| /* |
| * GIF demuxer |
| * Copyright (c) 2012 Vitaliy E Sugrobov |
| * |
| * This file is part of FFmpeg. |
| * |
| * FFmpeg is free software; you can redistribute it and/or |
| * modify it under the terms of the GNU Lesser General Public |
| * License as published by the Free Software Foundation; either |
| * version 2.1 of the License, or (at your option) any later version. |
| * |
| * FFmpeg is distributed in the hope that it will be useful, |
| * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| * Lesser General Public License for more details. |
| * |
| * You should have received a copy of the GNU Lesser General Public |
| * License along with FFmpeg; if not, write to the Free Software |
| * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
| */ |
| |
| /** |
| * @file |
| * GIF demuxer. |
| */ |
| |
| #include "avformat.h" |
| #include "demux.h" |
| #include "libavutil/bprint.h" |
| #include "libavutil/intreadwrite.h" |
| #include "libavutil/opt.h" |
| #include "avio_internal.h" |
| #include "internal.h" |
| #include "libavcodec/gif.h" |
| |
| #define GIF_PACKET_SIZE 1024 |
| |
| typedef struct GIFDemuxContext { |
| const AVClass *class; |
| /** |
| * Time span in hundredths of second before |
| * the next frame should be drawn on screen. |
| */ |
| int delay; |
| /** |
| * Minimum allowed delay between frames in hundredths of |
| * second. Values below this threshold considered to be |
| * invalid and set to value of default_delay. |
| */ |
| int min_delay; |
| int max_delay; |
| int default_delay; |
| |
| /** |
| * loop options |
| */ |
| int total_iter; |
| int iter_count; |
| int ignore_loop; |
| } GIFDemuxContext; |
| |
| /** |
| * Major web browsers display gifs at ~10-15fps when rate |
| * is not explicitly set or have too low values. We assume default rate to be 10. |
| * Default delay = 100hundredths of second / 10fps = 10hos per frame. |
| */ |
| #define GIF_DEFAULT_DELAY 10 |
| /** |
| * By default delay values less than this threshold considered to be invalid. |
| */ |
| #define GIF_MIN_DELAY 2 |
| |
| static int gif_probe(const AVProbeData *p) |
| { |
| /* check magick */ |
| if (memcmp(p->buf, gif87a_sig, 6) && memcmp(p->buf, gif89a_sig, 6)) |
| return 0; |
| |
| /* width or height contains zero? */ |
| if (!AV_RL16(&p->buf[6]) || !AV_RL16(&p->buf[8])) |
| return 0; |
| |
| return AVPROBE_SCORE_MAX; |
| } |
| |
| static int resync(AVIOContext *pb) |
| { |
| int ret = ffio_ensure_seekback(pb, 13); |
| if (ret < 0) |
| return ret; |
| |
| for (int i = 0; i < 6; i++) { |
| int b = avio_r8(pb); |
| if (b != gif87a_sig[i] && b != gif89a_sig[i]) |
| i = -(b != 'G'); |
| if (avio_feof(pb)) |
| return AVERROR_EOF; |
| } |
| return 0; |
| } |
| |
| static int gif_skip_subblocks(AVIOContext *pb) |
| { |
| int sb_size, ret = 0; |
| |
| while (0x00 != (sb_size = avio_r8(pb))) { |
| if ((ret = avio_skip(pb, sb_size)) < 0) |
| return ret; |
| } |
| |
| return ret; |
| } |
| |
| static int gif_read_header(AVFormatContext *s) |
| { |
| GIFDemuxContext *gdc = s->priv_data; |
| AVIOContext *pb = s->pb; |
| AVStream *st; |
| int type, width, height, ret, n, flags; |
| int64_t nb_frames = 0, duration = 0, pos; |
| |
| if ((ret = resync(pb)) < 0) |
| return ret; |
| |
| pos = avio_tell(pb); |
| gdc->delay = gdc->default_delay; |
| width = avio_rl16(pb); |
| height = avio_rl16(pb); |
| flags = avio_r8(pb); |
| avio_skip(pb, 1); |
| n = avio_r8(pb); |
| |
| if (width == 0 || height == 0) |
| return AVERROR_INVALIDDATA; |
| |
| st = avformat_new_stream(s, NULL); |
| if (!st) |
| return AVERROR(ENOMEM); |
| |
| if (!(pb->seekable & AVIO_SEEKABLE_NORMAL)) |
| goto skip; |
| |
| if (flags & 0x80) |
| avio_skip(pb, 3 * (1 << ((flags & 0x07) + 1))); |
| |
| while ((type = avio_r8(pb)) != GIF_TRAILER) { |
| if (avio_feof(pb)) |
| break; |
| if (type == GIF_EXTENSION_INTRODUCER) { |
| int subtype = avio_r8(pb); |
| if (subtype == GIF_COM_EXT_LABEL) { |
| AVBPrint bp; |
| int block_size; |
| |
| av_bprint_init(&bp, 0, AV_BPRINT_SIZE_UNLIMITED); |
| while ((block_size = avio_r8(pb)) != 0) { |
| avio_read_to_bprint(pb, &bp, block_size); |
| } |
| av_dict_set(&s->metadata, "comment", bp.str, 0); |
| av_bprint_finalize(&bp, NULL); |
| } else if (subtype == GIF_GCE_EXT_LABEL) { |
| int block_size = avio_r8(pb); |
| |
| if (block_size == 4) { |
| int delay; |
| |
| avio_skip(pb, 1); |
| delay = avio_rl16(pb); |
| delay = delay ? delay : gdc->default_delay; |
| duration += delay; |
| avio_skip(pb, 1); |
| } else { |
| avio_skip(pb, block_size); |
| } |
| gif_skip_subblocks(pb); |
| } else if (subtype == GIF_APP_EXT_LABEL) { |
| uint8_t data[256]; |
| int sb_size; |
| |
| sb_size = avio_r8(pb); |
| ret = avio_read(pb, data, sb_size); |
| if (ret < 0 || !sb_size) |
| break; |
| |
| if (sb_size == strlen(NETSCAPE_EXT_STR)) { |
| sb_size = avio_r8(pb); |
| ret = avio_read(pb, data, sb_size); |
| if (ret < 0 || !sb_size) |
| break; |
| |
| if (sb_size == 3 && data[0] == 1) { |
| gdc->total_iter = AV_RL16(data+1); |
| av_log(s, AV_LOG_DEBUG, "Loop count is %d\n", gdc->total_iter); |
| |
| if (gdc->total_iter == 0) |
| gdc->total_iter = -1; |
| } |
| } |
| gif_skip_subblocks(pb); |
| } else { |
| gif_skip_subblocks(pb); |
| } |
| } else if (type == GIF_IMAGE_SEPARATOR) { |
| avio_skip(pb, 8); |
| flags = avio_r8(pb); |
| if (flags & 0x80) |
| avio_skip(pb, 3 * (1 << ((flags & 0x07) + 1))); |
| avio_skip(pb, 1); |
| gif_skip_subblocks(pb); |
| nb_frames++; |
| } else { |
| break; |
| } |
| } |
| |
| skip: |
| /* jump to start because gif decoder needs header data too */ |
| if (avio_seek(pb, pos - 6, SEEK_SET) != pos - 6) |
| return AVERROR(EIO); |
| |
| /* GIF format operates with time in "hundredths of second", |
| * therefore timebase is 1/100 */ |
| avpriv_set_pts_info(st, 64, 1, 100); |
| ffstream(st)->need_parsing = AVSTREAM_PARSE_FULL_RAW; |
| st->codecpar->codec_type = AVMEDIA_TYPE_VIDEO; |
| st->codecpar->codec_id = AV_CODEC_ID_GIF; |
| st->codecpar->width = width; |
| st->codecpar->height = height; |
| if (nb_frames > 1) { |
| av_reduce(&st->avg_frame_rate.num, &st->avg_frame_rate.den, |
| 100, duration / nb_frames, INT_MAX); |
| } else if (duration) { |
| st->avg_frame_rate = (AVRational) { 100, duration }; |
| } |
| st->start_time = 0; |
| st->duration = duration; |
| st->nb_frames = nb_frames; |
| if (n) |
| st->codecpar->sample_aspect_ratio = av_make_q(n + 15, 64); |
| |
| return 0; |
| } |
| |
| static int gif_read_packet(AVFormatContext *s, AVPacket *pkt) |
| { |
| GIFDemuxContext *gdc = s->priv_data; |
| AVIOContext *pb = s->pb; |
| int ret; |
| |
| if ((pb->seekable & AVIO_SEEKABLE_NORMAL) && |
| !gdc->ignore_loop && avio_feof(pb) && |
| (gdc->total_iter < 0 || (++gdc->iter_count < gdc->total_iter))) { |
| avio_seek(pb, 0, SEEK_SET); |
| } |
| if ((ret = av_new_packet(pkt, GIF_PACKET_SIZE)) < 0) |
| return ret; |
| |
| pkt->pos = avio_tell(pb); |
| pkt->stream_index = 0; |
| ret = avio_read_partial(pb, pkt->data, GIF_PACKET_SIZE); |
| if (ret < 0) { |
| av_packet_unref(pkt); |
| return ret; |
| } |
| av_shrink_packet(pkt, ret); |
| return ret; |
| } |
| |
| static const AVOption options[] = { |
| { "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 }, |
| { "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 }, |
| { "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 }, |
| { "ignore_loop" , "ignore loop setting (netscape extension)" , offsetof(GIFDemuxContext, ignore_loop) , AV_OPT_TYPE_BOOL,{.i64 = 1} , 0, 1, AV_OPT_FLAG_DECODING_PARAM }, |
| { NULL }, |
| }; |
| |
| static const AVClass demuxer_class = { |
| .class_name = "GIF demuxer", |
| .item_name = av_default_item_name, |
| .option = options, |
| .version = LIBAVUTIL_VERSION_INT, |
| .category = AV_CLASS_CATEGORY_DEMUXER, |
| }; |
| |
| const FFInputFormat ff_gif_demuxer = { |
| .p.name = "gif", |
| .p.long_name = NULL_IF_CONFIG_SMALL("CompuServe Graphics Interchange Format (GIF)"), |
| .p.flags = AVFMT_GENERIC_INDEX, |
| .p.extensions = "gif", |
| .p.priv_class = &demuxer_class, |
| .priv_data_size = sizeof(GIFDemuxContext), |
| .read_probe = gif_probe, |
| .read_header = gif_read_header, |
| .read_packet = gif_read_packet, |
| }; |
