(&alac->gb, alac->setinfo_sample_size - 16);
603

    
604
                    alac->outputsamples_buffer[chan][i] = audiobits;
605
                }
606
              }
607
            }
608
            /* wasted_bytes = 0; */
609
            interlacing_shift = 0;
610
            interlacing_leftweight = 0;
611
        }
612

    
613
        switch(alac->setinfo_sample_size) {
614
        case 16: {
615
          if (channels == 2) {
616
            deinterlace_16(alac->outputsamples_buffer[0],
617
                           alac->outputsamples_buffer[1],
618
                           (int16_t*)outbuffer,
619
                           alac->numchannels,
620
                           outputsamples,
621
                           interlacing_shift,
622
                           interlacing_leftweight);
623
          } else {
624
              int i;
625
              for (i = 0; i < outputsamples; i++) {
626
                  int16_t sample = alac->outputsamples_buffer[0][i];
627
                  ((int16_t*)outbuffer)[i * alac->numchannels] = sample;
628
              }
629
          }
630
            break;
631
        }
632
        case 20:
633
        case 24:
634
        case 32:
635
            av_log(avctx, AV_LOG_ERROR, "FIXME: unimplemented sample size %i\n", alac->setinfo_sample_size);
636
            break;
637
        default:
638
            break;
639
        }
640

    
641

    
642
    return input_buffer_size;
643
}
644

    
645
static int alac_decode_init(AVCodecContext * avctx)
646
{
647
    ALACContext *alac = avctx->priv_data;
648
    alac->avctx = avctx;
649
    alac->context_initialized = 0;
650

    
651
    alac->samplesize = alac->avctx->bits_per_sample;
652
    alac->numchannels = alac->avctx->channels;
653
    alac->bytespersample = (alac->samplesize / 8) * alac->numchannels;
654

    
655
    return 0;
656
}
657

    
658
static int alac_decode_close(AVCodecContext *avctx)
659
{
660
    ALACContext *alac = avctx->priv_data;
661

    
662
    int chan;
663
    for (chan = 0; chan < MAX_CHANNELS; chan++) {
664
        av_free(alac->predicterror_buffer[chan]);
665
        av_free(alac->outputsamples_buffer[chan]);
666
    }
667

    
668
    return 0;
669
}
670

    
671
AVCodec alac_decoder = {
672
    "alac",
673
    CODEC_TYPE_AUDIO,
674
    CODEC_ID_ALAC,
675
    sizeof(ALACContext),
676
    alac_decode_init,
677
    NULL,
678
    alac_decode_close,
679
    alac_decode_frame,
680
};