/* * Animated GIF muxer * Copyright (c) 2000 Fabrice Bellard * * first version by Francois Revol * * 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 */ #include "avformat.h" #include "libavutil/avassert.h" #include "libavutil/imgutils.h" #include "libavutil/log.h" #include "libavutil/opt.h" /* slows down the decoding (and some browsers don't like it) */ /* update on the 'some browsers don't like it issue from above: * this was probably due to missing 'Data Sub-block Terminator' * (byte 19) in the app_header */ #define GIF_ADD_APP_HEADER // required to enable looping of animated gif static int gif_image_write_header(AVIOContext *pb, int width, int height, int loop_count, uint32_t *palette) { int i; avio_write(pb, "GIF", 3); avio_write(pb, "89a", 3); avio_wl16(pb, width); avio_wl16(pb, height); if (palette) { avio_w8(pb, 0xf7); /* flags: global clut, 256 entries */ avio_w8(pb, 0x1f); /* background color index */ avio_w8(pb, 0); /* aspect ratio */ for (i = 0; i < 256; i++) { const uint32_t v = palette[i]; avio_wb24(pb, v); } } else { avio_w8(pb, 0); /* flags */ avio_w8(pb, 0); /* background color index */ avio_w8(pb, 0); /* aspect ratio */ } /* update: this is the 'NETSCAPE EXTENSION' that allows for looped animated * GIF, see http://members.aol.com/royalef/gifabout.htm#net-extension * * byte 1 : 33 (hex 0x21) GIF Extension code * byte 2 : 255 (hex 0xFF) Application Extension Label * byte 3 : 11 (hex (0x0B) Length of Application Block * (eleven bytes of data to follow) * bytes 4 to 11 : "NETSCAPE" * bytes 12 to 14 : "2.0" * byte 15 : 3 (hex 0x03) Length of Data Sub-Block * (three bytes of data to follow) * byte 16 : 1 (hex 0x01) * bytes 17 to 18 : 0 to 65535, an unsigned integer in * lo-hi byte format. This indicate the * number of iterations the loop should * be executed. * bytes 19 : 0 (hex 0x00) a Data Sub-block Terminator */ /* application extension header */ #ifdef GIF_ADD_APP_HEADER if (loop_count >= 0 && loop_count <= 65535) { avio_w8(pb, 0x21); avio_w8(pb, 0xff); avio_w8(pb, 0x0b); // bytes 4 to 14 avio_write(pb, "NETSCAPE2.0", sizeof("NETSCAPE2.0") - 1); avio_w8(pb, 0x03); // byte 15 avio_w8(pb, 0x01); // byte 16 avio_wl16(pb, (uint16_t)loop_count); avio_w8(pb, 0x00); // byte 19 } #endif return 0; } typedef struct { AVClass *class; /** Class for private options. */ int64_t time, file_time; uint8_t buffer[100]; /* data chunks */ int loop; } GIFContext; static int gif_write_header(AVFormatContext *s) { GIFContext *gif = s->priv_data; AVIOContext *pb = s->pb; AVCodecContext *enc, *video_enc; int i, width, height /*, rate*/; uint32_t palette[AVPALETTE_COUNT]; /* XXX: do we reject audio streams or just ignore them ? * if (s->nb_streams > 1) * return -1; */ gif->time = 0; gif->file_time = 0; video_enc = NULL; for (i = 0; i < s->nb_streams; i++) { enc = s->streams[i]->codec; if (enc->codec_type != AVMEDIA_TYPE_AUDIO) video_enc = enc; } if (!video_enc) { av_free(gif); return -1; } else { width = video_enc->width; height = video_enc->height; // rate = video_enc->time_base.den; } if (avpriv_set_systematic_pal2(palette, video_enc->pix_fmt) < 0) { av_assert0(video_enc->pix_fmt == AV_PIX_FMT_PAL8); gif_image_write_header(pb, width, height, gif->loop, NULL); } else { gif_image_write_header(pb, width, height, gif->loop, palette); } avio_flush(s->pb); return 0; } static int gif_write_video(AVFormatContext *s, AVCodecContext *enc, const uint8_t *buf, int size) { AVIOContext *pb = s->pb; int jiffies; /* graphic control extension block */ avio_w8(pb, 0x21); avio_w8(pb, 0xf9); avio_w8(pb, 0x04); /* block size */ avio_w8(pb, 0x04); /* flags */ /* 1 jiffy is 1/70 s */ /* the delay_time field indicates the number of jiffies - 1 */ /* XXX: should use delay, in order to be more accurate */ /* instead of using the same rounded value each time */ /* XXX: don't even remember if I really use it for now */ jiffies = (70 * enc->time_base.num / enc->time_base.den) - 1; avio_wl16(pb, jiffies); avio_w8(pb, 0x1f); /* transparent color index */ avio_w8(pb, 0x00); avio_write(pb, buf, size); return 0; } static int gif_write_packet(AVFormatContext *s, AVPacket *pkt) { AVCodecContext *codec = s->streams[pkt->stream_index]->codec; if (codec->codec_type == AVMEDIA_TYPE_AUDIO) return 0; /* just ignore audio */ else return gif_write_video(s, codec, pkt->data, pkt->size); } static int gif_write_trailer(AVFormatContext *s) { AVIOContext *pb = s->pb; avio_w8(pb, 0x3b); return 0; } #define OFFSET(x) offsetof(GIFContext, x) #define ENC AV_OPT_FLAG_ENCODING_PARAM static const AVOption options[] = { { "loop", "Number of times to loop the output.", OFFSET(loop), AV_OPT_TYPE_INT, { .i64 = 0 }, 0, 65535, ENC }, { NULL }, }; static const AVClass gif_muxer_class = { .class_name = "GIF muxer", .item_name = av_default_item_name, .version = LIBAVUTIL_VERSION_INT, .option = options, }; AVOutputFormat ff_gif_muxer = { .name = "gif", .long_name = NULL_IF_CONFIG_SMALL("GIF Animation"), .mime_type = "image/gif", .extensions = "gif", .priv_data_size = sizeof(GIFContext), .audio_codec = AV_CODEC_ID_NONE, .video_codec = AV_CODEC_ID_GIF, .write_header = gif_write_header, .write_packet = gif_write_packet, .write_trailer = gif_write_trailer, .priv_class = &gif_muxer_class, };