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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
*/
#include "avformat.h"
#include "internal.h"
#include "libavutil/avassert.h"
#include "libavutil/imgutils.h"
#include "libavutil/log.h"
#include "libavutil/opt.h"
/* XXX: random value that shouldn't be taken into effect if there is no
* transparent color in the palette (the transparency bit will be set to 0) */
#define DEFAULT_TRANSPARENCY_INDEX 0x1f
static int get_palette_transparency_index(const uint32_t *palette)
{
int transparent_color_index = -1;
unsigned i, smallest_alpha = 0xff;
if (!palette)
return -1;
for (i = 0; i < AVPALETTE_COUNT; i++) {
const uint32_t v = palette[i];
if (v >> 24 < smallest_alpha) {
smallest_alpha = v >> 24;
transparent_color_index = i;
}
}
return smallest_alpha < 128 ? transparent_color_index : -1;
}
static int gif_image_write_header(AVIOContext *pb, const AVCodecContext *avctx,
int loop_count, uint32_t *palette)
{
int i;
int64_t aspect = 0;
const AVRational sar = avctx->sample_aspect_ratio;
if (sar.num > 0 && sar.den > 0) {
aspect = sar.num * 64LL / sar.den - 15;
if (aspect < 0 || aspect > 255)
aspect = 0;
}
avio_write(pb, "GIF", 3);
avio_write(pb, "89a", 3);
avio_wl16(pb, avctx->width);
avio_wl16(pb, avctx->height);
if (palette) {
const int bcid = get_palette_transparency_index(palette);
avio_w8(pb, 0xf7); /* flags: global clut, 256 entries */
avio_w8(pb, bcid < 0 ? DEFAULT_TRANSPARENCY_INDEX : bcid); /* background color index */
avio_w8(pb, aspect);
for (i = 0; i < 256; i++) {
const uint32_t v = palette[i] & 0xffffff;
avio_wb24(pb, v);
}
} else {
avio_w8(pb, 0); /* flags */
avio_w8(pb, 0); /* background color index */
avio_w8(pb, aspect);
}
if (loop_count >= 0 ) {
/* "NETSCAPE EXTENSION" for looped animation GIF */
avio_w8(pb, 0x21); /* GIF Extension code */
avio_w8(pb, 0xff); /* Application Extension Label */
avio_w8(pb, 0x0b); /* Length of Application Block */
avio_write(pb, "NETSCAPE2.0", sizeof("NETSCAPE2.0") - 1);
avio_w8(pb, 0x03); /* Length of Data Sub-Block */
avio_w8(pb, 0x01);
avio_wl16(pb, (uint16_t)loop_count);
avio_w8(pb, 0x00); /* Data Sub-block Terminator */
}
avio_flush(pb);
return 0;
}
typedef struct GIFContext {
AVClass *class;
int loop;
int last_delay;
AVPacket *prev_pkt;
int duration;
} GIFContext;
static int gif_write_header(AVFormatContext *s)
{
GIFContext *gif = s->priv_data;
AVCodecContext *video_enc;
uint32_t palette[AVPALETTE_COUNT];
if (s->nb_streams != 1 ||
s->streams[0]->codec->codec_type != AVMEDIA_TYPE_VIDEO ||
s->streams[0]->codec->codec_id != AV_CODEC_ID_GIF) {
av_log(s, AV_LOG_ERROR,
"GIF muxer supports only a single video GIF stream.\n");
return AVERROR(EINVAL);
}
video_enc = s->streams[0]->codec;
avpriv_set_pts_info(s->streams[0], 64, 1, 100);
if (avpriv_set_systematic_pal2(palette, video_enc->pix_fmt) < 0) {
av_assert0(video_enc->pix_fmt == AV_PIX_FMT_PAL8);
/* delay header writing: we wait for the first palette to put it
* globally */
} else {
gif_image_write_header(s->pb, video_enc, gif->loop, palette);
}
return 0;
}
static int flush_packet(AVFormatContext *s, AVPacket *new)
{
GIFContext *gif = s->priv_data;
int size, bcid;
AVIOContext *pb = s->pb;
const uint32_t *palette;
AVPacket *pkt = gif->prev_pkt;
if (!pkt)
return 0;
/* Mark one colour as transparent if the input palette contains at least
* one colour that is more than 50% transparent. */
palette = (uint32_t*)av_packet_get_side_data(pkt, AV_PKT_DATA_PALETTE, &size);
if (palette && size != AVPALETTE_SIZE) {
av_log(s, AV_LOG_ERROR, "Invalid palette extradata\n");
return AVERROR_INVALIDDATA;
}
bcid = get_palette_transparency_index(palette);
if (new && new->pts != AV_NOPTS_VALUE)
gif->duration = av_clip_uint16(new->pts - gif->prev_pkt->pts);
else if (!new && gif->last_delay >= 0)
gif->duration = gif->last_delay;
/* graphic control extension block */
avio_w8(pb, 0x21);
avio_w8(pb, 0xf9);
avio_w8(pb, 0x04); /* block size */
avio_w8(pb, 1<<2 | (bcid >= 0));
avio_wl16(pb, gif->duration);
avio_w8(pb, bcid < 0 ? DEFAULT_TRANSPARENCY_INDEX : bcid);
avio_w8(pb, 0x00);
avio_write(pb, pkt->data, pkt->size);
av_free_packet(gif->prev_pkt);
if (new)
av_copy_packet(gif->prev_pkt, new);
return 0;
}
static int gif_write_packet(AVFormatContext *s, AVPacket *pkt)
{
GIFContext *gif = s->priv_data;
const AVCodecContext *video_enc = s->streams[0]->codec;
if (!gif->prev_pkt) {
gif->prev_pkt = av_malloc(sizeof(*gif->prev_pkt));
if (!gif->prev_pkt)
return AVERROR(ENOMEM);
/* Write the first palette as global palette */
if (video_enc->pix_fmt == AV_PIX_FMT_PAL8) {
int size;
void *palette = av_packet_get_side_data(pkt, AV_PKT_DATA_PALETTE, &size);
if (!palette) {
av_log(s, AV_LOG_ERROR, "PAL8 packet is missing palette in extradata\n");
return AVERROR_INVALIDDATA;
}
if (size != AVPALETTE_SIZE) {
av_log(s, AV_LOG_ERROR, "Invalid palette extradata\n");
return AVERROR_INVALIDDATA;
}
gif_image_write_header(s->pb, video_enc, gif->loop, palette);
}
return av_copy_packet(gif->prev_pkt, pkt);
}
return flush_packet(s, pkt);
}
static int gif_write_trailer(AVFormatContext *s)
{
GIFContext *gif = s->priv_data;
AVIOContext *pb = s->pb;
flush_packet(s, NULL);
av_freep(&gif->prev_pkt);
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: -1 - no loop, 0 - infinite loop", OFFSET(loop),
AV_OPT_TYPE_INT, { .i64 = 0 }, -1, 65535, ENC },
{ "final_delay", "Force delay (in centiseconds) after the last frame", OFFSET(last_delay),
AV_OPT_TYPE_INT, { .i64 = -1 }, -1, 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,
.flags = AVFMT_VARIABLE_FPS,
};
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