3
* Copyright (c) 2010 Michael Chinen
5
* This file is part of Libav.
7
* Libav 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.
12
* Libav 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.
17
* You should have received a copy of the GNU Lesser General Public
18
* License along with Libav; if not, write to the Free Software
19
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
26
* The FLAC parser buffers input until FLAC_MIN_HEADERS has been found.
27
* Each time it finds and verifies a CRC-8 header it sees which of the
28
* FLAC_MAX_SEQUENTIAL_HEADERS that came before it have a valid CRC-16 footer
29
* that ends at the newly found header.
30
* Headers are scored by FLAC_HEADER_BASE_SCORE plus the max of it's crc-verified
31
* children, penalized by changes in sample rate, frame number, etc.
32
* The parser returns the frame with the highest score.
35
#include "libavutil/crc.h"
36
#include "libavutil/fifo.h"
37
#include "bytestream.h"
41
/** maximum number of adjacent headers that compare CRCs against each other */
42
#define FLAC_MAX_SEQUENTIAL_HEADERS 3
43
/** minimum number of headers buffered and checked before returning frames */
44
#define FLAC_MIN_HEADERS 10
45
/** estimate for average size of a FLAC frame */
46
#define FLAC_AVG_FRAME_SIZE 8192
48
/** scoring settings for score_header */
49
#define FLAC_HEADER_BASE_SCORE 10
50
#define FLAC_HEADER_CHANGED_PENALTY 7
51
#define FLAC_HEADER_CRC_FAIL_PENALTY 50
52
#define FLAC_HEADER_NOT_PENALIZED_YET 100000
53
#define FLAC_HEADER_NOT_SCORED_YET -100000
55
/** largest possible size of flac header */
56
#define MAX_FRAME_HEADER_SIZE 16
58
typedef struct FLACHeaderMarker {
59
int offset; /**< byte offset from start of FLACParseContext->buffer */
60
int *link_penalty; /**< pointer to array of local scores between this header
61
and the one at a distance equal array position */
62
int max_score; /**< maximum score found after checking each child that
64
FLACFrameInfo fi; /**< decoded frame header info */
65
struct FLACHeaderMarker *next; /**< next CRC-8 verified header that
66
immediately follows this one in
68
struct FLACHeaderMarker *best_child; /**< following frame header with
69
which this frame has the best
73
typedef struct FLACParseContext {
74
AVCodecContext *avctx; /**< codec context pointer for logging */
75
FLACHeaderMarker *headers; /**< linked-list that starts at the first
76
CRC-8 verified header within buffer */
77
FLACHeaderMarker *best_header; /**< highest scoring header within buffer */
78
int nb_headers_found; /**< number of headers found in the last
80
int nb_headers_buffered; /**< number of headers that are buffered */
81
int best_header_valid; /**< flag set when the parser returns junk;
82
if set return best_header next time */
83
AVFifoBuffer *fifo_buf; /**< buffer to store all data until headers
85
int end_padded; /**< specifies if fifo_buf's end is padded */
86
uint8_t *wrap_buf; /**< general fifo read buffer when wrapped */
87
int wrap_buf_allocated_size; /**< actual allocated size of the buffer */
90
static int frame_header_is_valid(AVCodecContext *avctx, const uint8_t *buf,
94
init_get_bits(&gb, buf, MAX_FRAME_HEADER_SIZE * 8);
95
return !ff_flac_decode_frame_header(avctx, &gb, fi, 127);
99
* Non-destructive fast fifo pointer fetching
100
* Returns a pointer from the specified offset.
101
* If possible the pointer points within the fifo buffer.
102
* Otherwise (if it would cause a wrap around,) a pointer to a user-specified
104
* The pointer can be NULL. In any case it will be reallocated to hold the size.
105
* If the returned pointer will be used after subsequent calls to flac_fifo_read_wrap
106
* then the subsequent calls should pass in a different wrap_buf so as to not
107
* overwrite the contents of the previous wrap_buf.
108
* This function is based on av_fifo_generic_read, which is why there is a comment
109
* about a memory barrier for SMP.
111
static uint8_t* flac_fifo_read_wrap(FLACParseContext *fpc, int offset, int len,
112
uint8_t** wrap_buf, int* allocated_size)
114
AVFifoBuffer *f = fpc->fifo_buf;
115
uint8_t *start = f->rptr + offset;
119
start -= f->end - f->buffer;
120
if (f->end - start >= len)
123
tmp_buf = av_fast_realloc(*wrap_buf, allocated_size, len);
126
av_log(fpc->avctx, AV_LOG_ERROR,
127
"couldn't reallocate wrap buffer of size %d", len);
132
int seg_len = FFMIN(f->end - start, len);
133
memcpy(tmp_buf, start, seg_len);
134
tmp_buf = (uint8_t*)tmp_buf + seg_len;
135
// memory barrier needed for SMP here in theory
137
start += seg_len - (f->end - f->buffer);
145
* Return a pointer in the fifo buffer where the offset starts at until
146
* the wrap point or end of request.
147
* len will contain the valid length of the returned buffer.
148
* A second call to flac_fifo_read (with new offset and len) should be called
149
* to get the post-wrap buf if the returned len is less than the requested.
151
static uint8_t* flac_fifo_read(FLACParseContext *fpc, int offset, int *len)
153
AVFifoBuffer *f = fpc->fifo_buf;
154
uint8_t *start = f->rptr + offset;
157
start -= f->end - f->buffer;
158
*len = FFMIN(*len, f->end - start);
162
static int find_headers_search_validate(FLACParseContext *fpc, int offset)
167
header_buf = flac_fifo_read_wrap(fpc, offset,
168
MAX_FRAME_HEADER_SIZE,
170
&fpc->wrap_buf_allocated_size);
171
if (frame_header_is_valid(fpc->avctx, header_buf, &fi)) {
172
FLACHeaderMarker **end_handle = &fpc->headers;
176
while (*end_handle) {
177
end_handle = &(*end_handle)->next;
181
*end_handle = av_mallocz(sizeof(FLACHeaderMarker));
183
av_log(fpc->avctx, AV_LOG_ERROR,
184
"couldn't allocate FLACHeaderMarker\n");
185
return AVERROR(ENOMEM);
187
(*end_handle)->fi = fi;
188
(*end_handle)->offset = offset;
189
(*end_handle)->link_penalty = av_malloc(sizeof(int) *
190
FLAC_MAX_SEQUENTIAL_HEADERS);
191
for (i = 0; i < FLAC_MAX_SEQUENTIAL_HEADERS; i++)
192
(*end_handle)->link_penalty[i] = FLAC_HEADER_NOT_PENALIZED_YET;
194
fpc->nb_headers_found++;
200
static int find_headers_search(FLACParseContext *fpc, uint8_t *buf, int buf_size,
204
int size = 0, mod_offset = (buf_size - 1) % 4, i, j;
207
for (i = 0; i < mod_offset; i++) {
208
if ((AV_RB16(buf + i) & 0xFFFE) == 0xFFF8)
209
size = find_headers_search_validate(fpc, search_start + i);
212
for (; i < buf_size - 1; i += 4) {
213
x = AV_RB32(buf + i);
214
if (((x & ~(x + 0x01010101)) & 0x80808080)) {
215
for (j = 0; j < 4; j++) {
216
if ((AV_RB16(buf + i + j) & 0xFFFE) == 0xFFF8)
217
size = find_headers_search_validate(fpc, search_start + i + j);
224
static int find_new_headers(FLACParseContext *fpc, int search_start)
226
FLACHeaderMarker *end;
227
int search_end, size = 0, read_len, temp;
229
fpc->nb_headers_found = 0;
231
/* Search for a new header of at most 16 bytes. */
232
search_end = av_fifo_size(fpc->fifo_buf) - (MAX_FRAME_HEADER_SIZE - 1);
233
read_len = search_end - search_start + 1;
234
buf = flac_fifo_read(fpc, search_start, &read_len);
235
size = find_headers_search(fpc, buf, read_len, search_start);
236
search_start += read_len - 1;
238
/* If fifo end was hit do the wrap around. */
239
if (search_start != search_end) {
242
wrap[0] = buf[read_len - 1];
243
read_len = search_end - search_start + 1;
245
/* search_start + 1 is the post-wrap offset in the fifo. */
246
buf = flac_fifo_read(fpc, search_start + 1, &read_len);
249
if ((AV_RB16(wrap) & 0xFFFE) == 0xFFF8) {
250
temp = find_headers_search_validate(fpc, search_start);
251
size = FFMAX(size, temp);
255
/* Continue to do the last half of the wrap. */
256
temp = find_headers_search(fpc, buf, read_len, search_start);
257
size = FFMAX(size, temp);
258
search_start += read_len - 1;
261
/* Return the size even if no new headers were found. */
262
if (!size && fpc->headers)
263
for (end = fpc->headers; end; end = end->next)
268
static int check_header_mismatch(FLACParseContext *fpc,
269
FLACHeaderMarker *header,
270
FLACHeaderMarker *child,
271
int log_level_offset)
273
FLACFrameInfo *header_fi = &header->fi, *child_fi = &child->fi;
274
int deduction = 0, deduction_expected = 0, i;
275
if (child_fi->samplerate != header_fi->samplerate) {
276
deduction += FLAC_HEADER_CHANGED_PENALTY;
277
av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
278
"sample rate change detected in adjacent frames\n");
280
if (child_fi->bps != header_fi->bps) {
281
deduction += FLAC_HEADER_CHANGED_PENALTY;
282
av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
283
"bits per sample change detected in adjacent frames\n");
285
if (child_fi->is_var_size != header_fi->is_var_size) {
286
/* Changing blocking strategy not allowed per the spec */
287
deduction += FLAC_HEADER_BASE_SCORE;
288
av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
289
"blocking strategy change detected in adjacent frames\n");
291
if (child_fi->channels != header_fi->channels) {
292
deduction += FLAC_HEADER_CHANGED_PENALTY;
293
av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
294
"number of channels change detected in adjacent frames\n");
296
/* Check sample and frame numbers. */
297
if ((child_fi->frame_or_sample_num - header_fi->frame_or_sample_num
298
!= header_fi->blocksize) &&
299
(child_fi->frame_or_sample_num
300
!= header_fi->frame_or_sample_num + 1)) {
301
FLACHeaderMarker *curr;
302
int expected_frame_num, expected_sample_num;
303
/* If there are frames in the middle we expect this deduction,
304
as they are probably valid and this one follows it */
306
expected_frame_num = expected_sample_num = header_fi->frame_or_sample_num;
308
while (curr != child) {
309
/* Ignore frames that failed all crc checks */
310
for (i = 0; i < FLAC_MAX_SEQUENTIAL_HEADERS; i++) {
311
if (curr->link_penalty[i] < FLAC_HEADER_CRC_FAIL_PENALTY) {
312
expected_frame_num++;
313
expected_sample_num += curr->fi.blocksize;
320
if (expected_frame_num == child_fi->frame_or_sample_num ||
321
expected_sample_num == child_fi->frame_or_sample_num)
322
deduction_expected = deduction ? 0 : 1;
324
deduction += FLAC_HEADER_CHANGED_PENALTY;
325
av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
326
"sample/frame number mismatch in adjacent frames\n");
329
/* If we have suspicious headers, check the CRC between them */
330
if (deduction && !deduction_expected) {
331
FLACHeaderMarker *curr;
335
int inverted_test = 0;
337
/* Since CRC is expensive only do it if we haven't yet.
338
This assumes a CRC penalty is greater than all other check penalties */
340
for (i = 0; i < FLAC_MAX_SEQUENTIAL_HEADERS && curr != child; i++)
343
if (header->link_penalty[i] < FLAC_HEADER_CRC_FAIL_PENALTY ||
344
header->link_penalty[i] == FLAC_HEADER_NOT_PENALIZED_YET) {
345
FLACHeaderMarker *start, *end;
347
/* Although overlapping chains are scored, the crc should never
348
have to be computed twice for a single byte. */
352
header->link_penalty[i - 1] >= FLAC_HEADER_CRC_FAIL_PENALTY) {
353
while (start->next != child)
357
header->next->link_penalty[i-1] >=
358
FLAC_HEADER_CRC_FAIL_PENALTY ) {
363
read_len = end->offset - start->offset;
364
buf = flac_fifo_read(fpc, start->offset, &read_len);
365
crc = av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0, buf, read_len);
366
read_len = (end->offset - start->offset) - read_len;
369
buf = flac_fifo_read(fpc, end->offset - read_len, &read_len);
370
crc = av_crc(av_crc_get_table(AV_CRC_16_ANSI), crc, buf, read_len);
374
if (!crc ^ !inverted_test) {
375
deduction += FLAC_HEADER_CRC_FAIL_PENALTY;
376
av_log(fpc->avctx, AV_LOG_WARNING + log_level_offset,
377
"crc check failed from offset %i (frame %"PRId64") to %i (frame %"PRId64")\n",
378
header->offset, header_fi->frame_or_sample_num,
379
child->offset, child_fi->frame_or_sample_num);
388
* Give FLAC_HEADER_BASE_SCORE points to a frame for existing.
389
* If it has children, (subsequent frames of which the preceding CRC footer
390
* validates against this one,) then take the maximum score of the children,
391
* with a penalty of FLAC_HEADER_CHANGED_PENALTY applied for each change to
392
* bps, sample rate, channels, but not decorrelation mode, or blocksize,
393
* because it can change often.
395
static int score_header(FLACParseContext *fpc, FLACHeaderMarker *header)
397
FLACHeaderMarker *child;
401
if (header->max_score != FLAC_HEADER_NOT_SCORED_YET)
402
return header->max_score;
404
header->max_score = FLAC_HEADER_BASE_SCORE;
406
/* Check and compute the children's scores. */
407
child = header->next;
408
for (dist = 0; dist < FLAC_MAX_SEQUENTIAL_HEADERS && child; dist++) {
409
/* Look at the child's frame header info and penalize suspicious
410
changes between the headers. */
411
if (header->link_penalty[dist] == FLAC_HEADER_NOT_PENALIZED_YET) {
412
header->link_penalty[dist] = check_header_mismatch(fpc, header,
413
child, AV_LOG_DEBUG);
415
child_score = score_header(fpc, child) - header->link_penalty[dist];
417
if (FLAC_HEADER_BASE_SCORE + child_score > header->max_score) {
418
/* Keep the child because the frame scoring is dynamic. */
419
header->best_child = child;
420
header->max_score = FLAC_HEADER_BASE_SCORE + child_score;
425
return header->max_score;
428
static void score_sequences(FLACParseContext *fpc)
430
FLACHeaderMarker *curr;
431
int best_score = FLAC_HEADER_NOT_SCORED_YET;
432
/* First pass to clear all old scores. */
433
for (curr = fpc->headers; curr; curr = curr->next)
434
curr->max_score = FLAC_HEADER_NOT_SCORED_YET;
436
/* Do a second pass to score them all. */
437
for (curr = fpc->headers; curr; curr = curr->next) {
438
if (score_header(fpc, curr) > best_score) {
439
fpc->best_header = curr;
440
best_score = curr->max_score;
445
static int get_best_header(FLACParseContext* fpc, const uint8_t **poutbuf,
448
FLACHeaderMarker *header = fpc->best_header;
449
FLACHeaderMarker *child = header->best_child;
451
*poutbuf_size = av_fifo_size(fpc->fifo_buf) - header->offset;
453
*poutbuf_size = child->offset - header->offset;
455
/* If the child has suspicious changes, log them */
456
check_header_mismatch(fpc, header, child, 0);
459
fpc->avctx->sample_rate = header->fi.samplerate;
460
fpc->avctx->channels = header->fi.channels;
461
fpc->avctx->frame_size = header->fi.blocksize;
462
*poutbuf = flac_fifo_read_wrap(fpc, header->offset, *poutbuf_size,
464
&fpc->wrap_buf_allocated_size);
466
fpc->best_header_valid = 0;
467
/* Return the negative overread index so the client can compute pos.
468
This should be the amount overread to the beginning of the child */
470
return child->offset - av_fifo_size(fpc->fifo_buf);
474
static int flac_parse(AVCodecParserContext *s, AVCodecContext *avctx,
475
const uint8_t **poutbuf, int *poutbuf_size,
476
const uint8_t *buf, int buf_size)
478
FLACParseContext *fpc = s->priv_data;
479
FLACHeaderMarker *curr;
481
const uint8_t *read_end = buf;
482
const uint8_t *read_start = buf;
484
if (s->flags & PARSER_FLAG_COMPLETE_FRAMES) {
486
if (frame_header_is_valid(avctx, buf, &fi))
487
avctx->frame_size = fi.blocksize;
489
*poutbuf_size = buf_size;
494
if (fpc->best_header_valid)
495
return get_best_header(fpc, poutbuf, poutbuf_size);
497
/* If a best_header was found last call remove it with the buffer data. */
498
if (fpc->best_header && fpc->best_header->best_child) {
499
FLACHeaderMarker *temp;
500
FLACHeaderMarker *best_child = fpc->best_header->best_child;
502
/* Remove headers in list until the end of the best_header. */
503
for (curr = fpc->headers; curr != best_child; curr = temp) {
504
if (curr != fpc->best_header) {
505
av_log(avctx, AV_LOG_DEBUG,
506
"dropping low score %i frame header from offset %i to %i\n",
507
curr->max_score, curr->offset, curr->next->offset);
510
av_freep(&curr->link_penalty);
512
fpc->nb_headers_buffered--;
514
/* Release returned data from ring buffer. */
515
av_fifo_drain(fpc->fifo_buf, best_child->offset);
517
/* Fix the offset for the headers remaining to match the new buffer. */
518
for (curr = best_child->next; curr; curr = curr->next)
519
curr->offset -= best_child->offset;
521
fpc->nb_headers_buffered--;
522
best_child->offset = 0;
523
fpc->headers = best_child;
524
if (fpc->nb_headers_buffered >= FLAC_MIN_HEADERS) {
525
fpc->best_header = best_child;
526
return get_best_header(fpc, poutbuf, poutbuf_size);
528
fpc->best_header = NULL;
529
} else if (fpc->best_header) {
530
/* No end frame no need to delete the buffer; probably eof */
531
FLACHeaderMarker *temp;
533
for (curr = fpc->headers; curr != fpc->best_header; curr = temp) {
535
av_freep(&curr->link_penalty);
538
fpc->headers = fpc->best_header->next;
539
av_freep(&fpc->best_header->link_penalty);
540
av_freep(&fpc->best_header);
543
/* Find and score new headers. */
544
while ((buf && read_end < buf + buf_size &&
545
fpc->nb_headers_buffered < FLAC_MIN_HEADERS)
546
|| (!buf && !fpc->end_padded)) {
549
/* Pad the end once if EOF, to check the final region for headers. */
552
buf_size = MAX_FRAME_HEADER_SIZE;
553
read_end = read_start + MAX_FRAME_HEADER_SIZE;
555
/* The maximum read size is the upper-bound of what the parser
556
needs to have the required number of frames buffered */
557
int nb_desired = FLAC_MIN_HEADERS - fpc->nb_headers_buffered + 1;
558
read_end = read_end + FFMIN(buf + buf_size - read_end,
559
nb_desired * FLAC_AVG_FRAME_SIZE);
562
/* Fill the buffer. */
563
if (av_fifo_realloc2(fpc->fifo_buf,
564
(read_end - read_start) + av_fifo_size(fpc->fifo_buf)) < 0) {
565
av_log(avctx, AV_LOG_ERROR,
566
"couldn't reallocate buffer of size %td\n",
567
(read_end - read_start) + av_fifo_size(fpc->fifo_buf));
572
av_fifo_generic_write(fpc->fifo_buf, (void*) read_start,
573
read_end - read_start, NULL);
575
int8_t pad[MAX_FRAME_HEADER_SIZE];
576
memset(pad, 0, sizeof(pad));
577
av_fifo_generic_write(fpc->fifo_buf, (void*) pad, sizeof(pad), NULL);
580
/* Tag headers and update sequences. */
581
start_offset = av_fifo_size(fpc->fifo_buf) -
582
((read_end - read_start) + (MAX_FRAME_HEADER_SIZE - 1));
583
start_offset = FFMAX(0, start_offset);
584
nb_headers = find_new_headers(fpc, start_offset);
586
if (nb_headers < 0) {
587
av_log(avctx, AV_LOG_ERROR,
588
"find_new_headers couldn't allocate FLAC header\n");
592
fpc->nb_headers_buffered = nb_headers;
593
/* Wait till FLAC_MIN_HEADERS to output a valid frame. */
594
if (!fpc->end_padded && fpc->nb_headers_buffered < FLAC_MIN_HEADERS) {
595
if (buf && read_end < buf + buf_size) {
596
read_start = read_end;
603
/* If headers found, update the scores since we have longer chains. */
604
if (fpc->end_padded || fpc->nb_headers_found)
605
score_sequences(fpc);
607
/* restore the state pre-padding */
608
if (fpc->end_padded) {
609
/* HACK: drain the tail of the fifo */
610
fpc->fifo_buf->wptr -= MAX_FRAME_HEADER_SIZE;
611
fpc->fifo_buf->wndx -= MAX_FRAME_HEADER_SIZE;
612
if (fpc->fifo_buf->wptr < 0) {
613
fpc->fifo_buf->wptr += fpc->fifo_buf->end -
614
fpc->fifo_buf->buffer;
617
read_start = read_end = NULL;
622
for (curr = fpc->headers; curr; curr = curr->next)
623
if (!fpc->best_header || curr->max_score > fpc->best_header->max_score)
624
fpc->best_header = curr;
626
if (fpc->best_header) {
627
fpc->best_header_valid = 1;
628
if (fpc->best_header->offset > 0) {
629
/* Output a junk frame. */
630
av_log(avctx, AV_LOG_DEBUG, "Junk frame till offset %i\n",
631
fpc->best_header->offset);
633
/* Set frame_size to 0. It is unknown or invalid in a junk frame. */
634
avctx->frame_size = 0;
635
*poutbuf_size = fpc->best_header->offset;
636
*poutbuf = flac_fifo_read_wrap(fpc, 0, *poutbuf_size,
638
&fpc->wrap_buf_allocated_size);
639
return buf_size ? (read_end - buf) : (fpc->best_header->offset -
640
av_fifo_size(fpc->fifo_buf));
643
return get_best_header(fpc, poutbuf, poutbuf_size);
649
return read_end - buf;
652
static int flac_parse_init(AVCodecParserContext *c)
654
FLACParseContext *fpc = c->priv_data;
655
/* There will generally be FLAC_MIN_HEADERS buffered in the fifo before
656
it drains. This is allocated early to avoid slow reallocation. */
657
fpc->fifo_buf = av_fifo_alloc(FLAC_AVG_FRAME_SIZE * (FLAC_MIN_HEADERS + 3));
661
static void flac_parse_close(AVCodecParserContext *c)
663
FLACParseContext *fpc = c->priv_data;
664
FLACHeaderMarker *curr = fpc->headers, *temp;
668
av_freep(&curr->link_penalty);
672
av_fifo_free(fpc->fifo_buf);
673
av_free(fpc->wrap_buf);
676
AVCodecParser ff_flac_parser = {
678
sizeof(FLACParseContext),
added
removed
libavcodec/flac_parser.c
