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 
59 typedef struct FLACHeaderMarker {
60  int offset; /**< byte offset from start of FLACParseContext->buffer */
61  int link_penalty[FLAC_MAX_SEQUENTIAL_HEADERS]; /**< array of local scores
62  between this header and the one at a distance equal
63  array position */
64  int max_score; /**< maximum score found after checking each child that
65  has a valid CRC */
66  FLACFrameInfo fi; /**< decoded frame header info */
67  struct FLACHeaderMarker *next; /**< next CRC-8 verified header that
68  immediately follows this one in
69  the bytestream */
70  struct FLACHeaderMarker *best_child; /**< following frame header with
71  which this frame has the best
72  score with */
74 
75 typedef struct FLACParseContext {
76  AVCodecParserContext *pc; /**< parent context */
77  AVCodecContext *avctx; /**< codec context pointer for logging */
78  FLACHeaderMarker *headers; /**< linked-list that starts at the first
79  CRC-8 verified header within buffer */
80  FLACHeaderMarker *best_header; /**< highest scoring header within buffer */
81  int nb_headers_found; /**< number of headers found in the last
82  flac_parse() call */
83  int nb_headers_buffered; /**< number of headers that are buffered */
84  int best_header_valid; /**< flag set when the parser returns junk;
85  if set return best_header next time */
86  AVFifoBuffer *fifo_buf; /**< buffer to store all data until headers
87  can be verified */
88  int end_padded; /**< specifies if fifo_buf's end is padded */
89  uint8_t *wrap_buf; /**< general fifo read buffer when wrapped */
90  int wrap_buf_allocated_size; /**< actual allocated size of the buffer */
91  FLACFrameInfo last_fi; /**< last decoded frame header info */
92  int last_fi_valid; /**< set if last_fi is valid */
94 
95 static int frame_header_is_valid(AVCodecContext *avctx, const uint8_t *buf,
96  FLACFrameInfo *fi)
97 {
98  GetBitContext gb;
99  uint8_t subframe_type;
100 
101  // header plus one byte from first subframe
102  init_get_bits(&gb, buf, MAX_FRAME_HEADER_SIZE * 8 + 8);
103  if (ff_flac_decode_frame_header(avctx, &gb, fi, 127)) {
104  return 0;
105  }
106  // subframe zero bit
107  if (get_bits1(&gb) != 0) {
108  return 0;
109  }
110  // subframe type
111  // 000000 : SUBFRAME_CONSTANT
112  // 000001 : SUBFRAME_VERBATIM
113  // 00001x : reserved
114  // 0001xx : reserved
115  // 001xxx : if(xxx <= 4) SUBFRAME_FIXED, xxx=order ; else reserved
116  // 01xxxx : reserved
117  // 1xxxxx : SUBFRAME_LPC, xxxxx=order-1
118  subframe_type = get_bits(&gb, 6);
119  if (!(subframe_type == 0 ||
120  subframe_type == 1 ||
121  ((subframe_type >= 8) && (subframe_type <= 12)) ||
122  (subframe_type >= 32))) {
123  return 0;
124  }
125 
126  return 1;
127 }
128 
129 /**
130  * Non-destructive fast fifo pointer fetching
131  * Returns a pointer from the specified offset.
132  * If possible the pointer points within the fifo buffer.
133  * Otherwise (if it would cause a wrap around,) a pointer to a user-specified
134  * buffer is used.
135  * The pointer can be NULL. In any case it will be reallocated to hold the size.
136  * If the returned pointer will be used after subsequent calls to flac_fifo_read_wrap
137  * then the subsequent calls should pass in a different wrap_buf so as to not
138  * overwrite the contents of the previous wrap_buf.
139  * This function is based on av_fifo_generic_read, which is why there is a comment
140  * about a memory barrier for SMP.
141  */
142 static uint8_t *flac_fifo_read_wrap(FLACParseContext *fpc, int offset, int len,
143  uint8_t **wrap_buf, int *allocated_size)
144 {
145  AVFifoBuffer *f = fpc->fifo_buf;
146  uint8_t *start = f->rptr + offset;
147  uint8_t *tmp_buf;
148 
149  if (start >= f->end)
150  start -= f->end - f->buffer;
151  if (f->end - start >= len)
152  return start;
153 
154  tmp_buf = av_fast_realloc(*wrap_buf, allocated_size, len);
155 
156  if (!tmp_buf) {
157  av_log(fpc->avctx, AV_LOG_ERROR,
158  "couldn't reallocate wrap buffer of size %d", len);
159  return NULL;
160  }
161  *wrap_buf = tmp_buf;
162  do {
163  int seg_len = FFMIN(f->end - start, len);
164  memcpy(tmp_buf, start, seg_len);
165  tmp_buf = (uint8_t*)tmp_buf + seg_len;
166 // memory barrier needed for SMP here in theory
167 
168  start += seg_len - (f->end - f->buffer);
169  len -= seg_len;
170  } while (len > 0);
171 
172  return *wrap_buf;
173 }
174 
175 /**
176  * Return a pointer in the fifo buffer where the offset starts at until
177  * the wrap point or end of request.
178  * len will contain the valid length of the returned buffer.
179  * A second call to flac_fifo_read (with new offset and len) should be called
180  * to get the post-wrap buf if the returned len is less than the requested.
181  **/
182 static uint8_t *flac_fifo_read(FLACParseContext *fpc, int offset, int *len)
183 {
184  AVFifoBuffer *f = fpc->fifo_buf;
185  uint8_t *start = f->rptr + offset;
186 
187  if (start >= f->end)
188  start -= f->end - f->buffer;
189  *len = FFMIN(*len, f->end - start);
190  return start;
191 }
192 
194 {
195  FLACFrameInfo fi;
196  uint8_t *header_buf;
197  int size = 0;
198  header_buf = flac_fifo_read_wrap(fpc, offset,
200  &fpc->wrap_buf,
202  if (frame_header_is_valid(fpc->avctx, header_buf, &fi)) {
203  FLACHeaderMarker **end_handle = &fpc->headers;
204  int i;
205 
206  size = 0;
207  while (*end_handle) {
208  end_handle = &(*end_handle)->next;
209  size++;
210  }
211 
212  *end_handle = av_mallocz(sizeof(**end_handle));
213  if (!*end_handle) {
214  av_log(fpc->avctx, AV_LOG_ERROR,
215  "couldn't allocate FLACHeaderMarker\n");
216  return AVERROR(ENOMEM);
217  }
218  (*end_handle)->fi = fi;
219  (*end_handle)->offset = offset;
220 
221  for (i = 0; i < FLAC_MAX_SEQUENTIAL_HEADERS; i++)
222  (*end_handle)->link_penalty[i] = FLAC_HEADER_NOT_PENALIZED_YET;
223 
224  fpc->nb_headers_found++;
225  size++;
226  }
227  return size;
228 }
229 
230 static int find_headers_search(FLACParseContext *fpc, uint8_t *buf,
231  int buf_size, int search_start)
232 {
233  int size = 0, mod_offset = (buf_size - 1) % 4, i, j;
234  uint32_t x;
235 
236  for (i = 0; i < mod_offset; i++) {
237  if ((AV_RB16(buf + i) & 0xFFFE) == 0xFFF8) {
238  int ret = find_headers_search_validate(fpc, search_start + i);
239  size = FFMAX(size, ret);
240  }
241  }
242 
243  for (; i < buf_size - 1; i += 4) {
244  x = AV_RN32(buf + i);
245  if (((x & ~(x + 0x01010101)) & 0x80808080)) {
246  for (j = 0; j < 4; j++) {
247  if ((AV_RB16(buf + i + j) & 0xFFFE) == 0xFFF8) {
248  int ret = find_headers_search_validate(fpc, search_start + i + j);
249  size = FFMAX(size, ret);
250  }
251  }
252  }
253  }
254  return size;
255 }
256 
257 static int find_new_headers(FLACParseContext *fpc, int search_start)
258 {
259  FLACHeaderMarker *end;
260  int search_end, size = 0, read_len, temp;
261  uint8_t *buf;
262  fpc->nb_headers_found = 0;
263 
264  /* Search for a new header of at most 16 bytes. */
265  search_end = av_fifo_size(fpc->fifo_buf) - (MAX_FRAME_HEADER_SIZE - 1);
266  read_len = search_end - search_start + 1;
267  buf = flac_fifo_read(fpc, search_start, &read_len);
268  size = find_headers_search(fpc, buf, read_len, search_start);
269  search_start += read_len - 1;
270 
271  /* If fifo end was hit do the wrap around. */
272  if (search_start != search_end) {
273  uint8_t wrap[2];
274 
275  wrap[0] = buf[read_len - 1];
276  /* search_start + 1 is the post-wrap offset in the fifo. */
277  read_len = search_end - (search_start + 1) + 1;
278 
279  buf = flac_fifo_read(fpc, search_start + 1, &read_len);
280  wrap[1] = buf[0];
281 
282  if ((AV_RB16(wrap) & 0xFFFE) == 0xFFF8) {
283  temp = find_headers_search_validate(fpc, search_start);
284  size = FFMAX(size, temp);
285  }
286  search_start++;
287 
288  /* Continue to do the last half of the wrap. */
289  temp = find_headers_search(fpc, buf, read_len, search_start);
290  size = FFMAX(size, temp);
291  search_start += read_len - 1;
292  }
293 
294  /* Return the size even if no new headers were found. */
295  if (!size && fpc->headers)
296  for (end = fpc->headers; end; end = end->next)
297  size++;
298  return size;
299 }
300 
302  FLACFrameInfo *header_fi,
303  FLACFrameInfo *child_fi,
304  int log_level_offset)
305 {
306  int deduction = 0;
307  if (child_fi->samplerate != header_fi->samplerate) {
308  deduction += FLAC_HEADER_CHANGED_PENALTY;
309  av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
310  "sample rate change detected in adjacent frames\n");
311  }
312  if (child_fi->bps != header_fi->bps) {
313  deduction += FLAC_HEADER_CHANGED_PENALTY;
314  av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
315  "bits per sample change detected in adjacent frames\n");
316  }
317  if (child_fi->is_var_size != header_fi->is_var_size) {
318  /* Changing blocking strategy not allowed per the spec */
319  deduction += FLAC_HEADER_BASE_SCORE;
320  av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
321  "blocking strategy change detected in adjacent frames\n");
322  }
323  if (child_fi->channels != header_fi->channels) {
324  deduction += FLAC_HEADER_CHANGED_PENALTY;
325  av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
326  "number of channels change detected in adjacent frames\n");
327  }
328  return deduction;
329 }
330 
333  FLACHeaderMarker *child,
334  int log_level_offset)
335 {
336  FLACFrameInfo *header_fi = &header->fi, *child_fi = &child->fi;
337  int deduction, deduction_expected = 0, i;
338  deduction = check_header_fi_mismatch(fpc, header_fi, child_fi,
339  log_level_offset);
340  /* Check sample and frame numbers. */
341  if ((child_fi->frame_or_sample_num - header_fi->frame_or_sample_num
342  != header_fi->blocksize) &&
343  (child_fi->frame_or_sample_num
344  != header_fi->frame_or_sample_num + 1)) {
345  FLACHeaderMarker *curr;
346  int64_t expected_frame_num, expected_sample_num;
347  /* If there are frames in the middle we expect this deduction,
348  as they are probably valid and this one follows it */
349 
350  expected_frame_num = expected_sample_num = header_fi->frame_or_sample_num;
351  curr = header;
352  while (curr != child) {
353  /* Ignore frames that failed all crc checks */
354  for (i = 0; i < FLAC_MAX_SEQUENTIAL_HEADERS; i++) {
356  expected_frame_num++;
357  expected_sample_num += curr->fi.blocksize;
358  break;
359  }
360  }
361  curr = curr->next;
362  }
363 
364  if (expected_frame_num == child_fi->frame_or_sample_num ||
365  expected_sample_num == child_fi->frame_or_sample_num)
366  deduction_expected = deduction ? 0 : 1;
367 
368  deduction += FLAC_HEADER_CHANGED_PENALTY;
369  av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
370  "sample/frame number mismatch in adjacent frames\n");
371  }
372 
373  /* If we have suspicious headers, check the CRC between them */
374  if (deduction && !deduction_expected) {
375  FLACHeaderMarker *curr;
376  int read_len;
377  uint8_t *buf;
378  uint32_t crc = 1;
379  int inverted_test = 0;
380 
381  /* Since CRC is expensive only do it if we haven't yet.
382  This assumes a CRC penalty is greater than all other check penalties */
383  curr = header->next;
384  for (i = 0; i < FLAC_MAX_SEQUENTIAL_HEADERS && curr != child; i++)
385  curr = curr->next;
386 
387  if (header->link_penalty[i] < FLAC_HEADER_CRC_FAIL_PENALTY ||
388  header->link_penalty[i] == FLAC_HEADER_NOT_PENALIZED_YET) {
389  FLACHeaderMarker *start, *end;
390 
391  /* Although overlapping chains are scored, the crc should never
392  have to be computed twice for a single byte. */
393  start = header;
394  end = child;
395  if (i > 0 &&
396  header->link_penalty[i - 1] >= FLAC_HEADER_CRC_FAIL_PENALTY) {
397  while (start->next != child)
398  start = start->next;
399  inverted_test = 1;
400  } else if (i > 0 &&
401  header->next->link_penalty[i-1] >=
403  end = header->next;
404  inverted_test = 1;
405  }
406 
407  read_len = end->offset - start->offset;
408  buf = flac_fifo_read(fpc, start->offset, &read_len);
409  crc = av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0, buf, read_len);
410  read_len = (end->offset - start->offset) - read_len;
411 
412  if (read_len) {
413  buf = flac_fifo_read(fpc, end->offset - read_len, &read_len);
414  crc = av_crc(av_crc_get_table(AV_CRC_16_ANSI), crc, buf, read_len);
415  }
416  }
417 
418  if (!crc ^ !inverted_test) {
419  deduction += FLAC_HEADER_CRC_FAIL_PENALTY;
420  av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
421  "crc check failed from offset %i (frame %"PRId64") to %i (frame %"PRId64")\n",
422  header->offset, header_fi->frame_or_sample_num,
423  child->offset, child_fi->frame_or_sample_num);
424  }
425  }
426  return deduction;
427 }
428 
429 /**
430  * Score a header.
431  *
432  * Give FLAC_HEADER_BASE_SCORE points to a frame for existing.
433  * If it has children, (subsequent frames of which the preceding CRC footer
434  * validates against this one,) then take the maximum score of the children,
435  * with a penalty of FLAC_HEADER_CHANGED_PENALTY applied for each change to
436  * bps, sample rate, channels, but not decorrelation mode, or blocksize,
437  * because it can change often.
438  **/
440 {
441  FLACHeaderMarker *child;
442  int dist = 0;
443  int child_score;
444  int base_score = FLAC_HEADER_BASE_SCORE;
445  if (header->max_score != FLAC_HEADER_NOT_SCORED_YET)
446  return header->max_score;
447 
448  /* Modify the base score with changes from the last output header */
449  if (fpc->last_fi_valid) {
450  /* Silence the log since this will be repeated if selected */
451  base_score -= check_header_fi_mismatch(fpc, &fpc->last_fi, &header->fi,
452  AV_LOG_DEBUG);
453  }
454 
455  header->max_score = base_score;
456 
457  /* Check and compute the children's scores. */
458  child = header->next;
459  for (dist = 0; dist < FLAC_MAX_SEQUENTIAL_HEADERS && child; dist++) {
460  /* Look at the child's frame header info and penalize suspicious
461  changes between the headers. */
462  if (header->link_penalty[dist] == FLAC_HEADER_NOT_PENALIZED_YET) {
463  header->link_penalty[dist] = check_header_mismatch(fpc, header,
464  child, AV_LOG_DEBUG);
465  }
466  child_score = score_header(fpc, child) - header->link_penalty[dist];
467 
468  if (FLAC_HEADER_BASE_SCORE + child_score > header->max_score) {
469  /* Keep the child because the frame scoring is dynamic. */
470  header->best_child = child;
471  header->max_score = base_score + child_score;
472  }
473  child = child->next;
474  }
475 
476  return header->max_score;
477 }
478 
480 {
481  FLACHeaderMarker *curr;
482  int best_score = 0;//FLAC_HEADER_NOT_SCORED_YET;
483  /* First pass to clear all old scores. */
484  for (curr = fpc->headers; curr; curr = curr->next)
486 
487  /* Do a second pass to score them all. */
488  for (curr = fpc->headers; curr; curr = curr->next) {
489  if (score_header(fpc, curr) > best_score) {
490  fpc->best_header = curr;
491  best_score = curr->max_score;
492  }
493  }
494 }
495 
496 static int get_best_header(FLACParseContext *fpc, const uint8_t **poutbuf,
497  int *poutbuf_size)
498 {
500  FLACHeaderMarker *child = header->best_child;
501  if (!child) {
502  *poutbuf_size = av_fifo_size(fpc->fifo_buf) - header->offset;
503  } else {
504  *poutbuf_size = child->offset - header->offset;
505 
506  /* If the child has suspicious changes, log them */
507  check_header_mismatch(fpc, header, child, 0);
508  }
509 
510  if (header->fi.channels != fpc->avctx->channels ||
511  !fpc->avctx->channel_layout) {
512  fpc->avctx->channels = header->fi.channels;
514  }
515  fpc->avctx->sample_rate = header->fi.samplerate;
516  fpc->pc->duration = header->fi.blocksize;
517  *poutbuf = flac_fifo_read_wrap(fpc, header->offset, *poutbuf_size,
518  &fpc->wrap_buf,
520 
521 
522  if (fpc->pc->flags & PARSER_FLAG_USE_CODEC_TS) {
523  if (header->fi.is_var_size)
524  fpc->pc->pts = header->fi.frame_or_sample_num;
525  else if (header->best_child)
526  fpc->pc->pts = header->fi.frame_or_sample_num * header->fi.blocksize;
527  }
528 
529  fpc->best_header_valid = 0;
530  fpc->last_fi_valid = 1;
531  fpc->last_fi = header->fi;
532 
533  /* Return the negative overread index so the client can compute pos.
534  This should be the amount overread to the beginning of the child */
535  if (child)
536  return child->offset - av_fifo_size(fpc->fifo_buf);
537  return 0;
538 }
539 
541  const uint8_t **poutbuf, int *poutbuf_size,
542  const uint8_t *buf, int buf_size)
543 {
544  FLACParseContext *fpc = s->priv_data;
545  FLACHeaderMarker *curr;
546  int nb_headers;
547  const uint8_t *read_end = buf;
548  const uint8_t *read_start = buf;
549 
550  if (s->flags & PARSER_FLAG_COMPLETE_FRAMES) {
551  FLACFrameInfo fi;
552  if (frame_header_is_valid(avctx, buf, &fi)) {
553  s->duration = fi.blocksize;
554  if (!avctx->sample_rate)
555  avctx->sample_rate = fi.samplerate;
556  if (fpc->pc->flags & PARSER_FLAG_USE_CODEC_TS) {
557  fpc->pc->pts = fi.frame_or_sample_num;
558  if (!fi.is_var_size)
559  fpc->pc->pts *= fi.blocksize;
560  }
561  }
562  *poutbuf = buf;
563  *poutbuf_size = buf_size;
564  return buf_size;
565  }
566 
567  fpc->avctx = avctx;
568  if (fpc->best_header_valid)
569  return get_best_header(fpc, poutbuf, poutbuf_size);
570 
571  /* If a best_header was found last call remove it with the buffer data. */
572  if (fpc->best_header && fpc->best_header->best_child) {
574  FLACHeaderMarker *best_child = fpc->best_header->best_child;
575 
576  /* Remove headers in list until the end of the best_header. */
577  for (curr = fpc->headers; curr != best_child; curr = temp) {
578  if (curr != fpc->best_header) {
579  av_log(avctx, AV_LOG_DEBUG,
580  "dropping low score %i frame header from offset %i to %i\n",
581  curr->max_score, curr->offset, curr->next->offset);
582  }
583  temp = curr->next;
584  av_free(curr);
585  fpc->nb_headers_buffered--;
586  }
587  /* Release returned data from ring buffer. */
588  av_fifo_drain(fpc->fifo_buf, best_child->offset);
589 
590  /* Fix the offset for the headers remaining to match the new buffer. */
591  for (curr = best_child->next; curr; curr = curr->next)
592  curr->offset -= best_child->offset;
593 
594  best_child->offset = 0;
595  fpc->headers = best_child;
597  fpc->best_header = best_child;
598  return get_best_header(fpc, poutbuf, poutbuf_size);
599  }
600  fpc->best_header = NULL;
601  } else if (fpc->best_header) {
602  /* No end frame no need to delete the buffer; probably eof */
604 
605  for (curr = fpc->headers; curr != fpc->best_header; curr = temp) {
606  temp = curr->next;
607  av_free(curr);
608  fpc->nb_headers_buffered--;
609  }
610  fpc->headers = fpc->best_header->next;
611  av_freep(&fpc->best_header);
612  fpc->nb_headers_buffered--;
613  }
614 
615  /* Find and score new headers. */
616  /* buf_size is zero when flushing, so check for this since we do */
617  /* not want to try to read more input once we have found the end. */
618  /* Also note that buf can't be NULL. */
619  while ((buf_size && read_end < buf + buf_size &&
621  || (!buf_size && !fpc->end_padded)) {
622  int start_offset;
623 
624  /* Pad the end once if EOF, to check the final region for headers. */
625  if (!buf_size) {
626  fpc->end_padded = 1;
627  read_end = read_start + MAX_FRAME_HEADER_SIZE;
628  } else {
629  /* The maximum read size is the upper-bound of what the parser
630  needs to have the required number of frames buffered */
631  int nb_desired = FLAC_MIN_HEADERS - fpc->nb_headers_buffered + 1;
632  read_end = read_end + FFMIN(buf + buf_size - read_end,
633  nb_desired * FLAC_AVG_FRAME_SIZE);
634  }
635 
636  if (!av_fifo_space(fpc->fifo_buf) &&
638  fpc->nb_headers_buffered * 20) {
639  /* There is less than one valid flac header buffered for 20 headers
640  * buffered. Therefore the fifo is most likely filled with invalid
641  * data and the input is not a flac file. */
642  goto handle_error;
643  }
644 
645  /* Fill the buffer. */
646  if ( av_fifo_space(fpc->fifo_buf) < read_end - read_start
647  && av_fifo_realloc2(fpc->fifo_buf, (read_end - read_start) + 2*av_fifo_size(fpc->fifo_buf)) < 0) {
648  av_log(avctx, AV_LOG_ERROR,
649  "couldn't reallocate buffer of size %"PTRDIFF_SPECIFIER"\n",
650  (read_end - read_start) + av_fifo_size(fpc->fifo_buf));
651  goto handle_error;
652  }
653 
654  if (buf_size) {
655  av_fifo_generic_write(fpc->fifo_buf, (void*) read_start,
656  read_end - read_start, NULL);
657  } else {
658  int8_t pad[MAX_FRAME_HEADER_SIZE] = { 0 };
659  av_fifo_generic_write(fpc->fifo_buf, pad, sizeof(pad), NULL);
660  }
661 
662  /* Tag headers and update sequences. */
663  start_offset = av_fifo_size(fpc->fifo_buf) -
664  ((read_end - read_start) + (MAX_FRAME_HEADER_SIZE - 1));
665  start_offset = FFMAX(0, start_offset);
666  nb_headers = find_new_headers(fpc, start_offset);
667 
668  if (nb_headers < 0) {
669  av_log(avctx, AV_LOG_ERROR,
670  "find_new_headers couldn't allocate FLAC header\n");
671  goto handle_error;
672  }
673 
674  fpc->nb_headers_buffered = nb_headers;
675  /* Wait till FLAC_MIN_HEADERS to output a valid frame. */
676  if (!fpc->end_padded && fpc->nb_headers_buffered < FLAC_MIN_HEADERS) {
677  if (read_end < buf + buf_size) {
678  read_start = read_end;
679  continue;
680  } else {
681  goto handle_error;
682  }
683  }
684 
685  /* If headers found, update the scores since we have longer chains. */
686  if (fpc->end_padded || fpc->nb_headers_found)
687  score_sequences(fpc);
688 
689  /* restore the state pre-padding */
690  if (fpc->end_padded) {
691  int warp = fpc->fifo_buf->wptr - fpc->fifo_buf->buffer < MAX_FRAME_HEADER_SIZE;
692  /* HACK: drain the tail of the fifo */
695  if (warp) {
696  fpc->fifo_buf->wptr += fpc->fifo_buf->end -
697  fpc->fifo_buf->buffer;
698  }
699  read_start = read_end = NULL;
700  }
701  }
702 
703  for (curr = fpc->headers; curr; curr = curr->next) {
704  if (!fpc->best_header || curr->max_score > fpc->best_header->max_score) {
705  fpc->best_header = curr;
706  }
707  }
708 
709  if (fpc->best_header && fpc->best_header->max_score <= 0) {
710  // Only accept a bad header if there is no other option to continue
711  if (!buf_size || read_end != buf || fpc->nb_headers_buffered < FLAC_MIN_HEADERS)
712  fpc->best_header = NULL;
713  }
714 
715  if (fpc->best_header) {
716  fpc->best_header_valid = 1;
717  if (fpc->best_header->offset > 0) {
718  /* Output a junk frame. */
719  av_log(avctx, AV_LOG_DEBUG, "Junk frame till offset %i\n",
720  fpc->best_header->offset);
721 
722  /* Set duration to 0. It is unknown or invalid in a junk frame. */
723  s->duration = 0;
724  *poutbuf_size = fpc->best_header->offset;
725  *poutbuf = flac_fifo_read_wrap(fpc, 0, *poutbuf_size,
726  &fpc->wrap_buf,
728  return buf_size ? (read_end - buf) : (fpc->best_header->offset -
729  av_fifo_size(fpc->fifo_buf));
730  }
731  if (!buf_size)
732  return get_best_header(fpc, poutbuf, poutbuf_size);
733  }
734 
735 handle_error:
736  *poutbuf = NULL;
737  *poutbuf_size = 0;
738  return buf_size ? read_end - buf : 0;
739 }
740 
742 {
743  FLACParseContext *fpc = c->priv_data;
744  fpc->pc = c;
745  /* There will generally be FLAC_MIN_HEADERS buffered in the fifo before
746  it drains. This is allocated early to avoid slow reallocation. */
748  if (!fpc->fifo_buf) {
749  av_log(fpc->avctx, AV_LOG_ERROR,
750  "couldn't allocate fifo_buf\n");
751  return AVERROR(ENOMEM);
752  }
753  return 0;
754 }
755 
757 {
758  FLACParseContext *fpc = c->priv_data;
759  FLACHeaderMarker *curr = fpc->headers, *temp;
760 
761  while (curr) {
762  temp = curr->next;
763  av_free(curr);
764  curr = temp;
765  }
766  fpc->headers = NULL;
767  av_fifo_freep(&fpc->fifo_buf);
768  av_freep(&fpc->wrap_buf);
769 }
770 
773  .priv_data_size = sizeof(FLACParseContext),
774  .parser_init = flac_parse_init,
775  .parser_parse = flac_parse,
776  .parser_close = flac_parse_close,
777 };
FLACParseContext
Definition: flac_parser.c:75
FLACParseContext::headers
FLACHeaderMarker * headers
linked-list that starts at the first CRC-8 verified header within buffer
Definition: flac_parser.c:78
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:95
AV_LOG_WARNING
#define AV_LOG_WARNING
Something somehow does not look correct.
Definition: log.h:186
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:301
FLACParseContext::nb_headers_buffered
int nb_headers_buffered
number of headers that are buffered
Definition: flac_parser.c:83
AVCodecParserContext::pts
int64_t pts
Definition: avcodec.h:2794
find_new_headers
static int find_new_headers(FLACParseContext *fpc, int search_start)
Definition: flac_parser.c:257
FLACHeaderMarker
Definition: flac_parser.c:59
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:1043
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:992
AVCodecParserContext::duration
int duration
Duration of the current frame.
Definition: avcodec.h:2889
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:89
FLACHeaderMarker::best_child
struct FLACHeaderMarker * best_child
following frame header with which this frame has the best score with
Definition: flac_parser.c:70
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:479
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:435
FFMAX
#define FFMAX(a, b)
Definition: macros.h:47
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:660
FLACParseContext::wrap_buf_allocated_size
int wrap_buf_allocated_size
actual allocated size of the buffer
Definition: flac_parser.c:90
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:142
get_bits
static unsigned int get_bits(GetBitContext *s, int n)
Read 1-25 bits.
Definition: get_bits.h:380
fifo.h
ff_flac_parser
const AVCodecParser ff_flac_parser
Definition: flac_parser.c:771
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:86
GetBitContext
Definition: get_bits.h:62
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:84
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:182
get_best_header
static int get_best_header(FLACParseContext *fpc, const uint8_t **poutbuf, int *poutbuf_size)
Definition: flac_parser.c:496
AV_LOG_ERROR
#define AV_LOG_ERROR
Something went wrong and cannot losslessly be recovered.
Definition: log.h:180
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:67
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:504
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:201
FLACParseContext::last_fi_valid
int last_fi_valid
set if last_fi is valid
Definition: flac_parser.c:92
FLACParseContext::avctx
AVCodecContext * avctx
codec context pointer for logging
Definition: flac_parser.c:77
find_headers_search_validate
static int find_headers_search_validate(FLACParseContext *fpc, int offset)
Definition: flac_parser.c:193
FLACParseContext::pc
AVCodecParserContext * pc
parent context
Definition: flac_parser.c:76
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
if
if(ret)
Definition: filter_design.txt:179
AV_CRC_16_ANSI
@ AV_CRC_16_ANSI
Definition: crc.h:50
score_header
static int score_header(FLACParseContext *fpc, FLACHeaderMarker *header)
Score a header.
Definition: flac_parser.c:439
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
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:540
find_headers_search
static int find_headers_search(FLACParseContext *fpc, uint8_t *buf, int buf_size, int search_start)
Definition: flac_parser.c:230
get_bits1
static unsigned int get_bits1(GetBitContext *s)
Definition: get_bits.h:499
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:2808
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
AVCodecParser::codec_ids
int codec_ids[7]
Definition: avcodec.h:2935
size
int size
Definition: twinvq_data.h:10344
header
static const uint8_t header[24]
Definition: sdr2.c:67
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:741
FLACHeaderMarker::fi
FLACFrameInfo fi
decoded frame header info
Definition: flac_parser.c:66
AVCodecContext::channels
int channels
number of audio channels
Definition: avcodec.h:993
FLACParseContext::best_header
FLACHeaderMarker * best_header
highest scoring header within buffer
Definition: flac_parser.c:80
PARSER_FLAG_COMPLETE_FRAMES
#define PARSER_FLAG_COMPLETE_FRAMES
Definition: avcodec.h:2809
i
#define i(width, name, range_min, range_max)
Definition: cbs_h2645.c:271
FLACHeaderMarker::max_score
int max_score
maximum score found after checking each child that has a valid CRC
Definition: flac_parser.c:64
FLACParseContext::end_padded
int end_padded
specifies if fifo_buf's end is padded
Definition: flac_parser.c:88
av_fifo_alloc_array
AVFifoBuffer * av_fifo_alloc_array(size_t nmemb, size_t size)
Initialize an AVFifoBuffer.
Definition: fifo.c:49
FFMIN
#define FFMIN(a, b)
Definition: macros.h:49
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:263
parser.h
len
int len
Definition: vorbis_enc_data.h:426
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:331
AVCodecParserContext
Definition: avcodec.h:2775
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:81
MAX_FRAME_HEADER_SIZE
#define MAX_FRAME_HEADER_SIZE
largest possible size of flac header
Definition: flac_parser.c:57
AVCodecContext
main external API structure.
Definition: avcodec.h:383
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:2813
temp
else temp
Definition: vf_mcdeint.c:248
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:61
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:60
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:2934
FLACParseContext::last_fi
FLACFrameInfo last_fi
last decoded frame header info
Definition: flac_parser.c:91
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:756
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