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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 {
64  AVClass *class;
67  int channels;
68 
69  int32_t *predict_error_buffer[2];
70  int32_t *output_samples_buffer[2];
71  int32_t *extra_bits_buffer[2];
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  decorr_shift = get_bits(&alac->gb, 8);
320  decorr_left_weight = get_bits(&alac->gb, 8);
321 
322  for (ch = 0; ch < channels; ch++) {
323  prediction_type[ch] = get_bits(&alac->gb, 4);
324  lpc_quant[ch] = get_bits(&alac->gb, 4);
325  rice_history_mult[ch] = get_bits(&alac->gb, 3);
326  lpc_order[ch] = get_bits(&alac->gb, 5);
327 
328  if (lpc_order[ch] >= alac->max_samples_per_frame)
329  return AVERROR_INVALIDDATA;
330 
331  /* read the predictor table */
332  for (i = lpc_order[ch] - 1; i >= 0; i--)
333  lpc_coefs[ch][i] = get_sbits(&alac->gb, 16);
334  }
335 
336  if (alac->extra_bits) {
337  for (i = 0; i < alac->nb_samples; i++) {
338  if(get_bits_left(&alac->gb) <= 0)
339  return -1;
340  for (ch = 0; ch < channels; ch++)
341  alac->extra_bits_buffer[ch][i] = get_bits(&alac->gb, alac->extra_bits);
342  }
343  }
344  for (ch = 0; ch < channels; ch++) {
345  int ret=rice_decompress(alac, alac->predict_error_buffer[ch],
346  alac->nb_samples, bps,
347  rice_history_mult[ch] * alac->rice_history_mult / 4);
348  if(ret<0)
349  return ret;
350 
351  /* adaptive FIR filter */
352  if (prediction_type[ch] == 15) {
353  /* Prediction type 15 runs the adaptive FIR twice.
354  * The first pass uses the special-case coef_num = 31, while
355  * the second pass uses the coefs from the bitstream.
356  *
357  * However, this prediction type is not currently used by the
358  * reference encoder.
359  */
361  alac->predict_error_buffer[ch],
362  alac->nb_samples, bps, NULL, 31, 0);
363  } else if (prediction_type[ch] > 0) {
364  av_log(avctx, AV_LOG_WARNING, "unknown prediction type: %i\n",
365  prediction_type[ch]);
366  }
368  alac->output_samples_buffer[ch], alac->nb_samples,
369  bps, lpc_coefs[ch], lpc_order[ch], lpc_quant[ch]);
370  }
371  } else {
372  /* not compressed, easy case */
373  for (i = 0; i < alac->nb_samples; i++) {
374  if(get_bits_left(&alac->gb) <= 0)
375  return -1;
376  for (ch = 0; ch < channels; ch++) {
377  alac->output_samples_buffer[ch][i] =
378  get_sbits_long(&alac->gb, alac->sample_size);
379  }
380  }
381  alac->extra_bits = 0;
382  decorr_shift = 0;
383  decorr_left_weight = 0;
384  }
385 
386  if (alac->extra_bits && alac->extra_bit_bug) {
388  alac->extra_bits, channels, alac->nb_samples);
389  }
390 
391  if (channels == 2 && decorr_left_weight) {
393  decorr_shift, decorr_left_weight);
394  }
395 
396  if (alac->extra_bits && !alac->extra_bit_bug) {
398  alac->extra_bits, channels, alac->nb_samples);
399  }
400 
401  if(av_sample_fmt_is_planar(avctx->sample_fmt)) {
402  switch(alac->sample_size) {
403  case 16: {
404  for (ch = 0; ch < channels; ch++) {
405  int16_t *outbuffer = (int16_t *)frame->extended_data[ch_index + ch];
406  for (i = 0; i < alac->nb_samples; i++)
407  *outbuffer++ = alac->output_samples_buffer[ch][i];
408  }}
409  break;
410  case 24: {
411  for (ch = 0; ch < channels; ch++) {
412  for (i = 0; i < alac->nb_samples; i++)
413  alac->output_samples_buffer[ch][i] <<= 8;
414  }}
415  break;
416  }
417  }else{
418  switch(alac->sample_size) {
419  case 16: {
420  int16_t *outbuffer = ((int16_t *)frame->extended_data[0]) + ch_index;
421  for (i = 0; i < alac->nb_samples; i++) {
422  for (ch = 0; ch < channels; ch++)
423  *outbuffer++ = alac->output_samples_buffer[ch][i];
424  outbuffer += alac->channels - channels;
425  }
426  }
427  break;
428  case 24: {
429  int32_t *outbuffer = ((int32_t *)frame->extended_data[0]) + ch_index;
430  for (i = 0; i < alac->nb_samples; i++) {
431  for (ch = 0; ch < channels; ch++)
432  *outbuffer++ = alac->output_samples_buffer[ch][i] << 8;
433  outbuffer += alac->channels - channels;
434  }
435  }
436  break;
437  case 32: {
438  int32_t *outbuffer = ((int32_t *)frame->extended_data[0]) + ch_index;
439  for (i = 0; i < alac->nb_samples; i++) {
440  for (ch = 0; ch < channels; ch++)
441  *outbuffer++ = alac->output_samples_buffer[ch][i];
442  outbuffer += alac->channels - channels;
443  }
444  }
445  break;
446  }
447  }
448 
449  return 0;
450 }
451 
452 static int alac_decode_frame(AVCodecContext *avctx, void *data,
453  int *got_frame_ptr, AVPacket *avpkt)
454 {
455  ALACContext *alac = avctx->priv_data;
456  AVFrame *frame = data;
457  enum AlacRawDataBlockType element;
458  int channels;
459  int ch, ret, got_end;
460 
461  if ((ret = init_get_bits8(&alac->gb, avpkt->data, avpkt->size)) < 0)
462  return ret;
463 
464  got_end = 0;
465  alac->nb_samples = 0;
466  ch = 0;
467  while (get_bits_left(&alac->gb) >= 3) {
468  element = get_bits(&alac->gb, 3);
469  if (element == TYPE_END) {
470  got_end = 1;
471  break;
472  }
473  if (element > TYPE_CPE && element != TYPE_LFE) {
474  av_log(avctx, AV_LOG_ERROR, "syntax element unsupported: %d\n", element);
475  return AVERROR_PATCHWELCOME;
476  }
477 
478  channels = (element == TYPE_CPE) ? 2 : 1;
479  if (ch + channels > alac->channels ||
480  ff_alac_channel_layout_offsets[alac->channels - 1][ch] + channels > alac->channels) {
481  av_log(avctx, AV_LOG_ERROR, "invalid element channel count\n");
482  return AVERROR_INVALIDDATA;
483  }
484 
485  ret = decode_element(avctx, frame,
487  channels);
488  if (ret < 0 && get_bits_left(&alac->gb))
489  return ret;
490 
491  ch += channels;
492  }
493  if (!got_end) {
494  av_log(avctx, AV_LOG_ERROR, "no end tag found. incomplete packet.\n");
495  return AVERROR_INVALIDDATA;
496  }
497 
498  if (avpkt->size * 8 - get_bits_count(&alac->gb) > 8) {
499  av_log(avctx, AV_LOG_ERROR, "Error : %d bits left\n",
500  avpkt->size * 8 - get_bits_count(&alac->gb));
501  }
502 
503  if (alac->channels == ch)
504  *got_frame_ptr = 1;
505  else
506  av_log(avctx, AV_LOG_WARNING, "Failed to decode all channels\n");
507 
508  return avpkt->size;
509 }
510 
512 {
513  ALACContext *alac = avctx->priv_data;
514 
515  int ch;
516  for (ch = 0; ch < FFMIN(alac->channels, 2); ch++) {
517  av_freep(&alac->predict_error_buffer[ch]);
518  if (!alac->direct_output)
519  av_freep(&alac->output_samples_buffer[ch]);
520  av_freep(&alac->extra_bits_buffer[ch]);
521  }
522 
523  return 0;
524 }
525 
526 static int allocate_buffers(ALACContext *alac)
527 {
528  int ch;
529  int buf_size = alac->max_samples_per_frame * sizeof(int32_t);
530 
531  for (ch = 0; ch < FFMIN(alac->channels, 2); ch++) {
533  buf_size, buf_alloc_fail);
534 
535  alac->direct_output = alac->sample_size > 16 && av_sample_fmt_is_planar(alac->avctx->sample_fmt);
536  if (!alac->direct_output) {
538  buf_size, buf_alloc_fail);
539  }
540 
541  FF_ALLOC_OR_GOTO(alac->avctx, alac->extra_bits_buffer[ch],
542  buf_size, buf_alloc_fail);
543  }
544  return 0;
545 buf_alloc_fail:
546  alac_decode_close(alac->avctx);
547  return AVERROR(ENOMEM);
548 }
549 
550 static int alac_set_info(ALACContext *alac)
551 {
552  GetByteContext gb;
553 
554  bytestream2_init(&gb, alac->avctx->extradata,
555  alac->avctx->extradata_size);
556 
557  bytestream2_skipu(&gb, 12); // size:4, alac:4, version:4
558 
559  alac->max_samples_per_frame = bytestream2_get_be32u(&gb);
560  if (!alac->max_samples_per_frame ||
561  alac->max_samples_per_frame > INT_MAX / sizeof(int32_t)) {
562  av_log(alac->avctx, AV_LOG_ERROR,
563  "max samples per frame invalid: %"PRIu32"\n",
564  alac->max_samples_per_frame);
565  return AVERROR_INVALIDDATA;
566  }
567  bytestream2_skipu(&gb, 1); // compatible version
568  alac->sample_size = bytestream2_get_byteu(&gb);
569  alac->rice_history_mult = bytestream2_get_byteu(&gb);
570  alac->rice_initial_history = bytestream2_get_byteu(&gb);
571  alac->rice_limit = bytestream2_get_byteu(&gb);
572  alac->channels = bytestream2_get_byteu(&gb);
573  bytestream2_get_be16u(&gb); // maxRun
574  bytestream2_get_be32u(&gb); // max coded frame size
575  bytestream2_get_be32u(&gb); // average bitrate
576  bytestream2_get_be32u(&gb); // samplerate
577 
578  return 0;
579 }
580 
582 {
583  int ret;
584  int req_packed;
585  ALACContext *alac = avctx->priv_data;
586  alac->avctx = avctx;
587 
588  /* initialize from the extradata */
590  av_log(avctx, AV_LOG_ERROR, "extradata is too small\n");
591  return AVERROR_INVALIDDATA;
592  }
593  if (alac_set_info(alac)) {
594  av_log(avctx, AV_LOG_ERROR, "set_info failed\n");
595  return -1;
596  }
597 
599  switch (alac->sample_size) {
600  case 16: avctx->sample_fmt = req_packed ? AV_SAMPLE_FMT_S16 : AV_SAMPLE_FMT_S16P;
601  break;
602  case 24:
603  case 32: avctx->sample_fmt = req_packed ? AV_SAMPLE_FMT_S32 : AV_SAMPLE_FMT_S32P;
604  break;
605  default: avpriv_request_sample(avctx, "Sample depth %d", alac->sample_size);
606  return AVERROR_PATCHWELCOME;
607  }
608  avctx->bits_per_raw_sample = alac->sample_size;
609 
610  if (alac->channels < 1) {
611  av_log(avctx, AV_LOG_WARNING, "Invalid channel count\n");
612  alac->channels = avctx->channels;
613  } else {
614  if (alac->channels > ALAC_MAX_CHANNELS)
615  alac->channels = avctx->channels;
616  else
617  avctx->channels = alac->channels;
618  }
619  if (avctx->channels > ALAC_MAX_CHANNELS || avctx->channels <= 0 ) {
620  av_log(avctx, AV_LOG_ERROR, "Unsupported channel count: %d\n",
621  avctx->channels);
622  return AVERROR_PATCHWELCOME;
623  }
624  avctx->channel_layout = ff_alac_channel_layouts[alac->channels - 1];
625 
626  if ((ret = allocate_buffers(alac)) < 0) {
627  av_log(avctx, AV_LOG_ERROR, "Error allocating buffers\n");
628  return ret;
629  }
630 
631  return 0;
632 }
633 
635 {
636  ALACContext *alac = avctx->priv_data;
637  alac->avctx = avctx;
638  return allocate_buffers(alac);
639 }
640 
641 static const AVOption options[] = {
642  { "extra_bits_bug", "Force non-standard decoding process",
643  offsetof(ALACContext, extra_bit_bug), AV_OPT_TYPE_INT, { .i64 = 0 },
645  { NULL },
646 };
647 
648 static const AVClass alac_class = {
649  .class_name = "alac",
650  .item_name = av_default_item_name,
651  .option = options,
652  .version = LIBAVUTIL_VERSION_INT,
653 };
654 
656  .name = "alac",
657  .long_name = NULL_IF_CONFIG_SMALL("ALAC (Apple Lossless Audio Codec)"),
658  .type = AVMEDIA_TYPE_AUDIO,
659  .id = AV_CODEC_ID_ALAC,
660  .priv_data_size = sizeof(ALACContext),
665  .capabilities = CODEC_CAP_DR1 | CODEC_CAP_FRAME_THREADS,
666  .priv_class = &alac_class
667 };