FFmpeg: libavformat/gif.c Source File

00001 /*
00002  * Animated GIF muxer
00003  * Copyright (c) 2000 Fabrice Bellard
00004  *
00005  * This file is part of FFmpeg.
00006  *
00007  * FFmpeg is free software; you can redistribute it and/or
00008  * modify it under the terms of the GNU Lesser General Public
00009  * License as published by the Free Software Foundation; either
00010  * version 2.1 of the License, or (at your option) any later version.
00011  *
00012  * FFmpeg is distributed in the hope that it will be useful,
00013  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00014  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00015  * Lesser General Public License for more details.
00016  *
00017  * You should have received a copy of the GNU Lesser General Public
00018  * License along with FFmpeg; if not, write to the Free Software
00019  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
00020  */
00021 
00022 /*
00023  * First version by Francois Revol revol@free.fr
00024  *
00025  * Features and limitations:
00026  * - currently no compression is performed,
00027  *   in fact the size of the data is 9/8 the size of the image in 8bpp
00028  * - uses only a global standard palette
00029  * - tested with IE 5.0, Opera for BeOS, NetPositive (BeOS), and Mozilla (BeOS).
00030  *
00031  * Reference documents:
00032  * http://www.goice.co.jp/member/mo/formats/gif.html
00033  * http://astronomy.swin.edu.au/pbourke/dataformats/gif/
00034  * http://www.dcs.ed.ac.uk/home/mxr/gfx/2d/GIF89a.txt
00035  *
00036  * this url claims to have an LZW algorithm not covered by Unisys patent:
00037  * http://www.msg.net/utility/whirlgif/gifencod.html
00038  * could help reduce the size of the files _a lot_...
00039  * some sites mentions an RLE type compression also.
00040  */
00041 
00042 #include "avformat.h"
00043 #include "libavutil/log.h"
00044 #include "libavutil/opt.h"
00045 
00046 /* The GIF format uses reversed order for bitstreams... */
00047 /* at least they don't use PDP_ENDIAN :) */
00048 #define BITSTREAM_WRITER_LE
00049 
00050 #include "libavcodec/put_bits.h"
00051 
00052 /* bitstream minipacket size */
00053 #define GIF_CHUNKS 100
00054 
00055 /* slows down the decoding (and some browsers don't like it) */
00056 /* update on the 'some browsers don't like it issue from above:
00057  * this was probably due to missing 'Data Sub-block Terminator'
00058  * (byte 19) in the app_header */
00059 #define GIF_ADD_APP_HEADER // required to enable looping of animated gif
00060 
00061 typedef struct {
00062     unsigned char r;
00063     unsigned char g;
00064     unsigned char b;
00065 } rgb_triplet;
00066 
00067 /* we use the standard 216 color palette */
00068 
00069 /* this script was used to create the palette:
00070  * for r in 00 33 66 99 cc ff; do
00071  *     for g in 00 33 66 99 cc ff; do
00072  *         echo -n "    "
00073  *         for b in 00 33 66 99 cc ff; do
00074  *             echo -n "{ 0x$r, 0x$g, 0x$b }, "
00075  *         done
00076  *         echo ""
00077  *     done
00078  * done
00079  */
00080 
00081 static const rgb_triplet gif_clut[216] = {
00082     { 0x00, 0x00, 0x00 }, { 0x00, 0x00, 0x33 }, { 0x00, 0x00, 0x66 }, { 0x00, 0x00, 0x99 }, { 0x00, 0x00, 0xcc }, { 0x00, 0x00, 0xff },
00083     { 0x00, 0x33, 0x00 }, { 0x00, 0x33, 0x33 }, { 0x00, 0x33, 0x66 }, { 0x00, 0x33, 0x99 }, { 0x00, 0x33, 0xcc }, { 0x00, 0x33, 0xff },
00084     { 0x00, 0x66, 0x00 }, { 0x00, 0x66, 0x33 }, { 0x00, 0x66, 0x66 }, { 0x00, 0x66, 0x99 }, { 0x00, 0x66, 0xcc }, { 0x00, 0x66, 0xff },
00085     { 0x00, 0x99, 0x00 }, { 0x00, 0x99, 0x33 }, { 0x00, 0x99, 0x66 }, { 0x00, 0x99, 0x99 }, { 0x00, 0x99, 0xcc }, { 0x00, 0x99, 0xff },
00086     { 0x00, 0xcc, 0x00 }, { 0x00, 0xcc, 0x33 }, { 0x00, 0xcc, 0x66 }, { 0x00, 0xcc, 0x99 }, { 0x00, 0xcc, 0xcc }, { 0x00, 0xcc, 0xff },
00087     { 0x00, 0xff, 0x00 }, { 0x00, 0xff, 0x33 }, { 0x00, 0xff, 0x66 }, { 0x00, 0xff, 0x99 }, { 0x00, 0xff, 0xcc }, { 0x00, 0xff, 0xff },
00088     { 0x33, 0x00, 0x00 }, { 0x33, 0x00, 0x33 }, { 0x33, 0x00, 0x66 }, { 0x33, 0x00, 0x99 }, { 0x33, 0x00, 0xcc }, { 0x33, 0x00, 0xff },
00089     { 0x33, 0x33, 0x00 }, { 0x33, 0x33, 0x33 }, { 0x33, 0x33, 0x66 }, { 0x33, 0x33, 0x99 }, { 0x33, 0x33, 0xcc }, { 0x33, 0x33, 0xff },
00090     { 0x33, 0x66, 0x00 }, { 0x33, 0x66, 0x33 }, { 0x33, 0x66, 0x66 }, { 0x33, 0x66, 0x99 }, { 0x33, 0x66, 0xcc }, { 0x33, 0x66, 0xff },
00091     { 0x33, 0x99, 0x00 }, { 0x33, 0x99, 0x33 }, { 0x33, 0x99, 0x66 }, { 0x33, 0x99, 0x99 }, { 0x33, 0x99, 0xcc }, { 0x33, 0x99, 0xff },
00092     { 0x33, 0xcc, 0x00 }, { 0x33, 0xcc, 0x33 }, { 0x33, 0xcc, 0x66 }, { 0x33, 0xcc, 0x99 }, { 0x33, 0xcc, 0xcc }, { 0x33, 0xcc, 0xff },
00093     { 0x33, 0xff, 0x00 }, { 0x33, 0xff, 0x33 }, { 0x33, 0xff, 0x66 }, { 0x33, 0xff, 0x99 }, { 0x33, 0xff, 0xcc }, { 0x33, 0xff, 0xff },
00094     { 0x66, 0x00, 0x00 }, { 0x66, 0x00, 0x33 }, { 0x66, 0x00, 0x66 }, { 0x66, 0x00, 0x99 }, { 0x66, 0x00, 0xcc }, { 0x66, 0x00, 0xff },
00095     { 0x66, 0x33, 0x00 }, { 0x66, 0x33, 0x33 }, { 0x66, 0x33, 0x66 }, { 0x66, 0x33, 0x99 }, { 0x66, 0x33, 0xcc }, { 0x66, 0x33, 0xff },
00096     { 0x66, 0x66, 0x00 }, { 0x66, 0x66, 0x33 }, { 0x66, 0x66, 0x66 }, { 0x66, 0x66, 0x99 }, { 0x66, 0x66, 0xcc }, { 0x66, 0x66, 0xff },
00097     { 0x66, 0x99, 0x00 }, { 0x66, 0x99, 0x33 }, { 0x66, 0x99, 0x66 }, { 0x66, 0x99, 0x99 }, { 0x66, 0x99, 0xcc }, { 0x66, 0x99, 0xff },
00098     { 0x66, 0xcc, 0x00 }, { 0x66, 0xcc, 0x33 }, { 0x66, 0xcc, 0x66 }, { 0x66, 0xcc, 0x99 }, { 0x66, 0xcc, 0xcc }, { 0x66, 0xcc, 0xff },
00099     { 0x66, 0xff, 0x00 }, { 0x66, 0xff, 0x33 }, { 0x66, 0xff, 0x66 }, { 0x66, 0xff, 0x99 }, { 0x66, 0xff, 0xcc }, { 0x66, 0xff, 0xff },
00100     { 0x99, 0x00, 0x00 }, { 0x99, 0x00, 0x33 }, { 0x99, 0x00, 0x66 }, { 0x99, 0x00, 0x99 }, { 0x99, 0x00, 0xcc }, { 0x99, 0x00, 0xff },
00101     { 0x99, 0x33, 0x00 }, { 0x99, 0x33, 0x33 }, { 0x99, 0x33, 0x66 }, { 0x99, 0x33, 0x99 }, { 0x99, 0x33, 0xcc }, { 0x99, 0x33, 0xff },
00102     { 0x99, 0x66, 0x00 }, { 0x99, 0x66, 0x33 }, { 0x99, 0x66, 0x66 }, { 0x99, 0x66, 0x99 }, { 0x99, 0x66, 0xcc }, { 0x99, 0x66, 0xff },
00103     { 0x99, 0x99, 0x00 }, { 0x99, 0x99, 0x33 }, { 0x99, 0x99, 0x66 }, { 0x99, 0x99, 0x99 }, { 0x99, 0x99, 0xcc }, { 0x99, 0x99, 0xff },
00104     { 0x99, 0xcc, 0x00 }, { 0x99, 0xcc, 0x33 }, { 0x99, 0xcc, 0x66 }, { 0x99, 0xcc, 0x99 }, { 0x99, 0xcc, 0xcc }, { 0x99, 0xcc, 0xff },
00105     { 0x99, 0xff, 0x00 }, { 0x99, 0xff, 0x33 }, { 0x99, 0xff, 0x66 }, { 0x99, 0xff, 0x99 }, { 0x99, 0xff, 0xcc }, { 0x99, 0xff, 0xff },
00106     { 0xcc, 0x00, 0x00 }, { 0xcc, 0x00, 0x33 }, { 0xcc, 0x00, 0x66 }, { 0xcc, 0x00, 0x99 }, { 0xcc, 0x00, 0xcc }, { 0xcc, 0x00, 0xff },
00107     { 0xcc, 0x33, 0x00 }, { 0xcc, 0x33, 0x33 }, { 0xcc, 0x33, 0x66 }, { 0xcc, 0x33, 0x99 }, { 0xcc, 0x33, 0xcc }, { 0xcc, 0x33, 0xff },
00108     { 0xcc, 0x66, 0x00 }, { 0xcc, 0x66, 0x33 }, { 0xcc, 0x66, 0x66 }, { 0xcc, 0x66, 0x99 }, { 0xcc, 0x66, 0xcc }, { 0xcc, 0x66, 0xff },
00109     { 0xcc, 0x99, 0x00 }, { 0xcc, 0x99, 0x33 }, { 0xcc, 0x99, 0x66 }, { 0xcc, 0x99, 0x99 }, { 0xcc, 0x99, 0xcc }, { 0xcc, 0x99, 0xff },
00110     { 0xcc, 0xcc, 0x00 }, { 0xcc, 0xcc, 0x33 }, { 0xcc, 0xcc, 0x66 }, { 0xcc, 0xcc, 0x99 }, { 0xcc, 0xcc, 0xcc }, { 0xcc, 0xcc, 0xff },
00111     { 0xcc, 0xff, 0x00 }, { 0xcc, 0xff, 0x33 }, { 0xcc, 0xff, 0x66 }, { 0xcc, 0xff, 0x99 }, { 0xcc, 0xff, 0xcc }, { 0xcc, 0xff, 0xff },
00112     { 0xff, 0x00, 0x00 }, { 0xff, 0x00, 0x33 }, { 0xff, 0x00, 0x66 }, { 0xff, 0x00, 0x99 }, { 0xff, 0x00, 0xcc }, { 0xff, 0x00, 0xff },
00113     { 0xff, 0x33, 0x00 }, { 0xff, 0x33, 0x33 }, { 0xff, 0x33, 0x66 }, { 0xff, 0x33, 0x99 }, { 0xff, 0x33, 0xcc }, { 0xff, 0x33, 0xff },
00114     { 0xff, 0x66, 0x00 }, { 0xff, 0x66, 0x33 }, { 0xff, 0x66, 0x66 }, { 0xff, 0x66, 0x99 }, { 0xff, 0x66, 0xcc }, { 0xff, 0x66, 0xff },
00115     { 0xff, 0x99, 0x00 }, { 0xff, 0x99, 0x33 }, { 0xff, 0x99, 0x66 }, { 0xff, 0x99, 0x99 }, { 0xff, 0x99, 0xcc }, { 0xff, 0x99, 0xff },
00116     { 0xff, 0xcc, 0x00 }, { 0xff, 0xcc, 0x33 }, { 0xff, 0xcc, 0x66 }, { 0xff, 0xcc, 0x99 }, { 0xff, 0xcc, 0xcc }, { 0xff, 0xcc, 0xff },
00117     { 0xff, 0xff, 0x00 }, { 0xff, 0xff, 0x33 }, { 0xff, 0xff, 0x66 }, { 0xff, 0xff, 0x99 }, { 0xff, 0xff, 0xcc }, { 0xff, 0xff, 0xff },
00118 };
00119 
00120 /* GIF header */
00121 static int gif_image_write_header(AVIOContext *pb, int width, int height,
00122                                   int loop_count, uint32_t *palette)
00123 {
00124     int i;
00125     unsigned int v;
00126 
00127     avio_write(pb, "GIF", 3);
00128     avio_write(pb, "89a", 3);
00129     avio_wl16(pb, width);
00130     avio_wl16(pb, height);
00131 
00132     avio_w8(pb, 0xf7); /* flags: global clut, 256 entries */
00133     avio_w8(pb, 0x1f); /* background color index */
00134     avio_w8(pb, 0);    /* aspect ratio */
00135 
00136     /* the global palette */
00137     if (!palette) {
00138         avio_write(pb, (const unsigned char *)gif_clut, 216 * 3);
00139         for (i = 0; i < ((256 - 216) * 3); i++)
00140             avio_w8(pb, 0);
00141     } else {
00142         for (i = 0; i < 256; i++) {
00143             v = palette[i];
00144             avio_w8(pb, (v >> 16) & 0xff);
00145             avio_w8(pb, (v >>  8) & 0xff);
00146             avio_w8(pb, (v)       & 0xff);
00147         }
00148     }
00149 
00150     /* update: this is the 'NETSCAPE EXTENSION' that allows for looped animated
00151      * GIF, see http://members.aol.com/royalef/gifabout.htm#net-extension
00152      *
00153      * byte   1       : 33 (hex 0x21) GIF Extension code
00154      * byte   2       : 255 (hex 0xFF) Application Extension Label
00155      * byte   3       : 11 (hex (0x0B) Length of Application Block
00156      *                          (eleven bytes of data to follow)
00157      * bytes  4 to 11 : "NETSCAPE"
00158      * bytes 12 to 14 : "2.0"
00159      * byte  15       : 3 (hex 0x03) Length of Data Sub-Block
00160      *                          (three bytes of data to follow)
00161      * byte  16       : 1 (hex 0x01)
00162      * bytes 17 to 18 : 0 to 65535, an unsigned integer in
00163      *                          lo-hi byte format. This indicate the
00164      *                          number of iterations the loop should
00165      *                          be executed.
00166      * bytes 19       : 0 (hex 0x00) a Data Sub-block Terminator
00167      */
00168 
00169     /* application extension header */
00170 #ifdef GIF_ADD_APP_HEADER
00171     if (loop_count >= 0 && loop_count <= 65535) {
00172         avio_w8(pb, 0x21);
00173         avio_w8(pb, 0xff);
00174         avio_w8(pb, 0x0b);
00175         // bytes 4 to 14
00176         avio_write(pb, "NETSCAPE2.0", sizeof("NETSCAPE2.0") - 1);
00177         avio_w8(pb, 0x03); // byte 15
00178         avio_w8(pb, 0x01); // byte 16
00179         avio_wl16(pb, (uint16_t)loop_count);
00180         avio_w8(pb, 0x00); // byte 19
00181     }
00182 #endif
00183     return 0;
00184 }
00185 
00186 /* this is maybe slow, but allows for extensions */
00187 static inline unsigned char gif_clut_index(uint8_t r, uint8_t g, uint8_t b)
00188 {
00189     return (((r) / 47) % 6) * 6 * 6 + (((g) / 47) % 6) * 6 + (((b) / 47) % 6);
00190 }
00191 
00192 static int gif_image_write_image(AVIOContext *pb,
00193                                  int x1, int y1, int width, int height,
00194                                  const uint8_t *buf, int linesize, int pix_fmt)
00195 {
00196     PutBitContext p;
00197     uint8_t buffer[200]; /* 100 * 9 / 8 = 113 */
00198     int i, left, w, v;
00199     const uint8_t *ptr;
00200     /* image block */
00201 
00202     avio_w8(pb, 0x2c);
00203     avio_wl16(pb, x1);
00204     avio_wl16(pb, y1);
00205     avio_wl16(pb, width);
00206     avio_wl16(pb, height);
00207     avio_w8(pb, 0x00); /* flags */
00208     /* no local clut */
00209 
00210     avio_w8(pb, 0x08);
00211 
00212     left = width * height;
00213 
00214     init_put_bits(&p, buffer, 130);
00215 
00216 /*
00217  * the thing here is the bitstream is written as little packets, with a size
00218  * byte before but it's still the same bitstream between packets (no flush !)
00219  */
00220     ptr = buf;
00221     w   = width;
00222     while (left > 0) {
00223         put_bits(&p, 9, 0x0100); /* clear code */
00224 
00225         for (i = (left < GIF_CHUNKS) ? left : GIF_CHUNKS; i; i--) {
00226             if (pix_fmt == PIX_FMT_RGB24) {
00227                 v    = gif_clut_index(ptr[0], ptr[1], ptr[2]);
00228                 ptr += 3;
00229             } else {
00230                 v = *ptr++;
00231             }
00232             put_bits(&p, 9, v);
00233             if (--w == 0) {
00234                 w    = width;
00235                 buf += linesize;
00236                 ptr  = buf;
00237             }
00238         }
00239 
00240         if (left <= GIF_CHUNKS) {
00241             put_bits(&p, 9, 0x101); /* end of stream */
00242             flush_put_bits(&p);
00243         }
00244         if (put_bits_ptr(&p) - p.buf > 0) {
00245             avio_w8(pb, put_bits_ptr(&p) - p.buf); /* byte count of the packet */
00246             avio_write(pb, p.buf, put_bits_ptr(&p) - p.buf); /* the actual buffer */
00247             p.buf_ptr = p.buf; /* dequeue the bytes off the bitstream */
00248         }
00249         left -= GIF_CHUNKS;
00250     }
00251     avio_w8(pb, 0x00); /* end of image block */
00252 
00253     return 0;
00254 }
00255 
00256 typedef struct {
00257     AVClass *class;         
00258     int64_t time, file_time;
00259     uint8_t buffer[100]; /* data chunks */
00260     int loop;
00261 } GIFContext;
00262 
00263 static int gif_write_header(AVFormatContext *s)
00264 {
00265     GIFContext *gif = s->priv_data;
00266     AVIOContext *pb = s->pb;
00267     AVCodecContext *enc, *video_enc;
00268     int i, width, height /*, rate*/;
00269 
00270 /* XXX: do we reject audio streams or just ignore them ?
00271  *  if (s->nb_streams > 1)
00272  *      return -1;
00273  */
00274     gif->time      = 0;
00275     gif->file_time = 0;
00276 
00277     video_enc = NULL;
00278     for (i = 0; i < s->nb_streams; i++) {
00279         enc = s->streams[i]->codec;
00280         if (enc->codec_type != AVMEDIA_TYPE_AUDIO)
00281             video_enc = enc;
00282     }
00283 
00284     if (!video_enc) {
00285         av_free(gif);
00286         return -1;
00287     } else {
00288         width  = video_enc->width;
00289         height = video_enc->height;
00290 //        rate = video_enc->time_base.den;
00291     }
00292 
00293     if (video_enc->pix_fmt != PIX_FMT_RGB24) {
00294         av_log(s, AV_LOG_ERROR,
00295                "ERROR: gif only handles the rgb24 pixel format. Use -pix_fmt rgb24.\n");
00296         return AVERROR(EIO);
00297     }
00298 
00299     gif_image_write_header(pb, width, height, gif->loop, NULL);
00300 
00301     avio_flush(s->pb);
00302     return 0;
00303 }
00304 
00305 static int gif_write_video(AVFormatContext *s, AVCodecContext *enc,
00306                            const uint8_t *buf, int size)
00307 {
00308     AVIOContext *pb = s->pb;
00309     int jiffies;
00310 
00311     /* graphic control extension block */
00312     avio_w8(pb, 0x21);
00313     avio_w8(pb, 0xf9);
00314     avio_w8(pb, 0x04); /* block size */
00315     avio_w8(pb, 0x04); /* flags */
00316 
00317     /* 1 jiffy is 1/70 s */
00318     /* the delay_time field indicates the number of jiffies - 1 */
00319     /* XXX: should use delay, in order to be more accurate */
00320     /* instead of using the same rounded value each time */
00321     /* XXX: don't even remember if I really use it for now */
00322     jiffies = (70 * enc->time_base.num / enc->time_base.den) - 1;
00323 
00324     avio_wl16(pb, jiffies);
00325 
00326     avio_w8(pb, 0x1f); /* transparent color index */
00327     avio_w8(pb, 0x00);
00328 
00329     gif_image_write_image(pb, 0, 0, enc->width, enc->height,
00330                           buf, enc->width * 3, PIX_FMT_RGB24);
00331 
00332     avio_flush(s->pb);
00333     return 0;
00334 }
00335 
00336 static int gif_write_packet(AVFormatContext *s, AVPacket *pkt)
00337 {
00338     AVCodecContext *codec = s->streams[pkt->stream_index]->codec;
00339     if (codec->codec_type == AVMEDIA_TYPE_AUDIO)
00340         return 0; /* just ignore audio */
00341     else
00342         return gif_write_video(s, codec, pkt->data, pkt->size);
00343 }
00344 
00345 static int gif_write_trailer(AVFormatContext *s)
00346 {
00347     AVIOContext *pb = s->pb;
00348 
00349     avio_w8(pb, 0x3b);
00350 
00351     return 0;
00352 }
00353 
00354 #define OFFSET(x) offsetof(GIFContext, x)
00355 #define ENC AV_OPT_FLAG_ENCODING_PARAM
00356 static const AVOption options[] = {
00357     { "loop", "Number of times to loop the output.", OFFSET(loop),
00358       AV_OPT_TYPE_INT, { .i64 = 0 }, 0, 65535, ENC },
00359     { NULL },
00360 };
00361 
00362 static const AVClass gif_muxer_class = {
00363     .class_name = "GIF muxer",
00364     .item_name  = av_default_item_name,
00365     .version    = LIBAVUTIL_VERSION_INT,
00366     .option     = options,
00367 };
00368 
00369 AVOutputFormat ff_gif_muxer = {
00370     .name           = "gif",
00371     .long_name      = NULL_IF_CONFIG_SMALL("GIF Animation"),
00372     .mime_type      = "image/gif",
00373     .extensions     = "gif",
00374     .priv_data_size = sizeof(GIFContext),
00375     .audio_codec    = AV_CODEC_ID_NONE,
00376     .video_codec    = AV_CODEC_ID_RAWVIDEO,
00377     .write_header   = gif_write_header,
00378     .write_packet   = gif_write_packet,
00379     .write_trailer  = gif_write_trailer,
00380     .priv_class     = &gif_muxer_class,
00381 };