FFmpeg
apngenc.c
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1 /*
2  * APNG muxer
3  * Copyright (c) 2015 Donny Yang
4  *
5  * first version by Donny Yang <work@kota.moe>
6  *
7  * This file is part of FFmpeg.
8  *
9  * FFmpeg is free software; you can redistribute it and/or
10  * modify it under the terms of the GNU Lesser General Public
11  * License as published by the Free Software Foundation; either
12  * version 2.1 of the License, or (at your option) any later version.
13  *
14  * FFmpeg is distributed in the hope that it will be useful,
15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
17  * Lesser General Public License for more details.
18  *
19  * You should have received a copy of the GNU Lesser General Public
20  * License along with FFmpeg; if not, write to the Free Software
21  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
22  */
23 
24 #include "avformat.h"
25 #include "libavutil/avassert.h"
26 #include "libavutil/crc.h"
27 #include "libavutil/intreadwrite.h"
28 #include "libavutil/log.h"
29 #include "libavutil/opt.h"
30 #include "libavcodec/apng.h"
31 #include "libavcodec/png.h"
32 
33 typedef struct APNGMuxContext {
34  AVClass *class;
35 
36  uint32_t plays;
38 
39  uint64_t acTL_offset;
40  uint32_t frame_number;
41 
44 
46 
47  uint8_t *extra_data;
50 
51 static const uint8_t *apng_find_chunk(uint32_t tag, const uint8_t *buf,
52  size_t length)
53 {
54  size_t b;
55  for (b = 0; AV_RB32(buf + b) + 12ULL <= length - b; b += AV_RB32(buf + b) + 12ULL)
56  if (AV_RB32(&buf[b + 4]) == tag)
57  return &buf[b];
58  return NULL;
59 }
60 
61 static void apng_write_chunk(AVIOContext *io_context, uint32_t tag,
62  uint8_t *buf, size_t length)
63 {
64  const AVCRC *crc_table = av_crc_get_table(AV_CRC_32_IEEE_LE);
65  uint32_t crc = ~0U;
66  uint8_t tagbuf[4];
67 
68  av_assert0(crc_table);
69 
70  avio_wb32(io_context, length);
71  AV_WB32(tagbuf, tag);
72  crc = av_crc(crc_table, crc, tagbuf, 4);
73  avio_wb32(io_context, tag);
74  if (length > 0) {
75  crc = av_crc(crc_table, crc, buf, length);
76  avio_write(io_context, buf, length);
77  }
78  avio_wb32(io_context, ~crc);
79 }
80 
81 static int apng_write_header(AVFormatContext *format_context)
82 {
83  APNGMuxContext *apng = format_context->priv_data;
84  AVCodecParameters *par = format_context->streams[0]->codecpar;
85 
86  if (format_context->nb_streams != 1 ||
87  format_context->streams[0]->codecpar->codec_type != AVMEDIA_TYPE_VIDEO ||
88  format_context->streams[0]->codecpar->codec_id != AV_CODEC_ID_APNG) {
89  av_log(format_context, AV_LOG_ERROR,
90  "APNG muxer supports only a single video APNG stream.\n");
91  return AVERROR(EINVAL);
92  }
93 
94  if (apng->last_delay.num > UINT16_MAX || apng->last_delay.den > UINT16_MAX) {
95  av_reduce(&apng->last_delay.num, &apng->last_delay.den,
96  apng->last_delay.num, apng->last_delay.den, UINT16_MAX);
97  av_log(format_context, AV_LOG_WARNING,
98  "Last frame delay is too precise. Reducing to %d/%d (%f).\n",
99  apng->last_delay.num, apng->last_delay.den, (double)apng->last_delay.num / apng->last_delay.den);
100  }
101 
102  avio_wb64(format_context->pb, PNGSIG);
103  // Remaining headers are written when they are copied from the encoder
104 
105  if (par->extradata_size) {
107  if (!apng->extra_data)
108  return AVERROR(ENOMEM);
109  apng->extra_data_size = par->extradata_size;
110  memcpy(apng->extra_data, par->extradata, par->extradata_size);
111  }
112 
113  return 0;
114 }
115 
116 static int flush_packet(AVFormatContext *format_context, AVPacket *packet)
117 {
118  APNGMuxContext *apng = format_context->priv_data;
119  AVIOContext *io_context = format_context->pb;
120  AVStream *codec_stream = format_context->streams[0];
121  uint8_t *side_data = NULL;
122  size_t side_data_size;
123 
124  av_assert0(apng->prev_packet);
125 
126  side_data = av_packet_get_side_data(apng->prev_packet, AV_PKT_DATA_NEW_EXTRADATA, &side_data_size);
127 
128  if (side_data_size) {
129  av_freep(&apng->extra_data);
130  apng->extra_data = av_mallocz(side_data_size + AV_INPUT_BUFFER_PADDING_SIZE);
131  if (!apng->extra_data)
132  return AVERROR(ENOMEM);
133  apng->extra_data_size = side_data_size;
134  memcpy(apng->extra_data, side_data, apng->extra_data_size);
135  }
136 
137  if (apng->frame_number == 0 && !packet) {
138  const uint8_t *existing_acTL_chunk;
139  const uint8_t *existing_fcTL_chunk;
140 
141  av_log(format_context, AV_LOG_INFO, "Only a single frame so saving as a normal PNG.\n");
142 
143  // Write normal PNG headers without acTL chunk
144  existing_acTL_chunk = apng_find_chunk(MKBETAG('a', 'c', 'T', 'L'), apng->extra_data, apng->extra_data_size);
145  if (existing_acTL_chunk) {
146  const uint8_t *chunk_after_acTL = existing_acTL_chunk + AV_RB32(existing_acTL_chunk) + 12;
147  avio_write(io_context, apng->extra_data, existing_acTL_chunk - apng->extra_data);
148  avio_write(io_context, chunk_after_acTL, apng->extra_data + apng->extra_data_size - chunk_after_acTL);
149  } else {
150  avio_write(io_context, apng->extra_data, apng->extra_data_size);
151  }
152 
153  // Write frame data without fcTL chunk
154  existing_fcTL_chunk = apng_find_chunk(MKBETAG('f', 'c', 'T', 'L'), apng->prev_packet->data, apng->prev_packet->size);
155  if (existing_fcTL_chunk) {
156  const uint8_t *chunk_after_fcTL = existing_fcTL_chunk + AV_RB32(existing_fcTL_chunk) + 12;
157  avio_write(io_context, apng->prev_packet->data, existing_fcTL_chunk - apng->prev_packet->data);
158  avio_write(io_context, chunk_after_fcTL, apng->prev_packet->data + apng->prev_packet->size - chunk_after_fcTL);
159  } else {
160  avio_write(io_context, apng->prev_packet->data, apng->prev_packet->size);
161  }
162  } else {
163  const uint8_t *data, *data_end;
164  const uint8_t *existing_fcTL_chunk;
165 
166  if (apng->frame_number == 0) {
167  const uint8_t *existing_acTL_chunk;
168 
169  // Write normal PNG headers
170  avio_write(io_context, apng->extra_data, apng->extra_data_size);
171 
172  existing_acTL_chunk = apng_find_chunk(MKBETAG('a', 'c', 'T', 'L'), apng->extra_data, apng->extra_data_size);
173  if (!existing_acTL_chunk) {
174  uint8_t buf[8];
175  // Write animation control header
176  apng->acTL_offset = avio_tell(io_context);
177  AV_WB32(buf, UINT_MAX); // number of frames (filled in later)
178  AV_WB32(buf + 4, apng->plays);
179  apng_write_chunk(io_context, MKBETAG('a', 'c', 'T', 'L'), buf, 8);
180  }
181  }
182 
183  data = apng->prev_packet->data;
184  data_end = data + apng->prev_packet->size;
185  existing_fcTL_chunk = apng_find_chunk(MKBETAG('f', 'c', 'T', 'L'), apng->prev_packet->data, apng->prev_packet->size);
186  if (existing_fcTL_chunk) {
187  AVRational delay;
188 
189  if (AV_RB32(existing_fcTL_chunk) != APNG_FCTL_CHUNK_SIZE)
190  return AVERROR_INVALIDDATA;
191 
192  existing_fcTL_chunk += 8;
193  delay.num = AV_RB16(existing_fcTL_chunk + 20);
194  delay.den = AV_RB16(existing_fcTL_chunk + 22);
195 
196  if (delay.num == 0 && delay.den == 0) {
197  uint8_t new_fcTL_chunk[APNG_FCTL_CHUNK_SIZE];
198 
199  if (packet) {
200  int64_t delay_num_raw = (packet->dts - apng->prev_packet->dts) * codec_stream->time_base.num;
201  int64_t delay_den_raw = codec_stream->time_base.den;
202  if (!av_reduce(&delay.num, &delay.den, delay_num_raw, delay_den_raw, UINT16_MAX) &&
203  !apng->framerate_warned) {
204  av_log(format_context, AV_LOG_WARNING,
205  "Frame rate is too high or specified too precisely. Unable to copy losslessly.\n");
206  apng->framerate_warned = 1;
207  }
208  } else if (apng->last_delay.num > 0) {
209  delay = apng->last_delay;
210  } else {
211  delay = apng->prev_delay;
212  }
213 
214  avio_write(io_context, data, (existing_fcTL_chunk - 8) - data);
215  data = existing_fcTL_chunk + APNG_FCTL_CHUNK_SIZE + 4 /* CRC-32 */;
216  // Update frame control header with new delay
217  memcpy(new_fcTL_chunk, existing_fcTL_chunk, sizeof(new_fcTL_chunk));
218  AV_WB16(new_fcTL_chunk + 20, delay.num);
219  AV_WB16(new_fcTL_chunk + 22, delay.den);
220  apng_write_chunk(io_context, MKBETAG('f', 'c', 'T', 'L'),
221  new_fcTL_chunk, sizeof(new_fcTL_chunk));
222  }
223  apng->prev_delay = delay;
224  }
225 
226  // Write frame data
227  avio_write(io_context, data, data_end - data);
228  }
229  ++apng->frame_number;
230 
232  if (packet)
233  av_packet_ref(apng->prev_packet, packet);
234  return 0;
235 }
236 
237 static int apng_write_packet(AVFormatContext *format_context, AVPacket *packet)
238 {
239  APNGMuxContext *apng = format_context->priv_data;
240  int ret;
241 
242  if (!apng->prev_packet) {
243  apng->prev_packet = av_packet_alloc();
244  if (!apng->prev_packet)
245  return AVERROR(ENOMEM);
246 
247  av_packet_ref(apng->prev_packet, packet);
248  } else {
249  ret = flush_packet(format_context, packet);
250  if (ret < 0)
251  return ret;
252  }
253 
254  return 0;
255 }
256 
257 static int apng_write_trailer(AVFormatContext *format_context)
258 {
259  APNGMuxContext *apng = format_context->priv_data;
260  AVIOContext *io_context = format_context->pb;
261  uint8_t buf[8];
262  int ret;
263 
264  if (apng->prev_packet) {
265  ret = flush_packet(format_context, NULL);
266  if (ret < 0)
267  return ret;
268  }
269 
270  apng_write_chunk(io_context, MKBETAG('I', 'E', 'N', 'D'), NULL, 0);
271 
272  if (apng->acTL_offset && (io_context->seekable & AVIO_SEEKABLE_NORMAL)) {
273  avio_seek(io_context, apng->acTL_offset, SEEK_SET);
274 
275  AV_WB32(buf, apng->frame_number);
276  AV_WB32(buf + 4, apng->plays);
277  apng_write_chunk(io_context, MKBETAG('a', 'c', 'T', 'L'), buf, 8);
278  }
279 
280  return 0;
281 }
282 
284 {
285  APNGMuxContext *apng = s->priv_data;
286 
287  av_packet_free(&apng->prev_packet);
288  av_freep(&apng->extra_data);
289  apng->extra_data_size = 0;
290 }
291 
292 #define OFFSET(x) offsetof(APNGMuxContext, x)
293 #define ENC AV_OPT_FLAG_ENCODING_PARAM
294 static const AVOption options[] = {
295  { "plays", "Number of times to play the output: 0 - infinite loop, 1 - no loop", OFFSET(plays),
296  AV_OPT_TYPE_INT, { .i64 = 1 }, 0, UINT16_MAX, ENC },
297  { "final_delay", "Force delay after the last frame", OFFSET(last_delay),
298  AV_OPT_TYPE_RATIONAL, { .dbl = 0 }, 0, UINT16_MAX, ENC },
299  { NULL },
300 };
301 
302 static const AVClass apng_muxer_class = {
303  .class_name = "APNG muxer",
304  .item_name = av_default_item_name,
305  .version = LIBAVUTIL_VERSION_INT,
306  .option = options,
307 };
308 
310  .name = "apng",
311  .long_name = NULL_IF_CONFIG_SMALL("Animated Portable Network Graphics"),
312  .mime_type = "image/png",
313  .extensions = "apng",
314  .priv_data_size = sizeof(APNGMuxContext),
315  .audio_codec = AV_CODEC_ID_NONE,
316  .video_codec = AV_CODEC_ID_APNG,
320  .deinit = apng_deinit,
321  .priv_class = &apng_muxer_class,
323 };
av_packet_unref
void av_packet_unref(AVPacket *pkt)
Wipe the packet.
Definition: avpacket.c:422
AV_LOG_WARNING
#define AV_LOG_WARNING
Something somehow does not look correct.
Definition: log.h:186
AVCodecParameters::extradata
uint8_t * extradata
Extra binary data needed for initializing the decoder, codec-dependent.
Definition: codec_par.h:76
AVOutputFormat::name
const char * name
Definition: avformat.h:510
APNGMuxContext
Definition: apngenc.c:33
AVERROR
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
opt.h
AVCodecParameters::codec_type
enum AVMediaType codec_type
General type of the encoded data.
Definition: codec_par.h:58
apng_muxer_class
static const AVClass apng_muxer_class
Definition: apngenc.c:302
apng_write_trailer
static int apng_write_trailer(AVFormatContext *format_context)
Definition: apngenc.c:257
AVCodecParameters
This struct describes the properties of an encoded stream.
Definition: codec_par.h:54
AVCRC
uint32_t AVCRC
Definition: crc.h:46
APNG_FCTL_CHUNK_SIZE
#define APNG_FCTL_CHUNK_SIZE
Definition: apng.h:42
AVFMT_VARIABLE_FPS
#define AVFMT_VARIABLE_FPS
Format allows variable fps.
Definition: avformat.h:484
APNGMuxContext::frame_number
uint32_t frame_number
Definition: apngenc.c:40
APNGMuxContext::last_delay
AVRational last_delay
Definition: apngenc.c:37
AVFormatContext::streams
AVStream ** streams
A list of all streams in the file.
Definition: avformat.h:1284
deinit
static void deinit(AVFormatContext *s)
Definition: chromaprint.c:49
ff_apng_muxer
const AVOutputFormat ff_apng_muxer
Definition: apngenc.c:309
AVPacket::data
uint8_t * data
Definition: packet.h:374
AVOption
AVOption.
Definition: opt.h:251
b
#define b
Definition: input.c:41
APNGMuxContext::extra_data_size
int extra_data_size
Definition: apngenc.c:48
data
const char data[16]
Definition: mxf.c:146
AV_CODEC_ID_APNG
@ AV_CODEC_ID_APNG
Definition: codec_id.h:268
AV_OPT_TYPE_RATIONAL
@ AV_OPT_TYPE_RATIONAL
Definition: opt.h:230
av_packet_free
void av_packet_free(AVPacket **pkt)
Free the packet, if the packet is reference counted, it will be unreferenced first.
Definition: avpacket.c:73
crc.h
APNGMuxContext::prev_delay
AVRational prev_delay
Definition: apngenc.c:43
avio_tell
static av_always_inline int64_t avio_tell(AVIOContext *s)
ftell() equivalent for AVIOContext.
Definition: avio.h:510
av_reduce
int av_reduce(int *dst_num, int *dst_den, int64_t num, int64_t den, int64_t max)
Reduce a fraction.
Definition: rational.c:35
AVRational::num
int num
Numerator.
Definition: rational.h:59
avassert.h
AV_LOG_ERROR
#define AV_LOG_ERROR
Something went wrong and cannot losslessly be recovered.
Definition: log.h:180
APNGMuxContext::prev_packet
AVPacket * prev_packet
Definition: apngenc.c:42
flush_packet
static int flush_packet(AVFormatContext *format_context, AVPacket *packet)
Definition: apngenc.c:116
intreadwrite.h
s
#define s(width, name)
Definition: cbs_vp9.c:256
apng_write_chunk
static void apng_write_chunk(AVIOContext *io_context, uint32_t tag, uint8_t *buf, size_t length)
Definition: apngenc.c:61
av_assert0
#define av_assert0(cond)
assert() equivalent, that is always enabled.
Definition: avassert.h:37
if
if(ret)
Definition: filter_design.txt:179
AVFormatContext
Format I/O context.
Definition: avformat.h:1216
AVStream::codecpar
AVCodecParameters * codecpar
Codec parameters associated with this stream.
Definition: avformat.h:1108
LIBAVUTIL_VERSION_INT
#define LIBAVUTIL_VERSION_INT
Definition: version.h:85
APNGMuxContext::extra_data
uint8_t * extra_data
Definition: apngenc.c:47
AVClass
Describe the class of an AVClass context structure.
Definition: log.h:66
AVStream::time_base
AVRational time_base
This is the fundamental unit of time (in seconds) in terms of which frame timestamps are represented.
Definition: avformat.h:978
NULL
#define NULL
Definition: coverity.c:32
apng.h
AV_WB16
#define AV_WB16(p, v)
Definition: intreadwrite.h:405
write_trailer
static int write_trailer(AVFormatContext *s1)
Definition: v4l2enc.c:100
AVRational
Rational number (pair of numerator and denominator).
Definition: rational.h:58
av_default_item_name
const char * av_default_item_name(void *ptr)
Return the context name.
Definition: log.c:237
AVFormatContext::pb
AVIOContext * pb
I/O context.
Definition: avformat.h:1258
av_packet_ref
int av_packet_ref(AVPacket *dst, const AVPacket *src)
Setup a new reference to the data described by a given packet.
Definition: avpacket.c:430
AVCodecParameters::extradata_size
int extradata_size
Size of the extradata content in bytes.
Definition: codec_par.h:80
AV_WB32
#define AV_WB32(p, v)
Definition: intreadwrite.h:419
AVFormatContext::nb_streams
unsigned int nb_streams
Number of elements in AVFormatContext.streams.
Definition: avformat.h:1272
AVIOContext
Bytestream IO Context.
Definition: avio.h:166
AVPacket::size
int size
Definition: packet.h:375
NULL_IF_CONFIG_SMALL
#define NULL_IF_CONFIG_SMALL(x)
Return NULL if CONFIG_SMALL is true, otherwise the argument without modification.
Definition: internal.h:115
AVIOContext::seekable
int seekable
A combination of AVIO_SEEKABLE_ flags or 0 when the stream is not seekable.
Definition: avio.h:267
MKBETAG
#define MKBETAG(a, b, c, d)
Definition: macros.h:56
AV_RB32
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:96
AVPacket::dts
int64_t dts
Decompression timestamp in AVStream->time_base units; the time at which the packet is decompressed.
Definition: packet.h:373
avio_write
void avio_write(AVIOContext *s, const unsigned char *buf, int size)
Definition: aviobuf.c:232
avio_wb32
void avio_wb32(AVIOContext *s, unsigned int val)
Definition: aviobuf.c:396
av_crc_get_table
const AVCRC * av_crc_get_table(AVCRCId crc_id)
Get an initialized standard CRC table.
Definition: crc.c:374
ENC
#define ENC
Definition: apngenc.c:293
av_packet_alloc
AVPacket * av_packet_alloc(void)
Allocate an AVPacket and set its fields to default values.
Definition: avpacket.c:62
options
static const AVOption options[]
Definition: apngenc.c:294
PNGSIG
#define PNGSIG
Definition: png.h:49
AV_LOG_INFO
#define AV_LOG_INFO
Standard information.
Definition: log.h:191
log.h
AV_CODEC_ID_NONE
@ AV_CODEC_ID_NONE
Definition: codec_id.h:50
AVOutputFormat
Definition: avformat.h:509
OFFSET
#define OFFSET(x)
Definition: apngenc.c:292
av_packet_get_side_data
uint8_t * av_packet_get_side_data(const AVPacket *pkt, enum AVPacketSideDataType type, size_t *size)
Get side information from packet.
Definition: avpacket.c:251
APNGMuxContext::framerate_warned
int framerate_warned
Definition: apngenc.c:45
apng_find_chunk
static const uint8_t * apng_find_chunk(uint32_t tag, const uint8_t *buf, size_t length)
Definition: apngenc.c:51
av_mallocz
void * av_mallocz(size_t size)
Allocate a memory block with alignment suitable for all memory accesses (including vectors if availab...
Definition: mem.c:264
write_packet
static int write_packet(Muxer *mux, OutputStream *ost, AVPacket *pkt)
Definition: ffmpeg_mux.c:61
tag
uint32_t tag
Definition: movenc.c:1647
ret
ret
Definition: filter_design.txt:187
AVStream
Stream structure.
Definition: avformat.h:948
apng_write_packet
static int apng_write_packet(AVFormatContext *format_context, AVPacket *packet)
Definition: apngenc.c:237
avio_seek
int64_t avio_seek(AVIOContext *s, int64_t offset, int whence)
fseek() equivalent for AVIOContext.
Definition: aviobuf.c:262
AVClass::class_name
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:71
avformat.h
AV_INPUT_BUFFER_PADDING_SIZE
#define AV_INPUT_BUFFER_PADDING_SIZE
Definition: defs.h:40
U
#define U(x)
Definition: vpx_arith.h:37
AVIO_SEEKABLE_NORMAL
#define AVIO_SEEKABLE_NORMAL
Seeking works like for a local file.
Definition: avio.h:41
av_crc
uint32_t av_crc(const AVCRC *ctx, uint32_t crc, const uint8_t *buffer, size_t length)
Calculate the CRC of a block.
Definition: crc.c:392
AV_PKT_DATA_NEW_EXTRADATA
@ AV_PKT_DATA_NEW_EXTRADATA
The AV_PKT_DATA_NEW_EXTRADATA is used to notify the codec or the format that the extradata buffer was...
Definition: packet.h:56
AVRational::den
int den
Denominator.
Definition: rational.h:60
AV_OPT_TYPE_INT
@ AV_OPT_TYPE_INT
Definition: opt.h:225
avio_wb64
void avio_wb64(AVIOContext *s, uint64_t val)
Definition: aviobuf.c:462
AV_CRC_32_IEEE_LE
@ AV_CRC_32_IEEE_LE
Definition: crc.h:53
APNGMuxContext::acTL_offset
uint64_t acTL_offset
Definition: apngenc.c:39
AVMEDIA_TYPE_VIDEO
@ AVMEDIA_TYPE_VIDEO
Definition: avutil.h:201
APNGMuxContext::plays
uint32_t plays
Definition: apngenc.c:36
AVCodecParameters::codec_id
enum AVCodecID codec_id
Specific type of the encoded data (the codec used).
Definition: codec_par.h:62
AVPacket
This structure stores compressed data.
Definition: packet.h:351
png.h
av_freep
#define av_freep(p)
Definition: tableprint_vlc.h:34
flags
#define flags(name, subs,...)
Definition: cbs_av1.c:561
av_log
#define av_log(a,...)
Definition: tableprint_vlc.h:27
AVERROR_INVALIDDATA
#define AVERROR_INVALIDDATA
Invalid data found when processing input.
Definition: error.h:61
apng_write_header
static int apng_write_header(AVFormatContext *format_context)
Definition: apngenc.c:81
write_header
static void write_header(FFV1Context *f)
Definition: ffv1enc.c:346
AVFormatContext::priv_data
void * priv_data
Format private data.
Definition: avformat.h:1244
AV_RB16
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_WB32 unsigned int_TMPL AV_WB24 unsigned int_TMPL AV_RB16
Definition: bytestream.h:98
apng_deinit
static void apng_deinit(AVFormatContext *s)
Definition: apngenc.c:283