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 #include "replaygain.h"
33 
34 #define AIFF 0
35 #define AIFF_C_VERSION1 0xA2805140
36 
37 typedef struct AIFFInputContext {
38  int64_t data_end;
41 
43 {
44  if (bps <= 8)
45  return AV_CODEC_ID_PCM_S8;
46  if (bps <= 16)
47  return AV_CODEC_ID_PCM_S16BE;
48  if (bps <= 24)
49  return AV_CODEC_ID_PCM_S24BE;
50  if (bps <= 32)
51  return AV_CODEC_ID_PCM_S32BE;
52 
53  /* bigger than 32 isn't allowed */
54  return AV_CODEC_ID_NONE;
55 }
56 
57 /* returns the size of the found tag */
58 static int get_tag(AVIOContext *pb, uint32_t * tag)
59 {
60  int size;
61 
62  if (avio_feof(pb))
63  return AVERROR(EIO);
64 
65  *tag = avio_rl32(pb);
66  size = avio_rb32(pb);
67 
68  if (size < 0)
69  size = 0x7fffffff;
70 
71  return size;
72 }
73 
74 /* Metadata string read */
75 static void get_meta(AVFormatContext *s, const char *key, int size)
76 {
77  uint8_t *str = av_malloc(size+1);
78 
79  if (str) {
80  int res = avio_read(s->pb, str, size);
81  if (res < 0){
82  av_free(str);
83  return;
84  }
85  size -= res;
86  str[res] = 0;
88  }
89 
90  avio_skip(s->pb, size);
91 }
92 
93 /* Returns the number of sound data frames or negative on error */
95  unsigned version)
96 {
97  AVIOContext *pb = s->pb;
98  AVCodecParameters *par = s->streams[0]->codecpar;
99  AIFFInputContext *aiff = s->priv_data;
100  int exp;
101  uint64_t val;
102  int sample_rate;
103  unsigned int num_frames;
104 
105  if (size & 1)
106  size++;
108  par->channels = avio_rb16(pb);
109  num_frames = avio_rb32(pb);
110  par->bits_per_coded_sample = avio_rb16(pb);
111 
112  exp = avio_rb16(pb) - 16383 - 63;
113  val = avio_rb64(pb);
114  if (exp <-63 || exp >63) {
115  av_log(s, AV_LOG_ERROR, "exp %d is out of range\n", exp);
116  return AVERROR_INVALIDDATA;
117  }
118  if (exp >= 0)
119  sample_rate = val << exp;
120  else
121  sample_rate = (val + (1ULL<<(-exp-1))) >> -exp;
122  par->sample_rate = sample_rate;
123  size -= 18;
124 
125  /* get codec id for AIFF-C */
126  if (size < 4) {
127  version = AIFF;
128  } else if (version == AIFF_C_VERSION1) {
129  par->codec_tag = avio_rl32(pb);
131  if (par->codec_id == AV_CODEC_ID_NONE)
132  avpriv_request_sample(s, "unknown or unsupported codec tag: %s",
133  av_fourcc2str(par->codec_tag));
134  size -= 4;
135  }
136 
137  if (version != AIFF_C_VERSION1 || par->codec_id == AV_CODEC_ID_PCM_S16BE) {
140  aiff->block_duration = 1;
141  } else {
142  switch (par->codec_id) {
148  aiff->block_duration = 1;
149  break;
151  par->block_align = 34 * par->channels;
152  break;
153  case AV_CODEC_ID_MACE3:
154  par->block_align = 2 * par->channels;
155  break;
157  par->bits_per_coded_sample = 5;
160  case AV_CODEC_ID_MACE6:
162  par->block_align = 1 * par->channels;
163  break;
164  case AV_CODEC_ID_GSM:
165  par->block_align = 33;
166  break;
167  default:
168  aiff->block_duration = 1;
169  break;
170  }
171  if (par->block_align > 0)
173  par->block_align);
174  }
175 
176  /* Block align needs to be computed in all cases, as the definition
177  * is specific to applications -> here we use the WAVE format definition */
178  if (!par->block_align)
179  par->block_align = (av_get_bits_per_sample(par->codec_id) * par->channels) >> 3;
180 
181  if (aiff->block_duration) {
182  par->bit_rate = (int64_t)par->sample_rate * (par->block_align << 3) /
183  aiff->block_duration;
184  }
185 
186  /* Chunk is over */
187  if (size)
188  avio_skip(pb, size);
189 
190  return num_frames;
191 }
192 
193 static int aiff_probe(const AVProbeData *p)
194 {
195  /* check file header */
196  if (p->buf[0] == 'F' && p->buf[1] == 'O' &&
197  p->buf[2] == 'R' && p->buf[3] == 'M' &&
198  p->buf[8] == 'A' && p->buf[9] == 'I' &&
199  p->buf[10] == 'F' && (p->buf[11] == 'F' || p->buf[11] == 'C'))
200  return AVPROBE_SCORE_MAX;
201  else
202  return 0;
203 }
204 
205 /* aiff input */
207 {
208  int ret, size, filesize;
209  int64_t offset = 0, position;
210  uint32_t tag;
211  unsigned version = AIFF_C_VERSION1;
212  AVIOContext *pb = s->pb;
213  AVStream * st;
214  AIFFInputContext *aiff = s->priv_data;
215  ID3v2ExtraMeta *id3v2_extra_meta = NULL;
216 
217  /* check FORM header */
218  filesize = get_tag(pb, &tag);
219  if (filesize < 0 || tag != MKTAG('F', 'O', 'R', 'M'))
220  return AVERROR_INVALIDDATA;
221 
222  /* AIFF data type */
223  tag = avio_rl32(pb);
224  if (tag == MKTAG('A', 'I', 'F', 'F')) /* Got an AIFF file */
225  version = AIFF;
226  else if (tag != MKTAG('A', 'I', 'F', 'C')) /* An AIFF-C file then */
227  return AVERROR_INVALIDDATA;
228 
229  filesize -= 4;
230 
231  st = avformat_new_stream(s, NULL);
232  if (!st)
233  return AVERROR(ENOMEM);
234 
235  while (filesize > 0) {
236  /* parse different chunks */
237  size = get_tag(pb, &tag);
238 
239  if (size == AVERROR_EOF && offset > 0 && st->codecpar->block_align) {
240  av_log(s, AV_LOG_WARNING, "header parser hit EOF\n");
241  goto got_sound;
242  }
243  if (size < 0)
244  return size;
245 
246  if (size >= 0x7fffffff - 8)
247  filesize = 0;
248  else
249  filesize -= size + 8;
250 
251  switch (tag) {
252  case MKTAG('C', 'O', 'M', 'M'): /* Common chunk */
253  /* Then for the complete header info */
254  st->nb_frames = get_aiff_header(s, size, version);
255  if (st->nb_frames < 0)
256  return st->nb_frames;
257  if (offset > 0) // COMM is after SSND
258  goto got_sound;
259  break;
260  case MKTAG('I', 'D', '3', ' '):
261  position = avio_tell(pb);
262  ff_id3v2_read(s, ID3v2_DEFAULT_MAGIC, &id3v2_extra_meta, size);
263  if (id3v2_extra_meta)
264  if ((ret = ff_id3v2_parse_apic(s, &id3v2_extra_meta)) < 0 ||
265  (ret = ff_id3v2_parse_chapters(s, &id3v2_extra_meta)) < 0) {
266  ff_id3v2_free_extra_meta(&id3v2_extra_meta);
267  return ret;
268  }
269  ff_id3v2_free_extra_meta(&id3v2_extra_meta);
270  if (position + size > avio_tell(pb))
271  avio_skip(pb, position + size - avio_tell(pb));
272  break;
273  case MKTAG('F', 'V', 'E', 'R'): /* Version chunk */
274  version = avio_rb32(pb);
275  break;
276  case MKTAG('N', 'A', 'M', 'E'): /* Sample name chunk */
277  get_meta(s, "title" , size);
278  break;
279  case MKTAG('A', 'U', 'T', 'H'): /* Author chunk */
280  get_meta(s, "author" , size);
281  break;
282  case MKTAG('(', 'c', ')', ' '): /* Copyright chunk */
283  get_meta(s, "copyright", size);
284  break;
285  case MKTAG('A', 'N', 'N', 'O'): /* Annotation chunk */
286  get_meta(s, "comment" , size);
287  break;
288  case MKTAG('S', 'S', 'N', 'D'): /* Sampled sound chunk */
289  aiff->data_end = avio_tell(pb) + size;
290  offset = avio_rb32(pb); /* Offset of sound data */
291  avio_rb32(pb); /* BlockSize... don't care */
292  offset += avio_tell(pb); /* Compute absolute data offset */
293  if (st->codecpar->block_align && !(pb->seekable & AVIO_SEEKABLE_NORMAL)) /* Assume COMM already parsed */
294  goto got_sound;
295  if (!(pb->seekable & AVIO_SEEKABLE_NORMAL)) {
296  av_log(s, AV_LOG_ERROR, "file is not seekable\n");
297  return -1;
298  }
299  avio_skip(pb, size - 8);
300  break;
301  case MKTAG('w', 'a', 'v', 'e'):
302  if ((uint64_t)size > (1<<30))
303  return -1;
304  if (ff_get_extradata(s, st->codecpar, pb, size) < 0)
305  return AVERROR(ENOMEM);
307  && size>=12*4 && !st->codecpar->block_align) {
308  st->codecpar->block_align = AV_RB32(st->codecpar->extradata+11*4);
309  aiff->block_duration = AV_RB32(st->codecpar->extradata+9*4);
310  } else if (st->codecpar->codec_id == AV_CODEC_ID_QCELP) {
311  char rate = 0;
312  if (size >= 25)
313  rate = st->codecpar->extradata[24];
314  switch (rate) {
315  case 'H': // RATE_HALF
316  st->codecpar->block_align = 17;
317  break;
318  case 'F': // RATE_FULL
319  default:
320  st->codecpar->block_align = 35;
321  }
322  aiff->block_duration = 160;
323  st->codecpar->bit_rate = (int64_t)st->codecpar->sample_rate * (st->codecpar->block_align << 3) /
324  aiff->block_duration;
325  }
326  break;
327  case MKTAG('C','H','A','N'):
328  if(ff_mov_read_chan(s, pb, st, size) < 0)
329  return AVERROR_INVALIDDATA;
330  break;
331  case MKTAG('A','P','C','M'): /* XA ADPCM compressed sound chunk */
333  aiff->data_end = avio_tell(pb) + size;
334  offset = avio_tell(pb) + 8;
335  /* This field is unknown and its data seems to be irrelevant */
336  avio_rb32(pb);
337  st->codecpar->block_align = avio_rb32(pb);
338 
339  goto got_sound;
340  break;
341  case 0:
342  if (offset > 0 && st->codecpar->block_align) // COMM && SSND
343  goto got_sound;
344  default: /* Jump */
345  avio_skip(pb, size);
346  }
347 
348  /* Skip required padding byte for odd-sized chunks. */
349  if (size & 1) {
350  filesize--;
351  avio_skip(pb, 1);
352  }
353  }
354 
355  ret = ff_replaygain_export(st, s->metadata);
356  if (ret < 0)
357  return ret;
358 
359 got_sound:
360  if (!st->codecpar->block_align && st->codecpar->codec_id == AV_CODEC_ID_QCELP) {
361  av_log(s, AV_LOG_WARNING, "qcelp without wave chunk, assuming full rate\n");
362  st->codecpar->block_align = 35;
363  } else if (!st->codecpar->block_align) {
364  av_log(s, AV_LOG_ERROR, "could not find COMM tag or invalid block_align value\n");
365  return -1;
366  }
367 
368  /* Now positioned, get the sound data start and end */
369  avpriv_set_pts_info(st, 64, 1, st->codecpar->sample_rate);
370  st->start_time = 0;
371  st->duration = st->nb_frames * aiff->block_duration;
372 
373  /* Position the stream at the first block */
374  avio_seek(pb, offset, SEEK_SET);
375 
376  return 0;
377 }
378 
379 #define MAX_SIZE 4096
380 
382  AVPacket *pkt)
383 {
384  AVStream *st = s->streams[0];
385  AIFFInputContext *aiff = s->priv_data;
386  int64_t max_size;
387  int res, size;
388 
389  /* calculate size of remaining data */
390  max_size = aiff->data_end - avio_tell(s->pb);
391  if (max_size <= 0)
392  return AVERROR_EOF;
393 
394  if (!st->codecpar->block_align) {
395  av_log(s, AV_LOG_ERROR, "block_align not set\n");
396  return AVERROR_INVALIDDATA;
397  }
398 
399  /* Now for that packet */
400  switch (st->codecpar->codec_id) {
402  case AV_CODEC_ID_GSM:
403  case AV_CODEC_ID_QDM2:
404  case AV_CODEC_ID_QCELP:
405  size = st->codecpar->block_align;
406  break;
407  default:
409  }
410  size = FFMIN(max_size, size);
411  res = av_get_packet(s->pb, pkt, size);
412  if (res < 0)
413  return res;
414 
415  if (size >= st->codecpar->block_align)
416  pkt->flags &= ~AV_PKT_FLAG_CORRUPT;
417  /* Only one stream in an AIFF file */
418  pkt->stream_index = 0;
419  pkt->duration = (res / st->codecpar->block_align) * aiff->block_duration;
420  return 0;
421 }
422 
424  .name = "aiff",
425  .long_name = NULL_IF_CONFIG_SMALL("Audio IFF"),
426  .priv_data_size = sizeof(AIFFInputContext),
431  .codec_tag = (const AVCodecTag* const []){ ff_codec_aiff_tags, 0 },
432 };
#define NULL
Definition: coverity.c:32
const char const char void * val
Definition: avisynth_c.h:863
static int get_aiff_header(AVFormatContext *s, int size, unsigned version)
Definition: aiffdec.c:94
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:38
enum AVCodecID ff_codec_get_id(const AVCodecTag *tags, unsigned int tag)
Definition: utils.c:3158
#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:4929
#define MAX_SIZE
Definition: aiffdec.c:379
#define avpriv_request_sample(...)
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:3968
#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:334
const char * key
static int aiff_read_header(AVFormatContext *s)
Definition: aiffdec.c:206
int version
Definition: avisynth_c.h:858
static AVPacket pkt
unsigned int avio_rb16(AVIOContext *s)
Definition: aviobuf.c:788
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:3960
Format I/O context.
Definition: avformat.h:1358
Public dictionary API.
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:803
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:1498
AVStream * avformat_new_stream(AVFormatContext *s, const AVCodec *c)
Add a new stream to a media file.
Definition: utils.c:4502
static int aiff_read_packet(AVFormatContext *s, AVPacket *pkt)
Definition: aiffdec.c:381
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:35
uint32_t tag
Definition: movenc.c:1531
#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:100
uint64_t avio_rb64(AVIOContext *s)
Definition: aviobuf.c:924
static av_always_inline int64_t avio_tell(AVIOContext *s)
ftell() equivalent for AVIOContext.
Definition: avio.h:557
int ff_replaygain_export(AVStream *st, AVDictionary *metadata)
Parse replaygain tags and export them as per-stream side data.
Definition: replaygain.c:91
#define av_log(a,...)
int avio_read(AVIOContext *s, unsigned char *buf, int size)
Read size bytes from AVIOContext into buf.
Definition: aviobuf.c:650
int64_t bit_rate
The average bitrate of the encoded data (in bits per second).
Definition: avcodec.h:3997
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:1533
AVDictionary * metadata
Metadata that applies to the whole file.
Definition: avformat.h:1598
unsigned int avio_rl32(AVIOContext *s)
Definition: aviobuf.c:772
#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:3964
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:75
static enum AVCodecID aiff_codec_get_id(int bps)
Definition: aiffdec.c:42
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:1746
int8_t exp
Definition: eval.c:72
int flags
A combination of AV_PKT_FLAG values.
Definition: avcodec.h:1486
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:4085
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:193
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:58
int block_duration
Definition: aiffdec.c:39
#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:4078
#define AVPROBE_SCORE_MAX
maximum score
Definition: avformat.h:458
Main libavformat public API header.
AVInputFormat ff_aiff_demuxer
Definition: aiffdec.c:423
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:3339
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:1513
unsigned bps
Definition: movenc.c:1532
#define AIFF
Definition: aiffdec.c:34
#define av_free(p)
as in Berlin toast format
Definition: avcodec.h:583
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:4010
uint8_t * extradata
Extra binary data needed for initializing the decoder, codec-dependent.
Definition: avcodec.h:3982
int channels
Audio only.
Definition: avcodec.h:4074
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:361
uint32_t codec_tag
Additional information about the codec (corresponds to the AVI FOURCC).
Definition: avcodec.h:3972
int stream_index
Definition: avcodec.h:1482
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:1457