gif.c

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/*
 * Animated GIF muxer
 * Copyright (c) 2000 Fabrice Bellard
 *
 * 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
 */

/*
 * First version by Francois Revol revol@free.fr
 *
 * 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,
};