| /* |
| * 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 "libavutil/bprint.h" |
| #include "libavutil/intreadwrite.h" |
| #include "libavutil/opt.h" |
| #include "internal.h" |
| #include "libavcodec/gif.h" |
| |
| 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; |
| |
| int nb_frames; |
| int last_duration; |
| } 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 i; |
| for (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; |
| |
| if ((ret = resync(pb)) < 0) |
| return ret; |
| |
| 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 (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); |
| if (delay < gdc->min_delay) |
| delay = gdc->default_delay; |
| delay = FFMIN(delay, gdc->max_delay); |
| duration += delay; |
| avio_skip(pb, 1); |
| } else { |
| avio_skip(pb, block_size); |
| } |
| 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; |
| } |
| } |
| |
| /* GIF format operates with time in "hundredths of second", |
| * therefore timebase is 1/100 */ |
| avpriv_set_pts_info(st, 64, 1, 100); |
| st->codecpar->codec_type = AVMEDIA_TYPE_VIDEO; |
| st->codecpar->codec_id = AV_CODEC_ID_GIF; |
| st->codecpar->width = width; |
| st->codecpar->height = height; |
| st->start_time = 0; |
| st->duration = duration; |
| st->nb_frames = nb_frames; |
| if (n) { |
| st->codecpar->sample_aspect_ratio.num = n + 15; |
| st->codecpar->sample_aspect_ratio.den = 64; |
| } |
| |
| /* jump to start because gif decoder needs header data too */ |
| if (avio_seek(pb, 0, SEEK_SET) != 0) |
| return AVERROR(EIO); |
| |
| return 0; |
| } |
| |
| static int gif_read_ext(AVFormatContext *s) |
| { |
| GIFDemuxContext *gdc = s->priv_data; |
| AVIOContext *pb = s->pb; |
| int sb_size, ext_label = avio_r8(pb); |
| int ret; |
| |
| if (ext_label == GIF_GCE_EXT_LABEL) { |
| if ((sb_size = avio_r8(pb)) < 4) { |
| av_log(s, AV_LOG_FATAL, "Graphic Control Extension block's size less than 4.\n"); |
| return AVERROR_INVALIDDATA; |
| } |
| |
| /* skip packed fields */ |
| if ((ret = avio_skip(pb, 1)) < 0) |
| return ret; |
| |
| gdc->delay = avio_rl16(pb); |
| |
| if (gdc->delay < gdc->min_delay) |
| gdc->delay = gdc->default_delay; |
| gdc->delay = FFMIN(gdc->delay, gdc->max_delay); |
| |
| /* skip the rest of the Graphic Control Extension block */ |
| if ((ret = avio_skip(pb, sb_size - 3)) < 0 ) |
| return ret; |
| } else if (ext_label == GIF_APP_EXT_LABEL) { |
| uint8_t data[256]; |
| |
| sb_size = avio_r8(pb); |
| ret = avio_read(pb, data, sb_size); |
| if (ret < 0 || !sb_size) |
| return ret; |
| |
| if (sb_size == strlen(NETSCAPE_EXT_STR)) { |
| sb_size = avio_r8(pb); |
| ret = avio_read(pb, data, sb_size); |
| if (ret < 0 || !sb_size) |
| return ret; |
| |
| if (sb_size == 3 && data[0] == 1) { |
| gdc->total_iter = AV_RL16(data+1); |
| |
| if (gdc->total_iter == 0) |
| gdc->total_iter = -1; |
| } |
| } |
| } |
| |
| if ((ret = gif_skip_subblocks(pb)) < 0) |
| return ret; |
| |
| return 0; |
| } |
| |
| static int gif_read_packet(AVFormatContext *s, AVPacket *pkt) |
| { |
| GIFDemuxContext *gdc = s->priv_data; |
| AVIOContext *pb = s->pb; |
| int packed_fields, block_label, ct_size, |
| keyframe, frame_parsed = 0, ret; |
| int64_t frame_start = avio_tell(pb), frame_end; |
| unsigned char buf[6]; |
| |
| if ((ret = avio_read(pb, buf, 6)) == 6) { |
| keyframe = memcmp(buf, gif87a_sig, 6) == 0 || |
| memcmp(buf, gif89a_sig, 6) == 0; |
| } else if (ret < 0) { |
| return ret; |
| } else { |
| keyframe = 0; |
| } |
| |
| if (keyframe) { |
| parse_keyframe: |
| /* skip 2 bytes of width and 2 of height */ |
| if ((ret = avio_skip(pb, 4)) < 0) |
| return ret; |
| |
| packed_fields = avio_r8(pb); |
| |
| /* skip 1 byte of Background Color Index and 1 byte of Pixel Aspect Ratio */ |
| if ((ret = avio_skip(pb, 2)) < 0) |
| return ret; |
| |
| /* global color table presence */ |
| if (packed_fields & 0x80) { |
| ct_size = 3 * (1 << ((packed_fields & 0x07) + 1)); |
| |
| if ((ret = avio_skip(pb, ct_size)) < 0) |
| return ret; |
| } |
| } else { |
| avio_seek(pb, -ret, SEEK_CUR); |
| ret = AVERROR_EOF; |
| } |
| |
| while (GIF_TRAILER != (block_label = avio_r8(pb)) && !avio_feof(pb)) { |
| if (block_label == GIF_EXTENSION_INTRODUCER) { |
| if ((ret = gif_read_ext (s)) < 0 ) |
| goto resync; |
| } else if (block_label == GIF_IMAGE_SEPARATOR) { |
| /* skip to last byte of Image Descriptor header */ |
| if ((ret = avio_skip(pb, 8)) < 0) |
| return ret; |
| |
| packed_fields = avio_r8(pb); |
| |
| /* local color table presence */ |
| if (packed_fields & 0x80) { |
| ct_size = 3 * (1 << ((packed_fields & 0x07) + 1)); |
| |
| if ((ret = avio_skip(pb, ct_size)) < 0) |
| return ret; |
| } |
| |
| /* read LZW Minimum Code Size */ |
| if (avio_r8(pb) < 1) { |
| av_log(s, AV_LOG_ERROR, "lzw minimum code size must be >= 1\n"); |
| goto resync; |
| } |
| |
| if ((ret = gif_skip_subblocks(pb)) < 0) |
| goto resync; |
| |
| frame_end = avio_tell(pb); |
| |
| if (avio_seek(pb, frame_start, SEEK_SET) != frame_start) |
| return AVERROR(EIO); |
| |
| ret = av_get_packet(pb, pkt, frame_end - frame_start); |
| if (ret < 0) |
| return ret; |
| |
| if (keyframe) |
| pkt->flags |= AV_PKT_FLAG_KEY; |
| |
| pkt->stream_index = 0; |
| pkt->duration = gdc->delay; |
| |
| gdc->nb_frames ++; |
| gdc->last_duration = pkt->duration; |
| |
| /* Graphic Control Extension's scope is single frame. |
| * Remove its influence. */ |
| gdc->delay = gdc->default_delay; |
| frame_parsed = 1; |
| |
| break; |
| } else { |
| av_log(s, AV_LOG_ERROR, "invalid block label\n"); |
| resync: |
| if (!keyframe) |
| avio_seek(pb, frame_start, SEEK_SET); |
| if ((ret = resync(pb)) < 0) |
| return ret; |
| frame_start = avio_tell(pb) - 6; |
| keyframe = 1; |
| goto parse_keyframe; |
| } |
| } |
| |
| if ((ret >= 0 && !frame_parsed) || ret == AVERROR_EOF) { |
| if (gdc->nb_frames == 1) { |
| s->streams[0]->r_frame_rate = (AVRational) {100, gdc->last_duration}; |
| } |
| /* This might happen when there is no image block |
| * between extension blocks and GIF_TRAILER or EOF */ |
| if (!gdc->ignore_loop && (block_label == GIF_TRAILER || avio_feof(pb)) |
| && (gdc->total_iter < 0 || ++gdc->iter_count < gdc->total_iter)) |
| return avio_seek(pb, 0, SEEK_SET); |
| return AVERROR_EOF; |
| } else |
| 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, |
| }; |
| |
| AVInputFormat ff_gif_demuxer = { |
| .name = "gif", |
| .long_name = NULL_IF_CONFIG_SMALL("CompuServe Graphics Interchange Format (GIF)"), |
| .priv_data_size = sizeof(GIFDemuxContext), |
| .read_probe = gif_probe, |
| .read_header = gif_read_header, |
| .read_packet = gif_read_packet, |
| .flags = AVFMT_GENERIC_INDEX, |
| .priv_class = &demuxer_class, |
| }; |
