FFmpeg  4.3.8
apngdec.c
Go to the documentation of this file.
1 /*
2  * APNG demuxer
3  * Copyright (c) 2014 Benoit Fouet
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  * APNG demuxer.
25  * @see https://wiki.mozilla.org/APNG_Specification
26  * @see http://www.w3.org/TR/PNG
27  */
28 
29 #include "avformat.h"
30 #include "avio_internal.h"
31 #include "internal.h"
32 #include "libavutil/imgutils.h"
33 #include "libavutil/intreadwrite.h"
34 #include "libavutil/opt.h"
35 #include "libavcodec/apng.h"
36 #include "libavcodec/png.h"
37 #include "libavcodec/bytestream.h"
38 
39 #define DEFAULT_APNG_FPS 15
40 
41 typedef struct APNGDemuxContext {
42  const AVClass *class;
43 
44  int max_fps;
46 
48 
50 
51  /*
52  * loop options
53  */
55  uint32_t num_frames;
56  uint32_t num_play;
57  uint32_t cur_loop;
59 
60 /*
61  * To be a valid APNG file, we mandate, in this order:
62  * PNGSIG
63  * IHDR
64  * ...
65  * acTL
66  * ...
67  * IDAT
68  */
69 static int apng_probe(const AVProbeData *p)
70 {
71  GetByteContext gb;
72  int state = 0;
73  uint32_t len, tag;
74 
75  bytestream2_init(&gb, p->buf, p->buf_size);
76 
77  if (bytestream2_get_be64(&gb) != PNGSIG)
78  return 0;
79 
80  for (;;) {
81  len = bytestream2_get_be32(&gb);
82  if (len > 0x7fffffff)
83  return 0;
84 
85  tag = bytestream2_get_le32(&gb);
86  /* we don't check IDAT size, as this is the last tag
87  * we check, and it may be larger than the probe buffer */
88  if (tag != MKTAG('I', 'D', 'A', 'T') &&
89  len + 4 > bytestream2_get_bytes_left(&gb))
90  return 0;
91 
92  switch (tag) {
93  case MKTAG('I', 'H', 'D', 'R'):
94  if (len != 13)
95  return 0;
96  if (av_image_check_size(bytestream2_get_be32(&gb), bytestream2_get_be32(&gb), 0, NULL))
97  return 0;
98  bytestream2_skip(&gb, 9);
99  state++;
100  break;
101  case MKTAG('a', 'c', 'T', 'L'):
102  if (state != 1 ||
103  len != 8 ||
104  bytestream2_get_be32(&gb) == 0) /* 0 is not a valid value for number of frames */
105  return 0;
106  bytestream2_skip(&gb, 8);
107  state++;
108  break;
109  case MKTAG('I', 'D', 'A', 'T'):
110  if (state != 2)
111  return 0;
112  goto end;
113  default:
114  /* skip other tags */
115  bytestream2_skip(&gb, len + 4);
116  break;
117  }
118  }
119 
120 end:
121  return AVPROBE_SCORE_MAX;
122 }
123 
125 {
126  int previous_size = par->extradata_size;
127  int new_size, ret;
128  uint8_t *new_extradata;
129 
130  if (len > INT_MAX - AV_INPUT_BUFFER_PADDING_SIZE - previous_size)
131  return AVERROR_INVALIDDATA;
132 
133  new_size = previous_size + len;
134  new_extradata = av_realloc(par->extradata, new_size + AV_INPUT_BUFFER_PADDING_SIZE);
135  if (!new_extradata)
136  return AVERROR(ENOMEM);
137  memset(new_extradata + new_size, 0, AV_INPUT_BUFFER_PADDING_SIZE);
138  par->extradata = new_extradata;
139  par->extradata_size = new_size;
140 
141  if ((ret = ffio_read_size(pb, par->extradata + previous_size, len)) < 0)
142  return ret;
143 
144  return previous_size;
145 }
146 
148 {
150  AVIOContext *pb = s->pb;
151  uint32_t len, tag;
152  AVStream *st;
153  int acTL_found = 0;
155 
156  /* verify PNGSIG */
157  if (avio_rb64(pb) != PNGSIG)
158  return ret;
159 
160  /* parse IHDR (must be first chunk) */
161  len = avio_rb32(pb);
162  tag = avio_rl32(pb);
163  if (len != 13 || tag != MKTAG('I', 'H', 'D', 'R'))
164  return ret;
165 
166  st = avformat_new_stream(s, NULL);
167  if (!st)
168  return AVERROR(ENOMEM);
169 
170  /* set the timebase to something large enough (1/100,000 of second)
171  * to hopefully cope with all sane frame durations */
172  avpriv_set_pts_info(st, 64, 1, 100000);
175  st->codecpar->width = avio_rb32(pb);
176  st->codecpar->height = avio_rb32(pb);
177  if ((ret = av_image_check_size(st->codecpar->width, st->codecpar->height, 0, s)) < 0)
178  return ret;
179 
180  /* extradata will contain every chunk up to the first fcTL (excluded) */
181  ret = ff_alloc_extradata(st->codecpar, len + 12);
182  if (ret < 0)
183  return ret;
184  AV_WB32(st->codecpar->extradata, len);
185  AV_WL32(st->codecpar->extradata+4, tag);
186  AV_WB32(st->codecpar->extradata+8, st->codecpar->width);
187  AV_WB32(st->codecpar->extradata+12, st->codecpar->height);
188  if ((ret = ffio_read_size(pb, st->codecpar->extradata + 16, 9)) < 0)
189  return ret;
190 
191  while (1) {
192  if (acTL_found && ctx->num_play != 1) {
193  int64_t size = avio_size(pb);
194  int64_t offset = avio_tell(pb);
195  if (size < 0) {
196  ret = size;
197  goto fail;
198  } else if (offset < 0) {
199  ret = offset;
200  goto fail;
201  } else if ((ret = ffio_ensure_seekback(pb, size - offset)) < 0) {
202  av_log(s, AV_LOG_WARNING, "Could not ensure seekback, will not loop\n");
203  ctx->num_play = 1;
204  }
205  }
206  if ((ctx->num_play == 1 || !acTL_found) &&
207  ((ret = ffio_ensure_seekback(pb, 4 /* len */ + 4 /* tag */)) < 0))
208  goto fail;
209 
210  len = avio_rb32(pb);
211  if (len > INT_MAX - 12) {
212  ret = AVERROR_INVALIDDATA;
213  goto fail;
214  }
215 
216  tag = avio_rl32(pb);
217  switch (tag) {
218  case MKTAG('a', 'c', 'T', 'L'):
219  if ((ret = avio_seek(pb, -8, SEEK_CUR)) < 0 ||
220  (ret = append_extradata(st->codecpar, pb, len + 12)) < 0)
221  goto fail;
222  acTL_found = 1;
223  ctx->num_frames = AV_RB32(st->codecpar->extradata + ret + 8);
224  ctx->num_play = AV_RB32(st->codecpar->extradata + ret + 12);
225  av_log(s, AV_LOG_DEBUG, "num_frames: %"PRIu32", num_play: %"PRIu32"\n",
226  ctx->num_frames, ctx->num_play);
227  break;
228  case MKTAG('f', 'c', 'T', 'L'):
229  if (!acTL_found) {
230  ret = AVERROR_INVALIDDATA;
231  goto fail;
232  }
233  if ((ret = avio_seek(pb, -8, SEEK_CUR)) < 0)
234  goto fail;
235  return 0;
236  default:
237  if ((ret = avio_seek(pb, -8, SEEK_CUR)) < 0 ||
238  (ret = append_extradata(st->codecpar, pb, len + 12)) < 0)
239  goto fail;
240  }
241  }
242 
243 fail:
244  return ret;
245 }
246 
248 {
249  uint32_t sequence_number, width, height, x_offset, y_offset;
250  uint16_t delay_num, delay_den;
251  uint8_t dispose_op, blend_op;
252 
253  sequence_number = avio_rb32(s->pb);
254  width = avio_rb32(s->pb);
255  height = avio_rb32(s->pb);
256  x_offset = avio_rb32(s->pb);
257  y_offset = avio_rb32(s->pb);
258  delay_num = avio_rb16(s->pb);
259  delay_den = avio_rb16(s->pb);
260  dispose_op = avio_r8(s->pb);
261  blend_op = avio_r8(s->pb);
262  avio_skip(s->pb, 4); /* crc */
263 
264  /* default is hundredths of seconds */
265  if (!delay_den)
266  delay_den = 100;
267  if (!delay_num || (ctx->max_fps && delay_den / delay_num > ctx->max_fps)) {
268  delay_num = 1;
269  delay_den = ctx->default_fps;
270  }
271  ctx->pkt_duration = av_rescale_q(delay_num,
272  (AVRational){ 1, delay_den },
273  s->streams[0]->time_base);
274 
275  av_log(s, AV_LOG_DEBUG, "%s: "
276  "sequence_number: %"PRId32", "
277  "width: %"PRIu32", "
278  "height: %"PRIu32", "
279  "x_offset: %"PRIu32", "
280  "y_offset: %"PRIu32", "
281  "delay_num: %"PRIu16", "
282  "delay_den: %"PRIu16", "
283  "dispose_op: %d, "
284  "blend_op: %d\n",
285  __FUNCTION__,
286  sequence_number,
287  width,
288  height,
289  x_offset,
290  y_offset,
291  delay_num,
292  delay_den,
293  dispose_op,
294  blend_op);
295 
296  if (width != s->streams[0]->codecpar->width ||
297  height != s->streams[0]->codecpar->height ||
298  x_offset != 0 ||
299  y_offset != 0) {
300  if (sequence_number == 0 ||
301  x_offset >= s->streams[0]->codecpar->width ||
302  width > s->streams[0]->codecpar->width - x_offset ||
303  y_offset >= s->streams[0]->codecpar->height ||
304  height > s->streams[0]->codecpar->height - y_offset)
305  return AVERROR_INVALIDDATA;
306  ctx->is_key_frame = 0;
307  } else {
308  if (sequence_number == 0 && dispose_op == APNG_DISPOSE_OP_PREVIOUS)
309  dispose_op = APNG_DISPOSE_OP_BACKGROUND;
310  ctx->is_key_frame = dispose_op == APNG_DISPOSE_OP_BACKGROUND ||
311  blend_op == APNG_BLEND_OP_SOURCE;
312  }
313 
314  return 0;
315 }
316 
318 {
320  int64_t ret;
321  int64_t size;
322  AVIOContext *pb = s->pb;
323  uint32_t len, tag;
324 
325  /*
326  * fcTL chunk length, in bytes:
327  * 4 (length)
328  * 4 (tag)
329  * 26 (actual chunk)
330  * 4 (crc) bytes
331  * and needed next:
332  * 4 (length)
333  * 4 (tag (must be fdAT or IDAT))
334  */
335  /* if num_play is not 1, then the seekback is already guaranteed */
336  if (ctx->num_play == 1 && (ret = ffio_ensure_seekback(pb, 46)) < 0)
337  return ret;
338 
339  len = avio_rb32(pb);
340  tag = avio_rl32(pb);
341 
342  if (avio_feof(pb))
343  return AVERROR_EOF;
344 
345  switch (tag) {
346  case MKTAG('f', 'c', 'T', 'L'):
347  if (len != 26)
348  return AVERROR_INVALIDDATA;
349 
350  if ((ret = decode_fctl_chunk(s, ctx, pkt)) < 0)
351  return ret;
352 
353  /* fcTL must precede fdAT or IDAT */
354  len = avio_rb32(pb);
355  tag = avio_rl32(pb);
356  if (len > 0x7fffffff ||
357  tag != MKTAG('f', 'd', 'A', 'T') &&
358  tag != MKTAG('I', 'D', 'A', 'T'))
359  return AVERROR_INVALIDDATA;
360 
361  size = 38 /* fcTL */ + 8 /* len, tag */ + len + 4 /* crc */;
362  if (size > INT_MAX)
363  return AVERROR(EINVAL);
364 
365  if ((ret = avio_seek(pb, -46, SEEK_CUR)) < 0 ||
366  (ret = av_append_packet(pb, pkt, size)) < 0)
367  return ret;
368 
369  if (ctx->num_play == 1 && (ret = ffio_ensure_seekback(pb, 8)) < 0)
370  return ret;
371 
372  len = avio_rb32(pb);
373  tag = avio_rl32(pb);
374  while (tag &&
375  tag != MKTAG('f', 'c', 'T', 'L') &&
376  tag != MKTAG('I', 'E', 'N', 'D')) {
377  if (len > 0x7fffffff)
378  return AVERROR_INVALIDDATA;
379  if ((ret = avio_seek(pb, -8, SEEK_CUR)) < 0 ||
380  (ret = av_append_packet(pb, pkt, len + 12)) < 0)
381  return ret;
382  if (ctx->num_play == 1 && (ret = ffio_ensure_seekback(pb, 8)) < 0)
383  return ret;
384  len = avio_rb32(pb);
385  tag = avio_rl32(pb);
386  }
387  if ((ret = avio_seek(pb, -8, SEEK_CUR)) < 0)
388  return ret;
389 
390  if (ctx->is_key_frame)
391  pkt->flags |= AV_PKT_FLAG_KEY;
392  pkt->pts = pkt->dts = AV_NOPTS_VALUE;
393  pkt->duration = ctx->pkt_duration;
394  return ret;
395  case MKTAG('I', 'E', 'N', 'D'):
396  ctx->cur_loop++;
397  if (ctx->ignore_loop || ctx->num_play >= 1 && ctx->cur_loop == ctx->num_play) {
398  avio_seek(pb, -8, SEEK_CUR);
399  return AVERROR_EOF;
400  }
401  if ((ret = avio_seek(pb, s->streams[0]->codecpar->extradata_size + 8, SEEK_SET)) < 0)
402  return ret;
403  return 0;
404  default:
405  avpriv_request_sample(s, "In-stream tag=%s (0x%08"PRIX32") len=%"PRIu32,
406  av_fourcc2str(tag), tag, len);
407  avio_skip(pb, len + 4);
408  }
409 
410  /* Handle the unsupported yet cases */
411  return AVERROR_PATCHWELCOME;
412 }
413 
414 static const AVOption options[] = {
415  { "ignore_loop", "ignore loop setting" , offsetof(APNGDemuxContext, ignore_loop),
416  AV_OPT_TYPE_BOOL, { .i64 = 1 } , 0, 1 , AV_OPT_FLAG_DECODING_PARAM },
417  { "max_fps" , "maximum framerate (0 is no limit)" , offsetof(APNGDemuxContext, max_fps),
418  AV_OPT_TYPE_INT, { .i64 = 0 }, 0, INT_MAX, AV_OPT_FLAG_DECODING_PARAM },
419  { "default_fps", "default framerate (0 is as fast as possible)", offsetof(APNGDemuxContext, default_fps),
420  AV_OPT_TYPE_INT, { .i64 = DEFAULT_APNG_FPS }, 0, INT_MAX, AV_OPT_FLAG_DECODING_PARAM },
421  { NULL },
422 };
423 
424 static const AVClass demuxer_class = {
425  .class_name = "APNG demuxer",
426  .item_name = av_default_item_name,
427  .option = options,
428  .version = LIBAVUTIL_VERSION_INT,
429  .category = AV_CLASS_CATEGORY_DEMUXER,
430 };
431 
433  .name = "apng",
434  .long_name = NULL_IF_CONFIG_SMALL("Animated Portable Network Graphics"),
435  .priv_data_size = sizeof(APNGDemuxContext),
440  .priv_class = &demuxer_class,
441 };
#define NULL
Definition: coverity.c:32
Bytestream IO Context.
Definition: avio.h:161
#define AVERROR_INVALIDDATA
Invalid data found when processing input.
Definition: error.h:59
int64_t avio_size(AVIOContext *s)
Get the filesize.
Definition: aviobuf.c:334
void * av_realloc(void *ptr, size_t size)
Allocate, reallocate, or free a block of memory.
Definition: mem.c:134
static struct @314 state
int size
AVOption.
Definition: opt.h:246
misc image utilities
#define AV_LOG_WARNING
Something somehow does not look correct.
Definition: log.h:182
#define LIBAVUTIL_VERSION_INT
Definition: version.h:85
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:4948
int ffio_read_size(AVIOContext *s, unsigned char *buf, int size)
Read size bytes from AVIOContext into buf.
Definition: aviobuf.c:674
#define avpriv_request_sample(...)
enum AVCodecID codec_id
Specific type of the encoded data (the codec used).
Definition: codec_par.h:60
int64_t avio_seek(AVIOContext *s, int64_t offset, int whence)
fseek() equivalent for AVIOContext.
Definition: aviobuf.c:241
const char * av_default_item_name(void *ptr)
Return the context name.
Definition: log.c:235
static av_always_inline void bytestream2_init(GetByteContext *g, const uint8_t *buf, int buf_size)
Definition: bytestream.h:133
int64_t avio_skip(AVIOContext *s, int64_t offset)
Skip given number of bytes forward.
Definition: aviobuf.c:329
AVInputFormat ff_apng_demuxer
Definition: apngdec.c:432
static AVPacket pkt
unsigned int avio_rb16(AVIOContext *s)
Definition: aviobuf.c:763
This struct describes the properties of an encoded stream.
Definition: codec_par.h:52
Format I/O context.
Definition: avformat.h:1351
const char * class_name
The name of the class; usually it is the same name as the context structure type to which the AVClass...
Definition: log.h:72
uint8_t
int width
Video only.
Definition: codec_par.h:126
AVOptions.
unsigned int avio_rb32(AVIOContext *s)
Definition: aviobuf.c:778
#define AV_RB32
Definition: intreadwrite.h:130
static av_cold int end(AVCodecContext *avctx)
Definition: avrndec.c:92
int64_t duration
Duration of this packet in AVStream->time_base units, 0 if unknown.
Definition: packet.h:373
AVStream * avformat_new_stream(AVFormatContext *s, const AVCodec *c)
Add a new stream to a media file.
Definition: utils.c:4526
AVStream ** streams
A list of all streams in the file.
Definition: avformat.h:1419
#define height
uint32_t tag
Definition: movenc.c:1532
#define AVERROR_EOF
End of file.
Definition: error.h:55
uint64_t avio_rb64(AVIOContext *s)
Definition: aviobuf.c:899
static av_always_inline int64_t avio_tell(AVIOContext *s)
ftell() equivalent for AVIOContext.
Definition: avio.h:557
#define av_log(a,...)
int av_append_packet(AVIOContext *s, AVPacket *pkt, int size)
Read data and append it to the current content of the AVPacket.
Definition: utils.c:317
#define AV_PKT_FLAG_KEY
The packet contains a keyframe.
Definition: packet.h:388
static av_always_inline int bytestream2_get_bytes_left(GetByteContext *g)
Definition: bytestream.h:154
int64_t av_rescale_q(int64_t a, AVRational bq, AVRational cq)
Rescale a 64-bit integer by 2 rational numbers.
Definition: mathematics.c:142
unsigned int avio_rl32(AVIOContext *s)
Definition: aviobuf.c:747
#define AVERROR(e)
Definition: error.h:43
static av_always_inline void bytestream2_skip(GetByteContext *g, unsigned int size)
Definition: bytestream.h:164
#define NULL_IF_CONFIG_SMALL(x)
Return NULL if CONFIG_SMALL is true, otherwise the argument without modification. ...
Definition: internal.h:188
#define AV_LOG_DEBUG
Stuff which is only useful for libav* developers.
Definition: log.h:197
#define av_fourcc2str(fourcc)
Definition: avutil.h:348
enum AVMediaType codec_type
General type of the encoded data.
Definition: codec_par.h:56
#define PNGSIG
Definition: png.h:47
uint32_t num_play
Definition: apngdec.c:56
static const uint8_t offset[127][2]
Definition: vf_spp.c:93
#define fail()
Definition: checkasm.h:123
#define DEFAULT_APNG_FPS
Definition: apngdec.c:39
int flags
A combination of AV_PKT_FLAG values.
Definition: packet.h:361
int extradata_size
Size of the extradata content in bytes.
Definition: codec_par.h:78
int avio_r8(AVIOContext *s)
Definition: aviobuf.c:616
int buf_size
Size of buf except extra allocated bytes.
Definition: avformat.h:444
unsigned char * buf
Buffer must have AVPROBE_PADDING_SIZE of extra allocated bytes filled with zero.
Definition: avformat.h:443
int av_image_check_size(unsigned int w, unsigned int h, int log_offset, void *log_ctx)
Check if the given dimension of an image is valid, meaning that all bytes of the image can be address...
Definition: imgutils.c:282
int ff_alloc_extradata(AVCodecParameters *par, int size)
Allocate extradata with additional AV_INPUT_BUFFER_PADDING_SIZE at end which is always set to 0...
Definition: utils.c:3328
#define width
static int decode_fctl_chunk(AVFormatContext *s, APNGDemuxContext *ctx, AVPacket *pkt)
Definition: apngdec.c:247
AVFormatContext * ctx
Definition: movenc.c:48
#define s(width, name)
Definition: cbs_vp9.c:257
static int append_extradata(AVCodecParameters *par, AVIOContext *pb, int len)
Definition: apngdec.c:124
static int apng_read_packet(AVFormatContext *s, AVPacket *pkt)
Definition: apngdec.c:317
static int read_header(FFV1Context *f)
Definition: ffv1dec.c:545
Stream structure.
Definition: avformat.h:876
#define AVERROR_PATCHWELCOME
Not yet implemented in FFmpeg, patches welcome.
Definition: error.h:62
static int read_packet(void *opaque, uint8_t *buf, int buf_size)
Definition: avio_reading.c:42
AVIOContext * pb
I/O context.
Definition: avformat.h:1393
long long int64_t
Definition: coverity.c:34
int pkt_duration
Definition: apngdec.c:47
int is_key_frame
Definition: apngdec.c:49
Describe the class of an AVClass context structure.
Definition: log.h:67
#define AV_WB32(p, v)
Definition: intreadwrite.h:419
#define AVFMT_GENERIC_INDEX
Use generic index building code.
Definition: avformat.h:463
Rational number (pair of numerator and denominator).
Definition: rational.h:58
#define AV_OPT_FLAG_DECODING_PARAM
a generic parameter which can be set by the user for demuxing or decoding
Definition: opt.h:277
static const AVOption options[]
Definition: apngdec.c:414
This structure contains the data a format has to probe a file.
Definition: avformat.h:441
static const AVClass demuxer_class
Definition: apngdec.c:424
#define flags(name, subs,...)
Definition: cbs_av1.c:576
static int read_probe(const AVProbeData *pd)
Definition: jvdec.c:55
int ffio_ensure_seekback(AVIOContext *s, int64_t buf_size)
Ensures that the requested seekback buffer size will be available.
Definition: aviobuf.c:982
#define AVPROBE_SCORE_MAX
maximum score
Definition: avformat.h:453
Main libavformat public API header.
uint32_t cur_loop
Definition: apngdec.c:57
#define AV_INPUT_BUFFER_PADDING_SIZE
Required number of additionally allocated bytes at the end of the input bitstream for decoding...
Definition: avcodec.h:215
int len
void * priv_data
Format private data.
Definition: avformat.h:1379
APNG common header.
uint8_t * extradata
Extra binary data needed for initializing the decoder, codec-dependent.
Definition: codec_par.h:74
uint32_t num_frames
Definition: apngdec.c:55
int64_t dts
Decompression timestamp in AVStream->time_base units; the time at which the packet is decompressed...
Definition: packet.h:354
const char * name
A comma separated list of short names for the format.
Definition: avformat.h:650
AVCodecParameters * codecpar
Codec parameters associated with this stream.
Definition: avformat.h:1023
int avio_feof(AVIOContext *s)
Similar to feof() but also returns nonzero on read errors.
Definition: aviobuf.c:356
static int apng_probe(const AVProbeData *p)
Definition: apngdec.c:69
AVRational time_base
This is the fundamental unit of time (in seconds) in terms of which frame timestamps are represented...
Definition: avformat.h:905
#define MKTAG(a, b, c, d)
Definition: common.h:406
This structure stores compressed data.
Definition: packet.h:332
static int apng_read_header(AVFormatContext *s)
Definition: apngdec.c:147
int64_t pts
Presentation timestamp in AVStream->time_base units; the time at which the decompressed packet will b...
Definition: packet.h:348
#define AV_NOPTS_VALUE
Undefined timestamp value.
Definition: avutil.h:248
#define AV_WL32(p, v)
Definition: intreadwrite.h:426