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flac_parser.c
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1 /*
2  * FLAC parser
3  * Copyright (c) 2010 Michael Chinen
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  * FLAC parser
25  *
26  * The FLAC parser buffers input until FLAC_MIN_HEADERS has been found.
27  * Each time it finds and verifies a CRC-8 header it sees which of the
28  * FLAC_MAX_SEQUENTIAL_HEADERS that came before it have a valid CRC-16 footer
29  * that ends at the newly found header.
30  * Headers are scored by FLAC_HEADER_BASE_SCORE plus the max of it's crc-verified
31  * children, penalized by changes in sample rate, frame number, etc.
32  * The parser returns the frame with the highest score.
33  **/
34 
35 #include "libavutil/crc.h"
36 #include "libavutil/fifo.h"
37 #include "bytestream.h"
38 #include "parser.h"
39 #include "flac.h"
40 
41 /** maximum number of adjacent headers that compare CRCs against each other */
42 #define FLAC_MAX_SEQUENTIAL_HEADERS 3
43 /** minimum number of headers buffered and checked before returning frames */
44 #define FLAC_MIN_HEADERS 10
45 /** estimate for average size of a FLAC frame */
46 #define FLAC_AVG_FRAME_SIZE 8192
47 
48 /** scoring settings for score_header */
49 #define FLAC_HEADER_BASE_SCORE 10
50 #define FLAC_HEADER_CHANGED_PENALTY 7
51 #define FLAC_HEADER_CRC_FAIL_PENALTY 50
52 #define FLAC_HEADER_NOT_PENALIZED_YET 100000
53 #define FLAC_HEADER_NOT_SCORED_YET -100000
54 
55 /** largest possible size of flac header */
56 #define MAX_FRAME_HEADER_SIZE 16
57 
58 typedef struct FLACHeaderMarker {
59  int offset; /**< byte offset from start of FLACParseContext->buffer */
60  int *link_penalty; /**< pointer to array of local scores between this header
61  and the one at a distance equal array position */
62  int max_score; /**< maximum score found after checking each child that
63  has a valid CRC */
64  FLACFrameInfo fi; /**< decoded frame header info */
65  struct FLACHeaderMarker *next; /**< next CRC-8 verified header that
66  immediately follows this one in
67  the bytestream */
68  struct FLACHeaderMarker *best_child; /**< following frame header with
69  which this frame has the best
70  score with */
72 
73 typedef struct FLACParseContext {
74  AVCodecParserContext *pc; /**< parent context */
75  AVCodecContext *avctx; /**< codec context pointer for logging */
76  FLACHeaderMarker *headers; /**< linked-list that starts at the first
77  CRC-8 verified header within buffer */
78  FLACHeaderMarker *best_header; /**< highest scoring header within buffer */
79  int nb_headers_found; /**< number of headers found in the last
80  flac_parse() call */
81  int nb_headers_buffered; /**< number of headers that are buffered */
82  int best_header_valid; /**< flag set when the parser returns junk;
83  if set return best_header next time */
84  AVFifoBuffer *fifo_buf; /**< buffer to store all data until headers
85  can be verified */
86  int end_padded; /**< specifies if fifo_buf's end is padded */
87  uint8_t *wrap_buf; /**< general fifo read buffer when wrapped */
88  int wrap_buf_allocated_size; /**< actual allocated size of the buffer */
90 
91 static int frame_header_is_valid(AVCodecContext *avctx, const uint8_t *buf,
92  FLACFrameInfo *fi)
93 {
94  GetBitContext gb;
95  init_get_bits(&gb, buf, MAX_FRAME_HEADER_SIZE * 8);
96  return !ff_flac_decode_frame_header(avctx, &gb, fi, 127);
97 }
98 
99 /**
100  * Non-destructive fast fifo pointer fetching
101  * Returns a pointer from the specified offset.
102  * If possible the pointer points within the fifo buffer.
103  * Otherwise (if it would cause a wrap around,) a pointer to a user-specified
104  * buffer is used.
105  * The pointer can be NULL. In any case it will be reallocated to hold the size.
106  * If the returned pointer will be used after subsequent calls to flac_fifo_read_wrap
107  * then the subsequent calls should pass in a different wrap_buf so as to not
108  * overwrite the contents of the previous wrap_buf.
109  * This function is based on av_fifo_generic_read, which is why there is a comment
110  * about a memory barrier for SMP.
111  */
113  uint8_t** wrap_buf, int* allocated_size)
114 {
115  AVFifoBuffer *f = fpc->fifo_buf;
116  uint8_t *start = f->rptr + offset;
117  uint8_t *tmp_buf;
118 
119  if (start >= f->end)
120  start -= f->end - f->buffer;
121  if (f->end - start >= len)
122  return start;
123 
124  tmp_buf = av_fast_realloc(*wrap_buf, allocated_size, len);
125 
126  if (!tmp_buf) {
127  av_log(fpc->avctx, AV_LOG_ERROR,
128  "couldn't reallocate wrap buffer of size %d", len);
129  return NULL;
130  }
131  *wrap_buf = tmp_buf;
132  do {
133  int seg_len = FFMIN(f->end - start, len);
134  memcpy(tmp_buf, start, seg_len);
135  tmp_buf = (uint8_t*)tmp_buf + seg_len;
136 // memory barrier needed for SMP here in theory
137 
138  start += seg_len - (f->end - f->buffer);
139  len -= seg_len;
140  } while (len > 0);
141 
142  return *wrap_buf;
143 }
144 
145 /**
146  * Return a pointer in the fifo buffer where the offset starts at until
147  * the wrap point or end of request.
148  * len will contain the valid length of the returned buffer.
149  * A second call to flac_fifo_read (with new offset and len) should be called
150  * to get the post-wrap buf if the returned len is less than the requested.
151  **/
153 {
154  AVFifoBuffer *f = fpc->fifo_buf;
155  uint8_t *start = f->rptr + offset;
156 
157  if (start >= f->end)
158  start -= f->end - f->buffer;
159  *len = FFMIN(*len, f->end - start);
160  return start;
161 }
162 
164 {
165  FLACFrameInfo fi;
166  uint8_t *header_buf;
167  int size = 0;
168  header_buf = flac_fifo_read_wrap(fpc, offset,
170  &fpc->wrap_buf,
172  if (frame_header_is_valid(fpc->avctx, header_buf, &fi)) {
173  FLACHeaderMarker **end_handle = &fpc->headers;
174  int i;
175 
176  size = 0;
177  while (*end_handle) {
178  end_handle = &(*end_handle)->next;
179  size++;
180  }
181 
182  *end_handle = av_mallocz(sizeof(FLACHeaderMarker));
183  if (!*end_handle) {
184  av_log(fpc->avctx, AV_LOG_ERROR,
185  "couldn't allocate FLACHeaderMarker\n");
186  return AVERROR(ENOMEM);
187  }
188  (*end_handle)->fi = fi;
189  (*end_handle)->offset = offset;
190  (*end_handle)->link_penalty = av_malloc(sizeof(int) *
192  for (i = 0; i < FLAC_MAX_SEQUENTIAL_HEADERS; i++)
193  (*end_handle)->link_penalty[i] = FLAC_HEADER_NOT_PENALIZED_YET;
194 
195  fpc->nb_headers_found++;
196  size++;
197  }
198  return size;
199 }
200 
201 static int find_headers_search(FLACParseContext *fpc, uint8_t *buf, int buf_size,
202  int search_start)
203 
204 {
205  int size = 0, mod_offset = (buf_size - 1) % 4, i, j;
206  uint32_t x;
207 
208  for (i = 0; i < mod_offset; i++) {
209  if ((AV_RB16(buf + i) & 0xFFFE) == 0xFFF8)
210  size = find_headers_search_validate(fpc, search_start + i);
211  }
212 
213  for (; i < buf_size - 1; i += 4) {
214  x = AV_RB32(buf + i);
215  if (((x & ~(x + 0x01010101)) & 0x80808080)) {
216  for (j = 0; j < 4; j++) {
217  if ((AV_RB16(buf + i + j) & 0xFFFE) == 0xFFF8)
218  size = find_headers_search_validate(fpc, search_start + i + j);
219  }
220  }
221  }
222  return size;
223 }
224 
225 static int find_new_headers(FLACParseContext *fpc, int search_start)
226 {
228  int search_end, size = 0, read_len, temp;
229  uint8_t *buf;
230  fpc->nb_headers_found = 0;
231 
232  /* Search for a new header of at most 16 bytes. */
233  search_end = av_fifo_size(fpc->fifo_buf) - (MAX_FRAME_HEADER_SIZE - 1);
234  read_len = search_end - search_start + 1;
235  buf = flac_fifo_read(fpc, search_start, &read_len);
236  size = find_headers_search(fpc, buf, read_len, search_start);
237  search_start += read_len - 1;
238 
239  /* If fifo end was hit do the wrap around. */
240  if (search_start != search_end) {
241  uint8_t wrap[2];
242 
243  wrap[0] = buf[read_len - 1];
244  read_len = search_end - search_start + 1;
245 
246  /* search_start + 1 is the post-wrap offset in the fifo. */
247  buf = flac_fifo_read(fpc, search_start + 1, &read_len);
248  wrap[1] = buf[0];
249 
250  if ((AV_RB16(wrap) & 0xFFFE) == 0xFFF8) {
251  temp = find_headers_search_validate(fpc, search_start);
252  size = FFMAX(size, temp);
253  }
254  search_start++;
255 
256  /* Continue to do the last half of the wrap. */
257  temp = find_headers_search(fpc, buf, read_len, search_start);
258  size = FFMAX(size, temp);
259  search_start += read_len - 1;
260  }
261 
262  /* Return the size even if no new headers were found. */
263  if (!size && fpc->headers)
264  for (end = fpc->headers; end; end = end->next)
265  size++;
266  return size;
267 }
268 
270  FLACHeaderMarker *header,
271  FLACHeaderMarker *child,
272  int log_level_offset)
273 {
274  FLACFrameInfo *header_fi = &header->fi, *child_fi = &child->fi;
275  int deduction = 0, deduction_expected = 0, i;
276  if (child_fi->samplerate != header_fi->samplerate) {
277  deduction += FLAC_HEADER_CHANGED_PENALTY;
278  av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
279  "sample rate change detected in adjacent frames\n");
280  }
281  if (child_fi->bps != header_fi->bps) {
282  deduction += FLAC_HEADER_CHANGED_PENALTY;
283  av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
284  "bits per sample change detected in adjacent frames\n");
285  }
286  if (child_fi->is_var_size != header_fi->is_var_size) {
287  /* Changing blocking strategy not allowed per the spec */
288  deduction += FLAC_HEADER_BASE_SCORE;
289  av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
290  "blocking strategy change detected in adjacent frames\n");
291  }
292  if (child_fi->channels != header_fi->channels) {
293  deduction += FLAC_HEADER_CHANGED_PENALTY;
294  av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
295  "number of channels change detected in adjacent frames\n");
296  }
297  /* Check sample and frame numbers. */
298  if ((child_fi->frame_or_sample_num - header_fi->frame_or_sample_num
299  != header_fi->blocksize) &&
300  (child_fi->frame_or_sample_num
301  != header_fi->frame_or_sample_num + 1)) {
302  FLACHeaderMarker *curr;
303  int expected_frame_num, expected_sample_num;
304  /* If there are frames in the middle we expect this deduction,
305  as they are probably valid and this one follows it */
306 
307  expected_frame_num = expected_sample_num = header_fi->frame_or_sample_num;
308  curr = header;
309  while (curr != child) {
310  /* Ignore frames that failed all crc checks */
311  for (i = 0; i < FLAC_MAX_SEQUENTIAL_HEADERS; i++) {
313  expected_frame_num++;
314  expected_sample_num += curr->fi.blocksize;
315  break;
316  }
317  }
318  curr = curr->next;
319  }
320 
321  if (expected_frame_num == child_fi->frame_or_sample_num ||
322  expected_sample_num == child_fi->frame_or_sample_num)
323  deduction_expected = deduction ? 0 : 1;
324 
325  deduction += FLAC_HEADER_CHANGED_PENALTY;
326  av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
327  "sample/frame number mismatch in adjacent frames\n");
328  }
329 
330  /* If we have suspicious headers, check the CRC between them */
331  if (deduction && !deduction_expected) {
332  FLACHeaderMarker *curr;
333  int read_len;
334  uint8_t *buf;
335  uint32_t crc = 1;
336  int inverted_test = 0;
337 
338  /* Since CRC is expensive only do it if we haven't yet.
339  This assumes a CRC penalty is greater than all other check penalties */
340  curr = header->next;
341  for (i = 0; i < FLAC_MAX_SEQUENTIAL_HEADERS && curr != child; i++)
342  curr = curr->next;
343 
346  FLACHeaderMarker *start, *end;
347 
348  /* Although overlapping chains are scored, the crc should never
349  have to be computed twice for a single byte. */
350  start = header;
351  end = child;
352  if (i > 0 &&
353  header->link_penalty[i - 1] >= FLAC_HEADER_CRC_FAIL_PENALTY) {
354  while (start->next != child)
355  start = start->next;
356  inverted_test = 1;
357  } else if (i > 0 &&
358  header->next->link_penalty[i-1] >=
360  end = header->next;
361  inverted_test = 1;
362  }
363 
364  read_len = end->offset - start->offset;
365  buf = flac_fifo_read(fpc, start->offset, &read_len);
366  crc = av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0, buf, read_len);
367  read_len = (end->offset - start->offset) - read_len;
368 
369  if (read_len) {
370  buf = flac_fifo_read(fpc, end->offset - read_len, &read_len);
371  crc = av_crc(av_crc_get_table(AV_CRC_16_ANSI), crc, buf, read_len);
372  }
373  }
374 
375  if (!crc ^ !inverted_test) {
376  deduction += FLAC_HEADER_CRC_FAIL_PENALTY;
377  av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
378  "crc check failed from offset %i (frame %"PRId64") to %i (frame %"PRId64")\n",
379  header->offset, header_fi->frame_or_sample_num,
380  child->offset, child_fi->frame_or_sample_num);
381  }
382  }
383  return deduction;
384 }
385 
386 /**
387  * Score a header.
388  *
389  * Give FLAC_HEADER_BASE_SCORE points to a frame for existing.
390  * If it has children, (subsequent frames of which the preceding CRC footer
391  * validates against this one,) then take the maximum score of the children,
392  * with a penalty of FLAC_HEADER_CHANGED_PENALTY applied for each change to
393  * bps, sample rate, channels, but not decorrelation mode, or blocksize,
394  * because it can change often.
395  **/
397 {
398  FLACHeaderMarker *child;
399  int dist = 0;
400  int child_score;
401 
402  if (header->max_score != FLAC_HEADER_NOT_SCORED_YET)
403  return header->max_score;
404 
406 
407  /* Check and compute the children's scores. */
408  child = header->next;
409  for (dist = 0; dist < FLAC_MAX_SEQUENTIAL_HEADERS && child; dist++) {
410  /* Look at the child's frame header info and penalize suspicious
411  changes between the headers. */
412  if (header->link_penalty[dist] == FLAC_HEADER_NOT_PENALIZED_YET) {
413  header->link_penalty[dist] = check_header_mismatch(fpc, header,
414  child, AV_LOG_DEBUG);
415  }
416  child_score = score_header(fpc, child) - header->link_penalty[dist];
417 
418  if (FLAC_HEADER_BASE_SCORE + child_score > header->max_score) {
419  /* Keep the child because the frame scoring is dynamic. */
420  header->best_child = child;
421  header->max_score = FLAC_HEADER_BASE_SCORE + child_score;
422  }
423  child = child->next;
424  }
425 
426  return header->max_score;
427 }
428 
430 {
431  FLACHeaderMarker *curr;
432  int best_score = FLAC_HEADER_NOT_SCORED_YET;
433  /* First pass to clear all old scores. */
434  for (curr = fpc->headers; curr; curr = curr->next)
436 
437  /* Do a second pass to score them all. */
438  for (curr = fpc->headers; curr; curr = curr->next) {
439  if (score_header(fpc, curr) > best_score) {
440  fpc->best_header = curr;
441  best_score = curr->max_score;
442  }
443  }
444 }
445 
446 static int get_best_header(FLACParseContext* fpc, const uint8_t **poutbuf,
447  int *poutbuf_size)
448 {
449  FLACHeaderMarker *header = fpc->best_header;
450  FLACHeaderMarker *child = header->best_child;
451  if (!child) {
452  *poutbuf_size = av_fifo_size(fpc->fifo_buf) - header->offset;
453  } else {
454  *poutbuf_size = child->offset - header->offset;
455 
456  /* If the child has suspicious changes, log them */
457  check_header_mismatch(fpc, header, child, 0);
458  }
459 
460  if (header->fi.channels != fpc->avctx->channels ||
461  (!fpc->avctx->channel_layout && header->fi.channels <= 6)) {
462  fpc->avctx->channels = header->fi.channels;
464  }
465  fpc->avctx->sample_rate = header->fi.samplerate;
466  fpc->pc->duration = header->fi.blocksize;
467  *poutbuf = flac_fifo_read_wrap(fpc, header->offset, *poutbuf_size,
468  &fpc->wrap_buf,
470 
471  fpc->best_header_valid = 0;
472  /* Return the negative overread index so the client can compute pos.
473  This should be the amount overread to the beginning of the child */
474  if (child)
475  return child->offset - av_fifo_size(fpc->fifo_buf);
476  return 0;
477 }
478 
480  const uint8_t **poutbuf, int *poutbuf_size,
481  const uint8_t *buf, int buf_size)
482 {
483  FLACParseContext *fpc = s->priv_data;
484  FLACHeaderMarker *curr;
485  int nb_headers;
486  const uint8_t *read_end = buf;
487  const uint8_t *read_start = buf;
488 
490  FLACFrameInfo fi;
491  if (frame_header_is_valid(avctx, buf, &fi))
492  s->duration = fi.blocksize;
493  *poutbuf = buf;
494  *poutbuf_size = buf_size;
495  return buf_size;
496  }
497 
498  fpc->avctx = avctx;
499  if (fpc->best_header_valid)
500  return get_best_header(fpc, poutbuf, poutbuf_size);
501 
502  /* If a best_header was found last call remove it with the buffer data. */
503  if (fpc->best_header && fpc->best_header->best_child) {
505  FLACHeaderMarker *best_child = fpc->best_header->best_child;
506 
507  /* Remove headers in list until the end of the best_header. */
508  for (curr = fpc->headers; curr != best_child; curr = temp) {
509  if (curr != fpc->best_header) {
510  av_log(avctx, AV_LOG_DEBUG,
511  "dropping low score %i frame header from offset %i to %i\n",
512  curr->max_score, curr->offset, curr->next->offset);
513  }
514  temp = curr->next;
515  av_freep(&curr->link_penalty);
516  av_free(curr);
517  fpc->nb_headers_buffered--;
518  }
519  /* Release returned data from ring buffer. */
520  av_fifo_drain(fpc->fifo_buf, best_child->offset);
521 
522  /* Fix the offset for the headers remaining to match the new buffer. */
523  for (curr = best_child->next; curr; curr = curr->next)
524  curr->offset -= best_child->offset;
525 
526  fpc->nb_headers_buffered--;
527  best_child->offset = 0;
528  fpc->headers = best_child;
530  fpc->best_header = best_child;
531  return get_best_header(fpc, poutbuf, poutbuf_size);
532  }
533  fpc->best_header = NULL;
534  } else if (fpc->best_header) {
535  /* No end frame no need to delete the buffer; probably eof */
537 
538  for (curr = fpc->headers; curr != fpc->best_header; curr = temp) {
539  temp = curr->next;
540  av_freep(&curr->link_penalty);
541  av_free(curr);
542  }
543  fpc->headers = fpc->best_header->next;
545  av_freep(&fpc->best_header);
546  }
547 
548  /* Find and score new headers. */
549  /* buf_size is to zero when padding, so check for this since we do */
550  /* not want to try to read more input once we have found the end. */
551  /* Note that as (non-modified) parameters, buf can be non-NULL, */
552  /* while buf_size is 0. */
553  while ((buf && buf_size && read_end < buf + buf_size &&
555  || ((!buf || !buf_size) && !fpc->end_padded)) {
556  int start_offset;
557 
558  /* Pad the end once if EOF, to check the final region for headers. */
559  if (!buf || !buf_size) {
560  fpc->end_padded = 1;
561  buf_size = MAX_FRAME_HEADER_SIZE;
562  read_end = read_start + MAX_FRAME_HEADER_SIZE;
563  } else {
564  /* The maximum read size is the upper-bound of what the parser
565  needs to have the required number of frames buffered */
566  int nb_desired = FLAC_MIN_HEADERS - fpc->nb_headers_buffered + 1;
567  read_end = read_end + FFMIN(buf + buf_size - read_end,
568  nb_desired * FLAC_AVG_FRAME_SIZE);
569  }
570 
571  /* Fill the buffer. */
572  if ( av_fifo_space(fpc->fifo_buf) < read_end - read_start
573  && av_fifo_realloc2(fpc->fifo_buf, (read_end - read_start) + 2*av_fifo_size(fpc->fifo_buf)) < 0) {
574  av_log(avctx, AV_LOG_ERROR,
575  "couldn't reallocate buffer of size %td\n",
576  (read_end - read_start) + av_fifo_size(fpc->fifo_buf));
577  goto handle_error;
578  }
579 
580  if (buf && buf_size) {
581  av_fifo_generic_write(fpc->fifo_buf, (void*) read_start,
582  read_end - read_start, NULL);
583  } else {
584  int8_t pad[MAX_FRAME_HEADER_SIZE] = { 0 };
585  av_fifo_generic_write(fpc->fifo_buf, (void*) pad, sizeof(pad), NULL);
586  }
587 
588  /* Tag headers and update sequences. */
589  start_offset = av_fifo_size(fpc->fifo_buf) -
590  ((read_end - read_start) + (MAX_FRAME_HEADER_SIZE - 1));
591  start_offset = FFMAX(0, start_offset);
592  nb_headers = find_new_headers(fpc, start_offset);
593 
594  if (nb_headers < 0) {
595  av_log(avctx, AV_LOG_ERROR,
596  "find_new_headers couldn't allocate FLAC header\n");
597  goto handle_error;
598  }
599 
600  fpc->nb_headers_buffered = nb_headers;
601  /* Wait till FLAC_MIN_HEADERS to output a valid frame. */
602  if (!fpc->end_padded && fpc->nb_headers_buffered < FLAC_MIN_HEADERS) {
603  if (buf && read_end < buf + buf_size) {
604  read_start = read_end;
605  continue;
606  } else {
607  goto handle_error;
608  }
609  }
610 
611  /* If headers found, update the scores since we have longer chains. */
612  if (fpc->end_padded || fpc->nb_headers_found)
613  score_sequences(fpc);
614 
615  /* restore the state pre-padding */
616  if (fpc->end_padded) {
617  int warp = fpc->fifo_buf->wptr - fpc->fifo_buf->buffer < MAX_FRAME_HEADER_SIZE;
618  /* HACK: drain the tail of the fifo */
621  if (warp) {
622  fpc->fifo_buf->wptr += fpc->fifo_buf->end -
623  fpc->fifo_buf->buffer;
624  }
625  buf_size = 0;
626  read_start = read_end = NULL;
627  }
628  }
629 
630  curr = fpc->headers;
631  for (curr = fpc->headers; curr; curr = curr->next)
632  if (!fpc->best_header || curr->max_score > fpc->best_header->max_score)
633  fpc->best_header = curr;
634 
635  if (fpc->best_header) {
636  fpc->best_header_valid = 1;
637  if (fpc->best_header->offset > 0) {
638  /* Output a junk frame. */
639  av_log(avctx, AV_LOG_DEBUG, "Junk frame till offset %i\n",
640  fpc->best_header->offset);
641 
642  /* Set duration to 0. It is unknown or invalid in a junk frame. */
643  s->duration = 0;
644  *poutbuf_size = fpc->best_header->offset;
645  *poutbuf = flac_fifo_read_wrap(fpc, 0, *poutbuf_size,
646  &fpc->wrap_buf,
648  return buf_size ? (read_end - buf) : (fpc->best_header->offset -
649  av_fifo_size(fpc->fifo_buf));
650  }
651  if (!buf_size)
652  return get_best_header(fpc, poutbuf, poutbuf_size);
653  }
654 
655 handle_error:
656  *poutbuf = NULL;
657  *poutbuf_size = 0;
658  return read_end - buf;
659 }
660 
662 {
663  FLACParseContext *fpc = c->priv_data;
664  fpc->pc = c;
665  /* There will generally be FLAC_MIN_HEADERS buffered in the fifo before
666  it drains. This is allocated early to avoid slow reallocation. */
668  return 0;
669 }
670 
672 {
673  FLACParseContext *fpc = c->priv_data;
674  FLACHeaderMarker *curr = fpc->headers, *temp;
675 
676  while (curr) {
677  temp = curr->next;
678  av_freep(&curr->link_penalty);
679  av_free(curr);
680  curr = temp;
681  }
682  av_fifo_free(fpc->fifo_buf);
683  av_free(fpc->wrap_buf);
684 }
685 
688  .priv_data_size = sizeof(FLACParseContext),
689  .parser_init = flac_parse_init,
690  .parser_parse = flac_parse,
691  .parser_close = flac_parse_close,
692 };