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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 FFmpeg.
6  *
7  * FFmpeg 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  * 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
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 FFmpeg; if not, write to the Free Software
19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20  */
21 
22 /**
23  * @file
24  * ALAC (Apple Lossless Audio Codec) decoder
25  * @author 2005 David Hammerton
26  * @see http://crazney.net/programs/itunes/alac.html
27  *
28  * Note: This decoder expects a 36-byte QuickTime atom to be
29  * passed through the extradata[_size] fields. This atom is tacked onto
30  * the end of an 'alac' stsd atom and has the following format:
31  *
32  * 32bit atom size
33  * 32bit tag ("alac")
34  * 32bit tag version (0)
35  * 32bit samples per frame (used when not set explicitly in the frames)
36  * 8bit compatible version (0)
37  * 8bit sample size
38  * 8bit history mult (40)
39  * 8bit initial history (10)
40  * 8bit rice param limit (14)
41  * 8bit channels
42  * 16bit maxRun (255)
43  * 32bit max coded frame size (0 means unknown)
44  * 32bit average bitrate (0 means unknown)
45  * 32bit samplerate
46  */
47 
48 #include <inttypes.h>
49 
51 #include "libavutil/opt.h"
52 #include "avcodec.h"
53 #include "get_bits.h"
54 #include "bytestream.h"
55 #include "internal.h"
56 #include "thread.h"
57 #include "unary.h"
58 #include "mathops.h"
59 #include "alac_data.h"
60 
61 #define ALAC_EXTRADATA_SIZE 36
62 
63 typedef struct ALACContext {
64  AVClass *class;
67  int channels;
68 
72 
78 
79  int extra_bits; /**< number of extra bits beyond 16-bit */
80  int nb_samples; /**< number of samples in the current frame */
81 
84 } ALACContext;
85 
86 static inline unsigned int decode_scalar(GetBitContext *gb, int k, int bps)
87 {
88  unsigned int x = get_unary_0_9(gb);
89 
90  if (x > 8) { /* RICE THRESHOLD */
91  /* use alternative encoding */
92  x = get_bits_long(gb, bps);
93  } else if (k != 1) {
94  int extrabits = show_bits(gb, k);
95 
96  /* multiply x by 2^k - 1, as part of their strange algorithm */
97  x = (x << k) - x;
98 
99  if (extrabits > 1) {
100  x += extrabits - 1;
101  skip_bits(gb, k);
102  } else
103  skip_bits(gb, k - 1);
104  }
105  return x;
106 }
107 
108 static int rice_decompress(ALACContext *alac, int32_t *output_buffer,
109  int nb_samples, int bps, int rice_history_mult)
110 {
111  int i;
112  unsigned int history = alac->rice_initial_history;
113  int sign_modifier = 0;
114 
115  for (i = 0; i < nb_samples; i++) {
116  int k;
117  unsigned int x;
118 
119  if(get_bits_left(&alac->gb) <= 0)
120  return -1;
121 
122  /* calculate rice param and decode next value */
123  k = av_log2((history >> 9) + 3);
124  k = FFMIN(k, alac->rice_limit);
125  x = decode_scalar(&alac->gb, k, bps);
126  x += sign_modifier;
127  sign_modifier = 0;
128  output_buffer[i] = (x >> 1) ^ -(x & 1);
129 
130  /* update the history */
131  if (x > 0xffff)
132  history = 0xffff;
133  else
134  history += x * rice_history_mult -
135  ((history * rice_history_mult) >> 9);
136 
137  /* special case: there may be compressed blocks of 0 */
138  if ((history < 128) && (i + 1 < nb_samples)) {
139  int block_size;
140 
141  /* calculate rice param and decode block size */
142  k = 7 - av_log2(history) + ((history + 16) >> 6);
143  k = FFMIN(k, alac->rice_limit);
144  block_size = decode_scalar(&alac->gb, k, 16);
145 
146  if (block_size > 0) {
147  if (block_size >= nb_samples - i) {
148  av_log(alac->avctx, AV_LOG_ERROR,
149  "invalid zero block size of %d %d %d\n", block_size,
150  nb_samples, i);
151  block_size = nb_samples - i - 1;
152  }
153  memset(&output_buffer[i + 1], 0,
154  block_size * sizeof(*output_buffer));
155  i += block_size;
156  }
157  if (block_size <= 0xffff)
158  sign_modifier = 1;
159  history = 0;
160  }
161  }
162  return 0;
163 }
164 
165 static inline int sign_only(int v)
166 {
167  return v ? FFSIGN(v) : 0;
168 }
169 
170 static void lpc_prediction(int32_t *error_buffer, int32_t *buffer_out,
171  int nb_samples, int bps, int16_t *lpc_coefs,
172  int lpc_order, int lpc_quant)
173 {
174  int i;
175  int32_t *pred = buffer_out;
176 
177  /* first sample always copies */
178  *buffer_out = *error_buffer;
179 
180  if (nb_samples <= 1)
181  return;
182 
183  if (!lpc_order) {
184  memcpy(&buffer_out[1], &error_buffer[1],
185  (nb_samples - 1) * sizeof(*buffer_out));
186  return;
187  }
188 
189  if (lpc_order == 31) {
190  /* simple 1st-order prediction */
191  for (i = 1; i < nb_samples; i++) {
192  buffer_out[i] = sign_extend(buffer_out[i - 1] + error_buffer[i],
193  bps);
194  }
195  return;
196  }
197 
198  /* read warm-up samples */
199  for (i = 1; i <= lpc_order && i < nb_samples; i++)
200  buffer_out[i] = sign_extend(buffer_out[i - 1] + error_buffer[i], bps);
201 
202  /* NOTE: 4 and 8 are very common cases that could be optimized. */
203 
204  for (; i < nb_samples; i++) {
205  int j;
206  int val = 0;
207  int error_val = error_buffer[i];
208  int error_sign;
209  int d = *pred++;
210 
211  /* LPC prediction */
212  for (j = 0; j < lpc_order; j++)
213  val += (pred[j] - d) * lpc_coefs[j];
214  val = (val + (1 << (lpc_quant - 1))) >> lpc_quant;
215  val += d + error_val;
216  buffer_out[i] = sign_extend(val, bps);
217 
218  /* adapt LPC coefficients */
219  error_sign = sign_only(error_val);
220  if (error_sign) {
221  for (j = 0; j < lpc_order && error_val * error_sign > 0; j++) {
222  int sign;
223  val = d - pred[j];
224  sign = sign_only(val) * error_sign;
225  lpc_coefs[j] -= sign;
226  val *= sign;
227  error_val -= (val >> lpc_quant) * (j + 1);
228  }
229  }
230  }
231 }
232 
233 static void decorrelate_stereo(int32_t *buffer[2], int nb_samples,
234  int decorr_shift, int decorr_left_weight)
235 {
236  int i;
237 
238  for (i = 0; i < nb_samples; i++) {
239  int32_t a, b;
240 
241  a = buffer[0][i];
242  b = buffer[1][i];
243 
244  a -= (b * decorr_left_weight) >> decorr_shift;
245  b += a;
246 
247  buffer[0][i] = b;
248  buffer[1][i] = a;
249  }
250 }
251 
252 static void append_extra_bits(int32_t *buffer[2], int32_t *extra_bits_buffer[2],
253  int extra_bits, int channels, int nb_samples)
254 {
255  int i, ch;
256 
257  for (ch = 0; ch < channels; ch++)
258  for (i = 0; i < nb_samples; i++)
259  buffer[ch][i] = (buffer[ch][i] << extra_bits) | extra_bits_buffer[ch][i];
260 }
261 
262 static int decode_element(AVCodecContext *avctx, AVFrame *frame, int ch_index,
263  int channels)
264 {
265  ALACContext *alac = avctx->priv_data;
266  int has_size, bps, is_compressed, decorr_shift, decorr_left_weight, ret;
267  uint32_t output_samples;
268  int i, ch;
269 
270  skip_bits(&alac->gb, 4); /* element instance tag */
271  skip_bits(&alac->gb, 12); /* unused header bits */
272 
273  /* the number of output samples is stored in the frame */
274  has_size = get_bits1(&alac->gb);
275 
276  alac->extra_bits = get_bits(&alac->gb, 2) << 3;
277  bps = alac->sample_size - alac->extra_bits + channels - 1;
278  if (bps > 32U) {
279  av_log(avctx, AV_LOG_ERROR, "bps is unsupported: %d\n", bps);
280  return AVERROR_PATCHWELCOME;
281  }
282 
283  /* whether the frame is compressed */
284  is_compressed = !get_bits1(&alac->gb);
285 
286  if (has_size)
287  output_samples = get_bits_long(&alac->gb, 32);
288  else
289  output_samples = alac->max_samples_per_frame;
290  if (!output_samples || output_samples > alac->max_samples_per_frame) {
291  av_log(avctx, AV_LOG_ERROR, "invalid samples per frame: %"PRIu32"\n",
292  output_samples);
293  return AVERROR_INVALIDDATA;
294  }
295  if (!alac->nb_samples) {
296  ThreadFrame tframe = { .f = frame };
297  /* get output buffer */
298  frame->nb_samples = output_samples;
299  if ((ret = ff_thread_get_buffer(avctx, &tframe, 0)) < 0)
300  return ret;
301  } else if (output_samples != alac->nb_samples) {
302  av_log(avctx, AV_LOG_ERROR, "sample count mismatch: %"PRIu32" != %d\n",
303  output_samples, alac->nb_samples);
304  return AVERROR_INVALIDDATA;
305  }
306  alac->nb_samples = output_samples;
307  if (alac->direct_output) {
308  for (ch = 0; ch < channels; ch++)
309  alac->output_samples_buffer[ch] = (int32_t *)frame->extended_data[ch_index + ch];
310  }
311 
312  if (is_compressed) {
313  int16_t lpc_coefs[2][32];
314  int lpc_order[2];
315  int prediction_type[2];
316  int lpc_quant[2];
317  int rice_history_mult[2];
318 
319  if (!alac->rice_limit) {
320  avpriv_request_sample(alac->avctx, "Compression with rice limit 0");
321  return AVERROR(ENOSYS);
322  }
323 
324  decorr_shift = get_bits(&alac->gb, 8);
325  decorr_left_weight = get_bits(&alac->gb, 8);
326 
327  for (ch = 0; ch < channels; ch++) {
328  prediction_type[ch] = get_bits(&alac->gb, 4);
329  lpc_quant[ch] = get_bits(&alac->gb, 4);
330  rice_history_mult[ch] = get_bits(&alac->gb, 3);
331  lpc_order[ch] = get_bits(&alac->gb, 5);
332 
333  if (lpc_order[ch] >= alac->max_samples_per_frame)
334  return AVERROR_INVALIDDATA;
335 
336  /* read the predictor table */
337  for (i = lpc_order[ch] - 1; i >= 0; i--)
338  lpc_coefs[ch][i] = get_sbits(&alac->gb, 16);
339  }
340 
341  if (alac->extra_bits) {
342  for (i = 0; i < alac->nb_samples; i++) {
343  if(get_bits_left(&alac->gb) <= 0)
344  return -1;
345  for (ch = 0; ch < channels; ch++)
346  alac->extra_bits_buffer[ch][i] = get_bits(&alac->gb, alac->extra_bits);
347  }
348  }
349  for (ch = 0; ch < channels; ch++) {
350  int ret=rice_decompress(alac, alac->predict_error_buffer[ch],
351  alac->nb_samples, bps,
352  rice_history_mult[ch] * alac->rice_history_mult / 4);
353  if(ret<0)
354  return ret;
355 
356  /* adaptive FIR filter */
357  if (prediction_type[ch] == 15) {
358  /* Prediction type 15 runs the adaptive FIR twice.
359  * The first pass uses the special-case coef_num = 31, while
360  * the second pass uses the coefs from the bitstream.
361  *
362  * However, this prediction type is not currently used by the
363  * reference encoder.
364  */
366  alac->predict_error_buffer[ch],
367  alac->nb_samples, bps, NULL, 31, 0);
368  } else if (prediction_type[ch] > 0) {
369  av_log(avctx, AV_LOG_WARNING, "unknown prediction type: %i\n",
370  prediction_type[ch]);
371  }
373  alac->output_samples_buffer[ch], alac->nb_samples,
374  bps, lpc_coefs[ch], lpc_order[ch], lpc_quant[ch]);
375  }
376  } else {
377  /* not compressed, easy case */
378  for (i = 0; i < alac->nb_samples; i++) {
379  if(get_bits_left(&alac->gb) <= 0)
380  return -1;
381  for (ch = 0; ch < channels; ch++) {
382  alac->output_samples_buffer[ch][i] =
383  get_sbits_long(&alac->gb, alac->sample_size);
384  }
385  }
386  alac->extra_bits = 0;
387  decorr_shift = 0;
388  decorr_left_weight = 0;
389  }
390 
391  if (alac->extra_bits && alac->extra_bit_bug) {
393  alac->extra_bits, channels, alac->nb_samples);
394  }
395 
396  if (channels == 2 && decorr_left_weight) {
398  decorr_shift, decorr_left_weight);
399  }
400 
401  if (alac->extra_bits && !alac->extra_bit_bug) {
403  alac->extra_bits, channels, alac->nb_samples);
404  }
405 
406  if(av_sample_fmt_is_planar(avctx->sample_fmt)) {
407  switch(alac->sample_size) {
408  case 16: {
409  for (ch = 0; ch < channels; ch++) {
410  int16_t *outbuffer = (int16_t *)frame->extended_data[ch_index + ch];
411  for (i = 0; i < alac->nb_samples; i++)
412  *outbuffer++ = alac->output_samples_buffer[ch][i];
413  }}
414  break;
415  case 24: {
416  for (ch = 0; ch < channels; ch++) {
417  for (i = 0; i < alac->nb_samples; i++)
418  alac->output_samples_buffer[ch][i] <<= 8;
419  }}
420  break;
421  }
422  }else{
423  switch(alac->sample_size) {
424  case 16: {
425  int16_t *outbuffer = ((int16_t *)frame->extended_data[0]) + ch_index;
426  for (i = 0; i < alac->nb_samples; i++) {
427  for (ch = 0; ch < channels; ch++)
428  *outbuffer++ = alac->output_samples_buffer[ch][i];
429  outbuffer += alac->channels - channels;
430  }
431  }
432  break;
433  case 24: {
434  int32_t *outbuffer = ((int32_t *)frame->extended_data[0]) + ch_index;
435  for (i = 0; i < alac->nb_samples; i++) {
436  for (ch = 0; ch < channels; ch++)
437  *outbuffer++ = alac->output_samples_buffer[ch][i] << 8;
438  outbuffer += alac->channels - channels;
439  }
440  }
441  break;
442  case 32: {
443  int32_t *outbuffer = ((int32_t *)frame->extended_data[0]) + ch_index;
444  for (i = 0; i < alac->nb_samples; i++) {
445  for (ch = 0; ch < channels; ch++)
446  *outbuffer++ = alac->output_samples_buffer[ch][i];
447  outbuffer += alac->channels - channels;
448  }
449  }
450  break;
451  }
452  }
453 
454  return 0;
455 }
456 
457 static int alac_decode_frame(AVCodecContext *avctx, void *data,
458  int *got_frame_ptr, AVPacket *avpkt)
459 {
460  ALACContext *alac = avctx->priv_data;
461  AVFrame *frame = data;
462  enum AlacRawDataBlockType element;
463  int channels;
464  int ch, ret, got_end;
465 
466  if ((ret = init_get_bits8(&alac->gb, avpkt->data, avpkt->size)) < 0)
467  return ret;
468 
469  got_end = 0;
470  alac->nb_samples = 0;
471  ch = 0;
472  while (get_bits_left(&alac->gb) >= 3) {
473  element = get_bits(&alac->gb, 3);
474  if (element == TYPE_END) {
475  got_end = 1;
476  break;
477  }
478  if (element > TYPE_CPE && element != TYPE_LFE) {
479  av_log(avctx, AV_LOG_ERROR, "syntax element unsupported: %d\n", element);
480  return AVERROR_PATCHWELCOME;
481  }
482 
483  channels = (element == TYPE_CPE) ? 2 : 1;
484  if (ch + channels > alac->channels ||
485  ff_alac_channel_layout_offsets[alac->channels - 1][ch] + channels > alac->channels) {
486  av_log(avctx, AV_LOG_ERROR, "invalid element channel count\n");
487  return AVERROR_INVALIDDATA;
488  }
489 
490  ret = decode_element(avctx, frame,
492  channels);
493  if (ret < 0 && get_bits_left(&alac->gb))
494  return ret;
495 
496  ch += channels;
497  }
498  if (!got_end) {
499  av_log(avctx, AV_LOG_ERROR, "no end tag found. incomplete packet.\n");
500  return AVERROR_INVALIDDATA;
501  }
502 
503  if (avpkt->size * 8 - get_bits_count(&alac->gb) > 8) {
504  av_log(avctx, AV_LOG_ERROR, "Error : %d bits left\n",
505  avpkt->size * 8 - get_bits_count(&alac->gb));
506  }
507 
508  if (alac->channels == ch)
509  *got_frame_ptr = 1;
510  else
511  av_log(avctx, AV_LOG_WARNING, "Failed to decode all channels\n");
512 
513  return avpkt->size;
514 }
515 
517 {
518  ALACContext *alac = avctx->priv_data;
519 
520  int ch;
521  for (ch = 0; ch < FFMIN(alac->channels, 2); ch++) {
522  av_freep(&alac->predict_error_buffer[ch]);
523  if (!alac->direct_output)
524  av_freep(&alac->output_samples_buffer[ch]);
525  av_freep(&alac->extra_bits_buffer[ch]);
526  }
527 
528  return 0;
529 }
530 
531 static int allocate_buffers(ALACContext *alac)
532 {
533  int ch;
534  int buf_size = alac->max_samples_per_frame * sizeof(int32_t);
535 
536  for (ch = 0; ch < FFMIN(alac->channels, 2); ch++) {
538  buf_size, buf_alloc_fail);
539 
540  alac->direct_output = alac->sample_size > 16 && av_sample_fmt_is_planar(alac->avctx->sample_fmt);
541  if (!alac->direct_output) {
543  buf_size, buf_alloc_fail);
544  }
545 
546  FF_ALLOC_OR_GOTO(alac->avctx, alac->extra_bits_buffer[ch],
547  buf_size, buf_alloc_fail);
548  }
549  return 0;
550 buf_alloc_fail:
551  alac_decode_close(alac->avctx);
552  return AVERROR(ENOMEM);
553 }
554 
555 static int alac_set_info(ALACContext *alac)
556 {
557  GetByteContext gb;
558 
559  bytestream2_init(&gb, alac->avctx->extradata,
560  alac->avctx->extradata_size);
561 
562  bytestream2_skipu(&gb, 12); // size:4, alac:4, version:4
563 
564  alac->max_samples_per_frame = bytestream2_get_be32u(&gb);
565  if (!alac->max_samples_per_frame ||
566  alac->max_samples_per_frame > INT_MAX / sizeof(int32_t)) {
567  av_log(alac->avctx, AV_LOG_ERROR,
568  "max samples per frame invalid: %"PRIu32"\n",
569  alac->max_samples_per_frame);
570  return AVERROR_INVALIDDATA;
571  }
572  bytestream2_skipu(&gb, 1); // compatible version
573  alac->sample_size = bytestream2_get_byteu(&gb);
574  alac->rice_history_mult = bytestream2_get_byteu(&gb);
575  alac->rice_initial_history = bytestream2_get_byteu(&gb);
576  alac->rice_limit = bytestream2_get_byteu(&gb);
577  alac->channels = bytestream2_get_byteu(&gb);
578  bytestream2_get_be16u(&gb); // maxRun
579  bytestream2_get_be32u(&gb); // max coded frame size
580  bytestream2_get_be32u(&gb); // average bitrate
581  bytestream2_get_be32u(&gb); // samplerate
582 
583  return 0;
584 }
585 
587 {
588  int ret;
589  int req_packed;
590  ALACContext *alac = avctx->priv_data;
591  alac->avctx = avctx;
592 
593  /* initialize from the extradata */
595  av_log(avctx, AV_LOG_ERROR, "extradata is too small\n");
596  return AVERROR_INVALIDDATA;
597  }
598  if (alac_set_info(alac)) {
599  av_log(avctx, AV_LOG_ERROR, "set_info failed\n");
600  return -1;
601  }
602 
604  switch (alac->sample_size) {
605  case 16: avctx->sample_fmt = req_packed ? AV_SAMPLE_FMT_S16 : AV_SAMPLE_FMT_S16P;
606  break;
607  case 24:
608  case 32: avctx->sample_fmt = req_packed ? AV_SAMPLE_FMT_S32 : AV_SAMPLE_FMT_S32P;
609  break;
610  default: avpriv_request_sample(avctx, "Sample depth %d", alac->sample_size);
611  return AVERROR_PATCHWELCOME;
612  }
613  avctx->bits_per_raw_sample = alac->sample_size;
614 
615  if (alac->channels < 1) {
616  av_log(avctx, AV_LOG_WARNING, "Invalid channel count\n");
617  alac->channels = avctx->channels;
618  } else {
619  if (alac->channels > ALAC_MAX_CHANNELS)
620  alac->channels = avctx->channels;
621  else
622  avctx->channels = alac->channels;
623  }
624  if (avctx->channels > ALAC_MAX_CHANNELS || avctx->channels <= 0 ) {
625  av_log(avctx, AV_LOG_ERROR, "Unsupported channel count: %d\n",
626  avctx->channels);
627  return AVERROR_PATCHWELCOME;
628  }
629  avctx->channel_layout = ff_alac_channel_layouts[alac->channels - 1];
630 
631  if ((ret = allocate_buffers(alac)) < 0) {
632  av_log(avctx, AV_LOG_ERROR, "Error allocating buffers\n");
633  return ret;
634  }
635 
636  return 0;
637 }
638 
640 {
641  ALACContext *alac = avctx->priv_data;
642  alac->avctx = avctx;
643  return allocate_buffers(alac);
644 }
645 
646 static const AVOption options[] = {
647  { "extra_bits_bug", "Force non-standard decoding process",
648  offsetof(ALACContext, extra_bit_bug), AV_OPT_TYPE_INT, { .i64 = 0 },
650  { NULL },
651 };
652 
653 static const AVClass alac_class = {
654  .class_name = "alac",
655  .item_name = av_default_item_name,
656  .option = options,
657  .version = LIBAVUTIL_VERSION_INT,
658 };
659 
661  .name = "alac",
662  .long_name = NULL_IF_CONFIG_SMALL("ALAC (Apple Lossless Audio Codec)"),
663  .type = AVMEDIA_TYPE_AUDIO,
664  .id = AV_CODEC_ID_ALAC,
665  .priv_data_size = sizeof(ALACContext),
667  .close = alac_decode_close,
670  .capabilities = CODEC_CAP_DR1 | CODEC_CAP_FRAME_THREADS,
671  .priv_class = &alac_class
672 };