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/*
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 * ALAC (Apple Lossless Audio Codec) decoder
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 * Copyright (c) 2005 David Hammerton
4
 *
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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
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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 */
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22
/**
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 * @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:
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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)
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 *  bytes 8-35  data bytes needed by decoder
36
 *
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 * Extradata:
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 * 32bit  size
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 * 32bit  tag (=alac)
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 * 32bit  zero?
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 * 32bit  max sample per frame
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 *  8bit  ?? (zero?)
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 *  8bit  sample size
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 *  8bit  history mult
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 *  8bit  initial history
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 *  8bit  kmodifier
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 *  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;
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    int numchannels;
72
    int bytespersample;
73

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

    
77
    int32_t *outputsamples_buffer[MAX_CHANNELS];
78

    
79
    /* stuff from setinfo */
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    uint32_t setinfo_max_samples_per_frame; /* 0x1000 = 4096 */    /* max samples per frame? */
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    uint8_t setinfo_7a; /* 0x00 */
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    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 */
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    uint8_t setinfo_7f; /* 0x02 */
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    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
static inline int count_leading_zeros(int32_t input)
143
{
144
    return 31-av_log2(input);
145
}
146

    
147
static void bastardized_rice_decompress(ALACContext *alac,
148
                                 int32_t *output_buffer,
149
                                 int output_size,
150
                                 int readsamplesize, /* arg_10 */
151
                                 int rice_initialhistory, /* arg424->b */
152
                                 int rice_kmodifier, /* arg424->d */
153
                                 int rice_historymult, /* arg424->c */
154
                                 int rice_kmodifier_mask /* arg424->e */
155
        )
156
{
157
    int output_count;
158
    unsigned int history = rice_initialhistory;
159
    int sign_modifier = 0;
160

    
161
    for (output_count = 0; output_count < output_size; output_count++) {
162
        int32_t x = 0;
163
        int32_t x_modified;
164
        int32_t final_val;
165

    
166
        /* read x - number of 1s before 0 represent the rice */
167
        while (x <= 8 && get_bits1(&alac->gb)) {
168
            x++;
169
        }
170

    
171

    
172
        if (x > 8) { /* RICE THRESHOLD */
173
            /* use alternative encoding */
174
            int32_t value;
175

    
176
            value = get_bits(&alac->gb, readsamplesize);
177

    
178
            /* mask value to readsamplesize size */
179
            if (readsamplesize != 32)
180
                value &= (0xffffffff >> (32 - readsamplesize));
181

    
182
            x = value;
183
        } else {
184
            /* standard rice encoding */
185
            int extrabits;
186
            int k; /* size of extra bits */
187

    
188
            /* read k, that is bits as is */
189
            k = 31 - rice_kmodifier - count_leading_zeros((history >> 9) + 3);
190

    
191
            if (k < 0)
192
                k += rice_kmodifier;
193
            else
194
                k = rice_kmodifier;
195

    
196
            if (k != 1) {
197
                extrabits = show_bits(&alac->gb, k);
198

    
199
                /* multiply x by 2^k - 1, as part of their strange algorithm */
200
                x = (x << k) - x;
201

    
202
                if (extrabits > 1) {
203
                    x += extrabits - 1;
204
                    get_bits(&alac->gb, k);
205
                } else
206
                    get_bits(&alac->gb, k - 1);
207
            }
208
        }
209

    
210
        x_modified = sign_modifier + x;
211
        final_val = (x_modified + 1) / 2;
212
        if (x_modified & 1) final_val *= -1;
213

    
214
        output_buffer[output_count] = final_val;
215

    
216
        sign_modifier = 0;
217

    
218
        /* now update the history */
219
        history += x_modified * rice_historymult
220
                   - ((history * rice_historymult) >> 9);
221

    
222
        if (x_modified > 0xffff)
223
            history = 0xffff;
224

    
225
        /* special case: there may be compressed blocks of 0 */
226
        if ((history < 128) && (output_count+1 < output_size)) {
227
            int block_size;
228

    
229
            sign_modifier = 1;
230

    
231
            x = 0;
232
            while (x <= 8 && get_bits1(&alac->gb)) {
233
                x++;
234
            }
235

    
236
            if (x > 8) {
237
                block_size = get_bits(&alac->gb, 16);
238
                block_size &= 0xffff;
239
            } else {
240
                int k;
241
                int extrabits;
242

    
243
                k = count_leading_zeros(history) + ((history + 16) >> 6 /* / 64 */) - 24;
244

    
245
                extrabits = show_bits(&alac->gb, k);
246

    
247
                block_size = (((1 << k) - 1) & rice_kmodifier_mask) * x
248
                           + extrabits - 1;
249

    
250
                if (extrabits < 2) {
251
                    x = 1 - extrabits;
252
                    block_size += x;
253
                    get_bits(&alac->gb, k - 1);
254
                } else {
255
                    get_bits(&alac->gb, k);
256
                }
257
            }
258

    
259
            if (block_size > 0) {
260
                memset(&output_buffer[output_count+1], 0, block_size * 4);
261
                output_count += block_size;
262
            }
263

    
264
            if (block_size > 0xffff)
265
                sign_modifier = 0;
266

    
267
            history = 0;
268
        }
269
    }
270
}
271

    
272
#define SIGN_EXTENDED32(val, bits) ((val << (32 - bits)) >> (32 - bits))
273

    
274
#define SIGN_ONLY(v) \
275
                     ((v < 0) ? (-1) : \
276
                                ((v > 0) ? (1) : \
277
                                           (0)))
278

    
279
static void predictor_decompress_fir_adapt(int32_t *error_buffer,
280
                                           int32_t *buffer_out,
281
                                           int output_size,
282
                                           int readsamplesize,
283
                                           int16_t *predictor_coef_table,
284
                                           int predictor_coef_num,
285
                                           int predictor_quantitization)
286
{
287
    int i;
288

    
289
    /* first sample always copies */
290
    *buffer_out = *error_buffer;
291

    
292
    if (!predictor_coef_num) {
293
        if (output_size <= 1)
294
            return;
295

    
296
        memcpy(buffer_out+1, error_buffer+1, (output_size-1) * 4);
297
        return;
298
    }
299

    
300
    if (predictor_coef_num == 0x1f) { /* 11111 - max value of predictor_coef_num */
301
      /* second-best case scenario for fir decompression,
302
       * error describes a small difference from the previous sample only
303
       */
304
        if (output_size <= 1)
305
            return;
306
        for (i = 0; i < output_size - 1; i++) {
307
            int32_t prev_value;
308
            int32_t error_value;
309

    
310
            prev_value = buffer_out[i];
311
            error_value = error_buffer[i+1];
312
            buffer_out[i+1] =
313
                SIGN_EXTENDED32((prev_value + error_value), readsamplesize);
314
        }
315
        return;
316
    }
317

    
318
    /* read warm-up samples */
319
    if (predictor_coef_num > 0)
320
        for (i = 0; i < predictor_coef_num; i++) {
321
            int32_t val;
322

    
323
            val = buffer_out[i] + error_buffer[i+1];
324
            val = SIGN_EXTENDED32(val, readsamplesize);
325
            buffer_out[i+1] = val;
326
        }
327

    
328
#if 0
329
    /* 4 and 8 are very common cases (the only ones i've seen). these
330
     * should be unrolled and optimised
331
     */
332
    if (predictor_coef_num == 4) {
333
        /* FIXME: optimised general case */
334
        return;
335
    }
336

337
    if (predictor_coef_table == 8) {
338
        /* FIXME: optimised general case */
339
        return;
340
    }
341
#endif
342

    
343
    /* general case */
344
    if (predictor_coef_num > 0) {
345
        for (i = predictor_coef_num + 1; i < output_size; i++) {
346
            int j;
347
            int sum = 0;
348
            int outval;
349
            int error_val = error_buffer[i];
350

    
351
            for (j = 0; j < predictor_coef_num; j++) {
352
                sum += (buffer_out[predictor_coef_num-j] - buffer_out[0]) *
353
                       predictor_coef_table[j];
354
            }
355

    
356
            outval = (1 << (predictor_quantitization-1)) + sum;
357
            outval = outval >> predictor_quantitization;
358
            outval = outval + buffer_out[0] + error_val;
359
            outval = SIGN_EXTENDED32(outval, readsamplesize);
360

    
361
            buffer_out[predictor_coef_num+1] = outval;
362

    
363
            if (error_val > 0) {
364
                int predictor_num = predictor_coef_num - 1;
365

    
366
                while (predictor_num >= 0 && error_val > 0) {
367
                    int val = buffer_out[0] - buffer_out[predictor_coef_num - predictor_num];
368
                    int sign = SIGN_ONLY(val);
369

    
370
                    predictor_coef_table[predictor_num] -= sign;
371

    
372
                    val *= sign; /* absolute value */
373

    
374
                    error_val -= ((val >> predictor_quantitization) *
375
                                  (predictor_coef_num - predictor_num));
376

    
377
                    predictor_num--;
378
                }
379
            } else if (error_val < 0) {
380
                int predictor_num = predictor_coef_num - 1;
381

    
382
                while (predictor_num >= 0 && error_val < 0) {
383
                    int val = buffer_out[0] - buffer_out[predictor_coef_num - predictor_num];
384
                    int sign = - SIGN_ONLY(val);
385

    
386
                    predictor_coef_table[predictor_num] -= sign;
387

    
388
                    val *= sign; /* neg value */
389

    
390
                    error_val -= ((val >> predictor_quantitization) *
391
                                  (predictor_coef_num - predictor_num));
392

    
393
                    predictor_num--;
394
                }
395
            }
396

    
397
            buffer_out++;
398
        }
399
    }
400
}
401

    
402
static void reconstruct_stereo_16(int32_t *buffer[MAX_CHANNELS],
403
                           int16_t *buffer_out,
404
                           int numchannels, int numsamples,
405
                           uint8_t interlacing_shift,
406
                           uint8_t interlacing_leftweight)
407
{
408
    int i;
409
    if (numsamples <= 0)
410
        return;
411

    
412
    /* weighted interlacing */
413
    if (interlacing_leftweight) {
414
        for (i = 0; i < numsamples; i++) {
415
            int32_t a, b;
416

    
417
            a = buffer[0][i];
418
            b = buffer[1][i];
419

    
420
            a -= (b * interlacing_leftweight) >> interlacing_shift;
421
            b += a;
422

    
423
            buffer_out[i*numchannels] = b;
424
            buffer_out[i*numchannels + 1] = a;
425
        }
426

    
427
        return;
428
    }
429

    
430
    /* otherwise basic interlacing took place */
431
    for (i = 0; i < numsamples; i++) {
432
        int16_t left, right;
433

    
434
        left = buffer[0][i];
435
        right = buffer[1][i];
436

    
437
        buffer_out[i*numchannels] = left;
438
        buffer_out[i*numchannels + 1] = right;
439
    }
440
}
441

    
442
static int alac_decode_frame(AVCodecContext *avctx,
443
                             void *outbuffer, int *outputsize,
444
                             uint8_t *inbuffer, int input_buffer_size)
445
{
446
    ALACContext *alac = avctx->priv_data;
447

    
448
    int channels;
449
    int32_t outputsamples;
450
    int hassize;
451
    int readsamplesize;
452
    int wasted_bytes;
453
    int isnotcompressed;
454
    uint8_t interlacing_shift;
455
    uint8_t interlacing_leftweight;
456

    
457
    /* short-circuit null buffers */
458
    if (!inbuffer || !input_buffer_size)
459
        return input_buffer_size;
460

    
461
    /* initialize from the extradata */
462
    if (!alac->context_initialized) {
463
        if (alac->avctx->extradata_size != ALAC_EXTRADATA_SIZE) {
464
            av_log(avctx, AV_LOG_ERROR, "alac: expected %d extradata bytes\n",
465
                ALAC_EXTRADATA_SIZE);
466
            return input_buffer_size;
467
        }
468
        if (alac_set_info(alac)) {
469
            av_log(avctx, AV_LOG_ERROR, "alac: set_info failed\n");
470
            return input_buffer_size;
471
        }
472
        alac->context_initialized = 1;
473
    }
474

    
475
    init_get_bits(&alac->gb, inbuffer, input_buffer_size * 8);
476

    
477
    channels = get_bits(&alac->gb, 3) + 1;
478
    if (channels > MAX_CHANNELS) {
479
        av_log(avctx, AV_LOG_ERROR, "channels > %d not supported\n",
480
               MAX_CHANNELS);
481
        return input_buffer_size;
482
    }
483

    
484
    /* 2^result = something to do with output waiting.
485
     * perhaps matters if we read > 1 frame in a pass?
486
     */
487
    get_bits(&alac->gb, 4);
488

    
489
    get_bits(&alac->gb, 12); /* unknown, skip 12 bits */
490

    
491
    /* the output sample size is stored soon */
492
    hassize = get_bits(&alac->gb, 1);
493

    
494
    wasted_bytes = get_bits(&alac->gb, 2); /* unknown ? */
495

    
496
    /* whether the frame is compressed */
497
    isnotcompressed = get_bits(&alac->gb, 1);
498

    
499
    if (hassize) {
500
        /* now read the number of samples as a 32bit integer */
501
        outputsamples = get_bits(&alac->gb, 32);
502
    } else
503
        outputsamples = alac->setinfo_max_samples_per_frame;
504

    
505
    *outputsize = outputsamples * alac->bytespersample;
506
    readsamplesize = alac->setinfo_sample_size - (wasted_bytes * 8) + channels - 1;
507

    
508
    if (!isnotcompressed) {
509
        /* so it is compressed */
510
        int16_t predictor_coef_table[channels][32];
511
        int predictor_coef_num[channels];
512
        int prediction_type[channels];
513
        int prediction_quantitization[channels];
514
        int ricemodifier[channels];
515
        int i, chan;
516

    
517
        interlacing_shift = get_bits(&alac->gb, 8);
518
        interlacing_leftweight = get_bits(&alac->gb, 8);
519

    
520
        for (chan = 0; chan < channels; chan++) {
521
            prediction_type[chan] = get_bits(&alac->gb, 4);
522
            prediction_quantitization[chan] = get_bits(&alac->gb, 4);
523

    
524
            ricemodifier[chan] = get_bits(&alac->gb, 3);
525
            predictor_coef_num[chan] = get_bits(&alac->gb, 5);
526

    
527
            /* read the predictor table */
528
            for (i = 0; i < predictor_coef_num[chan]; i++)
529
                predictor_coef_table[chan][i] = (int16_t)get_bits(&alac->gb, 16);
530
        }
531

    
532
        if (wasted_bytes)
533
            av_log(avctx, AV_LOG_ERROR, "FIXME: unimplemented, unhandling of wasted_bytes\n");
534

    
535
        for (chan = 0; chan < channels; chan++) {
536
            bastardized_rice_decompress(alac,
537
                                        alac->predicterror_buffer[chan],
538
                                        outputsamples,
539
                                        readsamplesize,
540
                                        alac->setinfo_rice_initialhistory,
541
                                        alac->setinfo_rice_kmodifier,
542
                                        ricemodifier[chan] * alac->setinfo_rice_historymult / 4,
543
                                        (1 << alac->setinfo_rice_kmodifier) - 1);
544

    
545
            if (prediction_type[chan] == 0) {
546
                /* adaptive fir */
547
                predictor_decompress_fir_adapt(alac->predicterror_buffer[chan],
548
                                               alac->outputsamples_buffer[chan],
549
                                               outputsamples,
550
                                               readsamplesize,
551
                                               predictor_coef_table[chan],
552
                                               predictor_coef_num[chan],
553
                                               prediction_quantitization[chan]);
554
            } else {
555
                av_log(avctx, AV_LOG_ERROR, "FIXME: unhandled prediction type: %i\n", prediction_type[chan]);
556
                /* I think the only other prediction type (or perhaps this is
557
                 * just a boolean?) runs adaptive fir twice.. like:
558
                 * predictor_decompress_fir_adapt(predictor_error, tempout, ...)
559
                 * predictor_decompress_fir_adapt(predictor_error, outputsamples ...)
560
                 * little strange..
561
                 */
562
            }
563
        }
564
    } else {
565
        /* not compressed, easy case */
566
        if (alac->setinfo_sample_size <= 16) {
567
            int i, chan;
568
            for (chan = 0; chan < channels; chan++)
569
                for (i = 0; i < outputsamples; i++) {
570
                    int32_t audiobits;
571

    
572
                    audiobits = get_bits(&alac->gb, alac->setinfo_sample_size);
573
                    audiobits = SIGN_EXTENDED32(audiobits, readsamplesize);
574

    
575
                    alac->outputsamples_buffer[chan][i] = audiobits;
576
                }
577
        } else {
578
            int i, chan;
579
            for (chan = 0; chan < channels; chan++)
580
                for (i = 0; i < outputsamples; i++) {
581
                    int32_t audiobits;
582

    
583
                    audiobits = get_bits(&alac->gb, 16);
584
                    /* special case of sign extension..
585
                     * as we'll be ORing the low 16bits into this */
586
                    audiobits = audiobits << 16;
587
                    audiobits = audiobits >> (32 - alac->setinfo_sample_size);
588
                    audiobits |= get_bits(&alac->gb, alac->setinfo_sample_size - 16);
589

    
590
                    alac->outputsamples_buffer[chan][i] = audiobits;
591
                }
592
        }
593
        /* wasted_bytes = 0; */
594
        interlacing_shift = 0;
595
        interlacing_leftweight = 0;
596
    }
597

    
598
    switch(alac->setinfo_sample_size) {
599
    case 16:
600
        if (channels == 2) {
601
            reconstruct_stereo_16(alac->outputsamples_buffer,
602
                           (int16_t*)outbuffer,
603
                           alac->numchannels,
604
                           outputsamples,
605
                           interlacing_shift,
606
                           interlacing_leftweight);
607
        } else {
608
            int i;
609
            for (i = 0; i < outputsamples; i++) {
610
                int16_t sample = alac->outputsamples_buffer[0][i];
611
                ((int16_t*)outbuffer)[i * alac->numchannels] = sample;
612
            }
613
        }
614
        break;
615
    case 20:
616
    case 24:
617
    case 32:
618
        av_log(avctx, AV_LOG_ERROR, "FIXME: unimplemented sample size %i\n", alac->setinfo_sample_size);
619
        break;
620
    default:
621
        break;
622
    }
623

    
624
    return input_buffer_size;
625
}
626

    
627
static int alac_decode_init(AVCodecContext * avctx)
628
{
629
    ALACContext *alac = avctx->priv_data;
630
    alac->avctx = avctx;
631
    alac->context_initialized = 0;
632

    
633
    alac->samplesize = alac->avctx->bits_per_sample;
634
    alac->numchannels = alac->avctx->channels;
635
    alac->bytespersample = (alac->samplesize / 8) * alac->numchannels;
636

    
637
    return 0;
638
}
639

    
640
static int alac_decode_close(AVCodecContext *avctx)
641
{
642
    ALACContext *alac = avctx->priv_data;
643

    
644
    int chan;
645
    for (chan = 0; chan < MAX_CHANNELS; chan++) {
646
        av_free(alac->predicterror_buffer[chan]);
647
        av_free(alac->outputsamples_buffer[chan]);
648
    }
649

    
650
    return 0;
651
}
652

    
653
AVCodec alac_decoder = {
654
    "alac",
655
    CODEC_TYPE_AUDIO,
656
    CODEC_ID_ALAC,
657
    sizeof(ALACContext),
658
    alac_decode_init,
659
    NULL,
660
    alac_decode_close,
661
    alac_decode_frame,
662
};