FFmpeg
aiffdec.c
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1 /*
2  * AIFF/AIFF-C demuxer
3  * Copyright (c) 2006 Patrick Guimond
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 #include "libavutil/intreadwrite.h"
23 #include "libavutil/mathematics.h"
24 #include "libavutil/dict.h"
25 #include "avformat.h"
26 #include "internal.h"
27 #include "pcm.h"
28 #include "aiff.h"
29 #include "isom.h"
30 #include "id3v2.h"
31 #include "mov_chan.h"
32 
33 #define AIFF 0
34 #define AIFF_C_VERSION1 0xA2805140
35 
36 typedef struct AIFFInputContext {
37  int64_t data_end;
40 
42 {
43  if (bps <= 8)
44  return AV_CODEC_ID_PCM_S8;
45  if (bps <= 16)
46  return AV_CODEC_ID_PCM_S16BE;
47  if (bps <= 24)
48  return AV_CODEC_ID_PCM_S24BE;
49  if (bps <= 32)
50  return AV_CODEC_ID_PCM_S32BE;
51 
52  /* bigger than 32 isn't allowed */
53  return AV_CODEC_ID_NONE;
54 }
55 
56 /* returns the size of the found tag */
57 static int get_tag(AVIOContext *pb, uint32_t * tag)
58 {
59  int size;
60 
61  if (avio_feof(pb))
62  return AVERROR(EIO);
63 
64  *tag = avio_rl32(pb);
65  size = avio_rb32(pb);
66 
67  if (size < 0)
68  size = 0x7fffffff;
69 
70  return size;
71 }
72 
73 /* Metadata string read */
74 static void get_meta(AVFormatContext *s, const char *key, int size)
75 {
76  uint8_t *str = av_malloc(size+1);
77 
78  if (str) {
79  int res = avio_read(s->pb, str, size);
80  if (res < 0){
81  av_free(str);
82  return;
83  }
84  size -= res;
85  str[res] = 0;
87  }
88 
89  avio_skip(s->pb, size);
90 }
91 
92 /* Returns the number of sound data frames or negative on error */
94  unsigned version)
95 {
96  AVIOContext *pb = s->pb;
97  AVCodecParameters *par = s->streams[0]->codecpar;
98  AIFFInputContext *aiff = s->priv_data;
99  int exp;
100  uint64_t val;
101  int sample_rate;
102  unsigned int num_frames;
103 
104  if (size & 1)
105  size++;
107  par->channels = avio_rb16(pb);
108  num_frames = avio_rb32(pb);
109  par->bits_per_coded_sample = avio_rb16(pb);
110 
111  exp = avio_rb16(pb) - 16383 - 63;
112  val = avio_rb64(pb);
113  if (exp <-63 || exp >63) {
114  av_log(s, AV_LOG_ERROR, "exp %d is out of range\n", exp);
115  return AVERROR_INVALIDDATA;
116  }
117  if (exp >= 0)
118  sample_rate = val << exp;
119  else
120  sample_rate = (val + (1ULL<<(-exp-1))) >> -exp;
121  par->sample_rate = sample_rate;
122  size -= 18;
123 
124  /* get codec id for AIFF-C */
125  if (size < 4) {
126  version = AIFF;
127  } else if (version == AIFF_C_VERSION1) {
128  par->codec_tag = avio_rl32(pb);
130  if (par->codec_id == AV_CODEC_ID_NONE)
131  avpriv_request_sample(s, "unknown or unsupported codec tag: %s",
132  av_fourcc2str(par->codec_tag));
133  size -= 4;
134  }
135 
136  if (version != AIFF_C_VERSION1 || par->codec_id == AV_CODEC_ID_PCM_S16BE) {
139  aiff->block_duration = 1;
140  } else {
141  switch (par->codec_id) {
147  aiff->block_duration = 1;
148  break;
150  par->block_align = 34 * par->channels;
151  break;
152  case AV_CODEC_ID_MACE3:
153  par->block_align = 2 * par->channels;
154  break;
156  par->bits_per_coded_sample = 5;
159  case AV_CODEC_ID_MACE6:
161  par->block_align = 1 * par->channels;
162  break;
163  case AV_CODEC_ID_GSM:
164  par->block_align = 33;
165  break;
166  default:
167  aiff->block_duration = 1;
168  break;
169  }
170  if (par->block_align > 0)
172  par->block_align);
173  }
174 
175  /* Block align needs to be computed in all cases, as the definition
176  * is specific to applications -> here we use the WAVE format definition */
177  if (!par->block_align)
178  par->block_align = (av_get_bits_per_sample(par->codec_id) * par->channels) >> 3;
179 
180  if (aiff->block_duration) {
181  par->bit_rate = (int64_t)par->sample_rate * (par->block_align << 3) /
182  aiff->block_duration;
183  }
184 
185  /* Chunk is over */
186  if (size)
187  avio_skip(pb, size);
188 
189  return num_frames;
190 }
191 
192 static int aiff_probe(const AVProbeData *p)
193 {
194  /* check file header */
195  if (p->buf[0] == 'F' && p->buf[1] == 'O' &&
196  p->buf[2] == 'R' && p->buf[3] == 'M' &&
197  p->buf[8] == 'A' && p->buf[9] == 'I' &&
198  p->buf[10] == 'F' && (p->buf[11] == 'F' || p->buf[11] == 'C'))
199  return AVPROBE_SCORE_MAX;
200  else
201  return 0;
202 }
203 
204 /* aiff input */
206 {
207  int ret, size, filesize;
208  int64_t offset = 0, position;
209  uint32_t tag;
210  unsigned version = AIFF_C_VERSION1;
211  AVIOContext *pb = s->pb;
212  AVStream * st;
213  AIFFInputContext *aiff = s->priv_data;
214  ID3v2ExtraMeta *id3v2_extra_meta = NULL;
215 
216  /* check FORM header */
217  filesize = get_tag(pb, &tag);
218  if (filesize < 0 || tag != MKTAG('F', 'O', 'R', 'M'))
219  return AVERROR_INVALIDDATA;
220 
221  /* AIFF data type */
222  tag = avio_rl32(pb);
223  if (tag == MKTAG('A', 'I', 'F', 'F')) /* Got an AIFF file */
224  version = AIFF;
225  else if (tag != MKTAG('A', 'I', 'F', 'C')) /* An AIFF-C file then */
226  return AVERROR_INVALIDDATA;
227 
228  filesize -= 4;
229 
230  st = avformat_new_stream(s, NULL);
231  if (!st)
232  return AVERROR(ENOMEM);
233 
234  while (filesize > 0) {
235  /* parse different chunks */
236  size = get_tag(pb, &tag);
237 
238  if (size == AVERROR_EOF && offset > 0 && st->codecpar->block_align) {
239  av_log(s, AV_LOG_WARNING, "header parser hit EOF\n");
240  goto got_sound;
241  }
242  if (size < 0)
243  return size;
244 
245  filesize -= size + 8;
246 
247  switch (tag) {
248  case MKTAG('C', 'O', 'M', 'M'): /* Common chunk */
249  /* Then for the complete header info */
250  st->nb_frames = get_aiff_header(s, size, version);
251  if (st->nb_frames < 0)
252  return st->nb_frames;
253  if (offset > 0) // COMM is after SSND
254  goto got_sound;
255  break;
256  case MKTAG('I', 'D', '3', ' '):
257  position = avio_tell(pb);
258  ff_id3v2_read(s, ID3v2_DEFAULT_MAGIC, &id3v2_extra_meta, size);
259  if (id3v2_extra_meta)
260  if ((ret = ff_id3v2_parse_apic(s, &id3v2_extra_meta)) < 0 ||
261  (ret = ff_id3v2_parse_chapters(s, &id3v2_extra_meta)) < 0) {
262  ff_id3v2_free_extra_meta(&id3v2_extra_meta);
263  return ret;
264  }
265  ff_id3v2_free_extra_meta(&id3v2_extra_meta);
266  if (position + size > avio_tell(pb))
267  avio_skip(pb, position + size - avio_tell(pb));
268  break;
269  case MKTAG('F', 'V', 'E', 'R'): /* Version chunk */
270  version = avio_rb32(pb);
271  break;
272  case MKTAG('N', 'A', 'M', 'E'): /* Sample name chunk */
273  get_meta(s, "title" , size);
274  break;
275  case MKTAG('A', 'U', 'T', 'H'): /* Author chunk */
276  get_meta(s, "author" , size);
277  break;
278  case MKTAG('(', 'c', ')', ' '): /* Copyright chunk */
279  get_meta(s, "copyright", size);
280  break;
281  case MKTAG('A', 'N', 'N', 'O'): /* Annotation chunk */
282  get_meta(s, "comment" , size);
283  break;
284  case MKTAG('S', 'S', 'N', 'D'): /* Sampled sound chunk */
285  aiff->data_end = avio_tell(pb) + size;
286  offset = avio_rb32(pb); /* Offset of sound data */
287  avio_rb32(pb); /* BlockSize... don't care */
288  offset += avio_tell(pb); /* Compute absolute data offset */
289  if (st->codecpar->block_align && !(pb->seekable & AVIO_SEEKABLE_NORMAL)) /* Assume COMM already parsed */
290  goto got_sound;
291  if (!(pb->seekable & AVIO_SEEKABLE_NORMAL)) {
292  av_log(s, AV_LOG_ERROR, "file is not seekable\n");
293  return -1;
294  }
295  avio_skip(pb, size - 8);
296  break;
297  case MKTAG('w', 'a', 'v', 'e'):
298  if ((uint64_t)size > (1<<30))
299  return -1;
300  if (ff_get_extradata(s, st->codecpar, pb, size) < 0)
301  return AVERROR(ENOMEM);
303  && size>=12*4 && !st->codecpar->block_align) {
304  st->codecpar->block_align = AV_RB32(st->codecpar->extradata+11*4);
305  aiff->block_duration = AV_RB32(st->codecpar->extradata+9*4);
306  } else if (st->codecpar->codec_id == AV_CODEC_ID_QCELP) {
307  char rate = 0;
308  if (size >= 25)
309  rate = st->codecpar->extradata[24];
310  switch (rate) {
311  case 'H': // RATE_HALF
312  st->codecpar->block_align = 17;
313  break;
314  case 'F': // RATE_FULL
315  default:
316  st->codecpar->block_align = 35;
317  }
318  aiff->block_duration = 160;
319  st->codecpar->bit_rate = (int64_t)st->codecpar->sample_rate * (st->codecpar->block_align << 3) /
320  aiff->block_duration;
321  }
322  break;
323  case MKTAG('C','H','A','N'):
324  if(ff_mov_read_chan(s, pb, st, size) < 0)
325  return AVERROR_INVALIDDATA;
326  break;
327  case MKTAG('A','P','C','M'): /* XA ADPCM compressed sound chunk */
329  aiff->data_end = avio_tell(pb) + size;
330  offset = avio_tell(pb) + 8;
331  /* This field is unknown and its data seems to be irrelevant */
332  avio_rb32(pb);
333  st->codecpar->block_align = avio_rb32(pb);
334 
335  goto got_sound;
336  break;
337  case 0:
338  if (offset > 0 && st->codecpar->block_align) // COMM && SSND
339  goto got_sound;
340  default: /* Jump */
341  avio_skip(pb, size);
342  }
343 
344  /* Skip required padding byte for odd-sized chunks. */
345  if (size & 1) {
346  filesize--;
347  avio_skip(pb, 1);
348  }
349  }
350 
351 got_sound:
352  if (!st->codecpar->block_align && st->codecpar->codec_id == AV_CODEC_ID_QCELP) {
353  av_log(s, AV_LOG_WARNING, "qcelp without wave chunk, assuming full rate\n");
354  st->codecpar->block_align = 35;
355  } else if (!st->codecpar->block_align) {
356  av_log(s, AV_LOG_ERROR, "could not find COMM tag or invalid block_align value\n");
357  return -1;
358  }
359 
360  /* Now positioned, get the sound data start and end */
361  avpriv_set_pts_info(st, 64, 1, st->codecpar->sample_rate);
362  st->start_time = 0;
363  st->duration = st->nb_frames * aiff->block_duration;
364 
365  /* Position the stream at the first block */
366  avio_seek(pb, offset, SEEK_SET);
367 
368  return 0;
369 }
370 
371 #define MAX_SIZE 4096
372 
374  AVPacket *pkt)
375 {
376  AVStream *st = s->streams[0];
377  AIFFInputContext *aiff = s->priv_data;
378  int64_t max_size;
379  int res, size;
380 
381  /* calculate size of remaining data */
382  max_size = aiff->data_end - avio_tell(s->pb);
383  if (max_size <= 0)
384  return AVERROR_EOF;
385 
386  if (!st->codecpar->block_align) {
387  av_log(s, AV_LOG_ERROR, "block_align not set\n");
388  return AVERROR_INVALIDDATA;
389  }
390 
391  /* Now for that packet */
392  switch (st->codecpar->codec_id) {
394  case AV_CODEC_ID_GSM:
395  case AV_CODEC_ID_QDM2:
396  case AV_CODEC_ID_QCELP:
397  size = st->codecpar->block_align;
398  break;
399  default:
401  }
402  size = FFMIN(max_size, size);
403  res = av_get_packet(s->pb, pkt, size);
404  if (res < 0)
405  return res;
406 
407  if (size >= st->codecpar->block_align)
408  pkt->flags &= ~AV_PKT_FLAG_CORRUPT;
409  /* Only one stream in an AIFF file */
410  pkt->stream_index = 0;
411  pkt->duration = (res / st->codecpar->block_align) * aiff->block_duration;
412  return 0;
413 }
414 
416  .name = "aiff",
417  .long_name = NULL_IF_CONFIG_SMALL("Audio IFF"),
418  .priv_data_size = sizeof(AIFFInputContext),
423  .codec_tag = (const AVCodecTag* const []){ ff_codec_aiff_tags, 0 },
424 };
#define NULL
Definition: coverity.c:32
const char const char void * val
Definition: avisynth_c.h:771
static int get_aiff_header(AVFormatContext *s, int size, unsigned version)
Definition: aiffdec.c:93
Bytestream IO Context.
Definition: avio.h:161
#define AVERROR_INVALIDDATA
Invalid data found when processing input.
Definition: error.h:59
int64_t data_end
Definition: aiffdec.c:37
enum AVCodecID ff_codec_get_id(const AVCodecTag *tags, unsigned int tag)
Definition: utils.c:3124
#define AV_LOG_WARNING
Something somehow does not look correct.
Definition: log.h:182
void avpriv_set_pts_info(AVStream *s, int pts_wrap_bits, unsigned int pts_num, unsigned int pts_den)
Set the time base and wrapping info for a given stream.
Definition: utils.c:4882
#define MAX_SIZE
Definition: aiffdec.c:371
static int read_seek(AVFormatContext *ctx, int stream_index, int64_t timestamp, int flags)
Definition: libcdio.c:153
enum AVCodecID codec_id
Specific type of the encoded data (the codec used).
Definition: avcodec.h:3944
#define ID3v2_DEFAULT_MAGIC
Default magic bytes for ID3v2 header: "ID3".
Definition: id3v2.h:35
int64_t avio_seek(AVIOContext *s, int64_t offset, int whence)
fseek() equivalent for AVIOContext.
Definition: aviobuf.c:246
int64_t avio_skip(AVIOContext *s, int64_t offset)
Skip given number of bytes forward.
Definition: aviobuf.c:331
const char * key
static int aiff_read_header(AVFormatContext *s)
Definition: aiffdec.c:205
int version
Definition: avisynth_c.h:766
static AVPacket pkt
unsigned int avio_rb16(AVIOContext *s)
Definition: aviobuf.c:786
int ff_id3v2_parse_apic(AVFormatContext *s, ID3v2ExtraMeta **extra_meta)
Create a stream for each APIC (attached picture) extracted from the ID3v2 header. ...
Definition: id3v2.c:1143
This struct describes the properties of an encoded stream.
Definition: avcodec.h:3936
Format I/O context.
Definition: avformat.h:1358
Public dictionary API.
void void avpriv_request_sample(void *avc, const char *msg,...) av_printf_format(2
Log a generic warning message about a missing feature.
uint8_t
#define av_malloc(s)
int ff_id3v2_parse_chapters(AVFormatContext *s, ID3v2ExtraMeta **extra_meta)
Create chapters for all CHAP tags found in the ID3v2 header.
Definition: id3v2.c:1183
unsigned int avio_rb32(AVIOContext *s)
Definition: aviobuf.c:801
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
int64_t duration
Duration of this packet in AVStream->time_base units, 0 if unknown.
Definition: avcodec.h:1486
AVStream * avformat_new_stream(AVFormatContext *s, const AVCodec *c)
Add a new stream to a media file.
Definition: utils.c:4455
static int aiff_read_packet(AVFormatContext *s, AVPacket *pkt)
Definition: aiffdec.c:373
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_RB32
Definition: bytestream.h:87
AVStream ** streams
A list of all streams in the file.
Definition: avformat.h:1426
#define AIFF_C_VERSION1
Definition: aiffdec.c:34
uint32_t tag
Definition: movenc.c:1501
#define AVERROR_EOF
End of file.
Definition: error.h:55
int av_get_packet(AVIOContext *s, AVPacket *pkt, int size)
Allocate and read the payload of a packet and initialize its fields with default values.
Definition: utils.c:310
ptrdiff_t size
Definition: opengl_enc.c:101
uint64_t avio_rb64(AVIOContext *s)
Definition: aviobuf.c:922
static av_always_inline int64_t avio_tell(AVIOContext *s)
ftell() equivalent for AVIOContext.
Definition: avio.h:557
#define av_log(a,...)
int avio_read(AVIOContext *s, unsigned char *buf, int size)
Read size bytes from AVIOContext into buf.
Definition: aviobuf.c:648
int64_t bit_rate
The average bitrate of the encoded data (in bits per second).
Definition: avcodec.h:3973
AVCodecID
Identify the syntax and semantics of the bitstream.
Definition: avcodec.h:215
#define AV_LOG_ERROR
Something went wrong and cannot losslessly be recovered.
Definition: log.h:176
int av_get_bits_per_sample(enum AVCodecID codec_id)
Return codec bits per sample.
Definition: utils.c:1506
AVDictionary * metadata
Metadata that applies to the whole file.
Definition: avformat.h:1598
unsigned int avio_rl32(AVIOContext *s)
Definition: aviobuf.c:770
#define NULL_IF_CONFIG_SMALL(x)
Return NULL if CONFIG_SMALL is true, otherwise the argument without modification. ...
Definition: internal.h:186
#define av_fourcc2str(fourcc)
Definition: avutil.h:348
enum AVMediaType codec_type
General type of the encoded data.
Definition: avcodec.h:3940
void ff_id3v2_free_extra_meta(ID3v2ExtraMeta **extra_meta)
Free memory allocated parsing special (non-text) metadata.
Definition: id3v2.c:1127
static void get_meta(AVFormatContext *s, const char *key, int size)
Definition: aiffdec.c:74
static enum AVCodecID aiff_codec_get_id(int bps)
Definition: aiffdec.c:41
int av_get_audio_frame_duration2(AVCodecParameters *par, int frame_bytes)
This function is the same as av_get_audio_frame_duration(), except it works with AVCodecParameters in...
Definition: utils.c:1719
int8_t exp
Definition: eval.c:72
int flags
A combination of AV_PKT_FLAG values.
Definition: avcodec.h:1474
unsigned char * buf
Buffer must have AVPROBE_PADDING_SIZE of extra allocated bytes filled with zero.
Definition: avformat.h:448
int block_align
Audio only.
Definition: avcodec.h:4061
int seekable
A combination of AVIO_SEEKABLE_ flags or 0 when the stream is not seekable.
Definition: avio.h:260
#define FFMIN(a, b)
Definition: common.h:96
#define AV_DICT_DONT_STRDUP_VAL
Take ownership of a value that&#39;s been allocated with av_malloc() or another memory allocation functio...
Definition: dict.h:76
#define s(width, name)
Definition: cbs_vp9.c:257
int ff_pcm_read_seek(AVFormatContext *s, int stream_index, int64_t timestamp, int flags)
Definition: pcm.c:52
static int aiff_probe(const AVProbeData *p)
Definition: aiffdec.c:192
int ff_mov_read_chan(AVFormatContext *s, AVIOContext *pb, AVStream *st, int64_t size)
Read &#39;chan&#39; tag from the input stream.
Definition: mov_chan.c:547
static int read_header(FFV1Context *f)
Definition: ffv1dec.c:530
Stream structure.
Definition: avformat.h:881
static int read_packet(void *opaque, uint8_t *buf, int buf_size)
Definition: avio_reading.c:42
static int get_tag(AVIOContext *pb, uint32_t *tag)
Definition: aiffdec.c:57
int block_duration
Definition: aiffdec.c:38
#define AVIO_SEEKABLE_NORMAL
Seeking works like for a local file.
Definition: avio.h:40
sample_rate
AVIOContext * pb
I/O context.
Definition: avformat.h:1400
int av_dict_set(AVDictionary **pm, const char *key, const char *value, int flags)
Set the given entry in *pm, overwriting an existing entry.
Definition: dict.c:70
This structure contains the data a format has to probe a file.
Definition: avformat.h:446
static int read_probe(const AVProbeData *pd)
Definition: jvdec.c:55
int64_t duration
Decoding: duration of the stream, in stream time base.
Definition: avformat.h:930
int sample_rate
Audio only.
Definition: avcodec.h:4054
#define AVPROBE_SCORE_MAX
maximum score
Definition: avformat.h:458
Main libavformat public API header.
AVInputFormat ff_aiff_demuxer
Definition: aiffdec.c:415
int64_t start_time
Decoding: pts of the first frame of the stream in presentation order, in stream time base...
Definition: avformat.h:920
int ff_get_extradata(AVFormatContext *s, AVCodecParameters *par, AVIOContext *pb, int size)
Allocate extradata with additional AV_INPUT_BUFFER_PADDING_SIZE at end which is always set to 0 and f...
Definition: utils.c:3305
static const AVCodecTag ff_codec_aiff_tags[]
Definition: aiff.h:33
void ff_id3v2_read(AVFormatContext *s, const char *magic, ID3v2ExtraMeta **extra_meta, unsigned int max_search_size)
Read an ID3v2 tag, including supported extra metadata.
Definition: id3v2.c:1121
int64_t nb_frames
number of frames in this stream if known or 0
Definition: avformat.h:932
#define AV_PKT_FLAG_CORRUPT
The packet content is corrupted.
Definition: avcodec.h:1501
unsigned bps
Definition: movenc.c:1502
#define AIFF
Definition: aiffdec.c:33
#define av_free(p)
as in Berlin toast format
Definition: avcodec.h:578
void * priv_data
Format private data.
Definition: avformat.h:1386
int bits_per_coded_sample
The number of bits per sample in the codedwords.
Definition: avcodec.h:3986
uint8_t * extradata
Extra binary data needed for initializing the decoder, codec-dependent.
Definition: avcodec.h:3958
int channels
Audio only.
Definition: avcodec.h:4050
common header for AIFF muxer and demuxer
const char * name
A comma separated list of short names for the format.
Definition: avformat.h:654
AVCodecParameters * codecpar
Codec parameters associated with this stream.
Definition: avformat.h:1028
int avio_feof(AVIOContext *s)
Similar to feof() but also returns nonzero on read errors.
Definition: aviobuf.c:358
uint32_t codec_tag
Additional information about the codec (corresponds to the AVI FOURCC).
Definition: avcodec.h:3948
int stream_index
Definition: avcodec.h:1470
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
#define MKTAG(a, b, c, d)
Definition: common.h:366
This structure stores compressed data.
Definition: avcodec.h:1445