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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 its 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/attributes.h"
36 #include "libavutil/crc.h"
37 #include "libavutil/fifo.h"
38 #include "bytestream.h"
39 #include "parser.h"
40 #include "flac.h"
41 
42 /** maximum number of adjacent headers that compare CRCs against each other */
43 #define FLAC_MAX_SEQUENTIAL_HEADERS 3
44 /** minimum number of headers buffered and checked before returning frames */
45 #define FLAC_MIN_HEADERS 10
46 /** estimate for average size of a FLAC frame */
47 #define FLAC_AVG_FRAME_SIZE 8192
48 
49 /** scoring settings for score_header */
50 #define FLAC_HEADER_BASE_SCORE 10
51 #define FLAC_HEADER_CHANGED_PENALTY 7
52 #define FLAC_HEADER_CRC_FAIL_PENALTY 50
53 #define FLAC_HEADER_NOT_PENALIZED_YET 100000
54 #define FLAC_HEADER_NOT_SCORED_YET -100000
55 
56 /** largest possible size of flac header */
57 #define MAX_FRAME_HEADER_SIZE 16
58 
59 typedef struct FLACHeaderMarker {
60  int offset; /**< byte offset from start of FLACParseContext->buffer */
61  int *link_penalty; /**< pointer to array of local scores between this header
62  and the one at a distance equal array position */
63  int max_score; /**< maximum score found after checking each child that
64  has a valid CRC */
65  FLACFrameInfo fi; /**< decoded frame header info */
66  struct FLACHeaderMarker *next; /**< next CRC-8 verified header that
67  immediately follows this one in
68  the bytestream */
69  struct FLACHeaderMarker *best_child; /**< following frame header with
70  which this frame has the best
71  score with */
73 
74 typedef struct FLACParseContext {
75  AVCodecParserContext *pc; /**< parent context */
76  AVCodecContext *avctx; /**< codec context pointer for logging */
77  FLACHeaderMarker *headers; /**< linked-list that starts at the first
78  CRC-8 verified header within buffer */
79  FLACHeaderMarker *best_header; /**< highest scoring header within buffer */
80  int nb_headers_found; /**< number of headers found in the last
81  flac_parse() call */
82  int nb_headers_buffered; /**< number of headers that are buffered */
83  int best_header_valid; /**< flag set when the parser returns junk;
84  if set return best_header next time */
85  AVFifoBuffer *fifo_buf; /**< buffer to store all data until headers
86  can be verified */
87  int end_padded; /**< specifies if fifo_buf's end is padded */
88  uint8_t *wrap_buf; /**< general fifo read buffer when wrapped */
89  int wrap_buf_allocated_size; /**< actual allocated size of the buffer */
90  FLACFrameInfo last_fi; /**< last decoded frame header info */
91  int last_fi_valid; /**< set if last_fi is valid */
93 
94 static int frame_header_is_valid(AVCodecContext *avctx, const uint8_t *buf,
96 {
97  GetBitContext gb;
98  init_get_bits(&gb, buf, MAX_FRAME_HEADER_SIZE * 8);
99  return !ff_flac_decode_frame_header(avctx, &gb, fi, 127);
100 }
101 
102 /**
103  * Non-destructive fast fifo pointer fetching
104  * Returns a pointer from the specified offset.
105  * If possible the pointer points within the fifo buffer.
106  * Otherwise (if it would cause a wrap around,) a pointer to a user-specified
107  * buffer is used.
108  * The pointer can be NULL. In any case it will be reallocated to hold the size.
109  * If the returned pointer will be used after subsequent calls to flac_fifo_read_wrap
110  * then the subsequent calls should pass in a different wrap_buf so as to not
111  * overwrite the contents of the previous wrap_buf.
112  * This function is based on av_fifo_generic_read, which is why there is a comment
113  * about a memory barrier for SMP.
114  */
116  uint8_t** wrap_buf, int* allocated_size)
117 {
118  AVFifoBuffer *f = fpc->fifo_buf;
119  uint8_t *start = f->rptr + offset;
120  uint8_t *tmp_buf;
121 
122  if (start >= f->end)
123  start -= f->end - f->buffer;
124  if (f->end - start >= len)
125  return start;
126 
127  tmp_buf = av_fast_realloc(*wrap_buf, allocated_size, len);
128 
129  if (!tmp_buf) {
130  av_log(fpc->avctx, AV_LOG_ERROR,
131  "couldn't reallocate wrap buffer of size %d", len);
132  return NULL;
133  }
134  *wrap_buf = tmp_buf;
135  do {
136  int seg_len = FFMIN(f->end - start, len);
137  memcpy(tmp_buf, start, seg_len);
138  tmp_buf = (uint8_t*)tmp_buf + seg_len;
139 // memory barrier needed for SMP here in theory
140 
141  start += seg_len - (f->end - f->buffer);
142  len -= seg_len;
143  } while (len > 0);
144 
145  return *wrap_buf;
146 }
147 
148 /**
149  * Return a pointer in the fifo buffer where the offset starts at until
150  * the wrap point or end of request.
151  * len will contain the valid length of the returned buffer.
152  * A second call to flac_fifo_read (with new offset and len) should be called
153  * to get the post-wrap buf if the returned len is less than the requested.
154  **/
156 {
157  AVFifoBuffer *f = fpc->fifo_buf;
158  uint8_t *start = f->rptr + offset;
159 
160  if (start >= f->end)
161  start -= f->end - f->buffer;
162  *len = FFMIN(*len, f->end - start);
163  return start;
164 }
165 
167 {
169  uint8_t *header_buf;
170  int size = 0;
171  header_buf = flac_fifo_read_wrap(fpc, offset,
173  &fpc->wrap_buf,
175  if (frame_header_is_valid(fpc->avctx, header_buf, &fi)) {
176  FLACHeaderMarker **end_handle = &fpc->headers;
177  int i;
178 
179  size = 0;
180  while (*end_handle) {
181  end_handle = &(*end_handle)->next;
182  size++;
183  }
184 
185  *end_handle = av_mallocz(sizeof(FLACHeaderMarker));
186  if (!*end_handle) {
187  av_log(fpc->avctx, AV_LOG_ERROR,
188  "couldn't allocate FLACHeaderMarker\n");
189  return AVERROR(ENOMEM);
190  }
191  (*end_handle)->fi = fi;
192  (*end_handle)->offset = offset;
193  (*end_handle)->link_penalty = av_malloc(sizeof(int) *
195  for (i = 0; i < FLAC_MAX_SEQUENTIAL_HEADERS; i++)
196  (*end_handle)->link_penalty[i] = FLAC_HEADER_NOT_PENALIZED_YET;
197 
198  fpc->nb_headers_found++;
199  size++;
200  }
201  return size;
202 }
203 
204 static int find_headers_search(FLACParseContext *fpc, uint8_t *buf, int buf_size,
205  int search_start)
206 
207 {
208  int size = 0, mod_offset = (buf_size - 1) % 4, i, j;
209  uint32_t x;
210 
211  for (i = 0; i < mod_offset; i++) {
212  if ((AV_RB16(buf + i) & 0xFFFE) == 0xFFF8)
213  size = find_headers_search_validate(fpc, search_start + i);
214  }
215 
216  for (; i < buf_size - 1; i += 4) {
217  x = AV_RB32(buf + i);
218  if (((x & ~(x + 0x01010101)) & 0x80808080)) {
219  for (j = 0; j < 4; j++) {
220  if ((AV_RB16(buf + i + j) & 0xFFFE) == 0xFFF8)
221  size = find_headers_search_validate(fpc, search_start + i + j);
222  }
223  }
224  }
225  return size;
226 }
227 
228 static int find_new_headers(FLACParseContext *fpc, int search_start)
229 {
231  int search_end, size = 0, read_len, temp;
232  uint8_t *buf;
233  fpc->nb_headers_found = 0;
234 
235  /* Search for a new header of at most 16 bytes. */
236  search_end = av_fifo_size(fpc->fifo_buf) - (MAX_FRAME_HEADER_SIZE - 1);
237  read_len = search_end - search_start + 1;
238  buf = flac_fifo_read(fpc, search_start, &read_len);
239  size = find_headers_search(fpc, buf, read_len, search_start);
240  search_start += read_len - 1;
241 
242  /* If fifo end was hit do the wrap around. */
243  if (search_start != search_end) {
244  uint8_t wrap[2];
245 
246  wrap[0] = buf[read_len - 1];
247  read_len = search_end - search_start + 1;
248 
249  /* search_start + 1 is the post-wrap offset in the fifo. */
250  buf = flac_fifo_read(fpc, search_start + 1, &read_len);
251  wrap[1] = buf[0];
252 
253  if ((AV_RB16(wrap) & 0xFFFE) == 0xFFF8) {
254  temp = find_headers_search_validate(fpc, search_start);
255  size = FFMAX(size, temp);
256  }
257  search_start++;
258 
259  /* Continue to do the last half of the wrap. */
260  temp = find_headers_search(fpc, buf, read_len, search_start);
261  size = FFMAX(size, temp);
262  search_start += read_len - 1;
263  }
264 
265  /* Return the size even if no new headers were found. */
266  if (!size && fpc->headers)
267  for (end = fpc->headers; end; end = end->next)
268  size++;
269  return size;
270 }
271 
273  FLACFrameInfo *header_fi,
274  FLACFrameInfo *child_fi,
275  int log_level_offset)
276 {
277  int deduction = 0;
278  if (child_fi->samplerate != header_fi->samplerate) {
279  deduction += FLAC_HEADER_CHANGED_PENALTY;
280  av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
281  "sample rate change detected in adjacent frames\n");
282  }
283  if (child_fi->bps != header_fi->bps) {
284  deduction += FLAC_HEADER_CHANGED_PENALTY;
285  av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
286  "bits per sample change detected in adjacent frames\n");
287  }
288  if (child_fi->is_var_size != header_fi->is_var_size) {
289  /* Changing blocking strategy not allowed per the spec */
290  deduction += FLAC_HEADER_BASE_SCORE;
291  av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
292  "blocking strategy change detected in adjacent frames\n");
293  }
294  if (child_fi->channels != header_fi->channels) {
295  deduction += FLAC_HEADER_CHANGED_PENALTY;
296  av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
297  "number of channels change detected in adjacent frames\n");
298  }
299  return deduction;
300 }
301 
305  int log_level_offset)
306 {
307  FLACFrameInfo *header_fi = &header->fi, *child_fi = &child->fi;
308  int deduction, deduction_expected = 0, i;
309  deduction = check_header_fi_mismatch(fpc, header_fi, child_fi,
310  log_level_offset);
311  /* Check sample and frame numbers. */
312  if ((child_fi->frame_or_sample_num - header_fi->frame_or_sample_num
313  != header_fi->blocksize) &&
314  (child_fi->frame_or_sample_num
315  != header_fi->frame_or_sample_num + 1)) {
316  FLACHeaderMarker *curr;
317  int expected_frame_num, expected_sample_num;
318  /* If there are frames in the middle we expect this deduction,
319  as they are probably valid and this one follows it */
320 
321  expected_frame_num = expected_sample_num = header_fi->frame_or_sample_num;
322  curr = header;
323  while (curr != child) {
324  /* Ignore frames that failed all crc checks */
325  for (i = 0; i < FLAC_MAX_SEQUENTIAL_HEADERS; i++) {
327  expected_frame_num++;
328  expected_sample_num += curr->fi.blocksize;
329  break;
330  }
331  }
332  curr = curr->next;
333  }
334 
335  if (expected_frame_num == child_fi->frame_or_sample_num ||
336  expected_sample_num == child_fi->frame_or_sample_num)
337  deduction_expected = deduction ? 0 : 1;
338 
339  deduction += FLAC_HEADER_CHANGED_PENALTY;
340  av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
341  "sample/frame number mismatch in adjacent frames\n");
342  }
343 
344  /* If we have suspicious headers, check the CRC between them */
345  if (deduction && !deduction_expected) {
346  FLACHeaderMarker *curr;
347  int read_len;
348  uint8_t *buf;
349  uint32_t crc = 1;
350  int inverted_test = 0;
351 
352  /* Since CRC is expensive only do it if we haven't yet.
353  This assumes a CRC penalty is greater than all other check penalties */
354  curr = header->next;
355  for (i = 0; i < FLAC_MAX_SEQUENTIAL_HEADERS && curr != child; i++)
356  curr = curr->next;
357 
361 
362  /* Although overlapping chains are scored, the crc should never
363  have to be computed twice for a single byte. */
364  start = header;
365  end = child;
366  if (i > 0 &&
367  header->link_penalty[i - 1] >= FLAC_HEADER_CRC_FAIL_PENALTY) {
368  while (start->next != child)
369  start = start->next;
370  inverted_test = 1;
371  } else if (i > 0 &&
372  header->next->link_penalty[i-1] >=
374  end = header->next;
375  inverted_test = 1;
376  }
377 
378  read_len = end->offset - start->offset;
379  buf = flac_fifo_read(fpc, start->offset, &read_len);
380  crc = av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0, buf, read_len);
381  read_len = (end->offset - start->offset) - read_len;
382 
383  if (read_len) {
384  buf = flac_fifo_read(fpc, end->offset - read_len, &read_len);
385  crc = av_crc(av_crc_get_table(AV_CRC_16_ANSI), crc, buf, read_len);
386  }
387  }
388 
389  if (!crc ^ !inverted_test) {
390  deduction += FLAC_HEADER_CRC_FAIL_PENALTY;
391  av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
392  "crc check failed from offset %i (frame %"PRId64") to %i (frame %"PRId64")\n",
393  header->offset, header_fi->frame_or_sample_num,
394  child->offset, child_fi->frame_or_sample_num);
395  }
396  }
397  return deduction;
398 }
399 
400 /**
401  * Score a header.
402  *
403  * Give FLAC_HEADER_BASE_SCORE points to a frame for existing.
404  * If it has children, (subsequent frames of which the preceding CRC footer
405  * validates against this one,) then take the maximum score of the children,
406  * with a penalty of FLAC_HEADER_CHANGED_PENALTY applied for each change to
407  * bps, sample rate, channels, but not decorrelation mode, or blocksize,
408  * because it can change often.
409  **/
411 {
413  int dist = 0;
414  int child_score;
415  int base_score = FLAC_HEADER_BASE_SCORE;
416  if (header->max_score != FLAC_HEADER_NOT_SCORED_YET)
417  return header->max_score;
418 
419  /* Modify the base score with changes from the last output header */
420  if (fpc->last_fi_valid) {
421  /* Silence the log since this will be repeated if selected */
422  base_score -= check_header_fi_mismatch(fpc, &fpc->last_fi, &header->fi,
423  AV_LOG_DEBUG);
424  }
425 
426  header->max_score = base_score;
427 
428  /* Check and compute the children's scores. */
429  child = header->next;
430  for (dist = 0; dist < FLAC_MAX_SEQUENTIAL_HEADERS && child; dist++) {
431  /* Look at the child's frame header info and penalize suspicious
432  changes between the headers. */
433  if (header->link_penalty[dist] == FLAC_HEADER_NOT_PENALIZED_YET) {
434  header->link_penalty[dist] = check_header_mismatch(fpc, header,
435  child, AV_LOG_DEBUG);
436  }
437  child_score = score_header(fpc, child) - header->link_penalty[dist];
438 
439  if (FLAC_HEADER_BASE_SCORE + child_score > header->max_score) {
440  /* Keep the child because the frame scoring is dynamic. */
441  header->best_child = child;
442  header->max_score = base_score + child_score;
443  }
444  child = child->next;
445  }
446 
447  return header->max_score;
448 }
449 
451 {
452  FLACHeaderMarker *curr;
453  int best_score = 0;//FLAC_HEADER_NOT_SCORED_YET;
454  /* First pass to clear all old scores. */
455  for (curr = fpc->headers; curr; curr = curr->next)
457 
458  /* Do a second pass to score them all. */
459  for (curr = fpc->headers; curr; curr = curr->next) {
460  if (score_header(fpc, curr) > best_score) {
461  fpc->best_header = curr;
462  best_score = curr->max_score;
463  }
464  }
465 }
466 
467 static int get_best_header(FLACParseContext* fpc, const uint8_t **poutbuf,
468  int *poutbuf_size)
469 {
471  FLACHeaderMarker *child = header->best_child;
472  if (!child) {
473  *poutbuf_size = av_fifo_size(fpc->fifo_buf) - header->offset;
474  } else {
475  *poutbuf_size = child->offset - header->offset;
476 
477  /* If the child has suspicious changes, log them */
478  check_header_mismatch(fpc, header, child, 0);
479  }
480 
481  if (header->fi.channels != fpc->avctx->channels ||
482  !fpc->avctx->channel_layout) {
483  fpc->avctx->channels = header->fi.channels;
485  }
486  fpc->avctx->sample_rate = header->fi.samplerate;
487  fpc->pc->duration = header->fi.blocksize;
488  *poutbuf = flac_fifo_read_wrap(fpc, header->offset, *poutbuf_size,
489  &fpc->wrap_buf,
491 
492 
493  if (fpc->pc->flags & PARSER_FLAG_USE_CODEC_TS){
494  if (header->fi.is_var_size)
495  fpc->pc->pts = header->fi.frame_or_sample_num;
496  else if (header->best_child)
497  fpc->pc->pts = header->fi.frame_or_sample_num * header->fi.blocksize;
498  }
499 
500  fpc->best_header_valid = 0;
501  fpc->last_fi_valid = 1;
502  fpc->last_fi = header->fi;
503 
504  /* Return the negative overread index so the client can compute pos.
505  This should be the amount overread to the beginning of the child */
506  if (child)
507  return child->offset - av_fifo_size(fpc->fifo_buf);
508  return 0;
509 }
510 
512  const uint8_t **poutbuf, int *poutbuf_size,
513  const uint8_t *buf, int buf_size)
514 {
515  FLACParseContext *fpc = s->priv_data;
516  FLACHeaderMarker *curr;
517  int nb_headers;
518  const uint8_t *read_end = buf;
519  const uint8_t *read_start = buf;
520 
523  if (frame_header_is_valid(avctx, buf, &fi)) {
524  s->duration = fi.blocksize;
525  if (!avctx->sample_rate)
526  avctx->sample_rate = fi.samplerate;
527  if (fpc->pc->flags & PARSER_FLAG_USE_CODEC_TS){
528  fpc->pc->pts = fi.frame_or_sample_num;
529  if (!fi.is_var_size)
530  fpc->pc->pts *= fi.blocksize;
531  }
532  }
533  *poutbuf = buf;
534  *poutbuf_size = buf_size;
535  return buf_size;
536  }
537 
538  fpc->avctx = avctx;
539  if (fpc->best_header_valid)
540  return get_best_header(fpc, poutbuf, poutbuf_size);
541 
542  /* If a best_header was found last call remove it with the buffer data. */
543  if (fpc->best_header && fpc->best_header->best_child) {
545  FLACHeaderMarker *best_child = fpc->best_header->best_child;
546 
547  /* Remove headers in list until the end of the best_header. */
548  for (curr = fpc->headers; curr != best_child; curr = temp) {
549  if (curr != fpc->best_header) {
550  av_log(avctx, AV_LOG_DEBUG,
551  "dropping low score %i frame header from offset %i to %i\n",
552  curr->max_score, curr->offset, curr->next->offset);
553  }
554  temp = curr->next;
555  av_freep(&curr->link_penalty);
556  av_free(curr);
557  fpc->nb_headers_buffered--;
558  }
559  /* Release returned data from ring buffer. */
560  av_fifo_drain(fpc->fifo_buf, best_child->offset);
561 
562  /* Fix the offset for the headers remaining to match the new buffer. */
563  for (curr = best_child->next; curr; curr = curr->next)
564  curr->offset -= best_child->offset;
565 
566  fpc->nb_headers_buffered--;
567  best_child->offset = 0;
568  fpc->headers = best_child;
570  fpc->best_header = best_child;
571  return get_best_header(fpc, poutbuf, poutbuf_size);
572  }
573  fpc->best_header = NULL;
574  } else if (fpc->best_header) {
575  /* No end frame no need to delete the buffer; probably eof */
577 
578  for (curr = fpc->headers; curr != fpc->best_header; curr = temp) {
579  temp = curr->next;
580  av_freep(&curr->link_penalty);
581  av_free(curr);
582  }
583  fpc->headers = fpc->best_header->next;
585  av_freep(&fpc->best_header);
586  }
587 
588  /* Find and score new headers. */
589  /* buf_size is to zero when padding, so check for this since we do */
590  /* not want to try to read more input once we have found the end. */
591  /* Note that as (non-modified) parameters, buf can be non-NULL, */
592  /* while buf_size is 0. */
593  while ((buf && buf_size && read_end < buf + buf_size &&
595  || ((!buf || !buf_size) && !fpc->end_padded)) {
596  int start_offset;
597 
598  /* Pad the end once if EOF, to check the final region for headers. */
599  if (!buf || !buf_size) {
600  fpc->end_padded = 1;
601  buf_size = MAX_FRAME_HEADER_SIZE;
602  read_end = read_start + MAX_FRAME_HEADER_SIZE;
603  } else {
604  /* The maximum read size is the upper-bound of what the parser
605  needs to have the required number of frames buffered */
606  int nb_desired = FLAC_MIN_HEADERS - fpc->nb_headers_buffered + 1;
607  read_end = read_end + FFMIN(buf + buf_size - read_end,
608  nb_desired * FLAC_AVG_FRAME_SIZE);
609  }
610 
611  /* Fill the buffer. */
612  if ( av_fifo_space(fpc->fifo_buf) < read_end - read_start
613  && av_fifo_realloc2(fpc->fifo_buf, (read_end - read_start) + 2*av_fifo_size(fpc->fifo_buf)) < 0) {
614  av_log(avctx, AV_LOG_ERROR,
615  "couldn't reallocate buffer of size %"PTRDIFF_SPECIFIER"\n",
616  (read_end - read_start) + av_fifo_size(fpc->fifo_buf));
617  goto handle_error;
618  }
619 
620  if (buf && buf_size) {
621  av_fifo_generic_write(fpc->fifo_buf, (void*) read_start,
622  read_end - read_start, NULL);
623  } else {
624  int8_t pad[MAX_FRAME_HEADER_SIZE] = { 0 };
625  av_fifo_generic_write(fpc->fifo_buf, (void*) pad, sizeof(pad), NULL);
626  }
627 
628  /* Tag headers and update sequences. */
629  start_offset = av_fifo_size(fpc->fifo_buf) -
630  ((read_end - read_start) + (MAX_FRAME_HEADER_SIZE - 1));
631  start_offset = FFMAX(0, start_offset);
632  nb_headers = find_new_headers(fpc, start_offset);
633 
634  if (nb_headers < 0) {
635  av_log(avctx, AV_LOG_ERROR,
636  "find_new_headers couldn't allocate FLAC header\n");
637  goto handle_error;
638  }
639 
640  fpc->nb_headers_buffered = nb_headers;
641  /* Wait till FLAC_MIN_HEADERS to output a valid frame. */
642  if (!fpc->end_padded && fpc->nb_headers_buffered < FLAC_MIN_HEADERS) {
643  if (buf && read_end < buf + buf_size) {
644  read_start = read_end;
645  continue;
646  } else {
647  goto handle_error;
648  }
649  }
650 
651  /* If headers found, update the scores since we have longer chains. */
652  if (fpc->end_padded || fpc->nb_headers_found)
653  score_sequences(fpc);
654 
655  /* restore the state pre-padding */
656  if (fpc->end_padded) {
657  int warp = fpc->fifo_buf->wptr - fpc->fifo_buf->buffer < MAX_FRAME_HEADER_SIZE;
658  /* HACK: drain the tail of the fifo */
661  if (warp) {
662  fpc->fifo_buf->wptr += fpc->fifo_buf->end -
663  fpc->fifo_buf->buffer;
664  }
665  buf_size = 0;
666  read_start = read_end = NULL;
667  }
668  }
669 
670  for (curr = fpc->headers; curr; curr = curr->next) {
671  if (curr->max_score > 0 &&
672  (!fpc->best_header || curr->max_score > fpc->best_header->max_score)) {
673  fpc->best_header = curr;
674  }
675  }
676 
677  if (fpc->best_header) {
678  fpc->best_header_valid = 1;
679  if (fpc->best_header->offset > 0) {
680  /* Output a junk frame. */
681  av_log(avctx, AV_LOG_DEBUG, "Junk frame till offset %i\n",
682  fpc->best_header->offset);
683 
684  /* Set duration to 0. It is unknown or invalid in a junk frame. */
685  s->duration = 0;
686  *poutbuf_size = fpc->best_header->offset;
687  *poutbuf = flac_fifo_read_wrap(fpc, 0, *poutbuf_size,
688  &fpc->wrap_buf,
690  return buf_size ? (read_end - buf) : (fpc->best_header->offset -
691  av_fifo_size(fpc->fifo_buf));
692  }
693  if (!buf_size)
694  return get_best_header(fpc, poutbuf, poutbuf_size);
695  }
696 
697 handle_error:
698  *poutbuf = NULL;
699  *poutbuf_size = 0;
700  return read_end - buf;
701 }
702 
704 {
705  FLACParseContext *fpc = c->priv_data;
706  fpc->pc = c;
707  /* There will generally be FLAC_MIN_HEADERS buffered in the fifo before
708  it drains. This is allocated early to avoid slow reallocation. */
710  if (!fpc->fifo_buf)
711  return AVERROR(ENOMEM);
712  return 0;
713 }
714 
716 {
717  FLACParseContext *fpc = c->priv_data;
718  FLACHeaderMarker *curr = fpc->headers, *temp;
719 
720  while (curr) {
721  temp = curr->next;
722  av_freep(&curr->link_penalty);
723  av_free(curr);
724  curr = temp;
725  }
726  av_fifo_freep(&fpc->fifo_buf);
727  av_free(fpc->wrap_buf);
728 }
729 
732  .priv_data_size = sizeof(FLACParseContext),
733  .parser_init = flac_parse_init,
734  .parser_parse = flac_parse,
735  .parser_close = flac_parse_close,
736 };