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gif.c
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gif.c
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/*
* Animated GIF muxer
* Copyright (c) 2000 Fabrice Bellard
*
* This file is part of Libav.
*
* Libav 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.
*
* Libav 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 Libav; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
/*
* First version by Francois Revol [email protected]
*
* 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/log.h"
#include "libavutil/opt.h"
/* The GIF format uses reversed order for bitstreams... */
/* at least they don't use PDP_ENDIAN :) */
#define BITSTREAM_WRITER_LE
#include "libavcodec/put_bits.h"
/* bitstream minipacket size */
#define GIF_CHUNKS 100
/* 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
typedef struct {
unsigned char r;
unsigned char g;
unsigned char b;
} rgb_triplet;
/* we use the standard 216 color palette */
/* this script was used to create the palette:
* for r in 00 33 66 99 cc ff; do
* for g in 00 33 66 99 cc ff; do
* echo -n " "
* for b in 00 33 66 99 cc ff; do
* echo -n "{ 0x$r, 0x$g, 0x$b }, "
* done
* echo ""
* done
* done
*/
static const rgb_triplet gif_clut[216] = {
{ 0x00, 0x00, 0x00 }, { 0x00, 0x00, 0x33 }, { 0x00, 0x00, 0x66 }, { 0x00, 0x00, 0x99 }, { 0x00, 0x00, 0xcc }, { 0x00, 0x00, 0xff },
{ 0x00, 0x33, 0x00 }, { 0x00, 0x33, 0x33 }, { 0x00, 0x33, 0x66 }, { 0x00, 0x33, 0x99 }, { 0x00, 0x33, 0xcc }, { 0x00, 0x33, 0xff },
{ 0x00, 0x66, 0x00 }, { 0x00, 0x66, 0x33 }, { 0x00, 0x66, 0x66 }, { 0x00, 0x66, 0x99 }, { 0x00, 0x66, 0xcc }, { 0x00, 0x66, 0xff },
{ 0x00, 0x99, 0x00 }, { 0x00, 0x99, 0x33 }, { 0x00, 0x99, 0x66 }, { 0x00, 0x99, 0x99 }, { 0x00, 0x99, 0xcc }, { 0x00, 0x99, 0xff },
{ 0x00, 0xcc, 0x00 }, { 0x00, 0xcc, 0x33 }, { 0x00, 0xcc, 0x66 }, { 0x00, 0xcc, 0x99 }, { 0x00, 0xcc, 0xcc }, { 0x00, 0xcc, 0xff },
{ 0x00, 0xff, 0x00 }, { 0x00, 0xff, 0x33 }, { 0x00, 0xff, 0x66 }, { 0x00, 0xff, 0x99 }, { 0x00, 0xff, 0xcc }, { 0x00, 0xff, 0xff },
{ 0x33, 0x00, 0x00 }, { 0x33, 0x00, 0x33 }, { 0x33, 0x00, 0x66 }, { 0x33, 0x00, 0x99 }, { 0x33, 0x00, 0xcc }, { 0x33, 0x00, 0xff },
{ 0x33, 0x33, 0x00 }, { 0x33, 0x33, 0x33 }, { 0x33, 0x33, 0x66 }, { 0x33, 0x33, 0x99 }, { 0x33, 0x33, 0xcc }, { 0x33, 0x33, 0xff },
{ 0x33, 0x66, 0x00 }, { 0x33, 0x66, 0x33 }, { 0x33, 0x66, 0x66 }, { 0x33, 0x66, 0x99 }, { 0x33, 0x66, 0xcc }, { 0x33, 0x66, 0xff },
{ 0x33, 0x99, 0x00 }, { 0x33, 0x99, 0x33 }, { 0x33, 0x99, 0x66 }, { 0x33, 0x99, 0x99 }, { 0x33, 0x99, 0xcc }, { 0x33, 0x99, 0xff },
{ 0x33, 0xcc, 0x00 }, { 0x33, 0xcc, 0x33 }, { 0x33, 0xcc, 0x66 }, { 0x33, 0xcc, 0x99 }, { 0x33, 0xcc, 0xcc }, { 0x33, 0xcc, 0xff },
{ 0x33, 0xff, 0x00 }, { 0x33, 0xff, 0x33 }, { 0x33, 0xff, 0x66 }, { 0x33, 0xff, 0x99 }, { 0x33, 0xff, 0xcc }, { 0x33, 0xff, 0xff },
{ 0x66, 0x00, 0x00 }, { 0x66, 0x00, 0x33 }, { 0x66, 0x00, 0x66 }, { 0x66, 0x00, 0x99 }, { 0x66, 0x00, 0xcc }, { 0x66, 0x00, 0xff },
{ 0x66, 0x33, 0x00 }, { 0x66, 0x33, 0x33 }, { 0x66, 0x33, 0x66 }, { 0x66, 0x33, 0x99 }, { 0x66, 0x33, 0xcc }, { 0x66, 0x33, 0xff },
{ 0x66, 0x66, 0x00 }, { 0x66, 0x66, 0x33 }, { 0x66, 0x66, 0x66 }, { 0x66, 0x66, 0x99 }, { 0x66, 0x66, 0xcc }, { 0x66, 0x66, 0xff },
{ 0x66, 0x99, 0x00 }, { 0x66, 0x99, 0x33 }, { 0x66, 0x99, 0x66 }, { 0x66, 0x99, 0x99 }, { 0x66, 0x99, 0xcc }, { 0x66, 0x99, 0xff },
{ 0x66, 0xcc, 0x00 }, { 0x66, 0xcc, 0x33 }, { 0x66, 0xcc, 0x66 }, { 0x66, 0xcc, 0x99 }, { 0x66, 0xcc, 0xcc }, { 0x66, 0xcc, 0xff },
{ 0x66, 0xff, 0x00 }, { 0x66, 0xff, 0x33 }, { 0x66, 0xff, 0x66 }, { 0x66, 0xff, 0x99 }, { 0x66, 0xff, 0xcc }, { 0x66, 0xff, 0xff },
{ 0x99, 0x00, 0x00 }, { 0x99, 0x00, 0x33 }, { 0x99, 0x00, 0x66 }, { 0x99, 0x00, 0x99 }, { 0x99, 0x00, 0xcc }, { 0x99, 0x00, 0xff },
{ 0x99, 0x33, 0x00 }, { 0x99, 0x33, 0x33 }, { 0x99, 0x33, 0x66 }, { 0x99, 0x33, 0x99 }, { 0x99, 0x33, 0xcc }, { 0x99, 0x33, 0xff },
{ 0x99, 0x66, 0x00 }, { 0x99, 0x66, 0x33 }, { 0x99, 0x66, 0x66 }, { 0x99, 0x66, 0x99 }, { 0x99, 0x66, 0xcc }, { 0x99, 0x66, 0xff },
{ 0x99, 0x99, 0x00 }, { 0x99, 0x99, 0x33 }, { 0x99, 0x99, 0x66 }, { 0x99, 0x99, 0x99 }, { 0x99, 0x99, 0xcc }, { 0x99, 0x99, 0xff },
{ 0x99, 0xcc, 0x00 }, { 0x99, 0xcc, 0x33 }, { 0x99, 0xcc, 0x66 }, { 0x99, 0xcc, 0x99 }, { 0x99, 0xcc, 0xcc }, { 0x99, 0xcc, 0xff },
{ 0x99, 0xff, 0x00 }, { 0x99, 0xff, 0x33 }, { 0x99, 0xff, 0x66 }, { 0x99, 0xff, 0x99 }, { 0x99, 0xff, 0xcc }, { 0x99, 0xff, 0xff },
{ 0xcc, 0x00, 0x00 }, { 0xcc, 0x00, 0x33 }, { 0xcc, 0x00, 0x66 }, { 0xcc, 0x00, 0x99 }, { 0xcc, 0x00, 0xcc }, { 0xcc, 0x00, 0xff },
{ 0xcc, 0x33, 0x00 }, { 0xcc, 0x33, 0x33 }, { 0xcc, 0x33, 0x66 }, { 0xcc, 0x33, 0x99 }, { 0xcc, 0x33, 0xcc }, { 0xcc, 0x33, 0xff },
{ 0xcc, 0x66, 0x00 }, { 0xcc, 0x66, 0x33 }, { 0xcc, 0x66, 0x66 }, { 0xcc, 0x66, 0x99 }, { 0xcc, 0x66, 0xcc }, { 0xcc, 0x66, 0xff },
{ 0xcc, 0x99, 0x00 }, { 0xcc, 0x99, 0x33 }, { 0xcc, 0x99, 0x66 }, { 0xcc, 0x99, 0x99 }, { 0xcc, 0x99, 0xcc }, { 0xcc, 0x99, 0xff },
{ 0xcc, 0xcc, 0x00 }, { 0xcc, 0xcc, 0x33 }, { 0xcc, 0xcc, 0x66 }, { 0xcc, 0xcc, 0x99 }, { 0xcc, 0xcc, 0xcc }, { 0xcc, 0xcc, 0xff },
{ 0xcc, 0xff, 0x00 }, { 0xcc, 0xff, 0x33 }, { 0xcc, 0xff, 0x66 }, { 0xcc, 0xff, 0x99 }, { 0xcc, 0xff, 0xcc }, { 0xcc, 0xff, 0xff },
{ 0xff, 0x00, 0x00 }, { 0xff, 0x00, 0x33 }, { 0xff, 0x00, 0x66 }, { 0xff, 0x00, 0x99 }, { 0xff, 0x00, 0xcc }, { 0xff, 0x00, 0xff },
{ 0xff, 0x33, 0x00 }, { 0xff, 0x33, 0x33 }, { 0xff, 0x33, 0x66 }, { 0xff, 0x33, 0x99 }, { 0xff, 0x33, 0xcc }, { 0xff, 0x33, 0xff },
{ 0xff, 0x66, 0x00 }, { 0xff, 0x66, 0x33 }, { 0xff, 0x66, 0x66 }, { 0xff, 0x66, 0x99 }, { 0xff, 0x66, 0xcc }, { 0xff, 0x66, 0xff },
{ 0xff, 0x99, 0x00 }, { 0xff, 0x99, 0x33 }, { 0xff, 0x99, 0x66 }, { 0xff, 0x99, 0x99 }, { 0xff, 0x99, 0xcc }, { 0xff, 0x99, 0xff },
{ 0xff, 0xcc, 0x00 }, { 0xff, 0xcc, 0x33 }, { 0xff, 0xcc, 0x66 }, { 0xff, 0xcc, 0x99 }, { 0xff, 0xcc, 0xcc }, { 0xff, 0xcc, 0xff },
{ 0xff, 0xff, 0x00 }, { 0xff, 0xff, 0x33 }, { 0xff, 0xff, 0x66 }, { 0xff, 0xff, 0x99 }, { 0xff, 0xff, 0xcc }, { 0xff, 0xff, 0xff },
};
/* GIF header */
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);
avio_w8(pb, 0xf7); /* flags: global clut, 256 entries */
avio_w8(pb, 0x1f); /* background color index */
avio_w8(pb, 0); /* aspect ratio */
/* the global palette */
if (!palette) {
avio_write(pb, (const unsigned char *)gif_clut, 216 * 3);
for (i = 0; i < ((256 - 216) * 3); i++)
avio_w8(pb, 0);
} else {
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);
}
}
/* 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;
}
/* this is maybe slow, but allows for extensions */
static inline unsigned char gif_clut_index(uint8_t r, uint8_t g, uint8_t b)
{
return (((r) / 47) % 6) * 6 * 6 + (((g) / 47) % 6) * 6 + (((b) / 47) % 6);
}
static int gif_image_write_image(AVIOContext *pb,
int x1, int y1, int width, int height,
const uint8_t *buf, int linesize, int pix_fmt)
{
PutBitContext p;
uint8_t buffer[200]; /* 100 * 9 / 8 = 113 */
int i, left, w, v;
const uint8_t *ptr;
/* image block */
avio_w8(pb, 0x2c);
avio_wl16(pb, x1);
avio_wl16(pb, y1);
avio_wl16(pb, width);
avio_wl16(pb, height);
avio_w8(pb, 0x00); /* flags */
/* no local clut */
avio_w8(pb, 0x08);
left = width * height;
init_put_bits(&p, buffer, 130);
/*
* the thing here is the bitstream is written as little packets, with a size
* byte before but it's still the same bitstream between packets (no flush !)
*/
ptr = buf;
w = width;
while (left > 0) {
put_bits(&p, 9, 0x0100); /* clear code */
for (i = (left < GIF_CHUNKS) ? left : GIF_CHUNKS; i; i--) {
if (pix_fmt == AV_PIX_FMT_RGB24) {
v = gif_clut_index(ptr[0], ptr[1], ptr[2]);
ptr += 3;
} else {
v = *ptr++;
}
put_bits(&p, 9, v);
if (--w == 0) {
w = width;
buf += linesize;
ptr = buf;
}
}
if (left <= GIF_CHUNKS) {
put_bits(&p, 9, 0x101); /* end of stream */
flush_put_bits(&p);
}
if (put_bits_ptr(&p) - p.buf > 0) {
avio_w8(pb, put_bits_ptr(&p) - p.buf); /* byte count of the packet */
avio_write(pb, p.buf, put_bits_ptr(&p) - p.buf); /* the actual buffer */
p.buf_ptr = p.buf; /* dequeue the bytes off the bitstream */
}
left -= GIF_CHUNKS;
}
avio_w8(pb, 0x00); /* end of image block */
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*/;
/* 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 (video_enc->pix_fmt != AV_PIX_FMT_RGB24) {
av_log(s, AV_LOG_ERROR,
"ERROR: gif only handles the rgb24 pixel format. Use -pix_fmt rgb24.\n");
return AVERROR(EIO);
}
gif_image_write_header(pb, width, height, gif->loop, NULL);
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);
gif_image_write_image(pb, 0, 0, enc->width, enc->height,
buf, enc->width * 3, AV_PIX_FMT_RGB24);
avio_flush(s->pb);
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_RAWVIDEO,
.write_header = gif_write_header,
.write_packet = gif_write_packet,
.write_trailer = gif_write_trailer,
.priv_class = &gif_muxer_class,
};