| 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/intreadwrite.h" |
| 29 | #include "libavutil/opt.h" |
| 30 | #include "internal.h" |
| 31 | #include "libavcodec/gif.h" |
| 32 | |
| 33 | typedef struct GIFDemuxContext { |
| 34 | const AVClass *class; |
| 35 | /** |
| 36 | * Time span in hundredths of second before |
| 37 | * the next frame should be drawn on screen. |
| 38 | */ |
| 39 | int delay; |
| 40 | /** |
| 41 | * Minimum allowed delay between frames in hundredths of |
| 42 | * second. Values below this threshold considered to be |
| 43 | * invalid and set to value of default_delay. |
| 44 | */ |
| 45 | int min_delay; |
| 46 | int default_delay; |
| 47 | |
| 48 | /** |
| 49 | * loop options |
| 50 | */ |
| 51 | int total_iter; |
| 52 | int iter_count; |
| 53 | int ignore_loop; |
| 54 | } GIFDemuxContext; |
| 55 | |
| 56 | /** |
| 57 | * Major web browsers display gifs at ~10-15fps when rate |
| 58 | * is not explicitly set or have too low values. We assume default rate to be 10. |
| 59 | * Default delay = 100hundredths of second / 10fps = 10hos per frame. |
| 60 | */ |
| 61 | #define GIF_DEFAULT_DELAY 10 |
| 62 | /** |
| 63 | * By default delay values less than this threshold considered to be invalid. |
| 64 | */ |
| 65 | #define GIF_MIN_DELAY 2 |
| 66 | |
| 67 | static int gif_probe(AVProbeData *p) |
| 68 | { |
| 69 | /* check magick */ |
| 70 | if (memcmp(p->buf, gif87a_sig, 6) && memcmp(p->buf, gif89a_sig, 6)) |
| 71 | return 0; |
| 72 | |
| 73 | /* width or height contains zero? */ |
| 74 | if (!AV_RL16(&p->buf[6]) || !AV_RL16(&p->buf[8])) |
| 75 | return 0; |
| 76 | |
| 77 | return AVPROBE_SCORE_MAX; |
| 78 | } |
| 79 | |
| 80 | static int resync(AVIOContext *pb) |
| 81 | { |
| 82 | int i; |
| 83 | for (i = 0; i < 6; i++) { |
| 84 | int b = avio_r8(pb); |
| 85 | if (b != gif87a_sig[i] && b != gif89a_sig[i]) |
| 86 | i = -(b != 'G'); |
| 87 | if (avio_feof(pb)) |
| 88 | return AVERROR_EOF; |
| 89 | } |
| 90 | return 0; |
| 91 | } |
| 92 | |
| 93 | static int gif_read_header(AVFormatContext *s) |
| 94 | { |
| 95 | GIFDemuxContext *gdc = s->priv_data; |
| 96 | AVIOContext *pb = s->pb; |
| 97 | AVStream *st; |
| 98 | int width, height, ret; |
| 99 | |
| 100 | if ((ret = resync(pb)) < 0) |
| 101 | return ret; |
| 102 | |
| 103 | gdc->delay = gdc->default_delay; |
| 104 | width = avio_rl16(pb); |
| 105 | height = avio_rl16(pb); |
| 106 | |
| 107 | if (width == 0 || height == 0) |
| 108 | return AVERROR_INVALIDDATA; |
| 109 | |
| 110 | st = avformat_new_stream(s, NULL); |
| 111 | if (!st) |
| 112 | return AVERROR(ENOMEM); |
| 113 | |
| 114 | /* GIF format operates with time in "hundredths of second", |
| 115 | * therefore timebase is 1/100 */ |
| 116 | avpriv_set_pts_info(st, 64, 1, 100); |
| 117 | st->codec->codec_type = AVMEDIA_TYPE_VIDEO; |
| 118 | st->codec->codec_id = AV_CODEC_ID_GIF; |
| 119 | st->codec->width = width; |
| 120 | st->codec->height = height; |
| 121 | |
| 122 | /* jump to start because gif decoder needs header data too */ |
| 123 | if (avio_seek(pb, 0, SEEK_SET) != 0) |
| 124 | return AVERROR(EIO); |
| 125 | |
| 126 | return 0; |
| 127 | } |
| 128 | |
| 129 | static int gif_skip_subblocks(AVIOContext *pb) |
| 130 | { |
| 131 | int sb_size, ret = 0; |
| 132 | |
| 133 | while (0x00 != (sb_size = avio_r8(pb))) { |
| 134 | if ((ret = avio_skip(pb, sb_size)) < 0) |
| 135 | return ret; |
| 136 | } |
| 137 | |
| 138 | return ret; |
| 139 | } |
| 140 | |
| 141 | static int gif_read_ext(AVFormatContext *s) |
| 142 | { |
| 143 | GIFDemuxContext *gdc = s->priv_data; |
| 144 | AVIOContext *pb = s->pb; |
| 145 | int sb_size, ext_label = avio_r8(pb); |
| 146 | int ret; |
| 147 | |
| 148 | if (ext_label == GIF_GCE_EXT_LABEL) { |
| 149 | if ((sb_size = avio_r8(pb)) < 4) { |
| 150 | av_log(s, AV_LOG_FATAL, "Graphic Control Extension block's size less than 4.\n"); |
| 151 | return AVERROR_INVALIDDATA; |
| 152 | } |
| 153 | |
| 154 | /* skip packed fields */ |
| 155 | if ((ret = avio_skip(pb, 1)) < 0) |
| 156 | return ret; |
| 157 | |
| 158 | gdc->delay = avio_rl16(pb); |
| 159 | |
| 160 | if (gdc->delay < gdc->min_delay) |
| 161 | gdc->delay = gdc->default_delay; |
| 162 | |
| 163 | /* skip the rest of the Graphic Control Extension block */ |
| 164 | if ((ret = avio_skip(pb, sb_size - 3)) < 0 ) |
| 165 | return ret; |
| 166 | } else if (ext_label == GIF_APP_EXT_LABEL) { |
| 167 | uint8_t data[256]; |
| 168 | |
| 169 | sb_size = avio_r8(pb); |
| 170 | ret = avio_read(pb, data, sb_size); |
| 171 | if (ret < 0 || !sb_size) |
| 172 | return ret; |
| 173 | |
| 174 | if (sb_size == strlen(NETSCAPE_EXT_STR)) { |
| 175 | sb_size = avio_r8(pb); |
| 176 | ret = avio_read(pb, data, sb_size); |
| 177 | if (ret < 0 || !sb_size) |
| 178 | return ret; |
| 179 | |
| 180 | if (sb_size == 3 && data[0] == 1) { |
| 181 | gdc->total_iter = AV_RL16(data+1); |
| 182 | |
| 183 | if (gdc->total_iter == 0) |
| 184 | gdc->total_iter = -1; |
| 185 | } |
| 186 | } |
| 187 | } |
| 188 | |
| 189 | if ((ret = gif_skip_subblocks(pb)) < 0) |
| 190 | return ret; |
| 191 | |
| 192 | return 0; |
| 193 | } |
| 194 | |
| 195 | static int gif_read_packet(AVFormatContext *s, AVPacket *pkt) |
| 196 | { |
| 197 | GIFDemuxContext *gdc = s->priv_data; |
| 198 | AVIOContext *pb = s->pb; |
| 199 | int packed_fields, block_label, ct_size, |
| 200 | keyframe, frame_parsed = 0, ret; |
| 201 | int64_t frame_start = avio_tell(pb), frame_end; |
| 202 | unsigned char buf[6]; |
| 203 | |
| 204 | if ((ret = avio_read(pb, buf, 6)) == 6) { |
| 205 | keyframe = memcmp(buf, gif87a_sig, 6) == 0 || |
| 206 | memcmp(buf, gif89a_sig, 6) == 0; |
| 207 | } else if (ret < 0) { |
| 208 | return ret; |
| 209 | } else { |
| 210 | keyframe = 0; |
| 211 | } |
| 212 | |
| 213 | if (keyframe) { |
| 214 | parse_keyframe: |
| 215 | /* skip 2 bytes of width and 2 of height */ |
| 216 | if ((ret = avio_skip(pb, 4)) < 0) |
| 217 | return ret; |
| 218 | |
| 219 | packed_fields = avio_r8(pb); |
| 220 | |
| 221 | /* skip 1 byte of Background Color Index and 1 byte of Pixel Aspect Ratio */ |
| 222 | if ((ret = avio_skip(pb, 2)) < 0) |
| 223 | return ret; |
| 224 | |
| 225 | /* global color table presence */ |
| 226 | if (packed_fields & 0x80) { |
| 227 | ct_size = 3 * (1 << ((packed_fields & 0x07) + 1)); |
| 228 | |
| 229 | if ((ret = avio_skip(pb, ct_size)) < 0) |
| 230 | return ret; |
| 231 | } |
| 232 | } else { |
| 233 | avio_seek(pb, -ret, SEEK_CUR); |
| 234 | ret = AVERROR_EOF; |
| 235 | } |
| 236 | |
| 237 | while (GIF_TRAILER != (block_label = avio_r8(pb)) && !avio_feof(pb)) { |
| 238 | if (block_label == GIF_EXTENSION_INTRODUCER) { |
| 239 | if ((ret = gif_read_ext (s)) < 0 ) |
| 240 | goto resync; |
| 241 | } else if (block_label == GIF_IMAGE_SEPARATOR) { |
| 242 | /* skip to last byte of Image Descriptor header */ |
| 243 | if ((ret = avio_skip(pb, 8)) < 0) |
| 244 | return ret; |
| 245 | |
| 246 | packed_fields = avio_r8(pb); |
| 247 | |
| 248 | /* local color table presence */ |
| 249 | if (packed_fields & 0x80) { |
| 250 | ct_size = 3 * (1 << ((packed_fields & 0x07) + 1)); |
| 251 | |
| 252 | if ((ret = avio_skip(pb, ct_size)) < 0) |
| 253 | return ret; |
| 254 | } |
| 255 | |
| 256 | /* read LZW Minimum Code Size */ |
| 257 | if (avio_r8(pb) < 1) { |
| 258 | av_log(s, AV_LOG_ERROR, "lzw minimum code size must be >= 1\n"); |
| 259 | goto resync; |
| 260 | } |
| 261 | |
| 262 | if ((ret = gif_skip_subblocks(pb)) < 0) |
| 263 | goto resync; |
| 264 | |
| 265 | frame_end = avio_tell(pb); |
| 266 | |
| 267 | if (avio_seek(pb, frame_start, SEEK_SET) != frame_start) |
| 268 | return AVERROR(EIO); |
| 269 | |
| 270 | ret = av_get_packet(pb, pkt, frame_end - frame_start); |
| 271 | if (ret < 0) |
| 272 | return ret; |
| 273 | |
| 274 | if (keyframe) |
| 275 | pkt->flags |= AV_PKT_FLAG_KEY; |
| 276 | |
| 277 | pkt->stream_index = 0; |
| 278 | pkt->duration = gdc->delay; |
| 279 | |
| 280 | /* Graphic Control Extension's scope is single frame. |
| 281 | * Remove its influence. */ |
| 282 | gdc->delay = gdc->default_delay; |
| 283 | frame_parsed = 1; |
| 284 | |
| 285 | break; |
| 286 | } else { |
| 287 | av_log(s, AV_LOG_ERROR, "invalid block label\n"); |
| 288 | resync: |
| 289 | if (!keyframe) |
| 290 | avio_seek(pb, frame_start, SEEK_SET); |
| 291 | if ((ret = resync(pb)) < 0) |
| 292 | return ret; |
| 293 | frame_start = avio_tell(pb) - 6; |
| 294 | keyframe = 1; |
| 295 | goto parse_keyframe; |
| 296 | } |
| 297 | } |
| 298 | |
| 299 | if ((ret >= 0 && !frame_parsed) || ret == AVERROR_EOF) { |
| 300 | /* This might happen when there is no image block |
| 301 | * between extension blocks and GIF_TRAILER or EOF */ |
| 302 | if (!gdc->ignore_loop && (block_label == GIF_TRAILER || avio_feof(pb)) |
| 303 | && (gdc->total_iter < 0 || ++gdc->iter_count < gdc->total_iter)) |
| 304 | return avio_seek(pb, 0, SEEK_SET); |
| 305 | return AVERROR_EOF; |
| 306 | } else |
| 307 | return ret; |
| 308 | } |
| 309 | |
| 310 | static const AVOption options[] = { |
| 311 | { "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 }, |
| 312 | { "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 }, |
| 313 | { "ignore_loop" , "ignore loop setting (netscape extension)" , offsetof(GIFDemuxContext, ignore_loop) , AV_OPT_TYPE_INT, {.i64 = 1} , 0, 1, AV_OPT_FLAG_DECODING_PARAM }, |
| 314 | { NULL }, |
| 315 | }; |
| 316 | |
| 317 | static const AVClass demuxer_class = { |
| 318 | .class_name = "GIF demuxer", |
| 319 | .item_name = av_default_item_name, |
| 320 | .option = options, |
| 321 | .version = LIBAVUTIL_VERSION_INT, |
| 322 | .category = AV_CLASS_CATEGORY_DEMUXER, |
| 323 | }; |
| 324 | |
| 325 | AVInputFormat ff_gif_demuxer = { |
| 326 | .name = "gif", |
| 327 | .long_name = NULL_IF_CONFIG_SMALL("CompuServe Graphics Interchange Format (GIF)"), |
| 328 | .priv_data_size = sizeof(GIFDemuxContext), |
| 329 | .read_probe = gif_probe, |
| 330 | .read_header = gif_read_header, |
| 331 | .read_packet = gif_read_packet, |
| 332 | .flags = AVFMT_GENERIC_INDEX, |
| 333 | .priv_class = &demuxer_class, |
| 334 | }; |