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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(**end_handle));
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  if (!(*end_handle)->link_penalty) {
196  av_freep(end_handle);
197  av_log(fpc->avctx, AV_LOG_ERROR,
198  "couldn't allocate link_penalty\n");
199  return AVERROR(ENOMEM);
200  }
201 
202  for (i = 0; i < FLAC_MAX_SEQUENTIAL_HEADERS; i++)
203  (*end_handle)->link_penalty[i] = FLAC_HEADER_NOT_PENALIZED_YET;
204 
205  fpc->nb_headers_found++;
206  size++;
207  }
208  return size;
209 }
210 
211 static int find_headers_search(FLACParseContext *fpc, uint8_t *buf, int buf_size,
212  int search_start)
213 
214 {
215  int size = 0, mod_offset = (buf_size - 1) % 4, i, j;
216  uint32_t x;
217 
218  for (i = 0; i < mod_offset; i++) {
219  if ((AV_RB16(buf + i) & 0xFFFE) == 0xFFF8)
220  size = find_headers_search_validate(fpc, search_start + i);
221  }
222 
223  for (; i < buf_size - 1; i += 4) {
224  x = AV_RB32(buf + i);
225  if (((x & ~(x + 0x01010101)) & 0x80808080)) {
226  for (j = 0; j < 4; j++) {
227  if ((AV_RB16(buf + i + j) & 0xFFFE) == 0xFFF8)
228  size = find_headers_search_validate(fpc, search_start + i + j);
229  }
230  }
231  }
232  return size;
233 }
234 
235 static int find_new_headers(FLACParseContext *fpc, int search_start)
236 {
238  int search_end, size = 0, read_len, temp;
239  uint8_t *buf;
240  fpc->nb_headers_found = 0;
241 
242  /* Search for a new header of at most 16 bytes. */
243  search_end = av_fifo_size(fpc->fifo_buf) - (MAX_FRAME_HEADER_SIZE - 1);
244  read_len = search_end - search_start + 1;
245  buf = flac_fifo_read(fpc, search_start, &read_len);
246  size = find_headers_search(fpc, buf, read_len, search_start);
247  search_start += read_len - 1;
248 
249  /* If fifo end was hit do the wrap around. */
250  if (search_start != search_end) {
251  uint8_t wrap[2];
252 
253  wrap[0] = buf[read_len - 1];
254  read_len = search_end - search_start + 1;
255 
256  /* search_start + 1 is the post-wrap offset in the fifo. */
257  buf = flac_fifo_read(fpc, search_start + 1, &read_len);
258  wrap[1] = buf[0];
259 
260  if ((AV_RB16(wrap) & 0xFFFE) == 0xFFF8) {
261  temp = find_headers_search_validate(fpc, search_start);
262  size = FFMAX(size, temp);
263  }
264  search_start++;
265 
266  /* Continue to do the last half of the wrap. */
267  temp = find_headers_search(fpc, buf, read_len, search_start);
268  size = FFMAX(size, temp);
269  search_start += read_len - 1;
270  }
271 
272  /* Return the size even if no new headers were found. */
273  if (!size && fpc->headers)
274  for (end = fpc->headers; end; end = end->next)
275  size++;
276  return size;
277 }
278 
280  FLACFrameInfo *header_fi,
281  FLACFrameInfo *child_fi,
282  int log_level_offset)
283 {
284  int deduction = 0;
285  if (child_fi->samplerate != header_fi->samplerate) {
286  deduction += FLAC_HEADER_CHANGED_PENALTY;
287  av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
288  "sample rate change detected in adjacent frames\n");
289  }
290  if (child_fi->bps != header_fi->bps) {
291  deduction += FLAC_HEADER_CHANGED_PENALTY;
292  av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
293  "bits per sample change detected in adjacent frames\n");
294  }
295  if (child_fi->is_var_size != header_fi->is_var_size) {
296  /* Changing blocking strategy not allowed per the spec */
297  deduction += FLAC_HEADER_BASE_SCORE;
298  av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
299  "blocking strategy change detected in adjacent frames\n");
300  }
301  if (child_fi->channels != header_fi->channels) {
302  deduction += FLAC_HEADER_CHANGED_PENALTY;
303  av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
304  "number of channels change detected in adjacent frames\n");
305  }
306  return deduction;
307 }
308 
312  int log_level_offset)
313 {
314  FLACFrameInfo *header_fi = &header->fi, *child_fi = &child->fi;
315  int deduction, deduction_expected = 0, i;
316  deduction = check_header_fi_mismatch(fpc, header_fi, child_fi,
317  log_level_offset);
318  /* Check sample and frame numbers. */
319  if ((child_fi->frame_or_sample_num - header_fi->frame_or_sample_num
320  != header_fi->blocksize) &&
321  (child_fi->frame_or_sample_num
322  != header_fi->frame_or_sample_num + 1)) {
323  FLACHeaderMarker *curr;
324  int expected_frame_num, expected_sample_num;
325  /* If there are frames in the middle we expect this deduction,
326  as they are probably valid and this one follows it */
327 
328  expected_frame_num = expected_sample_num = header_fi->frame_or_sample_num;
329  curr = header;
330  while (curr != child) {
331  /* Ignore frames that failed all crc checks */
332  for (i = 0; i < FLAC_MAX_SEQUENTIAL_HEADERS; i++) {
334  expected_frame_num++;
335  expected_sample_num += curr->fi.blocksize;
336  break;
337  }
338  }
339  curr = curr->next;
340  }
341 
342  if (expected_frame_num == child_fi->frame_or_sample_num ||
343  expected_sample_num == child_fi->frame_or_sample_num)
344  deduction_expected = deduction ? 0 : 1;
345 
346  deduction += FLAC_HEADER_CHANGED_PENALTY;
347  av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
348  "sample/frame number mismatch in adjacent frames\n");
349  }
350 
351  /* If we have suspicious headers, check the CRC between them */
352  if (deduction && !deduction_expected) {
353  FLACHeaderMarker *curr;
354  int read_len;
355  uint8_t *buf;
356  uint32_t crc = 1;
357  int inverted_test = 0;
358 
359  /* Since CRC is expensive only do it if we haven't yet.
360  This assumes a CRC penalty is greater than all other check penalties */
361  curr = header->next;
362  for (i = 0; i < FLAC_MAX_SEQUENTIAL_HEADERS && curr != child; i++)
363  curr = curr->next;
364 
368 
369  /* Although overlapping chains are scored, the crc should never
370  have to be computed twice for a single byte. */
371  start = header;
372  end = child;
373  if (i > 0 &&
374  header->link_penalty[i - 1] >= FLAC_HEADER_CRC_FAIL_PENALTY) {
375  while (start->next != child)
376  start = start->next;
377  inverted_test = 1;
378  } else if (i > 0 &&
379  header->next->link_penalty[i-1] >=
381  end = header->next;
382  inverted_test = 1;
383  }
384 
385  read_len = end->offset - start->offset;
386  buf = flac_fifo_read(fpc, start->offset, &read_len);
387  crc = av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0, buf, read_len);
388  read_len = (end->offset - start->offset) - read_len;
389 
390  if (read_len) {
391  buf = flac_fifo_read(fpc, end->offset - read_len, &read_len);
392  crc = av_crc(av_crc_get_table(AV_CRC_16_ANSI), crc, buf, read_len);
393  }
394  }
395 
396  if (!crc ^ !inverted_test) {
397  deduction += FLAC_HEADER_CRC_FAIL_PENALTY;
398  av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
399  "crc check failed from offset %i (frame %"PRId64") to %i (frame %"PRId64")\n",
400  header->offset, header_fi->frame_or_sample_num,
401  child->offset, child_fi->frame_or_sample_num);
402  }
403  }
404  return deduction;
405 }
406 
407 /**
408  * Score a header.
409  *
410  * Give FLAC_HEADER_BASE_SCORE points to a frame for existing.
411  * If it has children, (subsequent frames of which the preceding CRC footer
412  * validates against this one,) then take the maximum score of the children,
413  * with a penalty of FLAC_HEADER_CHANGED_PENALTY applied for each change to
414  * bps, sample rate, channels, but not decorrelation mode, or blocksize,
415  * because it can change often.
416  **/
418 {
420  int dist = 0;
421  int child_score;
422  int base_score = FLAC_HEADER_BASE_SCORE;
423  if (header->max_score != FLAC_HEADER_NOT_SCORED_YET)
424  return header->max_score;
425 
426  /* Modify the base score with changes from the last output header */
427  if (fpc->last_fi_valid) {
428  /* Silence the log since this will be repeated if selected */
429  base_score -= check_header_fi_mismatch(fpc, &fpc->last_fi, &header->fi,
430  AV_LOG_DEBUG);
431  }
432 
433  header->max_score = base_score;
434 
435  /* Check and compute the children's scores. */
436  child = header->next;
437  for (dist = 0; dist < FLAC_MAX_SEQUENTIAL_HEADERS && child; dist++) {
438  /* Look at the child's frame header info and penalize suspicious
439  changes between the headers. */
440  if (header->link_penalty[dist] == FLAC_HEADER_NOT_PENALIZED_YET) {
441  header->link_penalty[dist] = check_header_mismatch(fpc, header,
442  child, AV_LOG_DEBUG);
443  }
444  child_score = score_header(fpc, child) - header->link_penalty[dist];
445 
446  if (FLAC_HEADER_BASE_SCORE + child_score > header->max_score) {
447  /* Keep the child because the frame scoring is dynamic. */
448  header->best_child = child;
449  header->max_score = base_score + child_score;
450  }
451  child = child->next;
452  }
453 
454  return header->max_score;
455 }
456 
458 {
459  FLACHeaderMarker *curr;
460  int best_score = 0;//FLAC_HEADER_NOT_SCORED_YET;
461  /* First pass to clear all old scores. */
462  for (curr = fpc->headers; curr; curr = curr->next)
464 
465  /* Do a second pass to score them all. */
466  for (curr = fpc->headers; curr; curr = curr->next) {
467  if (score_header(fpc, curr) > best_score) {
468  fpc->best_header = curr;
469  best_score = curr->max_score;
470  }
471  }
472 }
473 
474 static int get_best_header(FLACParseContext* fpc, const uint8_t **poutbuf,
475  int *poutbuf_size)
476 {
478  FLACHeaderMarker *child = header->best_child;
479  if (!child) {
480  *poutbuf_size = av_fifo_size(fpc->fifo_buf) - header->offset;
481  } else {
482  *poutbuf_size = child->offset - header->offset;
483 
484  /* If the child has suspicious changes, log them */
485  check_header_mismatch(fpc, header, child, 0);
486  }
487 
488  if (header->fi.channels != fpc->avctx->channels ||
489  !fpc->avctx->channel_layout) {
490  fpc->avctx->channels = header->fi.channels;
492  }
493  fpc->avctx->sample_rate = header->fi.samplerate;
494  fpc->pc->duration = header->fi.blocksize;
495  *poutbuf = flac_fifo_read_wrap(fpc, header->offset, *poutbuf_size,
496  &fpc->wrap_buf,
498 
499 
500  if (fpc->pc->flags & PARSER_FLAG_USE_CODEC_TS){
501  if (header->fi.is_var_size)
502  fpc->pc->pts = header->fi.frame_or_sample_num;
503  else if (header->best_child)
504  fpc->pc->pts = header->fi.frame_or_sample_num * header->fi.blocksize;
505  }
506 
507  fpc->best_header_valid = 0;
508  fpc->last_fi_valid = 1;
509  fpc->last_fi = header->fi;
510 
511  /* Return the negative overread index so the client can compute pos.
512  This should be the amount overread to the beginning of the child */
513  if (child)
514  return child->offset - av_fifo_size(fpc->fifo_buf);
515  return 0;
516 }
517 
519  const uint8_t **poutbuf, int *poutbuf_size,
520  const uint8_t *buf, int buf_size)
521 {
522  FLACParseContext *fpc = s->priv_data;
523  FLACHeaderMarker *curr;
524  int nb_headers;
525  const uint8_t *read_end = buf;
526  const uint8_t *read_start = buf;
527 
530  if (frame_header_is_valid(avctx, buf, &fi)) {
531  s->duration = fi.blocksize;
532  if (!avctx->sample_rate)
533  avctx->sample_rate = fi.samplerate;
534  if (fpc->pc->flags & PARSER_FLAG_USE_CODEC_TS){
535  fpc->pc->pts = fi.frame_or_sample_num;
536  if (!fi.is_var_size)
537  fpc->pc->pts *= fi.blocksize;
538  }
539  }
540  *poutbuf = buf;
541  *poutbuf_size = buf_size;
542  return buf_size;
543  }
544 
545  fpc->avctx = avctx;
546  if (fpc->best_header_valid)
547  return get_best_header(fpc, poutbuf, poutbuf_size);
548 
549  /* If a best_header was found last call remove it with the buffer data. */
550  if (fpc->best_header && fpc->best_header->best_child) {
552  FLACHeaderMarker *best_child = fpc->best_header->best_child;
553 
554  /* Remove headers in list until the end of the best_header. */
555  for (curr = fpc->headers; curr != best_child; curr = temp) {
556  if (curr != fpc->best_header) {
557  av_log(avctx, AV_LOG_DEBUG,
558  "dropping low score %i frame header from offset %i to %i\n",
559  curr->max_score, curr->offset, curr->next->offset);
560  }
561  temp = curr->next;
562  av_freep(&curr->link_penalty);
563  av_free(curr);
564  fpc->nb_headers_buffered--;
565  }
566  /* Release returned data from ring buffer. */
567  av_fifo_drain(fpc->fifo_buf, best_child->offset);
568 
569  /* Fix the offset for the headers remaining to match the new buffer. */
570  for (curr = best_child->next; curr; curr = curr->next)
571  curr->offset -= best_child->offset;
572 
573  fpc->nb_headers_buffered--;
574  best_child->offset = 0;
575  fpc->headers = best_child;
577  fpc->best_header = best_child;
578  return get_best_header(fpc, poutbuf, poutbuf_size);
579  }
580  fpc->best_header = NULL;
581  } else if (fpc->best_header) {
582  /* No end frame no need to delete the buffer; probably eof */
584 
585  for (curr = fpc->headers; curr != fpc->best_header; curr = temp) {
586  temp = curr->next;
587  av_freep(&curr->link_penalty);
588  av_free(curr);
589  }
590  fpc->headers = fpc->best_header->next;
592  av_freep(&fpc->best_header);
593  }
594 
595  /* Find and score new headers. */
596  /* buf_size is to zero when padding, so check for this since we do */
597  /* not want to try to read more input once we have found the end. */
598  /* Note that as (non-modified) parameters, buf can be non-NULL, */
599  /* while buf_size is 0. */
600  while ((buf && buf_size && read_end < buf + buf_size &&
602  || ((!buf || !buf_size) && !fpc->end_padded)) {
603  int start_offset;
604 
605  /* Pad the end once if EOF, to check the final region for headers. */
606  if (!buf || !buf_size) {
607  fpc->end_padded = 1;
608  buf_size = MAX_FRAME_HEADER_SIZE;
609  read_end = read_start + MAX_FRAME_HEADER_SIZE;
610  } else {
611  /* The maximum read size is the upper-bound of what the parser
612  needs to have the required number of frames buffered */
613  int nb_desired = FLAC_MIN_HEADERS - fpc->nb_headers_buffered + 1;
614  read_end = read_end + FFMIN(buf + buf_size - read_end,
615  nb_desired * FLAC_AVG_FRAME_SIZE);
616  }
617 
618  if (!av_fifo_space(fpc->fifo_buf) &&
620  fpc->nb_headers_buffered * 10) {
621  /* There is less than one valid flac header buffered for 10 headers
622  * buffered. Therefore the fifo is most likely filled with invalid
623  * data and the input is not a flac file. */
624  goto handle_error;
625  }
626 
627  /* Fill the buffer. */
628  if ( av_fifo_space(fpc->fifo_buf) < read_end - read_start
629  && av_fifo_realloc2(fpc->fifo_buf, (read_end - read_start) + 2*av_fifo_size(fpc->fifo_buf)) < 0) {
630  av_log(avctx, AV_LOG_ERROR,
631  "couldn't reallocate buffer of size %"PTRDIFF_SPECIFIER"\n",
632  (read_end - read_start) + av_fifo_size(fpc->fifo_buf));
633  goto handle_error;
634  }
635 
636  if (buf && buf_size) {
637  av_fifo_generic_write(fpc->fifo_buf, (void*) read_start,
638  read_end - read_start, NULL);
639  } else {
640  int8_t pad[MAX_FRAME_HEADER_SIZE] = { 0 };
641  av_fifo_generic_write(fpc->fifo_buf, (void*) pad, sizeof(pad), NULL);
642  }
643 
644  /* Tag headers and update sequences. */
645  start_offset = av_fifo_size(fpc->fifo_buf) -
646  ((read_end - read_start) + (MAX_FRAME_HEADER_SIZE - 1));
647  start_offset = FFMAX(0, start_offset);
648  nb_headers = find_new_headers(fpc, start_offset);
649 
650  if (nb_headers < 0) {
651  av_log(avctx, AV_LOG_ERROR,
652  "find_new_headers couldn't allocate FLAC header\n");
653  goto handle_error;
654  }
655 
656  fpc->nb_headers_buffered = nb_headers;
657  /* Wait till FLAC_MIN_HEADERS to output a valid frame. */
658  if (!fpc->end_padded && fpc->nb_headers_buffered < FLAC_MIN_HEADERS) {
659  if (buf && read_end < buf + buf_size) {
660  read_start = read_end;
661  continue;
662  } else {
663  goto handle_error;
664  }
665  }
666 
667  /* If headers found, update the scores since we have longer chains. */
668  if (fpc->end_padded || fpc->nb_headers_found)
669  score_sequences(fpc);
670 
671  /* restore the state pre-padding */
672  if (fpc->end_padded) {
673  int warp = fpc->fifo_buf->wptr - fpc->fifo_buf->buffer < MAX_FRAME_HEADER_SIZE;
674  /* HACK: drain the tail of the fifo */
677  if (warp) {
678  fpc->fifo_buf->wptr += fpc->fifo_buf->end -
679  fpc->fifo_buf->buffer;
680  }
681  buf_size = 0;
682  read_start = read_end = NULL;
683  }
684  }
685 
686  for (curr = fpc->headers; curr; curr = curr->next) {
687  if (curr->max_score > 0 &&
688  (!fpc->best_header || curr->max_score > fpc->best_header->max_score)) {
689  fpc->best_header = curr;
690  }
691  }
692 
693  if (fpc->best_header) {
694  fpc->best_header_valid = 1;
695  if (fpc->best_header->offset > 0) {
696  /* Output a junk frame. */
697  av_log(avctx, AV_LOG_DEBUG, "Junk frame till offset %i\n",
698  fpc->best_header->offset);
699 
700  /* Set duration to 0. It is unknown or invalid in a junk frame. */
701  s->duration = 0;
702  *poutbuf_size = fpc->best_header->offset;
703  *poutbuf = flac_fifo_read_wrap(fpc, 0, *poutbuf_size,
704  &fpc->wrap_buf,
706  return buf_size ? (read_end - buf) : (fpc->best_header->offset -
707  av_fifo_size(fpc->fifo_buf));
708  }
709  if (!buf_size)
710  return get_best_header(fpc, poutbuf, poutbuf_size);
711  }
712 
713 handle_error:
714  *poutbuf = NULL;
715  *poutbuf_size = 0;
716  return buf_size ? read_end - buf : 0;
717 }
718 
720 {
721  FLACParseContext *fpc = c->priv_data;
722  fpc->pc = c;
723  /* There will generally be FLAC_MIN_HEADERS buffered in the fifo before
724  it drains. This is allocated early to avoid slow reallocation. */
726  if (!fpc->fifo_buf) {
727  av_log(fpc->avctx, AV_LOG_ERROR,
728  "couldn't allocate fifo_buf\n");
729  return AVERROR(ENOMEM);
730  }
731  return 0;
732 }
733 
735 {
736  FLACParseContext *fpc = c->priv_data;
737  FLACHeaderMarker *curr = fpc->headers, *temp;
738 
739  while (curr) {
740  temp = curr->next;
741  av_freep(&curr->link_penalty);
742  av_free(curr);
743  curr = temp;
744  }
745  av_fifo_freep(&fpc->fifo_buf);
746  av_freep(&fpc->wrap_buf);
747 }
748 
751  .priv_data_size = sizeof(FLACParseContext),
752  .parser_init = flac_parse_init,
753  .parser_parse = flac_parse,
754  .parser_close = flac_parse_close,
755 };