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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 = s->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(s->extradata, new_size + FF_INPUT_BUFFER_PADDING_SIZE);
136  if (!new_extradata)
137  return AVERROR(ENOMEM);
138  s->extradata = new_extradata;
139  s->extradata_size = new_size;
140 
141  if ((ret = avio_read(pb, s->extradata + previous_size, len)) < 0)
142  return ret;
143 
144  return previous_size;
145 }
146 
148 {
149  APNGDemuxContext *ctx = s->priv_data;
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->codec->width = avio_rb32(pb);
176  st->codec->height = avio_rb32(pb);
177  if ((ret = av_image_check_size(st->codec->width, st->codec->height, 0, s)) < 0)
178  return ret;
179 
180  /* extradata will contain every chunk up to the first fcTL (excluded) */
182  if (!st->codec->extradata)
183  return AVERROR(ENOMEM);
184  st->codec->extradata_size = len + 12;
185  AV_WB32(st->codec->extradata, len);
186  AV_WL32(st->codec->extradata+4, tag);
187  AV_WB32(st->codec->extradata+8, st->codec->width);
188  AV_WB32(st->codec->extradata+12, st->codec->height);
189  if ((ret = avio_read(pb, st->codec->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->codec, pb, len + 12)) < 0)
222  goto fail;
223  acTL_found = 1;
224  ctx->num_frames = AV_RB32(st->codec->extradata + ret + 8);
225  ctx->num_play = AV_RB32(st->codec->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->codec, pb, len + 12)) < 0)
240  goto fail;
241  }
242  }
243 
244 fail:
245  if (st->codec->extradata_size) {
246  av_freep(&st->codec->extradata);
247  st->codec->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]->codec->width ||
302  height != s->streams[0]->codec->height ||
303  x_offset != 0 ||
304  y_offset != 0) {
305  if (sequence_number == 0 ||
306  x_offset >= s->streams[0]->codec->width ||
307  width > s->streams[0]->codec->width - x_offset ||
308  y_offset >= s->streams[0]->codec->height ||
309  height > s->streams[0]->codec->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 {
324  APNGDemuxContext *ctx = s->priv_data;
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]->codec->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_INT, { .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 };