FFmpeg coverage

Directory: ../../../ffmpeg/
File: src/libavformat/gifdec.c
Date: 2026-04-19 20:43:40
Exec Total Coverage
Lines: 107 127 84.3%
Functions: 5 5 100.0%
Branches: 57 94 60.6%
Line Branch Exec Source
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 "demux.h"
29 #include "libavutil/bprint.h"
30 #include "libavutil/intreadwrite.h"
31 #include "libavutil/opt.h"
32 #include "avio_internal.h"
33 #include "internal.h"
34 #include "libavcodec/gif.h"
35
36 #define GIF_PACKET_SIZE 1024
37
38 typedef struct GIFDemuxContext {
39 const AVClass *class;
40 /**
41 * Time span in hundredths of second before
42 * the next frame should be drawn on screen.
43 */
44 int delay;
45 /**
46 * Minimum allowed delay between frames in hundredths of
47 * second. Values below this threshold considered to be
48 * invalid and set to value of default_delay.
49 */
50 int min_delay;
51 int max_delay;
52 int default_delay;
53
54 /**
55 * loop options
56 */
57 int total_iter;
58 int iter_count;
59 int ignore_loop;
60 } GIFDemuxContext;
61
62 /**
63 * Major web browsers display gifs at ~10-15fps when rate
64 * is not explicitly set or have too low values. We assume default rate to be 10.
65 * Default delay = 100hundredths of second / 10fps = 10hos per frame.
66 */
67 #define GIF_DEFAULT_DELAY 10
68 /**
69 * By default delay values less than this threshold considered to be invalid.
70 */
71 #define GIF_MIN_DELAY 2
72
73 7467 static int gif_probe(const AVProbeData *p)
74 {
75 /* check magick */
76
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 7467 if (memcmp(p->buf, gif87a_sig, 6) && memcmp(p->buf, gif89a_sig, 6))
77 7452 return 0;
78
79 /* width or height contains zero? */
80
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 15 if (!AV_RL16(&p->buf[6]) || !AV_RL16(&p->buf[8]))
81 ✗ return 0;
82
83 15 return AVPROBE_SCORE_MAX;
84 }
85
86 15 static int resync(AVIOContext *pb)
87 {
88 15 int ret = ffio_ensure_seekback(pb, 13);
89
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 15 if (ret < 0)
90 ✗ return ret;
91
92
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 105 for (int i = 0; i < 6; i++) {
93 90 int b = avio_r8(pb);
94
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 90 if (b != gif87a_sig[i] && b != gif89a_sig[i])
95 ✗ i = -(b != 'G');
96
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 90 if (avio_feof(pb))
97 ✗ return AVERROR_EOF;
98 }
99 15 return 0;
100 }
101
102 2719 static int gif_skip_subblocks(AVIOContext *pb)
103 {
104 2719 int sb_size, ret = 0;
105
106
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 24402 while (0x00 != (sb_size = avio_r8(pb))) {
107
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 21683 if ((ret = avio_skip(pb, sb_size)) < 0)
108 ✗ return ret;
109 }
110
111 2719 return ret;
112 }
113
114 15 static int gif_read_header(AVFormatContext *s)
115 {
116 15 GIFDemuxContext *gdc = s->priv_data;
117 15 AVIOContext *pb = s->pb;
118 AVStream *st;
119 int type, width, height, ret, n, flags;
120 15 int64_t nb_frames = 0, duration = 0, pos;
121 int64_t ret64;
122
123
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 15 if ((ret = resync(pb)) < 0)
124 ✗ return ret;
125
126 15 pos = avio_tell(pb);
127 15 gdc->delay = gdc->default_delay;
128 15 width = avio_rl16(pb);
129 15 height = avio_rl16(pb);
130 15 flags = avio_r8(pb);
131 15 avio_skip(pb, 1);
132 15 n = avio_r8(pb);
133
134
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 15 if (width == 0 || height == 0)
135 ✗ return AVERROR_INVALIDDATA;
136
137 15 st = avformat_new_stream(s, NULL);
138
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 15 if (!st)
139 ✗ return AVERROR(ENOMEM);
140
141
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 15 if (!(pb->seekable & AVIO_SEEKABLE_NORMAL))
142 ✗ goto skip;
143
144
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 15 if (flags & 0x80)
145 8 avio_skip(pb, 3 * (1 << ((flags & 0x07) + 1)));
146
147
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 2736 while ((type = avio_r8(pb)) != GIF_TRAILER) {
148
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 2721 if (avio_feof(pb))
149 ✗ break;
150
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 2721 if (type == GIF_EXTENSION_INTRODUCER) {
151 1366 int subtype = avio_r8(pb);
152
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 1366 if (subtype == GIF_COM_EXT_LABEL) {
153 AVBPrint bp;
154 int block_size;
155
156 2 av_bprint_init(&bp, 0, AV_BPRINT_SIZE_UNLIMITED);
157
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 4 while ((block_size = avio_r8(pb)) != 0) {
158 2 avio_read_to_bprint(pb, &bp, block_size);
159 }
160 2 av_dict_set(&s->metadata, "comment", bp.str, 0);
161 2 av_bprint_finalize(&bp, NULL);
162
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 1364 } else if (subtype == GIF_GCE_EXT_LABEL) {
163 1355 int block_size = avio_r8(pb);
164
165
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 1355 if (block_size == 4) {
166 int delay;
167
168 1355 avio_skip(pb, 1);
169 1355 delay = avio_rl16(pb);
170
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 1355 delay = delay ? delay : gdc->default_delay;
171 1355 duration += delay;
172 1355 avio_skip(pb, 1);
173 } else {
174 ✗ avio_skip(pb, block_size);
175 }
176 1355 gif_skip_subblocks(pb);
177
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 9 } else if (subtype == GIF_APP_EXT_LABEL) {
178 uint8_t data[256];
179 int sb_size;
180
181 9 sb_size = avio_r8(pb);
182 9 ret = avio_read(pb, data, sb_size);
183
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 9 if (ret < 0 || !sb_size)
184 break;
185
186
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 9 if (sb_size == strlen(NETSCAPE_EXT_STR)) {
187 9 sb_size = avio_r8(pb);
188 9 ret = avio_read(pb, data, sb_size);
189
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 9 if (ret < 0 || !sb_size)
190 break;
191
192
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 9 if (sb_size == 3 && data[0] == 1) {
193 8 gdc->total_iter = AV_RL16(data+1);
194 8 av_log(s, AV_LOG_DEBUG, "Loop count is %d\n", gdc->total_iter);
195
196
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 8 if (gdc->total_iter == 0)
197 8 gdc->total_iter = -1;
198 }
199 }
200 9 gif_skip_subblocks(pb);
201 } else {
202 ✗ gif_skip_subblocks(pb);
203 }
204
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 1355 } else if (type == GIF_IMAGE_SEPARATOR) {
205 1355 avio_skip(pb, 8);
206 1355 flags = avio_r8(pb);
207
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 1355 if (flags & 0x80)
208 1213 avio_skip(pb, 3 * (1 << ((flags & 0x07) + 1)));
209 1355 avio_skip(pb, 1);
210 1355 gif_skip_subblocks(pb);
211 1355 nb_frames++;
212 } else {
213 ✗ break;
214 }
215 }
216
217 15 skip:
218 /* jump to start because gif decoder needs header data too */
219 15 ret64 = avio_seek(pb, pos - 6, SEEK_SET);
220
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 15 if (ret64 < 0)
221 ✗ return (int)ret64;
222
223 /* GIF format operates with time in "hundredths of second",
224 * therefore timebase is 1/100 */
225 15 avpriv_set_pts_info(st, 64, 1, 100);
226 15 ffstream(st)->need_parsing = AVSTREAM_PARSE_FULL_RAW;
227 15 st->codecpar->codec_type = AVMEDIA_TYPE_VIDEO;
228 15 st->codecpar->codec_id = AV_CODEC_ID_GIF;
229 15 st->codecpar->width = width;
230 15 st->codecpar->height = height;
231
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 15 if (nb_frames > 1) {
232 15 av_reduce(&st->avg_frame_rate.num, &st->avg_frame_rate.den,
233 100, duration / nb_frames, INT_MAX);
234 ✗ } else if (duration) {
235 ✗ st->avg_frame_rate = (AVRational) { 100, duration };
236 }
237 15 st->start_time = 0;
238 15 st->duration = duration;
239 15 st->nb_frames = nb_frames;
240
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 15 if (n)
241 ✗ st->codecpar->sample_aspect_ratio = av_make_q(n + 15, 64);
242
243 15 return 0;
244 }
245
246 42872 static int gif_read_packet(AVFormatContext *s, AVPacket *pkt)
247 {
248 42872 GIFDemuxContext *gdc = s->priv_data;
249 42872 AVIOContext *pb = s->pb;
250 int ret;
251
252
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 42872 if ((pb->seekable & AVIO_SEEKABLE_NORMAL) &&
253
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 42872 !gdc->ignore_loop && avio_feof(pb) &&
254 ✗ (gdc->total_iter < 0 || (++gdc->iter_count < gdc->total_iter))) {
255 ✗ avio_seek(pb, 0, SEEK_SET);
256 }
257
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 42872 if ((ret = av_new_packet(pkt, GIF_PACKET_SIZE)) < 0)
258 ✗ return ret;
259
260 42872 pkt->pos = avio_tell(pb);
261 42872 pkt->stream_index = 0;
262 42872 ret = avio_read_partial(pb, pkt->data, GIF_PACKET_SIZE);
263
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 42872 if (ret < 0) {
264 73 av_packet_unref(pkt);
265 73 return ret;
266 }
267 42799 av_shrink_packet(pkt, ret);
268 42799 return ret;
269 }
270
271 static const AVOption options[] = {
272 { "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 },
273 { "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 },
274 { "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 },
275 { "ignore_loop" , "ignore loop setting (netscape extension)" , offsetof(GIFDemuxContext, ignore_loop) , AV_OPT_TYPE_BOOL,{.i64 = 1} , 0, 1, AV_OPT_FLAG_DECODING_PARAM },
276 { NULL },
277 };
278
279 static const AVClass demuxer_class = {
280 .class_name = "GIF demuxer",
281 .item_name = av_default_item_name,
282 .option = options,
283 .version = LIBAVUTIL_VERSION_INT,
284 .category = AV_CLASS_CATEGORY_DEMUXER,
285 };
286
287 const FFInputFormat ff_gif_demuxer = {
288 .p.name = "gif",
289 .p.long_name = NULL_IF_CONFIG_SMALL("CompuServe Graphics Interchange Format (GIF)"),
290 .p.flags = AVFMT_GENERIC_INDEX,
291 .p.extensions = "gif",
292 .p.priv_class = &demuxer_class,
293 .priv_data_size = sizeof(GIFDemuxContext),
294 .read_probe = gif_probe,
295 .read_header = gif_read_header,
296 .read_packet = gif_read_packet,
297 };
298