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/*
* Animated GIF muxer
* Copyright (c) 2000 Fabrice Bellard
*
* first version by Francois Revol <revol@free.fr>
*
* 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
*/
/*
* Features and limitations:
* - currently no compression is performed,
* in fact the size of the data is 9/8 the size of the image in 8bpp
* - uses only a global standard palette
* - tested with IE 5.0, Opera for BeOS, NetPositive (BeOS), and Mozilla (BeOS).
*
* Reference documents:
* http://www.goice.co.jp/member/mo/formats/gif.html
* http://astronomy.swin.edu.au/pbourke/dataformats/gif/
* http://www.dcs.ed.ac.uk/home/mxr/gfx/2d/GIF89a.txt
*
* this url claims to have an LZW algorithm not covered by Unisys patent:
* http://www.msg.net/utility/whirlgif/gifencod.html
* could help reduce the size of the files _a lot_...
* some sites mentions an RLE type compression also.
*/
#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;
unsigned int v;
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++) {
v = palette[i];
avio_w8(pb, (v >> 16) & 0xff);
avio_w8(pb, (v >> 8) & 0xff);
avio_w8(pb, (v) & 0xff);
}
} 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,
};
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