FFmpeg
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 4
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 #define MAX_FRAME_VERIFY_SIZE (MAX_FRAME_HEADER_SIZE)
59 
60 typedef struct FLACHeaderMarker {
61  int offset; /**< byte offset from start of FLACParseContext->buffer */
62  int link_penalty[FLAC_MAX_SEQUENTIAL_HEADERS]; /**< array of local scores
63  between this header and the one at a distance equal
64  array position */
65  int max_score; /**< maximum score found after checking each child that
66  has a valid CRC */
67  FLACFrameInfo fi; /**< decoded frame header info */
68  struct FLACHeaderMarker *next; /**< next CRC-8 verified header that
69  immediately follows this one in
70  the bytestream */
71  struct FLACHeaderMarker *best_child; /**< following frame header with
72  which this frame has the best
73  score with */
75 
76 typedef struct FLACParseContext {
77  AVCodecParserContext *pc; /**< parent context */
78  AVCodecContext *avctx; /**< codec context pointer for logging */
79  FLACHeaderMarker *headers; /**< linked-list that starts at the first
80  CRC-8 verified header within buffer */
81  FLACHeaderMarker *best_header; /**< highest scoring header within buffer */
82  int nb_headers_found; /**< number of headers found in the last
83  flac_parse() call */
84  int nb_headers_buffered; /**< number of headers that are buffered */
85  int best_header_valid; /**< flag set when the parser returns junk;
86  if set return best_header next time */
87  AVFifoBuffer *fifo_buf; /**< buffer to store all data until headers
88  can be verified */
89  int end_padded; /**< specifies if fifo_buf's end is padded */
90  uint8_t *wrap_buf; /**< general fifo read buffer when wrapped */
91  int wrap_buf_allocated_size; /**< actual allocated size of the buffer */
92  FLACFrameInfo last_fi; /**< last decoded frame header info */
93  int last_fi_valid; /**< set if last_fi is valid */
95 
96 static int frame_header_is_valid(AVCodecContext *avctx, const uint8_t *buf,
97  FLACFrameInfo *fi)
98 {
99  GetBitContext gb;
100  init_get_bits(&gb, buf, MAX_FRAME_HEADER_SIZE * 8);
101  return !ff_flac_decode_frame_header(avctx, &gb, fi, 127);
102 }
103 
104 /**
105  * Non-destructive fast fifo pointer fetching
106  * Returns a pointer from the specified offset.
107  * If possible the pointer points within the fifo buffer.
108  * Otherwise (if it would cause a wrap around,) a pointer to a user-specified
109  * buffer is used.
110  * The pointer can be NULL. In any case it will be reallocated to hold the size.
111  * If the returned pointer will be used after subsequent calls to flac_fifo_read_wrap
112  * then the subsequent calls should pass in a different wrap_buf so as to not
113  * overwrite the contents of the previous wrap_buf.
114  * This function is based on av_fifo_generic_read, which is why there is a comment
115  * about a memory barrier for SMP.
116  */
118  uint8_t **wrap_buf, int *allocated_size)
119 {
120  AVFifoBuffer *f = fpc->fifo_buf;
121  uint8_t *start = f->rptr + offset;
122  uint8_t *tmp_buf;
123 
124  if (start >= f->end)
125  start -= f->end - f->buffer;
126  if (f->end - start >= len)
127  return start;
128 
129  tmp_buf = av_fast_realloc(*wrap_buf, allocated_size, len);
130 
131  if (!tmp_buf) {
132  av_log(fpc->avctx, AV_LOG_ERROR,
133  "couldn't reallocate wrap buffer of size %d", len);
134  return NULL;
135  }
136  *wrap_buf = tmp_buf;
137  do {
138  int seg_len = FFMIN(f->end - start, len);
139  memcpy(tmp_buf, start, seg_len);
140  tmp_buf = (uint8_t*)tmp_buf + seg_len;
141 // memory barrier needed for SMP here in theory
142 
143  start += seg_len - (f->end - f->buffer);
144  len -= seg_len;
145  } while (len > 0);
146 
147  return *wrap_buf;
148 }
149 
150 /**
151  * Return a pointer in the fifo buffer where the offset starts at until
152  * the wrap point or end of request.
153  * len will contain the valid length of the returned buffer.
154  * A second call to flac_fifo_read (with new offset and len) should be called
155  * to get the post-wrap buf if the returned len is less than the requested.
156  **/
158 {
159  AVFifoBuffer *f = fpc->fifo_buf;
160  uint8_t *start = f->rptr + offset;
161 
162  if (start >= f->end)
163  start -= f->end - f->buffer;
164  *len = FFMIN(*len, f->end - start);
165  return start;
166 }
167 
169 {
170  FLACFrameInfo fi;
171  uint8_t *header_buf;
172  int size = 0;
173  header_buf = flac_fifo_read_wrap(fpc, offset,
175  &fpc->wrap_buf,
177  if (frame_header_is_valid(fpc->avctx, header_buf, &fi)) {
178  FLACHeaderMarker **end_handle = &fpc->headers;
179  int i;
180 
181  size = 0;
182  while (*end_handle) {
183  end_handle = &(*end_handle)->next;
184  size++;
185  }
186 
187  *end_handle = av_mallocz(sizeof(**end_handle));
188  if (!*end_handle) {
189  av_log(fpc->avctx, AV_LOG_ERROR,
190  "couldn't allocate FLACHeaderMarker\n");
191  return AVERROR(ENOMEM);
192  }
193  (*end_handle)->fi = fi;
194  (*end_handle)->offset = offset;
195 
196  for (i = 0; i < FLAC_MAX_SEQUENTIAL_HEADERS; i++)
197  (*end_handle)->link_penalty[i] = FLAC_HEADER_NOT_PENALIZED_YET;
198 
199  fpc->nb_headers_found++;
200  size++;
201  }
202  return size;
203 }
204 
206  int buf_size, int search_start)
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  int ret = find_headers_search_validate(fpc, search_start + i);
214  size = FFMAX(size, ret);
215  }
216  }
217 
218  for (; i < buf_size - 1; i += 4) {
219  x = AV_RN32(buf + i);
220  if (((x & ~(x + 0x01010101)) & 0x80808080)) {
221  for (j = 0; j < 4; j++) {
222  if ((AV_RB16(buf + i + j) & 0xFFFE) == 0xFFF8) {
223  int ret = find_headers_search_validate(fpc, search_start + i + j);
224  size = FFMAX(size, ret);
225  }
226  }
227  }
228  }
229  return size;
230 }
231 
232 static int find_new_headers(FLACParseContext *fpc, int search_start)
233 {
234  FLACHeaderMarker *end;
235  int search_end, size = 0, read_len, temp;
236  uint8_t *buf;
237  fpc->nb_headers_found = 0;
238 
239  /* Search for a new header of at most 16 bytes. */
240  search_end = av_fifo_size(fpc->fifo_buf) - (MAX_FRAME_HEADER_SIZE - 1);
241  read_len = search_end - search_start + 1;
242  buf = flac_fifo_read(fpc, search_start, &read_len);
243  size = find_headers_search(fpc, buf, read_len, search_start);
244  search_start += read_len - 1;
245 
246  /* If fifo end was hit do the wrap around. */
247  if (search_start != search_end) {
248  uint8_t wrap[2];
249 
250  wrap[0] = buf[read_len - 1];
251  /* search_start + 1 is the post-wrap offset in the fifo. */
252  read_len = search_end - (search_start + 1) + 1;
253 
254  buf = flac_fifo_read(fpc, search_start + 1, &read_len);
255  wrap[1] = buf[0];
256 
257  if ((AV_RB16(wrap) & 0xFFFE) == 0xFFF8) {
258  temp = find_headers_search_validate(fpc, search_start);
259  size = FFMAX(size, temp);
260  }
261  search_start++;
262 
263  /* Continue to do the last half of the wrap. */
264  temp = find_headers_search(fpc, buf, read_len, search_start);
265  size = FFMAX(size, temp);
266  search_start += read_len - 1;
267  }
268 
269  /* Return the size even if no new headers were found. */
270  if (!size && fpc->headers)
271  for (end = fpc->headers; end; end = end->next)
272  size++;
273  return size;
274 }
275 
277  FLACFrameInfo *header_fi,
278  FLACFrameInfo *child_fi,
279  int log_level_offset)
280 {
281  int deduction = 0;
282  if (child_fi->samplerate != header_fi->samplerate) {
283  deduction += FLAC_HEADER_CHANGED_PENALTY;
284  av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
285  "sample rate change detected in adjacent frames\n");
286  }
287  if (child_fi->bps != header_fi->bps) {
288  deduction += FLAC_HEADER_CHANGED_PENALTY;
289  av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
290  "bits per sample change detected in adjacent frames\n");
291  }
292  if (child_fi->is_var_size != header_fi->is_var_size) {
293  /* Changing blocking strategy not allowed per the spec */
294  deduction += FLAC_HEADER_BASE_SCORE;
295  av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
296  "blocking strategy change detected in adjacent frames\n");
297  }
298  if (child_fi->channels != header_fi->channels) {
299  deduction += FLAC_HEADER_CHANGED_PENALTY;
300  av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
301  "number of channels change detected in adjacent frames\n");
302  }
303  return deduction;
304 }
305 
308  FLACHeaderMarker *child,
309  int log_level_offset)
310 {
311  FLACFrameInfo *header_fi = &header->fi, *child_fi = &child->fi;
312  int deduction, deduction_expected = 0, i;
313  deduction = check_header_fi_mismatch(fpc, header_fi, child_fi,
314  log_level_offset);
315  /* Check sample and frame numbers. */
316  if ((child_fi->frame_or_sample_num - header_fi->frame_or_sample_num
317  != header_fi->blocksize) &&
318  (child_fi->frame_or_sample_num
319  != header_fi->frame_or_sample_num + 1)) {
320  FLACHeaderMarker *curr;
321  int64_t expected_frame_num, expected_sample_num;
322  /* If there are frames in the middle we expect this deduction,
323  as they are probably valid and this one follows it */
324 
325  expected_frame_num = expected_sample_num = header_fi->frame_or_sample_num;
326  curr = header;
327  while (curr != child) {
328  /* Ignore frames that failed all crc checks */
329  for (i = 0; i < FLAC_MAX_SEQUENTIAL_HEADERS; i++) {
331  expected_frame_num++;
332  expected_sample_num += curr->fi.blocksize;
333  break;
334  }
335  }
336  curr = curr->next;
337  }
338 
339  if (expected_frame_num == child_fi->frame_or_sample_num ||
340  expected_sample_num == child_fi->frame_or_sample_num)
341  deduction_expected = deduction ? 0 : 1;
342 
343  deduction += FLAC_HEADER_CHANGED_PENALTY;
344  av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
345  "sample/frame number mismatch in adjacent frames\n");
346  }
347 
348  /* If we have suspicious headers, check the CRC between them */
349  if (deduction && !deduction_expected) {
350  FLACHeaderMarker *curr;
351  int read_len;
352  uint8_t *buf;
353  uint32_t crc = 1;
354  int inverted_test = 0;
355 
356  /* Since CRC is expensive only do it if we haven't yet.
357  This assumes a CRC penalty is greater than all other check penalties */
358  curr = header->next;
359  for (i = 0; i < FLAC_MAX_SEQUENTIAL_HEADERS && curr != child; i++)
360  curr = curr->next;
361 
362  if (header->link_penalty[i] < FLAC_HEADER_CRC_FAIL_PENALTY ||
363  header->link_penalty[i] == FLAC_HEADER_NOT_PENALIZED_YET) {
364  FLACHeaderMarker *start, *end;
365 
366  /* Although overlapping chains are scored, the crc should never
367  have to be computed twice for a single byte. */
368  start = header;
369  end = child;
370  if (i > 0 &&
371  header->link_penalty[i - 1] >= FLAC_HEADER_CRC_FAIL_PENALTY) {
372  while (start->next != child)
373  start = start->next;
374  inverted_test = 1;
375  } else if (i > 0 &&
376  header->next->link_penalty[i-1] >=
378  end = header->next;
379  inverted_test = 1;
380  }
381 
382  read_len = end->offset - start->offset;
383  buf = flac_fifo_read(fpc, start->offset, &read_len);
384  crc = av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0, buf, read_len);
385  read_len = (end->offset - start->offset) - read_len;
386 
387  if (read_len) {
388  buf = flac_fifo_read(fpc, end->offset - read_len, &read_len);
389  crc = av_crc(av_crc_get_table(AV_CRC_16_ANSI), crc, buf, read_len);
390  }
391  }
392 
393  if (!crc ^ !inverted_test) {
394  deduction += FLAC_HEADER_CRC_FAIL_PENALTY;
395  av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
396  "crc check failed from offset %i (frame %"PRId64") to %i (frame %"PRId64")\n",
397  header->offset, header_fi->frame_or_sample_num,
398  child->offset, child_fi->frame_or_sample_num);
399  }
400  }
401  return deduction;
402 }
403 
404 /**
405  * Score a header.
406  *
407  * Give FLAC_HEADER_BASE_SCORE points to a frame for existing.
408  * If it has children, (subsequent frames of which the preceding CRC footer
409  * validates against this one,) then take the maximum score of the children,
410  * with a penalty of FLAC_HEADER_CHANGED_PENALTY applied for each change to
411  * bps, sample rate, channels, but not decorrelation mode, or blocksize,
412  * because it can change often.
413  **/
415 {
416  FLACHeaderMarker *child;
417  int dist = 0;
418  int child_score;
419  int base_score = FLAC_HEADER_BASE_SCORE;
420  if (header->max_score != FLAC_HEADER_NOT_SCORED_YET)
421  return header->max_score;
422 
423  /* Modify the base score with changes from the last output header */
424  if (fpc->last_fi_valid) {
425  /* Silence the log since this will be repeated if selected */
426  base_score -= check_header_fi_mismatch(fpc, &fpc->last_fi, &header->fi,
427  AV_LOG_DEBUG);
428  }
429 
430  header->max_score = base_score;
431 
432  /* Check and compute the children's scores. */
433  child = header->next;
434  for (dist = 0; dist < FLAC_MAX_SEQUENTIAL_HEADERS && child; dist++) {
435  /* Look at the child's frame header info and penalize suspicious
436  changes between the headers. */
437  if (header->link_penalty[dist] == FLAC_HEADER_NOT_PENALIZED_YET) {
438  header->link_penalty[dist] = check_header_mismatch(fpc, header,
439  child, AV_LOG_DEBUG);
440  }
441  child_score = score_header(fpc, child) - header->link_penalty[dist];
442 
443  if (FLAC_HEADER_BASE_SCORE + child_score > header->max_score) {
444  /* Keep the child because the frame scoring is dynamic. */
445  header->best_child = child;
446  header->max_score = base_score + child_score;
447  }
448  child = child->next;
449  }
450 
451  return header->max_score;
452 }
453 
455 {
456  FLACHeaderMarker *curr;
457  int best_score = 0;//FLAC_HEADER_NOT_SCORED_YET;
458  /* First pass to clear all old scores. */
459  for (curr = fpc->headers; curr; curr = curr->next)
461 
462  /* Do a second pass to score them all. */
463  for (curr = fpc->headers; curr; curr = curr->next) {
464  if (score_header(fpc, curr) > best_score) {
465  fpc->best_header = curr;
466  best_score = curr->max_score;
467  }
468  }
469 }
470 
471 static int get_best_header(FLACParseContext *fpc, const uint8_t **poutbuf,
472  int *poutbuf_size)
473 {
475  FLACHeaderMarker *child = header->best_child;
476  if (!child) {
477  *poutbuf_size = av_fifo_size(fpc->fifo_buf) - header->offset;
478  } else {
479  *poutbuf_size = child->offset - header->offset;
480 
481  /* If the child has suspicious changes, log them */
482  check_header_mismatch(fpc, header, child, 0);
483  }
484 
485  if (header->fi.channels != fpc->avctx->channels ||
486  !fpc->avctx->channel_layout) {
487  fpc->avctx->channels = header->fi.channels;
489  }
490  fpc->avctx->sample_rate = header->fi.samplerate;
491  fpc->pc->duration = header->fi.blocksize;
492  *poutbuf = flac_fifo_read_wrap(fpc, header->offset, *poutbuf_size,
493  &fpc->wrap_buf,
495 
496 
497  if (fpc->pc->flags & PARSER_FLAG_USE_CODEC_TS) {
498  if (header->fi.is_var_size)
499  fpc->pc->pts = header->fi.frame_or_sample_num;
500  else if (header->best_child)
501  fpc->pc->pts = header->fi.frame_or_sample_num * header->fi.blocksize;
502  }
503 
504  fpc->best_header_valid = 0;
505  fpc->last_fi_valid = 1;
506  fpc->last_fi = header->fi;
507 
508  /* Return the negative overread index so the client can compute pos.
509  This should be the amount overread to the beginning of the child */
510  if (child)
511  return child->offset - av_fifo_size(fpc->fifo_buf);
512  return 0;
513 }
514 
516  const uint8_t **poutbuf, int *poutbuf_size,
517  const uint8_t *buf, int buf_size)
518 {
519  FLACParseContext *fpc = s->priv_data;
520  FLACHeaderMarker *curr;
521  int nb_headers;
522  const uint8_t *read_end = buf;
523  const uint8_t *read_start = buf;
524 
525  if (s->flags & PARSER_FLAG_COMPLETE_FRAMES) {
526  FLACFrameInfo fi;
527  if (frame_header_is_valid(avctx, buf, &fi)) {
528  s->duration = fi.blocksize;
529  if (!avctx->sample_rate)
530  avctx->sample_rate = fi.samplerate;
531  if (fpc->pc->flags & PARSER_FLAG_USE_CODEC_TS) {
532  fpc->pc->pts = fi.frame_or_sample_num;
533  if (!fi.is_var_size)
534  fpc->pc->pts *= fi.blocksize;
535  }
536  }
537  *poutbuf = buf;
538  *poutbuf_size = buf_size;
539  return buf_size;
540  }
541 
542  fpc->avctx = avctx;
543  if (fpc->best_header_valid)
544  return get_best_header(fpc, poutbuf, poutbuf_size);
545 
546  /* If a best_header was found last call remove it with the buffer data. */
547  if (fpc->best_header && fpc->best_header->best_child) {
549  FLACHeaderMarker *best_child = fpc->best_header->best_child;
550 
551  /* Remove headers in list until the end of the best_header. */
552  for (curr = fpc->headers; curr != best_child; curr = temp) {
553  if (curr != fpc->best_header) {
554  av_log(avctx, AV_LOG_DEBUG,
555  "dropping low score %i frame header from offset %i to %i\n",
556  curr->max_score, curr->offset, curr->next->offset);
557  }
558  temp = curr->next;
559  av_free(curr);
560  fpc->nb_headers_buffered--;
561  }
562  /* Release returned data from ring buffer. */
563  av_fifo_drain(fpc->fifo_buf, best_child->offset);
564 
565  /* Fix the offset for the headers remaining to match the new buffer. */
566  for (curr = best_child->next; curr; curr = curr->next)
567  curr->offset -= best_child->offset;
568 
569  best_child->offset = 0;
570  fpc->headers = best_child;
572  fpc->best_header = best_child;
573  return get_best_header(fpc, poutbuf, poutbuf_size);
574  }
575  fpc->best_header = NULL;
576  } else if (fpc->best_header) {
577  /* No end frame no need to delete the buffer; probably eof */
579 
580  for (curr = fpc->headers; curr != fpc->best_header; curr = temp) {
581  temp = curr->next;
582  av_free(curr);
583  fpc->nb_headers_buffered--;
584  }
585  fpc->headers = fpc->best_header->next;
586  av_freep(&fpc->best_header);
587  fpc->nb_headers_buffered--;
588  }
589 
590  /* Find and score new headers. */
591  /* buf_size is zero when flushing, so check for this since we do */
592  /* not want to try to read more input once we have found the end. */
593  /* Also note that buf can't be NULL. */
594  while ((buf_size && read_end < buf + buf_size &&
596  || (!buf_size && !fpc->end_padded)) {
597  int start_offset;
598 
599  /* Pad the end once if EOF, to check the final region for headers. */
600  if (!buf_size) {
601  fpc->end_padded = 1;
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  if (!av_fifo_space(fpc->fifo_buf) &&
613  fpc->nb_headers_buffered * 20) {
614  /* There is less than one valid flac header buffered for 20 headers
615  * buffered. Therefore the fifo is most likely filled with invalid
616  * data and the input is not a flac file. */
617  goto handle_error;
618  }
619 
620  /* Fill the buffer. */
621  if ( av_fifo_space(fpc->fifo_buf) < read_end - read_start
622  && av_fifo_realloc2(fpc->fifo_buf, (read_end - read_start) + 2*av_fifo_size(fpc->fifo_buf)) < 0) {
623  av_log(avctx, AV_LOG_ERROR,
624  "couldn't reallocate buffer of size %"PTRDIFF_SPECIFIER"\n",
625  (read_end - read_start) + av_fifo_size(fpc->fifo_buf));
626  goto handle_error;
627  }
628 
629  if (buf_size) {
630  av_fifo_generic_write(fpc->fifo_buf, (void*) read_start,
631  read_end - read_start, NULL);
632  } else {
633  int8_t pad[MAX_FRAME_HEADER_SIZE] = { 0 };
634  av_fifo_generic_write(fpc->fifo_buf, pad, sizeof(pad), NULL);
635  }
636 
637  /* Tag headers and update sequences. */
638  start_offset = av_fifo_size(fpc->fifo_buf) -
639  ((read_end - read_start) + (MAX_FRAME_HEADER_SIZE - 1));
640  start_offset = FFMAX(0, start_offset);
641  nb_headers = find_new_headers(fpc, start_offset);
642 
643  if (nb_headers < 0) {
644  av_log(avctx, AV_LOG_ERROR,
645  "find_new_headers couldn't allocate FLAC header\n");
646  goto handle_error;
647  }
648 
649  fpc->nb_headers_buffered = nb_headers;
650  /* Wait till FLAC_MIN_HEADERS to output a valid frame. */
651  if (!fpc->end_padded && fpc->nb_headers_buffered < FLAC_MIN_HEADERS) {
652  if (read_end < buf + buf_size) {
653  read_start = read_end;
654  continue;
655  } else {
656  goto handle_error;
657  }
658  }
659 
660  /* If headers found, update the scores since we have longer chains. */
661  if (fpc->end_padded || fpc->nb_headers_found)
662  score_sequences(fpc);
663 
664  /* restore the state pre-padding */
665  if (fpc->end_padded) {
666  int warp = fpc->fifo_buf->wptr - fpc->fifo_buf->buffer < MAX_FRAME_HEADER_SIZE;
667  /* HACK: drain the tail of the fifo */
670  if (warp) {
671  fpc->fifo_buf->wptr += fpc->fifo_buf->end -
672  fpc->fifo_buf->buffer;
673  }
674  read_start = read_end = NULL;
675  }
676  }
677 
678  for (curr = fpc->headers; curr; curr = curr->next) {
679  if (!fpc->best_header || curr->max_score > fpc->best_header->max_score) {
680  fpc->best_header = curr;
681  }
682  }
683 
684  if (fpc->best_header && fpc->best_header->max_score <= 0) {
685  // Only accept a bad header if there is no other option to continue
686  if (!buf_size || read_end != buf || fpc->nb_headers_buffered < FLAC_MIN_HEADERS)
687  fpc->best_header = NULL;
688  }
689 
690  if (fpc->best_header) {
691  fpc->best_header_valid = 1;
692  if (fpc->best_header->offset > 0) {
693  /* Output a junk frame. */
694  av_log(avctx, AV_LOG_DEBUG, "Junk frame till offset %i\n",
695  fpc->best_header->offset);
696 
697  /* Set duration to 0. It is unknown or invalid in a junk frame. */
698  s->duration = 0;
699  *poutbuf_size = fpc->best_header->offset;
700  *poutbuf = flac_fifo_read_wrap(fpc, 0, *poutbuf_size,
701  &fpc->wrap_buf,
703  return buf_size ? (read_end - buf) : (fpc->best_header->offset -
704  av_fifo_size(fpc->fifo_buf));
705  }
706  if (!buf_size)
707  return get_best_header(fpc, poutbuf, poutbuf_size);
708  }
709 
710 handle_error:
711  *poutbuf = NULL;
712  *poutbuf_size = 0;
713  return buf_size ? read_end - buf : 0;
714 }
715 
717 {
718  FLACParseContext *fpc = c->priv_data;
719  fpc->pc = c;
720  /* There will generally be FLAC_MIN_HEADERS buffered in the fifo before
721  it drains. This is allocated early to avoid slow reallocation. */
723  if (!fpc->fifo_buf) {
724  av_log(fpc->avctx, AV_LOG_ERROR,
725  "couldn't allocate fifo_buf\n");
726  return AVERROR(ENOMEM);
727  }
728  return 0;
729 }
730 
732 {
733  FLACParseContext *fpc = c->priv_data;
734  FLACHeaderMarker *curr = fpc->headers, *temp;
735 
736  while (curr) {
737  temp = curr->next;
738  av_free(curr);
739  curr = temp;
740  }
741  fpc->headers = NULL;
742  av_fifo_freep(&fpc->fifo_buf);
743  av_freep(&fpc->wrap_buf);
744 }
745 
748  .priv_data_size = sizeof(FLACParseContext),
749  .parser_init = flac_parse_init,
750  .parser_parse = flac_parse,
751  .parser_close = flac_parse_close,
752 };
FLACParseContext
Definition: flac_parser.c:76
FLACParseContext::headers
FLACHeaderMarker * headers
linked-list that starts at the first CRC-8 verified header within buffer
Definition: flac_parser.c:79
FLAC_HEADER_BASE_SCORE
#define FLAC_HEADER_BASE_SCORE
scoring settings for score_header
Definition: flac_parser.c:50
frame_header_is_valid
static int frame_header_is_valid(AVCodecContext *avctx, const uint8_t *buf, FLACFrameInfo *fi)
Definition: flac_parser.c:96
AV_LOG_WARNING
#define AV_LOG_WARNING
Something somehow does not look correct.
Definition: log.h:200
check_header_fi_mismatch
static int check_header_fi_mismatch(FLACParseContext *fpc, FLACFrameInfo *header_fi, FLACFrameInfo *child_fi, int log_level_offset)
Definition: flac_parser.c:276
FLACParseContext::nb_headers_buffered
int nb_headers_buffered
number of headers that are buffered
Definition: flac_parser.c:84
AVCodecParserContext::pts
int64_t pts
Definition: avcodec.h:3396
find_new_headers
static int find_new_headers(FLACParseContext *fpc, int search_start)
Definition: flac_parser.c:232
FLACHeaderMarker
Definition: flac_parser.c:60
AVERROR
Filter the word “frame” indicates either a video frame or a group of audio as stored in an AVFrame structure Format for each input and each output the list of supported formats For video that means pixel format For audio that means channel sample they are references to shared objects When the negotiation mechanism computes the intersection of the formats supported at each end of a all references to both lists are replaced with a reference to the intersection And when a single format is eventually chosen for a link amongst the remaining all references to the list are updated That means that if a filter requires that its input and output have the same format amongst a supported all it has to do is use a reference to the same list of formats query_formats can leave some formats unset and return AVERROR(EAGAIN) to cause the negotiation mechanism toagain later. That can be used by filters with complex requirements to use the format negotiated on one link to set the formats supported on another. Frame references ownership and permissions
AVCodecContext::channel_layout
uint64_t channel_layout
Audio channel layout.
Definition: avcodec.h:1247
av_fifo_generic_write
int av_fifo_generic_write(AVFifoBuffer *f, void *src, int size, int(*func)(void *, void *, int))
Feed data from a user-supplied callback to an AVFifoBuffer.
Definition: fifo.c:122
AVCodecContext::sample_rate
int sample_rate
samples per second
Definition: avcodec.h:1196
AVCodecParserContext::duration
int duration
Duration of the current frame.
Definition: avcodec.h:3499
AVFifoBuffer::wptr
uint8_t * wptr
Definition: fifo.h:33
FLACParseContext::wrap_buf
uint8_t * wrap_buf
general fifo read buffer when wrapped
Definition: flac_parser.c:90
FLACHeaderMarker::best_child
struct FLACHeaderMarker * best_child
following frame header with which this frame has the best score with
Definition: flac_parser.c:71
FLACFrameInfo::frame_or_sample_num
int64_t frame_or_sample_num
frame number or sample number
Definition: flac.h:88
FLACFrameInfo::is_var_size
int is_var_size
specifies if the stream uses variable block sizes or a fixed block size; also determines the meaning ...
Definition: flac.h:89
score_sequences
static void score_sequences(FLACParseContext *fpc)
Definition: flac_parser.c:454
ff_flac_decode_frame_header
int ff_flac_decode_frame_header(AVCodecContext *avctx, GetBitContext *gb, FLACFrameInfo *fi, int log_level_offset)
Validate and decode a frame header.
Definition: flac.c:50
AV_CODEC_ID_FLAC
@ AV_CODEC_ID_FLAC
Definition: codec_id.h:436
FLAC_HEADER_CHANGED_PENALTY
#define FLAC_HEADER_CHANGED_PENALTY
Definition: flac_parser.c:51
FLAC_MAX_SEQUENTIAL_HEADERS
#define FLAC_MAX_SEQUENTIAL_HEADERS
maximum number of adjacent headers that compare CRCs against each other
Definition: flac_parser.c:43
init_get_bits
static int init_get_bits(GetBitContext *s, const uint8_t *buffer, int bit_size)
Initialize GetBitContext.
Definition: get_bits.h:659
FLACParseContext::wrap_buf_allocated_size
int wrap_buf_allocated_size
actual allocated size of the buffer
Definition: flac_parser.c:91
av_fifo_drain
void av_fifo_drain(AVFifoBuffer *f, int size)
Discard data from the FIFO.
Definition: fifo.c:233
AVFifoBuffer
Definition: fifo.h:31
crc.h
flac_fifo_read_wrap
static uint8_t * flac_fifo_read_wrap(FLACParseContext *fpc, int offset, int len, uint8_t **wrap_buf, int *allocated_size)
Non-destructive fast fifo pointer fetching Returns a pointer from the specified offset.
Definition: flac_parser.c:117
fifo.h
wrap
#define wrap(func)
Definition: neontest.h:65
FLACParseContext::fifo_buf
AVFifoBuffer * fifo_buf
buffer to store all data until headers can be verified
Definition: flac_parser.c:87
GetBitContext
Definition: get_bits.h:61
FLACParseContext::best_header_valid
int best_header_valid
flag set when the parser returns junk; if set return best_header next time
Definition: flac_parser.c:85
flac_fifo_read
static uint8_t * flac_fifo_read(FLACParseContext *fpc, int offset, int *len)
Return a pointer in the fifo buffer where the offset starts at until the wrap point or end of request...
Definition: flac_parser.c:157
get_best_header
static int get_best_header(FLACParseContext *fpc, const uint8_t **poutbuf, int *poutbuf_size)
Definition: flac_parser.c:471
AV_LOG_ERROR
#define AV_LOG_ERROR
Something went wrong and cannot losslessly be recovered.
Definition: log.h:194
av_fifo_space
int av_fifo_space(const AVFifoBuffer *f)
Return the amount of space in bytes in the AVFifoBuffer, that is the amount of data you can write int...
Definition: fifo.c:82
av_cold
#define av_cold
Definition: attributes.h:90
FLACHeaderMarker::next
struct FLACHeaderMarker * next
next CRC-8 verified header that immediately follows this one in the bytestream
Definition: flac_parser.c:68
av_fast_realloc
void * av_fast_realloc(void *ptr, unsigned int *size, size_t min_size)
Reallocate the given buffer if it is not large enough, otherwise do nothing.
Definition: mem.c:478
FLAC_AVG_FRAME_SIZE
#define FLAC_AVG_FRAME_SIZE
estimate for average size of a FLAC frame
Definition: flac_parser.c:47
s
#define s(width, name)
Definition: cbs_vp9.c:257
AV_LOG_DEBUG
#define AV_LOG_DEBUG
Stuff which is only useful for libav* developers.
Definition: log.h:215
FLACParseContext::last_fi_valid
int last_fi_valid
set if last_fi is valid
Definition: flac_parser.c:93
FLACParseContext::avctx
AVCodecContext * avctx
codec context pointer for logging
Definition: flac_parser.c:78
find_headers_search_validate
static int find_headers_search_validate(FLACParseContext *fpc, int offset)
Definition: flac_parser.c:168
FLACParseContext::pc
AVCodecParserContext * pc
parent context
Definition: flac_parser.c:77
av_fifo_realloc2
int av_fifo_realloc2(AVFifoBuffer *f, unsigned int new_size)
Resize an AVFifoBuffer.
Definition: fifo.c:87
f
#define f(width, name)
Definition: cbs_vp9.c:255
ff_flac_parser
AVCodecParser ff_flac_parser
Definition: flac_parser.c:746
if
if(ret)
Definition: filter_design.txt:179
AV_CRC_16_ANSI
@ AV_CRC_16_ANSI
Definition: crc.h:51
score_header
static int score_header(FLACParseContext *fpc, FLACHeaderMarker *header)
Score a header.
Definition: flac_parser.c:414
PTRDIFF_SPECIFIER
#define PTRDIFF_SPECIFIER
Definition: internal.h:192
NULL
#define NULL
Definition: coverity.c:32
FLACFrameInfo::blocksize
FLACCOMMONINFO int blocksize
block size of the frame
Definition: flac.h:86
AVCodecParser::codec_ids
int codec_ids[5]
Definition: avcodec.h:3545
flac_parse
static int flac_parse(AVCodecParserContext *s, AVCodecContext *avctx, const uint8_t **poutbuf, int *poutbuf_size, const uint8_t *buf, int buf_size)
Definition: flac_parser.c:515
find_headers_search
static int find_headers_search(FLACParseContext *fpc, uint8_t *buf, int buf_size, int search_start)
Definition: flac_parser.c:205
AV_RN32
#define AV_RN32(p)
Definition: intreadwrite.h:364
AVFifoBuffer::end
uint8_t * end
Definition: fifo.h:33
ff_flac_set_channel_layout
void ff_flac_set_channel_layout(AVCodecContext *avctx)
Definition: flac.c:196
AVCodecParserContext::flags
int flags
Definition: avcodec.h:3410
FLACFrameInfo
Definition: flac.h:84
FLAC_HEADER_CRC_FAIL_PENALTY
#define FLAC_HEADER_CRC_FAIL_PENALTY
Definition: flac_parser.c:52
c
Undefined Behavior In the C some operations are like signed integer dereferencing freed accessing outside allocated Undefined Behavior must not occur in a C it is not safe even if the output of undefined operations is unused The unsafety may seem nit picking but Optimizing compilers have in fact optimized code on the assumption that no undefined Behavior occurs Optimizing code based on wrong assumptions can and has in some cases lead to effects beyond the output of computations The signed integer overflow problem in speed critical code Code which is highly optimized and works with signed integers sometimes has the problem that often the output of the computation does not c
Definition: undefined.txt:32
FLAC_HEADER_NOT_SCORED_YET
#define FLAC_HEADER_NOT_SCORED_YET
Definition: flac_parser.c:54
FFMAX
#define FFMAX(a, b)
Definition: common.h:103
size
int size
Definition: twinvq_data.h:10344
header
static const uint8_t header[24]
Definition: sdr2.c:67
FFMIN
#define FFMIN(a, b)
Definition: common.h:105
av_crc_get_table
const AVCRC * av_crc_get_table(AVCRCId crc_id)
Get an initialized standard CRC table.
Definition: crc.c:374
offset
it s the only field you need to keep assuming you have a context There is some magic you don t need to care about around this just let it vf offset
Definition: writing_filters.txt:86
attributes.h
flac_parse_init
static av_cold int flac_parse_init(AVCodecParserContext *c)
Definition: flac_parser.c:716
FLACHeaderMarker::fi
FLACFrameInfo fi
decoded frame header info
Definition: flac_parser.c:67
AVCodecContext::channels
int channels
number of audio channels
Definition: avcodec.h:1197
FLACParseContext::best_header
FLACHeaderMarker * best_header
highest scoring header within buffer
Definition: flac_parser.c:81
i
int i
Definition: input.c:407
PARSER_FLAG_COMPLETE_FRAMES
#define PARSER_FLAG_COMPLETE_FRAMES
Definition: avcodec.h:3411
FLACHeaderMarker::max_score
int max_score
maximum score found after checking each child that has a valid CRC
Definition: flac_parser.c:65
FLACParseContext::end_padded
int end_padded
specifies if fifo_buf's end is padded
Definition: flac_parser.c:89
av_fifo_alloc_array
AVFifoBuffer * av_fifo_alloc_array(size_t nmemb, size_t size)
Initialize an AVFifoBuffer.
Definition: fifo.c:49
uint8_t
uint8_t
Definition: audio_convert.c:194
av_mallocz
void * av_mallocz(size_t size)
Allocate a memory block with alignment suitable for all memory accesses (including vectors if availab...
Definition: mem.c:237
MAX_FRAME_VERIFY_SIZE
#define MAX_FRAME_VERIFY_SIZE
Definition: flac_parser.c:58
parser.h
len
int len
Definition: vorbis_enc_data.h:452
AVFifoBuffer::buffer
uint8_t * buffer
Definition: fifo.h:32
AVFifoBuffer::wndx
uint32_t wndx
Definition: fifo.h:34
check_header_mismatch
static int check_header_mismatch(FLACParseContext *fpc, FLACHeaderMarker *header, FLACHeaderMarker *child, int log_level_offset)
Definition: flac_parser.c:306
AVCodecParserContext
Definition: avcodec.h:3377
ret
ret
Definition: filter_design.txt:187
FLACParseContext::nb_headers_found
int nb_headers_found
number of headers found in the last flac_parse() call
Definition: flac_parser.c:82
MAX_FRAME_HEADER_SIZE
#define MAX_FRAME_HEADER_SIZE
largest possible size of flac header
Definition: flac_parser.c:57
AV_INPUT_BUFFER_PADDING_SIZE
#define AV_INPUT_BUFFER_PADDING_SIZE
Definition: avcodec.h:215
AVCodecContext
main external API structure.
Definition: avcodec.h:536
av_crc
uint32_t av_crc(const AVCRC *ctx, uint32_t crc, const uint8_t *buffer, size_t length)
Calculate the CRC of a block.
Definition: crc.c:392
PARSER_FLAG_USE_CODEC_TS
#define PARSER_FLAG_USE_CODEC_TS
Definition: avcodec.h:3415
temp
else temp
Definition: vf_mcdeint.c:259
FLACHeaderMarker::link_penalty
int link_penalty[FLAC_MAX_SEQUENTIAL_HEADERS]
array of local scores between this header and the one at a distance equal array position
Definition: flac_parser.c:62
FLAC_MIN_HEADERS
#define FLAC_MIN_HEADERS
minimum number of headers buffered and checked before returning frames
Definition: flac_parser.c:45
av_fifo_size
int av_fifo_size(const AVFifoBuffer *f)
Return the amount of data in bytes in the AVFifoBuffer, that is the amount of data you can read from ...
Definition: fifo.c:77
FLACHeaderMarker::offset
int offset
byte offset from start of FLACParseContext->buffer
Definition: flac_parser.c:61
av_fifo_freep
void av_fifo_freep(AVFifoBuffer **f)
Free an AVFifoBuffer and reset pointer to NULL.
Definition: fifo.c:63
av_free
#define av_free(p)
Definition: tableprint_vlc.h:34
av_freep
#define av_freep(p)
Definition: tableprint_vlc.h:35
FLAC_HEADER_NOT_PENALIZED_YET
#define FLAC_HEADER_NOT_PENALIZED_YET
Definition: flac_parser.c:53
AVCodecParser
Definition: avcodec.h:3544
FLACParseContext::last_fi
FLACFrameInfo last_fi
last decoded frame header info
Definition: flac_parser.c:92
bytestream.h
av_log
#define av_log(a,...)
Definition: tableprint_vlc.h:28
flac.h
flac_parse_close
static void flac_parse_close(AVCodecParserContext *c)
Definition: flac_parser.c:731
AV_RB16
uint64_t_TMPL AV_WL64 unsigned int_TMPL AV_WL32 unsigned int_TMPL AV_WL24 unsigned int_TMPL AV_WL16 uint64_t_TMPL AV_WB64 unsigned int_TMPL AV_WB32 unsigned int_TMPL AV_WB24 unsigned int_TMPL AV_RB16
Definition: bytestream.h:98