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apngdec.c
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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 
47  int64_t pkt_pts;
49 
51 
52  /*
53  * loop options
54  */
56  uint32_t num_frames;
57  uint32_t num_play;
58  uint32_t cur_loop;
60 
61 /*
62  * To be a valid APNG file, we mandate, in this order:
63  * PNGSIG
64  * IHDR
65  * ...
66  * acTL
67  * ...
68  * IDAT
69  */
70 static int apng_probe(AVProbeData *p)
71 {
72  GetByteContext gb;
73  int state = 0;
74  uint32_t len, tag;
75 
76  bytestream2_init(&gb, p->buf, p->buf_size);
77 
78  if (bytestream2_get_be64(&gb) != PNGSIG)
79  return 0;
80 
81  for (;;) {
82  len = bytestream2_get_be32(&gb);
83  if (len > 0x7fffffff)
84  return 0;
85 
86  tag = bytestream2_get_le32(&gb);
87  /* we don't check IDAT size, as this is the last tag
88  * we check, and it may be larger than the probe buffer */
89  if (tag != MKTAG('I', 'D', 'A', 'T') &&
90  len + 4 > bytestream2_get_bytes_left(&gb))
91  return 0;
92 
93  switch (tag) {
94  case MKTAG('I', 'H', 'D', 'R'):
95  if (len != 13)
96  return 0;
97  if (av_image_check_size(bytestream2_get_be32(&gb), bytestream2_get_be32(&gb), 0, NULL))
98  return 0;
99  bytestream2_skip(&gb, 9);
100  state++;
101  break;
102  case MKTAG('a', 'c', 'T', 'L'):
103  if (state != 1 ||
104  len != 8 ||
105  bytestream2_get_be32(&gb) == 0) /* 0 is not a valid value for number of frames */
106  return 0;
107  bytestream2_skip(&gb, 8);
108  state++;
109  break;
110  case MKTAG('I', 'D', 'A', 'T'):
111  if (state != 2)
112  return 0;
113  goto end;
114  default:
115  /* skip other tags */
116  bytestream2_skip(&gb, len + 4);
117  break;
118  }
119  }
120 
121 end:
122  return AVPROBE_SCORE_MAX;
123 }
124 
126 {
127  int previous_size = par->extradata_size;
128  int new_size, ret;
129  uint8_t *new_extradata;
130 
131  if (previous_size > INT_MAX - len)
132  return AVERROR_INVALIDDATA;
133 
134  new_size = previous_size + len;
135  new_extradata = av_realloc(par->extradata, new_size + AV_INPUT_BUFFER_PADDING_SIZE);
136  if (!new_extradata)
137  return AVERROR(ENOMEM);
138  par->extradata = new_extradata;
139  par->extradata_size = new_size;
140 
141  if ((ret = avio_read(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;
154  int64_t ret = AVERROR_INVALIDDATA;
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) */
182  if (!st->codecpar->extradata)
183  return AVERROR(ENOMEM);
184  st->codecpar->extradata_size = len + 12;
185  AV_WB32(st->codecpar->extradata, len);
186  AV_WL32(st->codecpar->extradata+4, tag);
187  AV_WB32(st->codecpar->extradata+8, st->codecpar->width);
188  AV_WB32(st->codecpar->extradata+12, st->codecpar->height);
189  if ((ret = avio_read(pb, st->codecpar->extradata+16, 9)) < 0)
190  goto fail;
191 
192  while (!avio_feof(pb)) {
193  if (acTL_found && ctx->num_play != 1) {
194  int64_t size = avio_size(pb);
195  int64_t offset = avio_tell(pb);
196  if (size < 0) {
197  ret = size;
198  goto fail;
199  } else if (offset < 0) {
200  ret = offset;
201  goto fail;
202  } else if ((ret = ffio_ensure_seekback(pb, size - offset)) < 0) {
203  av_log(s, AV_LOG_WARNING, "Could not ensure seekback, will not loop\n");
204  ctx->num_play = 1;
205  }
206  }
207  if ((ctx->num_play == 1 || !acTL_found) &&
208  ((ret = ffio_ensure_seekback(pb, 4 /* len */ + 4 /* tag */)) < 0))
209  goto fail;
210 
211  len = avio_rb32(pb);
212  if (len > 0x7fffffff) {
213  ret = AVERROR_INVALIDDATA;
214  goto fail;
215  }
216 
217  tag = avio_rl32(pb);
218  switch (tag) {
219  case MKTAG('a', 'c', 'T', 'L'):
220  if ((ret = avio_seek(pb, -8, SEEK_CUR)) < 0 ||
221  (ret = append_extradata(st->codecpar, pb, len + 12)) < 0)
222  goto fail;
223  acTL_found = 1;
224  ctx->num_frames = AV_RB32(st->codecpar->extradata + ret + 8);
225  ctx->num_play = AV_RB32(st->codecpar->extradata + ret + 12);
226  av_log(s, AV_LOG_DEBUG, "num_frames: %"PRIu32", num_play: %"PRIu32"\n",
227  ctx->num_frames, ctx->num_play);
228  break;
229  case MKTAG('f', 'c', 'T', 'L'):
230  if (!acTL_found) {
231  ret = AVERROR_INVALIDDATA;
232  goto fail;
233  }
234  if ((ret = avio_seek(pb, -8, SEEK_CUR)) < 0)
235  goto fail;
236  return 0;
237  default:
238  if ((ret = avio_seek(pb, -8, SEEK_CUR)) < 0 ||
239  (ret = append_extradata(st->codecpar, pb, len + 12)) < 0)
240  goto fail;
241  }
242  }
243 
244 fail:
245  if (st->codecpar->extradata_size) {
246  av_freep(&st->codecpar->extradata);
247  st->codecpar->extradata_size = 0;
248  }
249  return ret;
250 }
251 
253 {
254  uint32_t sequence_number, width, height, x_offset, y_offset;
255  uint16_t delay_num, delay_den;
256  uint8_t dispose_op, blend_op;
257 
258  sequence_number = avio_rb32(s->pb);
259  width = avio_rb32(s->pb);
260  height = avio_rb32(s->pb);
261  x_offset = avio_rb32(s->pb);
262  y_offset = avio_rb32(s->pb);
263  delay_num = avio_rb16(s->pb);
264  delay_den = avio_rb16(s->pb);
265  dispose_op = avio_r8(s->pb);
266  blend_op = avio_r8(s->pb);
267  avio_skip(s->pb, 4); /* crc */
268 
269  /* default is hundredths of seconds */
270  if (!delay_den)
271  delay_den = 100;
272  if (!delay_num || delay_den / delay_num > ctx->max_fps) {
273  delay_num = 1;
274  delay_den = ctx->default_fps;
275  }
276  ctx->pkt_duration = av_rescale_q(delay_num,
277  (AVRational){ 1, delay_den },
278  s->streams[0]->time_base);
279 
280  av_log(s, AV_LOG_DEBUG, "%s: "
281  "sequence_number: %"PRId32", "
282  "width: %"PRIu32", "
283  "height: %"PRIu32", "
284  "x_offset: %"PRIu32", "
285  "y_offset: %"PRIu32", "
286  "delay_num: %"PRIu16", "
287  "delay_den: %"PRIu16", "
288  "dispose_op: %d, "
289  "blend_op: %d\n",
290  __FUNCTION__,
291  sequence_number,
292  width,
293  height,
294  x_offset,
295  y_offset,
296  delay_num,
297  delay_den,
298  dispose_op,
299  blend_op);
300 
301  if (width != s->streams[0]->codecpar->width ||
302  height != s->streams[0]->codecpar->height ||
303  x_offset != 0 ||
304  y_offset != 0) {
305  if (sequence_number == 0 ||
306  x_offset >= s->streams[0]->codecpar->width ||
307  width > s->streams[0]->codecpar->width - x_offset ||
308  y_offset >= s->streams[0]->codecpar->height ||
309  height > s->streams[0]->codecpar->height - y_offset)
310  return AVERROR_INVALIDDATA;
311  ctx->is_key_frame = 0;
312  } else {
313  if (sequence_number == 0 && dispose_op == APNG_DISPOSE_OP_PREVIOUS)
314  dispose_op = APNG_DISPOSE_OP_BACKGROUND;
315  ctx->is_key_frame = dispose_op == APNG_DISPOSE_OP_BACKGROUND ||
316  blend_op == APNG_BLEND_OP_SOURCE;
317  }
318 
319  return 0;
320 }
321 
323 {
325  int64_t ret;
326  int64_t size;
327  AVIOContext *pb = s->pb;
328  uint32_t len, tag;
329 
330  /*
331  * fcTL chunk length, in bytes:
332  * 4 (length)
333  * 4 (tag)
334  * 26 (actual chunk)
335  * 4 (crc) bytes
336  * and needed next:
337  * 4 (length)
338  * 4 (tag (must be fdAT or IDAT))
339  */
340  /* if num_play is not 1, then the seekback is already guaranteed */
341  if (ctx->num_play == 1 && (ret = ffio_ensure_seekback(pb, 46)) < 0)
342  return ret;
343 
344  len = avio_rb32(pb);
345  tag = avio_rl32(pb);
346  switch (tag) {
347  case MKTAG('f', 'c', 'T', 'L'):
348  if (len != 26)
349  return AVERROR_INVALIDDATA;
350 
351  if ((ret = decode_fctl_chunk(s, ctx, pkt)) < 0)
352  return ret;
353 
354  /* fcTL must precede fdAT or IDAT */
355  len = avio_rb32(pb);
356  tag = avio_rl32(pb);
357  if (len > 0x7fffffff ||
358  tag != MKTAG('f', 'd', 'A', 'T') &&
359  tag != MKTAG('I', 'D', 'A', 'T'))
360  return AVERROR_INVALIDDATA;
361 
362  size = 38 /* fcTL */ + 8 /* len, tag */ + len + 4 /* crc */;
363  if (size > INT_MAX)
364  return AVERROR(EINVAL);
365 
366  if ((ret = avio_seek(pb, -46, SEEK_CUR)) < 0 ||
367  (ret = av_append_packet(pb, pkt, size)) < 0)
368  return ret;
369 
370  if (ctx->num_play == 1 && (ret = ffio_ensure_seekback(pb, 8)) < 0)
371  return ret;
372 
373  len = avio_rb32(pb);
374  tag = avio_rl32(pb);
375  while (tag &&
376  tag != MKTAG('f', 'c', 'T', 'L') &&
377  tag != MKTAG('I', 'E', 'N', 'D')) {
378  if (len > 0x7fffffff)
379  return AVERROR_INVALIDDATA;
380  if ((ret = avio_seek(pb, -8, SEEK_CUR)) < 0 ||
381  (ret = av_append_packet(pb, pkt, len + 12)) < 0)
382  return ret;
383  if (ctx->num_play == 1 && (ret = ffio_ensure_seekback(pb, 8)) < 0)
384  return ret;
385  len = avio_rb32(pb);
386  tag = avio_rl32(pb);
387  }
388  if ((ret = avio_seek(pb, -8, SEEK_CUR)) < 0)
389  return ret;
390 
391  if (ctx->is_key_frame)
392  pkt->flags |= AV_PKT_FLAG_KEY;
393  pkt->pts = ctx->pkt_pts;
394  pkt->duration = ctx->pkt_duration;
395  ctx->pkt_pts += ctx->pkt_duration;
396  return ret;
397  case MKTAG('I', 'E', 'N', 'D'):
398  ctx->cur_loop++;
399  if (ctx->ignore_loop || ctx->num_play >= 1 && ctx->cur_loop == ctx->num_play) {
400  avio_seek(pb, -8, SEEK_CUR);
401  return AVERROR_EOF;
402  }
403  if ((ret = avio_seek(pb, s->streams[0]->codecpar->extradata_size + 8, SEEK_SET)) < 0)
404  return ret;
405  return 0;
406  default:
407  {
408  char tag_buf[32];
409 
410  av_get_codec_tag_string(tag_buf, sizeof(tag_buf), tag);
411  avpriv_request_sample(s, "In-stream tag=%s (0x%08X) len=%"PRIu32, tag_buf, tag, len);
412  avio_skip(pb, len + 4);
413  }
414  }
415 
416  /* Handle the unsupported yet cases */
417  return AVERROR_PATCHWELCOME;
418 }
419 
420 static const AVOption options[] = {
421  { "ignore_loop", "ignore loop setting" , offsetof(APNGDemuxContext, ignore_loop),
422  AV_OPT_TYPE_BOOL, { .i64 = 1 } , 0, 1 , AV_OPT_FLAG_DECODING_PARAM },
423  { "max_fps" , "maximum framerate (0 is no limit)" , offsetof(APNGDemuxContext, max_fps),
425  { "default_fps", "default framerate (0 is as fast as possible)", offsetof(APNGDemuxContext, default_fps),
427  { NULL },
428 };
429 
430 static const AVClass demuxer_class = {
431  .class_name = "APNG demuxer",
432  .item_name = av_default_item_name,
433  .option = options,
434  .version = LIBAVUTIL_VERSION_INT,
435  .category = AV_CLASS_CATEGORY_DEMUXER,
436 };
437 
439  .name = "apng",
440  .long_name = NULL_IF_CONFIG_SMALL("Animated Portable Network Graphics"),
441  .priv_data_size = sizeof(APNGDemuxContext),
446  .priv_class = &demuxer_class,
447 };
#define NULL
Definition: coverity.c:32
const char * s
Definition: avisynth_c.h:631
Bytestream IO Context.
Definition: avio.h:147
#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:309
AVOption.
Definition: opt.h:245
misc image utilities
#define AV_LOG_WARNING
Something somehow does not look correct.
Definition: log.h:182
#define LIBAVUTIL_VERSION_INT
Definition: version.h:70
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:4427
static int apng_probe(AVProbeData *p)
Definition: apngdec.c:70
enum AVCodecID codec_id
Specific type of the encoded data (the codec used).
Definition: avcodec.h:3922
int64_t avio_seek(AVIOContext *s, int64_t offset, int whence)
fseek() equivalent for AVIOContext.
Definition: aviobuf.c:230
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:304
size_t av_get_codec_tag_string(char *buf, size_t buf_size, unsigned int codec_tag)
Put a string representing the codec tag codec_tag in buf.
Definition: utils.c:3102
AVInputFormat ff_apng_demuxer
Definition: apngdec.c:438
static AVPacket pkt
unsigned int avio_rb16(AVIOContext *s)
Definition: aviobuf.c:736
This struct describes the properties of an encoded stream.
Definition: avcodec.h:3914
Format I/O context.
Definition: avformat.h:1325
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
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 width
Video only.
Definition: avcodec.h:3988
AVOptions.
unsigned int avio_rb32(AVIOContext *s)
Definition: aviobuf.c:751
static av_cold int end(AVCodecContext *avctx)
Definition: avrndec.c:90
int64_t duration
Duration of this packet in AVStream->time_base units, 0 if unknown.
Definition: avcodec.h:1598
AVStream * avformat_new_stream(AVFormatContext *s, const AVCodec *c)
Add a new stream to a media file.
Definition: utils.c:4065
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:1393
#define height
int64_t pkt_pts
Definition: apngdec.c:47
uint32_t tag
Definition: movenc.c:1367
#define AVERROR_EOF
End of file.
Definition: error.h:55
ptrdiff_t size
Definition: opengl_enc.c:101
uint64_t avio_rb64(AVIOContext *s)
Definition: aviobuf.c:818
static av_always_inline int64_t avio_tell(AVIOContext *s)
ftell() equivalent for AVIOContext.
Definition: avio.h:511
#define av_log(a,...)
int avio_read(AVIOContext *s, unsigned char *buf, int size)
Read size bytes from AVIOContext into buf.
Definition: aviobuf.c:598
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:270
#define AV_PKT_FLAG_KEY
The packet contains a keyframe.
Definition: avcodec.h:1612
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
av_default_item_name
unsigned int avio_rl32(AVIOContext *s)
Definition: aviobuf.c:720
#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:176
#define AV_LOG_DEBUG
Stuff which is only useful for libav* developers.
Definition: log.h:197
enum AVMediaType codec_type
General type of the encoded data.
Definition: avcodec.h:3918
static av_always_inline unsigned int bytestream2_get_bytes_left(GetByteContext *g)
Definition: bytestream.h:154
#define PNGSIG
Definition: png.h:52
uint32_t num_play
Definition: apngdec.c:57
static const uint8_t offset[127][2]
Definition: vf_spp.c:92
#define fail()
Definition: checkasm.h:81
#define DEFAULT_APNG_FPS
Definition: apngdec.c:39
int flags
A combination of AV_PKT_FLAG values.
Definition: avcodec.h:1586
int extradata_size
Size of the extradata content in bytes.
Definition: avcodec.h:3940
int avio_r8(AVIOContext *s)
Definition: aviobuf.c:589
int buf_size
Size of buf except extra allocated bytes.
Definition: avformat.h:462
unsigned char * buf
Buffer must have AVPROBE_PADDING_SIZE of extra allocated bytes filled with zero.
Definition: avformat.h:461
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:251
#define width
static int decode_fctl_chunk(AVFormatContext *s, APNGDemuxContext *ctx, AVPacket *pkt)
Definition: apngdec.c:252
static int read_probe(AVProbeData *pd)
Definition: jvdec.c:55
AVFormatContext * ctx
Definition: movenc.c:48
static int append_extradata(AVCodecParameters *par, AVIOContext *pb, int len)
Definition: apngdec.c:125
static int apng_read_packet(AVFormatContext *s, AVPacket *pkt)
Definition: apngdec.c:322
static int read_header(FFV1Context *f)
Definition: ffv1dec.c:638
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:1367
int pkt_duration
Definition: apngdec.c:48
int is_key_frame
Definition: apngdec.c:50
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:485
rational number numerator/denominator
Definition: rational.h:43
#define AV_OPT_FLAG_DECODING_PARAM
a generic parameter which can be set by the user for demuxing or decoding
Definition: opt.h:276
static const AVOption options[]
Definition: apngdec.c:420
This structure contains the data a format has to probe a file.
Definition: avformat.h:459
static struct @228 state
static const AVClass demuxer_class
Definition: apngdec.c:430
static int flags
Definition: cpu.c:47
int ffio_ensure_seekback(AVIOContext *s, int64_t buf_size)
Ensures that the requested seekback buffer size will be available.
Definition: aviobuf.c:924
#define AVPROBE_SCORE_MAX
maximum score
Definition: avformat.h:471
Main libavformat public API header.
void * av_realloc(void *ptr, size_t size)
Allocate or reallocate a block of memory.
Definition: mem.c:145
uint32_t cur_loop
Definition: apngdec.c:58
#define AV_INPUT_BUFFER_PADDING_SIZE
Required number of additionally allocated bytes at the end of the input bitstream for decoding...
Definition: avcodec.h:731
int len
void * priv_data
Format private data.
Definition: avformat.h:1353
APNG common header.
uint8_t * extradata
Extra binary data needed for initializing the decoder, codec-dependent.
Definition: avcodec.h:3936
uint32_t num_frames
Definition: apngdec.c:56
#define av_freep(p)
const char * name
A comma separated list of short names for the format.
Definition: avformat.h:660
AVCodecParameters * codecpar
Definition: avformat.h:1006
int avio_feof(AVIOContext *s)
feof() equivalent for AVIOContext.
Definition: aviobuf.c:328
AVRational time_base
This is the fundamental unit of time (in seconds) in terms of which frame timestamps are represented...
Definition: avformat.h:913
#define MKTAG(a, b, c, d)
Definition: common.h:342
This structure stores compressed data.
Definition: avcodec.h:1557
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: avcodec.h:1573
#define AV_WL32(p, v)
Definition: intreadwrite.h:426