FFmpeg coverage

Directory: ../../../ffmpeg/
File: src/libavformat/apngdec.c
Date: 2026-04-30 08:04:40
Exec Total Coverage
Lines: 165 211 78.2%
Functions: 5 5 100.0%
Branches: 103 170 60.6%
Line Branch Exec Source
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 "demux.h"
32 #include "internal.h"
33 #include "libavutil/imgutils.h"
34 #include "libavutil/intreadwrite.h"
35 #include "libavutil/mem.h"
36 #include "libavutil/opt.h"
37 #include "libavcodec/apng.h"
38 #include "libavcodec/png.h"
39 #include "libavcodec/bytestream.h"
40
41 #define DEFAULT_APNG_FPS 15
42
43 typedef struct APNGDemuxContext {
44 const AVClass *class;
45
46 int max_fps;
47 int default_fps;
48
49 int pkt_duration;
50
51 int is_key_frame;
52
53 /*
54 * loop options
55 */
56 int ignore_loop;
57 uint32_t num_frames;
58 uint32_t num_play;
59 uint32_t cur_loop;
60 } APNGDemuxContext;
61
62 /*
63 * To be a valid APNG file, we mandate, in this order:
64 * PNGSIG
65 * IHDR
66 * ...
67 * acTL
68 * ...
69 * IDAT
70 */
71 7480 static int apng_probe(const AVProbeData *p)
72 {
73 GetByteContext gb;
74 7480 int state = 0;
75 uint32_t len, tag;
76
77 7480 bytestream2_init(&gb, p->buf, p->buf_size);
78
79
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 7480 if (bytestream2_get_be64(&gb) != PNGSIG)
80 7431 return 0;
81
82 for (;;) {
83 218 len = bytestream2_get_be32(&gb);
84
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 218 if (len > 0x7fffffff)
85 ✗ return 0;
86
87 218 tag = bytestream2_get_le32(&gb);
88 /* we don't check IDAT size, as this is the last tag
89 * we check, and it may be larger than the probe buffer */
90
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 218 if (tag != MKTAG('I', 'D', 'A', 'T') &&
91
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 173 len + 4 > bytestream2_get_bytes_left(&gb))
92 4 return 0;
93
94
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 214 switch (tag) {
95 49 case MKTAG('I', 'H', 'D', 'R'):
96
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 49 if (len != 13)
97 ✗ return 0;
98
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 49 if (av_image_check_size(bytestream2_get_be32(&gb), bytestream2_get_be32(&gb), 0, NULL))
99 ✗ return 0;
100 49 bytestream2_skip(&gb, 9);
101 49 state++;
102 49 break;
103 8 case MKTAG('a', 'c', 'T', 'L'):
104
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 8 if (state != 1 ||
105
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 8 len != 8 ||
106 8 bytestream2_get_be32(&gb) == 0) /* 0 is not a valid value for number of frames */
107 ✗ return 0;
108 8 bytestream2_skip(&gb, 8);
109 8 state++;
110 8 break;
111 45 case MKTAG('I', 'D', 'A', 'T'):
112
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 45 if (state != 2)
113 37 return 0;
114 8 goto end;
115 112 default:
116 /* skip other tags */
117 112 bytestream2_skip(&gb, len + 4);
118 112 break;
119 }
120 }
121
122 8 end:
123 8 return AVPROBE_SCORE_MAX;
124 }
125
126 17 static int append_extradata(AVCodecParameters *par, AVIOContext *pb, int len)
127 {
128 17 int previous_size = par->extradata_size;
129 int new_size, ret;
130 uint8_t *new_extradata;
131
132
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 17 if (len > INT_MAX - AV_INPUT_BUFFER_PADDING_SIZE - previous_size)
133 ✗ return AVERROR_INVALIDDATA;
134
135 17 new_size = previous_size + len;
136 17 new_extradata = av_realloc(par->extradata, new_size + AV_INPUT_BUFFER_PADDING_SIZE);
137
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 17 if (!new_extradata)
138 ✗ return AVERROR(ENOMEM);
139 17 memset(new_extradata + new_size, 0, AV_INPUT_BUFFER_PADDING_SIZE);
140 17 par->extradata = new_extradata;
141 17 par->extradata_size = new_size;
142
143
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 17 if ((ret = ffio_read_size(pb, par->extradata + previous_size, len)) < 0)
144 ✗ return ret;
145
146 17 return previous_size;
147 }
148
149 9 static int apng_read_header(AVFormatContext *s)
150 {
151 9 APNGDemuxContext *ctx = s->priv_data;
152 9 AVIOContext *pb = s->pb;
153 uint32_t len, tag;
154 AVStream *st;
155 9 int acTL_found = 0;
156 int64_t ret;
157
158 /* verify PNGSIG */
159
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 9 if (avio_rb64(pb) != PNGSIG)
160 ✗ return AVERROR_INVALIDDATA;
161
162 /* parse IHDR (must be first chunk) */
163 9 len = avio_rb32(pb);
164 9 tag = avio_rl32(pb);
165
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 9 if (len != 13 || tag != MKTAG('I', 'H', 'D', 'R'))
166 ✗ return AVERROR_INVALIDDATA;
167
168 9 st = avformat_new_stream(s, NULL);
169
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 9 if (!st)
170 ✗ return AVERROR(ENOMEM);
171
172 /* set the timebase to something large enough (1/100,000 of second)
173 * to hopefully cope with all sane frame durations */
174 9 avpriv_set_pts_info(st, 64, 1, 100000);
175 9 st->codecpar->codec_type = AVMEDIA_TYPE_VIDEO;
176 9 st->codecpar->codec_id = AV_CODEC_ID_APNG;
177 9 st->codecpar->width = avio_rb32(pb);
178 9 st->codecpar->height = avio_rb32(pb);
179
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 9 if ((ret = av_image_check_size(st->codecpar->width, st->codecpar->height, 0, s)) < 0)
180 ✗ return ret;
181
182 /* extradata will contain every chunk up to the first fcTL (excluded) */
183 9 ret = ff_alloc_extradata(st->codecpar, len + 12);
184
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 9 if (ret < 0)
185 ✗ return ret;
186 9 AV_WB32(st->codecpar->extradata, len);
187 9 AV_WL32(st->codecpar->extradata+4, tag);
188 9 AV_WB32(st->codecpar->extradata+8, st->codecpar->width);
189 9 AV_WB32(st->codecpar->extradata+12, st->codecpar->height);
190
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 9 if ((ret = ffio_read_size(pb, st->codecpar->extradata + 16, 9)) < 0)
191 ✗ return ret;
192
193 while (1) {
194
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 26 if (acTL_found && ctx->num_play != 1) {
195 10 int64_t size = avio_size(pb);
196 10 int64_t offset = avio_tell(pb);
197
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 10 if (size < 0 || offset < 0 ||
198
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 10 (ret = ffio_ensure_seekback(pb, size - offset)) < 0) {
199 ✗ av_log(s, AV_LOG_WARNING, "Could not ensure seekback, will not loop\n");
200 ✗ ctx->num_play = 1;
201 }
202 }
203
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 26 if ((ctx->num_play == 1 || !acTL_found) &&
204
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 16 ((ret = ffio_ensure_seekback(pb, 4 /* len */ + 4 /* tag */)) < 0))
205 ✗ return ret;
206
207 26 len = avio_rb32(pb);
208
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 26 if (len > INT_MAX - 12)
209 ✗ return AVERROR_INVALIDDATA;
210
211 26 tag = avio_rl32(pb);
212
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 26 switch (tag) {
213 9 case MKTAG('a', 'c', 'T', 'L'):
214
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 9 if ((ret = avio_seek(pb, -8, SEEK_CUR)) < 0 ||
215
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 9 (ret = append_extradata(st->codecpar, pb, len + 12)) < 0)
216 ✗ return ret;
217 9 acTL_found = 1;
218 9 ctx->num_frames = AV_RB32(st->codecpar->extradata + ret + 8);
219 9 ctx->num_play = AV_RB32(st->codecpar->extradata + ret + 12);
220 9 av_log(s, AV_LOG_DEBUG, "num_frames: %"PRIu32", num_play: %"PRIu32"\n",
221 ctx->num_frames, ctx->num_play);
222 9 break;
223 9 case MKTAG('f', 'c', 'T', 'L'):
224
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 9 if (!acTL_found || len != APNG_FCTL_CHUNK_SIZE) {
225 ✗ return AVERROR_INVALIDDATA;
226 }
227
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 9 if ((ret = avio_seek(pb, -8, SEEK_CUR)) < 0)
228 ✗ return ret;
229 9 return 0;
230 8 default:
231
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 8 if ((ret = avio_seek(pb, -8, SEEK_CUR)) < 0 ||
232
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 8 (ret = append_extradata(st->codecpar, pb, len + 12)) < 0)
233 ✗ return ret;
234 }
235 }
236 }
237
238 318 static int decode_fctl_chunk(AVFormatContext *s, APNGDemuxContext *ctx)
239 {
240 uint32_t sequence_number, width, height, x_offset, y_offset;
241 uint16_t delay_num, delay_den;
242 uint8_t dispose_op, blend_op;
243
244 318 sequence_number = avio_rb32(s->pb);
245 318 width = avio_rb32(s->pb);
246 318 height = avio_rb32(s->pb);
247 318 x_offset = avio_rb32(s->pb);
248 318 y_offset = avio_rb32(s->pb);
249 318 delay_num = avio_rb16(s->pb);
250 318 delay_den = avio_rb16(s->pb);
251 318 dispose_op = avio_r8(s->pb);
252 318 blend_op = avio_r8(s->pb);
253 318 avio_skip(s->pb, 4); /* crc */
254
255 /* default is hundredths of seconds */
256
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 318 if (!delay_den)
257 ✗ delay_den = 100;
258
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 318 if (!delay_num || (ctx->max_fps && delay_den / delay_num > ctx->max_fps)) {
259 ✗ delay_num = 1;
260 ✗ delay_den = ctx->default_fps;
261 }
262 318 ctx->pkt_duration = av_rescale_q(delay_num,
263 318 (AVRational){ 1, delay_den },
264 318 s->streams[0]->time_base);
265
266 318 av_log(s, AV_LOG_DEBUG, "%s: "
267 "sequence_number: %"PRId32", "
268 "width: %"PRIu32", "
269 "height: %"PRIu32", "
270 "x_offset: %"PRIu32", "
271 "y_offset: %"PRIu32", "
272 "delay_num: %"PRIu16", "
273 "delay_den: %"PRIu16", "
274 "dispose_op: %d, "
275 "blend_op: %d\n",
276 __func__,
277 sequence_number,
278 width,
279 height,
280 x_offset,
281 y_offset,
282 delay_num,
283 delay_den,
284 dispose_op,
285 blend_op);
286
287
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 318 if (width != s->streams[0]->codecpar->width ||
288
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 218 height != s->streams[0]->codecpar->height ||
289
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 218 x_offset != 0 ||
290 y_offset != 0) {
291
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 100 if (sequence_number == 0 ||
292
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 100 x_offset >= s->streams[0]->codecpar->width ||
293
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 100 width > s->streams[0]->codecpar->width - x_offset ||
294
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 100 y_offset >= s->streams[0]->codecpar->height ||
295
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 100 height > s->streams[0]->codecpar->height - y_offset)
296 ✗ return AVERROR_INVALIDDATA;
297 100 ctx->is_key_frame = 0;
298 } else {
299
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 218 if (sequence_number == 0 && dispose_op == APNG_DISPOSE_OP_PREVIOUS)
300 ✗ dispose_op = APNG_DISPOSE_OP_BACKGROUND;
301
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 218 ctx->is_key_frame = dispose_op == APNG_DISPOSE_OP_BACKGROUND ||
302 blend_op == APNG_BLEND_OP_SOURCE;
303 }
304
305 318 return 0;
306 }
307
308 335 static int apng_read_packet(AVFormatContext *s, AVPacket *pkt)
309 {
310 335 APNGDemuxContext *ctx = s->priv_data;
311 int64_t ret;
312 int64_t size;
313 335 AVIOContext *pb = s->pb;
314 uint32_t len, tag;
315
316 /*
317 * fcTL chunk length, in bytes:
318 * 4 (length)
319 * 4 (tag)
320 * 26 (actual chunk)
321 * 4 (crc) bytes
322 * and needed next:
323 * 4 (length)
324 * 4 (tag (must be fdAT or IDAT))
325 */
326 /* if num_play is not 1, then the seekback is already guaranteed */
327
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 335 if (ctx->num_play == 1 && (ret = ffio_ensure_seekback(pb, 46)) < 0)
328 ✗ return ret;
329
330 335 len = avio_rb32(pb);
331 335 tag = avio_rl32(pb);
332
333
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 335 if (avio_feof(pb))
334 ✗ return AVERROR_EOF;
335
336
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 335 switch (tag) {
337 318 case MKTAG('f', 'c', 'T', 'L'):
338
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 318 if (len != APNG_FCTL_CHUNK_SIZE)
339 335 return AVERROR_INVALIDDATA;
340
341
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 318 if ((ret = decode_fctl_chunk(s, ctx)) < 0)
342 ✗ return ret;
343
344 /* fcTL may be followed by other chunks before fdAT or IDAT */
345 318 len = avio_rb32(pb);
346 318 tag = avio_rl32(pb);
347
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 318 if (len > 0x7fffffff)
348 ✗ return AVERROR_INVALIDDATA;
349
350 /* check for empty frame */
351
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 318 if (tag == MKTAG('f', 'c', 'T', 'L') ||
352 tag == MKTAG('I', 'E', 'N', 'D'))
353 ✗ return AVERROR_INVALIDDATA;
354
355 318 size = 38 /* fcTL */ + 8 /* len, tag */ + len + 4 /* crc */;
356
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 318 if (size > INT_MAX)
357 ✗ return AVERROR(EINVAL);
358
359
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 318 if ((ret = avio_seek(pb, -46, SEEK_CUR)) < 0 ||
360
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 318 (ret = av_append_packet(pb, pkt, size)) < 0)
361 ✗ return ret;
362
363
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 318 if (ctx->num_play == 1 && (ret = ffio_ensure_seekback(pb, 8)) < 0)
364 ✗ return ret;
365
366 318 len = avio_rb32(pb);
367 318 tag = avio_rl32(pb);
368
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 3464 while (tag &&
369
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 5983 tag != MKTAG('f', 'c', 'T', 'L') &&
370 tag != MKTAG('I', 'E', 'N', 'D')) {
371
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 2828 if (len > 0x7fffffff)
372 ✗ return AVERROR_INVALIDDATA;
373
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374
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 2828 (ret = av_append_packet(pb, pkt, len + 12)) < 0)
375 ✗ return ret;
376
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 2828 if (ctx->num_play == 1 && (ret = ffio_ensure_seekback(pb, 8)) < 0)
377 ✗ return ret;
378 2828 len = avio_rb32(pb);
379 2828 tag = avio_rl32(pb);
380 }
381
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 318 if ((ret = avio_seek(pb, -8, SEEK_CUR)) < 0)
382 ✗ return ret;
383
384
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 318 if (ctx->is_key_frame)
385 217 pkt->flags |= AV_PKT_FLAG_KEY;
386 318 pkt->pts = pkt->dts = AV_NOPTS_VALUE;
387 318 pkt->duration = ctx->pkt_duration;
388 318 return ret;
389 17 case MKTAG('I', 'E', 'N', 'D'):
390 17 ctx->cur_loop++;
391
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 17 if (ctx->ignore_loop || ctx->num_play >= 1 && ctx->cur_loop == ctx->num_play) {
392 17 avio_seek(pb, -8, SEEK_CUR);
393 17 return AVERROR_EOF;
394 }
395 ✗ if ((ret = avio_seek(pb, s->streams[0]->codecpar->extradata_size + 8, SEEK_SET)) < 0)
396 ✗ return ret;
397 ✗ return 0;
398 ✗ default:
399 ✗ avpriv_request_sample(s, "In-stream tag=%s (0x%08"PRIX32") len=%"PRIu32,
400 ✗ av_fourcc2str(tag), tag, len);
401 ✗ avio_skip(pb, len + 4);
402 }
403
404 /* Handle the unsupported yet cases */
405 ✗ return AVERROR_PATCHWELCOME;
406 }
407
408 static const AVOption options[] = {
409 { "ignore_loop", "ignore loop setting" , offsetof(APNGDemuxContext, ignore_loop),
410 AV_OPT_TYPE_BOOL, { .i64 = 1 } , 0, 1 , AV_OPT_FLAG_DECODING_PARAM },
411 { "max_fps" , "maximum framerate (0 is no limit)" , offsetof(APNGDemuxContext, max_fps),
412 AV_OPT_TYPE_INT, { .i64 = 0 }, 0, INT_MAX, AV_OPT_FLAG_DECODING_PARAM },
413 { "default_fps", "default framerate (0 is as fast as possible)", offsetof(APNGDemuxContext, default_fps),
414 AV_OPT_TYPE_INT, { .i64 = DEFAULT_APNG_FPS }, 0, INT_MAX, AV_OPT_FLAG_DECODING_PARAM },
415 { NULL },
416 };
417
418 static const AVClass demuxer_class = {
419 .class_name = "APNG demuxer",
420 .item_name = av_default_item_name,
421 .option = options,
422 .version = LIBAVUTIL_VERSION_INT,
423 .category = AV_CLASS_CATEGORY_DEMUXER,
424 };
425
426 const FFInputFormat ff_apng_demuxer = {
427 .p.name = "apng",
428 .p.long_name = NULL_IF_CONFIG_SMALL("Animated Portable Network Graphics"),
429 .p.flags = AVFMT_GENERIC_INDEX,
430 .p.priv_class = &demuxer_class,
431 .priv_data_size = sizeof(APNGDemuxContext),
432 .read_probe = apng_probe,
433 .read_header = apng_read_header,
434 .read_packet = apng_read_packet,
435 };
436