FFmpeg
gifdec.c
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1 /*
2  * GIF demuxer
3  * Copyright (c) 2012 Vitaliy E Sugrobov
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  * GIF demuxer.
25  */
26 
27 #include "avformat.h"
28 #include "libavutil/bprint.h"
29 #include "libavutil/intreadwrite.h"
30 #include "libavutil/opt.h"
31 #include "internal.h"
32 #include "libavcodec/gif.h"
33 
34 typedef struct GIFDemuxContext {
35  const AVClass *class;
36  /**
37  * Time span in hundredths of second before
38  * the next frame should be drawn on screen.
39  */
40  int delay;
41  /**
42  * Minimum allowed delay between frames in hundredths of
43  * second. Values below this threshold considered to be
44  * invalid and set to value of default_delay.
45  */
46  int min_delay;
47  int max_delay;
49 
50  /**
51  * loop options
52  */
56 
57  int nb_frames;
60 
61 /**
62  * Major web browsers display gifs at ~10-15fps when rate
63  * is not explicitly set or have too low values. We assume default rate to be 10.
64  * Default delay = 100hundredths of second / 10fps = 10hos per frame.
65  */
66 #define GIF_DEFAULT_DELAY 10
67 /**
68  * By default delay values less than this threshold considered to be invalid.
69  */
70 #define GIF_MIN_DELAY 2
71 
72 static int gif_probe(const AVProbeData *p)
73 {
74  /* check magick */
75  if (memcmp(p->buf, gif87a_sig, 6) && memcmp(p->buf, gif89a_sig, 6))
76  return 0;
77 
78  /* width or height contains zero? */
79  if (!AV_RL16(&p->buf[6]) || !AV_RL16(&p->buf[8]))
80  return 0;
81 
82  return AVPROBE_SCORE_MAX;
83 }
84 
85 static int resync(AVIOContext *pb)
86 {
87  int i;
88  for (i = 0; i < 6; i++) {
89  int b = avio_r8(pb);
90  if (b != gif87a_sig[i] && b != gif89a_sig[i])
91  i = -(b != 'G');
92  if (avio_feof(pb))
93  return AVERROR_EOF;
94  }
95  return 0;
96 }
97 
99 {
100  int sb_size, ret = 0;
101 
102  while (0x00 != (sb_size = avio_r8(pb))) {
103  if ((ret = avio_skip(pb, sb_size)) < 0)
104  return ret;
105  }
106 
107  return ret;
108 }
109 
111 {
112  GIFDemuxContext *gdc = s->priv_data;
113  AVIOContext *pb = s->pb;
114  AVStream *st;
115  int type, width, height, ret, n, flags;
116  int64_t nb_frames = 0, duration = 0;
117 
118  if ((ret = resync(pb)) < 0)
119  return ret;
120 
121  gdc->delay = gdc->default_delay;
122  width = avio_rl16(pb);
123  height = avio_rl16(pb);
124  flags = avio_r8(pb);
125  avio_skip(pb, 1);
126  n = avio_r8(pb);
127 
128  if (width == 0 || height == 0)
129  return AVERROR_INVALIDDATA;
130 
131  st = avformat_new_stream(s, NULL);
132  if (!st)
133  return AVERROR(ENOMEM);
134 
135  if (flags & 0x80)
136  avio_skip(pb, 3 * (1 << ((flags & 0x07) + 1)));
137 
138  while ((type = avio_r8(pb)) != GIF_TRAILER) {
139  if (avio_feof(pb))
140  break;
141  if (type == GIF_EXTENSION_INTRODUCER) {
142  int subtype = avio_r8(pb);
143  if (subtype == GIF_COM_EXT_LABEL) {
144  AVBPrint bp;
145  int block_size;
146 
147  av_bprint_init(&bp, 0, -1);
148  while ((block_size = avio_r8(pb)) != 0) {
149  avio_read_to_bprint(pb, &bp, block_size);
150  }
151  av_dict_set(&s->metadata, "comment", bp.str, 0);
152  av_bprint_finalize(&bp, NULL);
153  } else if (subtype == GIF_GCE_EXT_LABEL) {
154  int block_size = avio_r8(pb);
155 
156  if (block_size == 4) {
157  int delay;
158 
159  avio_skip(pb, 1);
160  delay = avio_rl16(pb);
161  if (delay < gdc->min_delay)
162  delay = gdc->default_delay;
163  delay = FFMIN(delay, gdc->max_delay);
164  duration += delay;
165  avio_skip(pb, 1);
166  } else {
167  avio_skip(pb, block_size);
168  }
169  gif_skip_subblocks(pb);
170  } else {
171  gif_skip_subblocks(pb);
172  }
173  } else if (type == GIF_IMAGE_SEPARATOR) {
174  avio_skip(pb, 8);
175  flags = avio_r8(pb);
176  if (flags & 0x80)
177  avio_skip(pb, 3 * (1 << ((flags & 0x07) + 1)));
178  avio_skip(pb, 1);
179  gif_skip_subblocks(pb);
180  nb_frames++;
181  } else {
182  break;
183  }
184  }
185 
186  /* GIF format operates with time in "hundredths of second",
187  * therefore timebase is 1/100 */
188  avpriv_set_pts_info(st, 64, 1, 100);
191  st->codecpar->width = width;
192  st->codecpar->height = height;
193  st->start_time = 0;
194  st->duration = duration;
195  st->nb_frames = nb_frames;
196  if (n) {
197  st->codecpar->sample_aspect_ratio.num = n + 15;
198  st->codecpar->sample_aspect_ratio.den = 64;
199  }
200 
201  /* jump to start because gif decoder needs header data too */
202  if (avio_seek(pb, 0, SEEK_SET) != 0)
203  return AVERROR(EIO);
204 
205  return 0;
206 }
207 
209 {
210  GIFDemuxContext *gdc = s->priv_data;
211  AVIOContext *pb = s->pb;
212  int sb_size, ext_label = avio_r8(pb);
213  int ret;
214 
215  if (ext_label == GIF_GCE_EXT_LABEL) {
216  if ((sb_size = avio_r8(pb)) < 4) {
217  av_log(s, AV_LOG_FATAL, "Graphic Control Extension block's size less than 4.\n");
218  return AVERROR_INVALIDDATA;
219  }
220 
221  /* skip packed fields */
222  if ((ret = avio_skip(pb, 1)) < 0)
223  return ret;
224 
225  gdc->delay = avio_rl16(pb);
226 
227  if (gdc->delay < gdc->min_delay)
228  gdc->delay = gdc->default_delay;
229  gdc->delay = FFMIN(gdc->delay, gdc->max_delay);
230 
231  /* skip the rest of the Graphic Control Extension block */
232  if ((ret = avio_skip(pb, sb_size - 3)) < 0 )
233  return ret;
234  } else if (ext_label == GIF_APP_EXT_LABEL) {
235  uint8_t data[256];
236 
237  sb_size = avio_r8(pb);
238  ret = avio_read(pb, data, sb_size);
239  if (ret < 0 || !sb_size)
240  return ret;
241 
242  if (sb_size == strlen(NETSCAPE_EXT_STR)) {
243  sb_size = avio_r8(pb);
244  ret = avio_read(pb, data, sb_size);
245  if (ret < 0 || !sb_size)
246  return ret;
247 
248  if (sb_size == 3 && data[0] == 1) {
249  gdc->total_iter = AV_RL16(data+1);
250 
251  if (gdc->total_iter == 0)
252  gdc->total_iter = -1;
253  }
254  }
255  }
256 
257  if ((ret = gif_skip_subblocks(pb)) < 0)
258  return ret;
259 
260  return 0;
261 }
262 
264 {
265  GIFDemuxContext *gdc = s->priv_data;
266  AVIOContext *pb = s->pb;
267  int packed_fields, block_label, ct_size,
268  keyframe, frame_parsed = 0, ret;
269  int64_t frame_start = avio_tell(pb), frame_end;
270  unsigned char buf[6];
271 
272  if ((ret = avio_read(pb, buf, 6)) == 6) {
273  keyframe = memcmp(buf, gif87a_sig, 6) == 0 ||
274  memcmp(buf, gif89a_sig, 6) == 0;
275  } else if (ret < 0) {
276  return ret;
277  } else {
278  keyframe = 0;
279  }
280 
281  if (keyframe) {
282 parse_keyframe:
283  /* skip 2 bytes of width and 2 of height */
284  if ((ret = avio_skip(pb, 4)) < 0)
285  return ret;
286 
287  packed_fields = avio_r8(pb);
288 
289  /* skip 1 byte of Background Color Index and 1 byte of Pixel Aspect Ratio */
290  if ((ret = avio_skip(pb, 2)) < 0)
291  return ret;
292 
293  /* global color table presence */
294  if (packed_fields & 0x80) {
295  ct_size = 3 * (1 << ((packed_fields & 0x07) + 1));
296 
297  if ((ret = avio_skip(pb, ct_size)) < 0)
298  return ret;
299  }
300  } else {
301  avio_seek(pb, -ret, SEEK_CUR);
302  ret = AVERROR_EOF;
303  }
304 
305  while (GIF_TRAILER != (block_label = avio_r8(pb)) && !avio_feof(pb)) {
306  if (block_label == GIF_EXTENSION_INTRODUCER) {
307  if ((ret = gif_read_ext (s)) < 0 )
308  goto resync;
309  } else if (block_label == GIF_IMAGE_SEPARATOR) {
310  /* skip to last byte of Image Descriptor header */
311  if ((ret = avio_skip(pb, 8)) < 0)
312  return ret;
313 
314  packed_fields = avio_r8(pb);
315 
316  /* local color table presence */
317  if (packed_fields & 0x80) {
318  ct_size = 3 * (1 << ((packed_fields & 0x07) + 1));
319 
320  if ((ret = avio_skip(pb, ct_size)) < 0)
321  return ret;
322  }
323 
324  /* read LZW Minimum Code Size */
325  if (avio_r8(pb) < 1) {
326  av_log(s, AV_LOG_ERROR, "lzw minimum code size must be >= 1\n");
327  goto resync;
328  }
329 
330  if ((ret = gif_skip_subblocks(pb)) < 0)
331  goto resync;
332 
333  frame_end = avio_tell(pb);
334 
335  if (avio_seek(pb, frame_start, SEEK_SET) != frame_start)
336  return AVERROR(EIO);
337 
338  ret = av_get_packet(pb, pkt, frame_end - frame_start);
339  if (ret < 0)
340  return ret;
341 
342  if (keyframe)
343  pkt->flags |= AV_PKT_FLAG_KEY;
344 
345  pkt->stream_index = 0;
346  pkt->duration = gdc->delay;
347 
348  gdc->nb_frames ++;
349  gdc->last_duration = pkt->duration;
350 
351  /* Graphic Control Extension's scope is single frame.
352  * Remove its influence. */
353  gdc->delay = gdc->default_delay;
354  frame_parsed = 1;
355 
356  break;
357  } else {
358  av_log(s, AV_LOG_ERROR, "invalid block label\n");
359 resync:
360  if (!keyframe)
361  avio_seek(pb, frame_start, SEEK_SET);
362  if ((ret = resync(pb)) < 0)
363  return ret;
364  frame_start = avio_tell(pb) - 6;
365  keyframe = 1;
366  goto parse_keyframe;
367  }
368  }
369 
370  if ((ret >= 0 && !frame_parsed) || ret == AVERROR_EOF) {
371  if (gdc->nb_frames == 1) {
372  s->streams[0]->r_frame_rate = (AVRational) {100, gdc->last_duration};
373  }
374  /* This might happen when there is no image block
375  * between extension blocks and GIF_TRAILER or EOF */
376  if (!gdc->ignore_loop && (block_label == GIF_TRAILER || avio_feof(pb))
377  && (gdc->total_iter < 0 || ++gdc->iter_count < gdc->total_iter))
378  return avio_seek(pb, 0, SEEK_SET);
379  return AVERROR_EOF;
380  } else
381  return ret;
382 }
383 
384 static const AVOption options[] = {
385  { "min_delay" , "minimum valid delay between frames (in hundredths of second)", offsetof(GIFDemuxContext, min_delay) , AV_OPT_TYPE_INT, {.i64 = GIF_MIN_DELAY} , 0, 100 * 60, AV_OPT_FLAG_DECODING_PARAM },
386  { "max_gif_delay", "maximum valid delay between frames (in hundredths of seconds)", offsetof(GIFDemuxContext, max_delay) , AV_OPT_TYPE_INT, {.i64 = 65535} , 0, 65535 , AV_OPT_FLAG_DECODING_PARAM },
387  { "default_delay", "default delay between frames (in hundredths of second)" , offsetof(GIFDemuxContext, default_delay), AV_OPT_TYPE_INT, {.i64 = GIF_DEFAULT_DELAY}, 0, 100 * 60, AV_OPT_FLAG_DECODING_PARAM },
388  { "ignore_loop" , "ignore loop setting (netscape extension)" , offsetof(GIFDemuxContext, ignore_loop) , AV_OPT_TYPE_BOOL,{.i64 = 1} , 0, 1, AV_OPT_FLAG_DECODING_PARAM },
389  { NULL },
390 };
391 
392 static const AVClass demuxer_class = {
393  .class_name = "GIF demuxer",
394  .item_name = av_default_item_name,
395  .option = options,
396  .version = LIBAVUTIL_VERSION_INT,
397  .category = AV_CLASS_CATEGORY_DEMUXER,
398 };
399 
401  .name = "gif",
402  .long_name = NULL_IF_CONFIG_SMALL("CompuServe Graphics Interchange Format (GIF)"),
403  .priv_data_size = sizeof(GIFDemuxContext),
408  .priv_class = &demuxer_class,
409 };
#define NULL
Definition: coverity.c:32
static int gif_read_header(AVFormatContext *s)
Definition: gifdec.c:110
Bytestream IO Context.
Definition: avio.h:161
#define AVERROR_INVALIDDATA
Invalid data found when processing input.
Definition: error.h:59
int default_delay
Definition: gifdec.c:48
AVOption.
Definition: opt.h:246
ptrdiff_t const GLvoid * data
Definition: opengl_enc.c:100
static const AVOption options[]
Definition: gifdec.c:384
#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:4929
AVRational sample_aspect_ratio
Video only.
Definition: avcodec.h:4044
int avio_read_to_bprint(AVIOContext *h, struct AVBPrint *pb, size_t max_size)
Read contents of h into print buffer, up to max_size bytes, or up to EOF.
Definition: aviobuf.c:1300
enum AVCodecID codec_id
Specific type of the encoded data (the codec used).
Definition: avcodec.h:3968
int num
Numerator.
Definition: rational.h:59
int64_t avio_seek(AVIOContext *s, int64_t offset, int whence)
fseek() equivalent for AVIOContext.
Definition: aviobuf.c:246
const char * av_default_item_name(void *ptr)
Return the context name.
Definition: log.c:191
static const uint8_t gif87a_sig[6]
Definition: gif.h:34
#define GIF_GCE_EXT_LABEL
Definition: gif.h:45
GLint GLenum type
Definition: opengl_enc.c:104
int64_t avio_skip(AVIOContext *s, int64_t offset)
Skip given number of bytes forward.
Definition: aviobuf.c:334
static AVPacket pkt
int nb_frames
Definition: gifdec.c:57
uint64_t_TMPL AV_WL64 unsigned int_TMPL AV_WL32 unsigned int_TMPL AV_WL24 unsigned int_TMPL AV_RL16
Definition: bytestream.h:87
int av_bprint_finalize(AVBPrint *buf, char **ret_str)
Finalize a print buffer.
Definition: bprint.c:235
Format I/O context.
Definition: avformat.h:1358
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: avcodec.h:4034
AVOptions.
int iter_count
Definition: gifdec.c:54
int64_t duration
Duration of this packet in AVStream->time_base units, 0 if unknown.
Definition: avcodec.h:1498
AVStream * avformat_new_stream(AVFormatContext *s, const AVCodec *c)
Add a new stream to a media file.
Definition: utils.c:4502
AVStream ** streams
A list of all streams in the file.
Definition: avformat.h:1426
int64_t duration
Definition: movenc.c:63
#define height
#define AVERROR_EOF
End of file.
Definition: error.h:55
int av_get_packet(AVIOContext *s, AVPacket *pkt, int size)
Allocate and read the payload of a packet and initialize its fields with default values.
Definition: utils.c:310
static av_always_inline int64_t avio_tell(AVIOContext *s)
ftell() equivalent for AVIOContext.
Definition: avio.h:557
#define av_log(a,...)
int avio_read(AVIOContext *s, unsigned char *buf, int size)
Read size bytes from AVIOContext into buf.
Definition: aviobuf.c:650
#define AV_PKT_FLAG_KEY
The packet contains a keyframe.
Definition: avcodec.h:1512
#define GIF_COM_EXT_LABEL
Definition: gif.h:46
#define i(width, name, range_min, range_max)
Definition: cbs_h2645.c:259
#define AV_LOG_ERROR
Something went wrong and cannot losslessly be recovered.
Definition: log.h:176
AVDictionary * metadata
Metadata that applies to the whole file.
Definition: avformat.h:1598
#define NULL_IF_CONFIG_SMALL(x)
Return NULL if CONFIG_SMALL is true, otherwise the argument without modification. ...
Definition: internal.h:186
void av_bprint_init(AVBPrint *buf, unsigned size_init, unsigned size_max)
Definition: bprint.c:69
int last_duration
Definition: gifdec.c:58
enum AVMediaType codec_type
General type of the encoded data.
Definition: avcodec.h:3964
int flags
A combination of AV_PKT_FLAG values.
Definition: avcodec.h:1486
int avio_r8(AVIOContext *s)
Definition: aviobuf.c:641
static void frame_end(MpegEncContext *s)
unsigned char * buf
Buffer must have AVPROBE_PADDING_SIZE of extra allocated bytes filled with zero.
Definition: avformat.h:448
#define GIF_IMAGE_SEPARATOR
Definition: gif.h:44
static int gif_skip_subblocks(AVIOContext *pb)
Definition: gifdec.c:98
#define b
Definition: input.c:41
int min_delay
Minimum allowed delay between frames in hundredths of second.
Definition: gifdec.c:46
static const AVClass demuxer_class
Definition: gifdec.c:392
#define FFMIN(a, b)
Definition: common.h:96
int ignore_loop
Definition: gifdec.c:55
#define width
#define GIF_APP_EXT_LABEL
Definition: gif.h:47
AVInputFormat ff_gif_demuxer
Definition: gifdec.c:400
#define s(width, name)
Definition: cbs_vp9.c:257
int n
Definition: avisynth_c.h:760
#define GIF_EXTENSION_INTRODUCER
Definition: gif.h:43
static int gif_read_packet(AVFormatContext *s, AVPacket *pkt)
Definition: gifdec.c:263
int max_delay
Definition: gifdec.c:47
static int read_header(FFV1Context *f)
Definition: ffv1dec.c:530
Stream structure.
Definition: avformat.h:881
static int read_packet(void *opaque, uint8_t *buf, int buf_size)
Definition: avio_reading.c:42
static int resync(AVIOContext *pb)
Definition: gifdec.c:85
AVIOContext * pb
I/O context.
Definition: avformat.h:1400
GIF format definitions.
static int frame_start(MpegEncContext *s)
int total_iter
loop options
Definition: gifdec.c:53
void * buf
Definition: avisynth_c.h:766
int av_dict_set(AVDictionary **pm, const char *key, const char *value, int flags)
Set the given entry in *pm, overwriting an existing entry.
Definition: dict.c:70
Describe the class of an AVClass context structure.
Definition: log.h:67
#define AVFMT_GENERIC_INDEX
Use generic index building code.
Definition: avformat.h:468
Rational number (pair of numerator and denominator).
Definition: rational.h:58
int delay
Time span in hundredths of second before the next frame should be drawn on screen.
Definition: gifdec.c:40
#define AV_OPT_FLAG_DECODING_PARAM
a generic parameter which can be set by the user for demuxing or decoding
Definition: opt.h:277
#define GIF_TRAILER
Definition: gif.h:42
This structure contains the data a format has to probe a file.
Definition: avformat.h:446
static int gif_read_ext(AVFormatContext *s)
Definition: gifdec.c:208
#define flags(name, subs,...)
Definition: cbs_av1.c:561
static int read_probe(const AVProbeData *pd)
Definition: jvdec.c:55
static int gif_probe(const AVProbeData *p)
Definition: gifdec.c:72
int64_t duration
Decoding: duration of the stream, in stream time base.
Definition: avformat.h:930
#define AVPROBE_SCORE_MAX
maximum score
Definition: avformat.h:458
unsigned int avio_rl16(AVIOContext *s)
Definition: aviobuf.c:756
Main libavformat public API header.
int64_t start_time
Decoding: pts of the first frame of the stream in presentation order, in stream time base...
Definition: avformat.h:920
#define NETSCAPE_EXT_STR
Definition: gif.h:48
static const uint8_t gif89a_sig[6]
Definition: gif.h:35
int64_t nb_frames
number of frames in this stream if known or 0
Definition: avformat.h:932
int den
Denominator.
Definition: rational.h:60
#define GIF_DEFAULT_DELAY
Major web browsers display gifs at ~10-15fps when rate is not explicitly set or have too low values...
Definition: gifdec.c:66
void * priv_data
Format private data.
Definition: avformat.h:1386
const char * name
A comma separated list of short names for the format.
Definition: avformat.h:654
#define AV_LOG_FATAL
Something went wrong and recovery is not possible.
Definition: log.h:170
AVCodecParameters * codecpar
Codec parameters associated with this stream.
Definition: avformat.h:1028
int avio_feof(AVIOContext *s)
Similar to feof() but also returns nonzero on read errors.
Definition: aviobuf.c:361
int stream_index
Definition: avcodec.h:1482
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
#define GIF_MIN_DELAY
By default delay values less than this threshold considered to be invalid.
Definition: gifdec.c:70
AVRational r_frame_rate
Real base framerate of the stream.
Definition: avformat.h:1005
This structure stores compressed data.
Definition: avcodec.h:1457