alac.c
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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 Libav.
6  *
7  * Libav is free software; you can redistribute it and/or
8  * modify it under the terms of the GNU Lesser General Public
9  * License as published by the Free Software Foundation; either
10  * version 2.1 of the License, or (at your option) any later version.
11  *
12  * Libav 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
15  * Lesser General Public License for more details.
16  *
17  * You should have received a copy of the GNU Lesser General Public
18  * License along with Libav; if not, write to the Free Software
19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20  */
21 
49 #include "avcodec.h"
50 #include "get_bits.h"
51 #include "bytestream.h"
52 #include "unary.h"
53 #include "mathops.h"
54 
55 #define ALAC_EXTRADATA_SIZE 36
56 #define MAX_CHANNELS 2
57 
58 typedef struct {
59 
63 
65 
66  /* buffers */
67  int32_t *predicterror_buffer[MAX_CHANNELS];
68 
69  int32_t *outputsamples_buffer[MAX_CHANNELS];
70 
71  int32_t *extra_bits_buffer[MAX_CHANNELS];
72 
73  /* stuff from setinfo */
74  uint32_t setinfo_max_samples_per_frame; /* 0x1000 = 4096 */ /* max samples per frame? */
75  uint8_t setinfo_sample_size; /* 0x10 */
76  uint8_t setinfo_rice_historymult; /* 0x28 */
77  uint8_t setinfo_rice_initialhistory; /* 0x0a */
78  uint8_t setinfo_rice_kmodifier; /* 0x0e */
79  /* end setinfo stuff */
80 
81  int extra_bits;
82 } ALACContext;
83 
84 static inline int decode_scalar(GetBitContext *gb, int k, int limit, int readsamplesize){
85  /* read x - number of 1s before 0 represent the rice */
86  int x = get_unary_0_9(gb);
87 
88  if (x > 8) { /* RICE THRESHOLD */
89  /* use alternative encoding */
90  x = get_bits(gb, readsamplesize);
91  } else {
92  if (k >= limit)
93  k = limit;
94 
95  if (k != 1) {
96  int extrabits = show_bits(gb, k);
97 
98  /* multiply x by 2^k - 1, as part of their strange algorithm */
99  x = (x << k) - x;
100 
101  if (extrabits > 1) {
102  x += extrabits - 1;
103  skip_bits(gb, k);
104  } else
105  skip_bits(gb, k - 1);
106  }
107  }
108  return x;
109 }
110 
112  int32_t *output_buffer,
113  int output_size,
114  int readsamplesize, /* arg_10 */
115  int rice_initialhistory, /* arg424->b */
116  int rice_kmodifier, /* arg424->d */
117  int rice_historymult, /* arg424->c */
118  int rice_kmodifier_mask /* arg424->e */
119  )
120 {
121  int output_count;
122  unsigned int history = rice_initialhistory;
123  int sign_modifier = 0;
124 
125  for (output_count = 0; output_count < output_size; output_count++) {
126  int32_t x;
127  int32_t x_modified;
128  int32_t final_val;
129 
130  /* standard rice encoding */
131  int k; /* size of extra bits */
132 
133  /* read k, that is bits as is */
134  k = av_log2((history >> 9) + 3);
135  x= decode_scalar(&alac->gb, k, rice_kmodifier, readsamplesize);
136 
137  x_modified = sign_modifier + x;
138  final_val = (x_modified + 1) / 2;
139  if (x_modified & 1) final_val *= -1;
140 
141  output_buffer[output_count] = final_val;
142 
143  sign_modifier = 0;
144 
145  /* now update the history */
146  history += x_modified * rice_historymult
147  - ((history * rice_historymult) >> 9);
148 
149  if (x_modified > 0xffff)
150  history = 0xffff;
151 
152  /* special case: there may be compressed blocks of 0 */
153  if ((history < 128) && (output_count+1 < output_size)) {
154  int k;
155  unsigned int block_size;
156 
157  sign_modifier = 1;
158 
159  k = 7 - av_log2(history) + ((history + 16) >> 6 /* / 64 */);
160 
161  block_size= decode_scalar(&alac->gb, k, rice_kmodifier, 16);
162 
163  if (block_size > 0) {
164  if(block_size >= output_size - output_count){
165  av_log(alac->avctx, AV_LOG_ERROR, "invalid zero block size of %d %d %d\n", block_size, output_size, output_count);
166  block_size= output_size - output_count - 1;
167  }
168  memset(&output_buffer[output_count+1], 0, block_size * 4);
169  output_count += block_size;
170  }
171 
172  if (block_size > 0xffff)
173  sign_modifier = 0;
174 
175  history = 0;
176  }
177  }
178 }
179 
180 static inline int sign_only(int v)
181 {
182  return v ? FFSIGN(v) : 0;
183 }
184 
185 static void predictor_decompress_fir_adapt(int32_t *error_buffer,
186  int32_t *buffer_out,
187  int output_size,
188  int readsamplesize,
189  int16_t *predictor_coef_table,
190  int predictor_coef_num,
191  int predictor_quantitization)
192 {
193  int i;
194 
195  /* first sample always copies */
196  *buffer_out = *error_buffer;
197 
198  if (!predictor_coef_num) {
199  if (output_size <= 1)
200  return;
201 
202  memcpy(buffer_out+1, error_buffer+1, (output_size-1) * 4);
203  return;
204  }
205 
206  if (predictor_coef_num == 0x1f) { /* 11111 - max value of predictor_coef_num */
207  /* second-best case scenario for fir decompression,
208  * error describes a small difference from the previous sample only
209  */
210  if (output_size <= 1)
211  return;
212  for (i = 0; i < output_size - 1; i++) {
213  int32_t prev_value;
214  int32_t error_value;
215 
216  prev_value = buffer_out[i];
217  error_value = error_buffer[i+1];
218  buffer_out[i+1] =
219  sign_extend((prev_value + error_value), readsamplesize);
220  }
221  return;
222  }
223 
224  /* read warm-up samples */
225  if (predictor_coef_num > 0)
226  for (i = 0; i < predictor_coef_num; i++) {
227  int32_t val;
228 
229  val = buffer_out[i] + error_buffer[i+1];
230  val = sign_extend(val, readsamplesize);
231  buffer_out[i+1] = val;
232  }
233 
234  /* 4 and 8 are very common cases (the only ones i've seen). these
235  * should be unrolled and optimized
236  */
237 
238  /* general case */
239  if (predictor_coef_num > 0) {
240  for (i = predictor_coef_num + 1; i < output_size; i++) {
241  int j;
242  int sum = 0;
243  int outval;
244  int error_val = error_buffer[i];
245 
246  for (j = 0; j < predictor_coef_num; j++) {
247  sum += (buffer_out[predictor_coef_num-j] - buffer_out[0]) *
248  predictor_coef_table[j];
249  }
250 
251  outval = (1 << (predictor_quantitization-1)) + sum;
252  outval = outval >> predictor_quantitization;
253  outval = outval + buffer_out[0] + error_val;
254  outval = sign_extend(outval, readsamplesize);
255 
256  buffer_out[predictor_coef_num+1] = outval;
257 
258  if (error_val > 0) {
259  int predictor_num = predictor_coef_num - 1;
260 
261  while (predictor_num >= 0 && error_val > 0) {
262  int val = buffer_out[0] - buffer_out[predictor_coef_num - predictor_num];
263  int sign = sign_only(val);
264 
265  predictor_coef_table[predictor_num] -= sign;
266 
267  val *= sign; /* absolute value */
268 
269  error_val -= ((val >> predictor_quantitization) *
270  (predictor_coef_num - predictor_num));
271 
272  predictor_num--;
273  }
274  } else if (error_val < 0) {
275  int predictor_num = predictor_coef_num - 1;
276 
277  while (predictor_num >= 0 && error_val < 0) {
278  int val = buffer_out[0] - buffer_out[predictor_coef_num - predictor_num];
279  int sign = - sign_only(val);
280 
281  predictor_coef_table[predictor_num] -= sign;
282 
283  val *= sign; /* neg value */
284 
285  error_val -= ((val >> predictor_quantitization) *
286  (predictor_coef_num - predictor_num));
287 
288  predictor_num--;
289  }
290  }
291 
292  buffer_out++;
293  }
294  }
295 }
296 
297 static void decorrelate_stereo(int32_t *buffer[MAX_CHANNELS],
298  int numsamples, uint8_t interlacing_shift,
299  uint8_t interlacing_leftweight)
300 {
301  int i;
302 
303  for (i = 0; i < numsamples; i++) {
304  int32_t a, b;
305 
306  a = buffer[0][i];
307  b = buffer[1][i];
308 
309  a -= (b * interlacing_leftweight) >> interlacing_shift;
310  b += a;
311 
312  buffer[0][i] = b;
313  buffer[1][i] = a;
314  }
315 }
316 
317 static void append_extra_bits(int32_t *buffer[MAX_CHANNELS],
318  int32_t *extra_bits_buffer[MAX_CHANNELS],
319  int extra_bits, int numchannels, int numsamples)
320 {
321  int i, ch;
322 
323  for (ch = 0; ch < numchannels; ch++)
324  for (i = 0; i < numsamples; i++)
325  buffer[ch][i] = (buffer[ch][i] << extra_bits) | extra_bits_buffer[ch][i];
326 }
327 
329  int16_t *buffer_out, int numsamples)
330 {
331  int i;
332 
333  for (i = 0; i < numsamples; i++) {
334  *buffer_out++ = buffer[0][i];
335  *buffer_out++ = buffer[1][i];
336  }
337 }
338 
340  int32_t *buffer_out, int numsamples)
341 {
342  int i;
343 
344  for (i = 0; i < numsamples; i++) {
345  *buffer_out++ = buffer[0][i] << 8;
346  *buffer_out++ = buffer[1][i] << 8;
347  }
348 }
349 
350 static int alac_decode_frame(AVCodecContext *avctx, void *data,
351  int *got_frame_ptr, AVPacket *avpkt)
352 {
353  const uint8_t *inbuffer = avpkt->data;
354  int input_buffer_size = avpkt->size;
355  ALACContext *alac = avctx->priv_data;
356 
357  int channels;
358  unsigned int outputsamples;
359  int hassize;
360  unsigned int readsamplesize;
361  int isnotcompressed;
362  uint8_t interlacing_shift;
363  uint8_t interlacing_leftweight;
364  int i, ch, ret;
365 
366  init_get_bits(&alac->gb, inbuffer, input_buffer_size * 8);
367 
368  channels = get_bits(&alac->gb, 3) + 1;
369  if (channels != avctx->channels) {
370  av_log(avctx, AV_LOG_ERROR, "frame header channel count mismatch\n");
371  return AVERROR_INVALIDDATA;
372  }
373 
374  /* 2^result = something to do with output waiting.
375  * perhaps matters if we read > 1 frame in a pass?
376  */
377  skip_bits(&alac->gb, 4);
378 
379  skip_bits(&alac->gb, 12); /* unknown, skip 12 bits */
380 
381  /* the output sample size is stored soon */
382  hassize = get_bits1(&alac->gb);
383 
384  alac->extra_bits = get_bits(&alac->gb, 2) << 3;
385 
386  /* whether the frame is compressed */
387  isnotcompressed = get_bits1(&alac->gb);
388 
389  if (hassize) {
390  /* now read the number of samples as a 32bit integer */
391  outputsamples = get_bits_long(&alac->gb, 32);
392  if(outputsamples > alac->setinfo_max_samples_per_frame){
393  av_log(avctx, AV_LOG_ERROR, "outputsamples %d > %d\n", outputsamples, alac->setinfo_max_samples_per_frame);
394  return -1;
395  }
396  } else
397  outputsamples = alac->setinfo_max_samples_per_frame;
398 
399  /* get output buffer */
400  if (outputsamples > INT32_MAX) {
401  av_log(avctx, AV_LOG_ERROR, "unsupported block size: %u\n", outputsamples);
402  return AVERROR_INVALIDDATA;
403  }
404  alac->frame.nb_samples = outputsamples;
405  if ((ret = avctx->get_buffer(avctx, &alac->frame)) < 0) {
406  av_log(avctx, AV_LOG_ERROR, "get_buffer() failed\n");
407  return ret;
408  }
409 
410  readsamplesize = alac->setinfo_sample_size - alac->extra_bits + channels - 1;
411  if (readsamplesize > MIN_CACHE_BITS) {
412  av_log(avctx, AV_LOG_ERROR, "readsamplesize too big (%d)\n", readsamplesize);
413  return -1;
414  }
415 
416  if (!isnotcompressed) {
417  /* so it is compressed */
418  int16_t predictor_coef_table[MAX_CHANNELS][32];
419  int predictor_coef_num[MAX_CHANNELS];
420  int prediction_type[MAX_CHANNELS];
421  int prediction_quantitization[MAX_CHANNELS];
422  int ricemodifier[MAX_CHANNELS];
423 
424  interlacing_shift = get_bits(&alac->gb, 8);
425  interlacing_leftweight = get_bits(&alac->gb, 8);
426 
427  for (ch = 0; ch < channels; ch++) {
428  prediction_type[ch] = get_bits(&alac->gb, 4);
429  prediction_quantitization[ch] = get_bits(&alac->gb, 4);
430 
431  ricemodifier[ch] = get_bits(&alac->gb, 3);
432  predictor_coef_num[ch] = get_bits(&alac->gb, 5);
433 
434  /* read the predictor table */
435  for (i = 0; i < predictor_coef_num[ch]; i++)
436  predictor_coef_table[ch][i] = (int16_t)get_bits(&alac->gb, 16);
437  }
438 
439  if (alac->extra_bits) {
440  for (i = 0; i < outputsamples; i++) {
441  for (ch = 0; ch < channels; ch++)
442  alac->extra_bits_buffer[ch][i] = get_bits(&alac->gb, alac->extra_bits);
443  }
444  }
445  for (ch = 0; ch < channels; ch++) {
447  alac->predicterror_buffer[ch],
448  outputsamples,
449  readsamplesize,
452  ricemodifier[ch] * alac->setinfo_rice_historymult / 4,
453  (1 << alac->setinfo_rice_kmodifier) - 1);
454 
455  /* adaptive FIR filter */
456  if (prediction_type[ch] == 15) {
457  /* Prediction type 15 runs the adaptive FIR twice.
458  * The first pass uses the special-case coef_num = 31, while
459  * the second pass uses the coefs from the bitstream.
460  *
461  * However, this prediction type is not currently used by the
462  * reference encoder.
463  */
465  alac->predicterror_buffer[ch],
466  outputsamples, readsamplesize,
467  NULL, 31, 0);
468  } else if (prediction_type[ch] > 0) {
469  av_log(avctx, AV_LOG_WARNING, "unknown prediction type: %i\n",
470  prediction_type[ch]);
471  }
473  alac->outputsamples_buffer[ch],
474  outputsamples, readsamplesize,
475  predictor_coef_table[ch],
476  predictor_coef_num[ch],
477  prediction_quantitization[ch]);
478  }
479  } else {
480  /* not compressed, easy case */
481  for (i = 0; i < outputsamples; i++) {
482  for (ch = 0; ch < channels; ch++) {
483  alac->outputsamples_buffer[ch][i] = get_sbits_long(&alac->gb,
484  alac->setinfo_sample_size);
485  }
486  }
487  alac->extra_bits = 0;
488  interlacing_shift = 0;
489  interlacing_leftweight = 0;
490  }
491  if (get_bits(&alac->gb, 3) != 7)
492  av_log(avctx, AV_LOG_ERROR, "Error : Wrong End Of Frame\n");
493 
494  if (channels == 2 && interlacing_leftweight) {
495  decorrelate_stereo(alac->outputsamples_buffer, outputsamples,
496  interlacing_shift, interlacing_leftweight);
497  }
498 
499  if (alac->extra_bits) {
501  alac->extra_bits, alac->numchannels, outputsamples);
502  }
503 
504  switch(alac->setinfo_sample_size) {
505  case 16:
506  if (channels == 2) {
508  (int16_t *)alac->frame.data[0], outputsamples);
509  } else {
510  int16_t *outbuffer = (int16_t *)alac->frame.data[0];
511  for (i = 0; i < outputsamples; i++) {
512  outbuffer[i] = alac->outputsamples_buffer[0][i];
513  }
514  }
515  break;
516  case 24:
517  if (channels == 2) {
519  (int32_t *)alac->frame.data[0], outputsamples);
520  } else {
521  int32_t *outbuffer = (int32_t *)alac->frame.data[0];
522  for (i = 0; i < outputsamples; i++)
523  outbuffer[i] = alac->outputsamples_buffer[0][i] << 8;
524  }
525  break;
526  }
527 
528  if (input_buffer_size * 8 - get_bits_count(&alac->gb) > 8)
529  av_log(avctx, AV_LOG_ERROR, "Error : %d bits left\n", input_buffer_size * 8 - get_bits_count(&alac->gb));
530 
531  *got_frame_ptr = 1;
532  *(AVFrame *)data = alac->frame;
533 
534  return input_buffer_size;
535 }
536 
538 {
539  ALACContext *alac = avctx->priv_data;
540 
541  int ch;
542  for (ch = 0; ch < alac->numchannels; ch++) {
543  av_freep(&alac->predicterror_buffer[ch]);
544  av_freep(&alac->outputsamples_buffer[ch]);
545  av_freep(&alac->extra_bits_buffer[ch]);
546  }
547 
548  return 0;
549 }
550 
551 static int allocate_buffers(ALACContext *alac)
552 {
553  int ch;
554  for (ch = 0; ch < alac->numchannels; ch++) {
555  int buf_size = alac->setinfo_max_samples_per_frame * sizeof(int32_t);
556 
557  FF_ALLOC_OR_GOTO(alac->avctx, alac->predicterror_buffer[ch],
558  buf_size, buf_alloc_fail);
559 
561  buf_size, buf_alloc_fail);
562 
563  FF_ALLOC_OR_GOTO(alac->avctx, alac->extra_bits_buffer[ch],
564  buf_size, buf_alloc_fail);
565  }
566  return 0;
567 buf_alloc_fail:
568  alac_decode_close(alac->avctx);
569  return AVERROR(ENOMEM);
570 }
571 
572 static int alac_set_info(ALACContext *alac)
573 {
574  const unsigned char *ptr = alac->avctx->extradata;
575 
576  ptr += 4; /* size */
577  ptr += 4; /* alac */
578  ptr += 4; /* version */
579 
580  if(AV_RB32(ptr) >= UINT_MAX/4){
581  av_log(alac->avctx, AV_LOG_ERROR, "setinfo_max_samples_per_frame too large\n");
582  return -1;
583  }
584 
585  /* buffer size / 2 ? */
586  alac->setinfo_max_samples_per_frame = bytestream_get_be32(&ptr);
587  ptr++; /* compatible version */
588  alac->setinfo_sample_size = *ptr++;
589  alac->setinfo_rice_historymult = *ptr++;
590  alac->setinfo_rice_initialhistory = *ptr++;
591  alac->setinfo_rice_kmodifier = *ptr++;
592  alac->numchannels = *ptr++;
593  bytestream_get_be16(&ptr); /* maxRun */
594  bytestream_get_be32(&ptr); /* max coded frame size */
595  bytestream_get_be32(&ptr); /* average bitrate */
596  bytestream_get_be32(&ptr); /* samplerate */
597 
598  return 0;
599 }
600 
602 {
603  int ret;
604  ALACContext *alac = avctx->priv_data;
605  alac->avctx = avctx;
606 
607  /* initialize from the extradata */
609  av_log(avctx, AV_LOG_ERROR, "alac: extradata is too small\n");
610  return AVERROR_INVALIDDATA;
611  }
612  if (alac_set_info(alac)) {
613  av_log(avctx, AV_LOG_ERROR, "alac: set_info failed\n");
614  return -1;
615  }
616 
617  switch (alac->setinfo_sample_size) {
618  case 16: avctx->sample_fmt = AV_SAMPLE_FMT_S16;
619  break;
620  case 24: avctx->sample_fmt = AV_SAMPLE_FMT_S32;
621  break;
622  default: av_log_ask_for_sample(avctx, "Sample depth %d is not supported.\n",
623  alac->setinfo_sample_size);
624  return AVERROR_PATCHWELCOME;
625  }
626 
627  if (alac->numchannels < 1) {
628  av_log(avctx, AV_LOG_WARNING, "Invalid channel count\n");
629  alac->numchannels = avctx->channels;
630  } else {
631  if (alac->numchannels > MAX_CHANNELS)
632  alac->numchannels = avctx->channels;
633  else
634  avctx->channels = alac->numchannels;
635  }
636  if (avctx->channels > MAX_CHANNELS) {
637  av_log(avctx, AV_LOG_ERROR, "Unsupported channel count: %d\n",
638  avctx->channels);
639  return AVERROR_PATCHWELCOME;
640  }
641 
642  if ((ret = allocate_buffers(alac)) < 0) {
643  av_log(avctx, AV_LOG_ERROR, "Error allocating buffers\n");
644  return ret;
645  }
646 
648  avctx->coded_frame = &alac->frame;
649 
650  return 0;
651 }
652 
654  .name = "alac",
655  .type = AVMEDIA_TYPE_AUDIO,
656  .id = CODEC_ID_ALAC,
657  .priv_data_size = sizeof(ALACContext),
661  .capabilities = CODEC_CAP_DR1,
662  .long_name = NULL_IF_CONFIG_SMALL("ALAC (Apple Lossless Audio Codec)"),
663 };