libavformat/gif.c

   1 /*
   2  * Animated GIF muxer
   3  * Copyright (c) 2000 Fabrice Bellard
   4  *
   5  * first version by Francois Revol <revol@free.fr>
   6  *
   7  * This file is part of FFmpeg.
   8  *
   9  * FFmpeg is free software; you can redistribute it and/or
  10  * modify it under the terms of the GNU Lesser General Public
  11  * License as published by the Free Software Foundation; either
  12  * version 2.1 of the License, or (at your option) any later version.
  13  *
  14  * FFmpeg is distributed in the hope that it will be useful,
  15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  17  * Lesser General Public License for more details.
  18  *
  19  * You should have received a copy of the GNU Lesser General Public
  20  * License along with FFmpeg; if not, write to the Free Software
  21  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  22  */
  23
  24 #include "avformat.h"
  25 #include "internal.h"
  26 #include "libavutil/avassert.h"
  27 #include "libavutil/imgutils.h"
  28 #include "libavutil/log.h"
  29 #include "libavutil/opt.h"
  30 #include "libavcodec/bytestream.h"
  31 #include "libavcodec/gif.h"
  32
  33 typedef struct GIFContext {
  34     AVClass *class;
  35     int loop;
  36     int last_delay;
  37     int duration;
  38     int64_t last_pos;
  39     int have_end;
  40     AVPacket *prev_pkt;
  41 } GIFContext;
  42
  43 static int gif_write_header(AVFormatContext *s)
  44 {
  45     if (s->nb_streams != 1 ||
  46         s->streams[0]->codecpar->codec_type != AVMEDIA_TYPE_VIDEO ||
  47         s->streams[0]->codecpar->codec_id   != AV_CODEC_ID_GIF) {
  48         av_log(s, AV_LOG_ERROR,
  49                "GIF muxer supports only a single video GIF stream.\n");
  50         return AVERROR(EINVAL);
  51     }
  52
  53     avpriv_set_pts_info(s->streams[0], 64, 1, 100);
  54
  55     return 0;
  56 }
  57
  58 static int gif_parse_packet(AVFormatContext *s, uint8_t *data, int size)
  59 {
  60     GetByteContext gb;
  61     int x;
  62
  63     bytestream2_init(&gb, data, size);
  64
  65     while (bytestream2_get_bytes_left(&gb) > 0) {
  66         x = bytestream2_get_byte(&gb);
  67         if (x != GIF_EXTENSION_INTRODUCER)
  68             return 0;
  69
  70         x = bytestream2_get_byte(&gb);
  71         while (x != GIF_GCE_EXT_LABEL && bytestream2_get_bytes_left(&gb) > 0) {
  72             int block_size = bytestream2_get_byte(&gb);
  73             if (!block_size)
  74                 break;
  75             bytestream2_skip(&gb, block_size);
  76         }
  77
  78         if (x == GIF_GCE_EXT_LABEL)
  79             return bytestream2_tell(&gb) + 2;
  80     }
  81
  82     return 0;
  83 }
  84
  85 static int gif_get_delay(GIFContext *gif, AVPacket *prev, AVPacket *new)
  86 {
  87     if (new && new->pts != AV_NOPTS_VALUE)
  88         gif->duration = av_clip_uint16(new->pts - prev->pts);
  89     else if (!new && gif->last_delay >= 0)
  90         gif->duration = gif->last_delay;
  91
  92     return gif->duration;
  93 }
  94
  95 static int gif_write_packet(AVFormatContext *s, AVPacket *new_pkt)
  96 {
  97     GIFContext *gif = s->priv_data;
  98     AVIOContext *pb = s->pb;
  99     AVPacket *pkt = gif->prev_pkt;
 100
 101     if (!gif->prev_pkt) {
 102         gif->prev_pkt = av_packet_alloc();
 103         if (!gif->prev_pkt)
 104             return AVERROR(ENOMEM);
 105         return av_packet_ref(gif->prev_pkt, new_pkt);
 106     }
 107
 108     gif->last_pos = avio_tell(pb);
 109     if (pkt->size > 0)
 110         gif->have_end = pkt->data[pkt->size - 1] == GIF_TRAILER;
 111
 112     if (!gif->last_pos) {
 113         int delay_pos;
 114         int off = 13;
 115
 116         if (pkt->size < 13)
 117             return AVERROR(EINVAL);
 118
 119         if (pkt->data[10] & 0x80)
 120             off += 3 * (1 << ((pkt->data[10] & 0x07) + 1));
 121
 122         if (pkt->size < off + 2)
 123             return AVERROR(EINVAL);
 124
 125         avio_write(pb, pkt->data, off);
 126
 127         if (pkt->data[off] == GIF_EXTENSION_INTRODUCER && pkt->data[off + 1] == 0xff)
 128             off += 19;
 129
 130         if (pkt->size <= off)
 131             return AVERROR(EINVAL);
 132
 133         /* "NETSCAPE EXTENSION" for looped animation GIF */
 134         if (gif->loop >= 0) {
 135             avio_w8(pb, GIF_EXTENSION_INTRODUCER); /* GIF Extension code */
 136             avio_w8(pb, GIF_APP_EXT_LABEL); /* Application Extension Label */
 137             avio_w8(pb, 0x0b); /* Length of Application Block */
 138             avio_write(pb, "NETSCAPE2.0", sizeof("NETSCAPE2.0") - 1);
 139             avio_w8(pb, 0x03); /* Length of Data Sub-Block */
 140             avio_w8(pb, 0x01);
 141             avio_wl16(pb, (uint16_t)gif->loop);
 142             avio_w8(pb, 0x00); /* Data Sub-block Terminator */
 143         }
 144
 145         delay_pos = gif_parse_packet(s, pkt->data + off, pkt->size - off);
 146         if (delay_pos > 0 && delay_pos < pkt->size - off - 2) {
 147             avio_write(pb, pkt->data + off, delay_pos);
 148             avio_wl16(pb, gif_get_delay(gif, pkt, new_pkt));
 149             avio_write(pb, pkt->data + off + delay_pos + 2, pkt->size - off - delay_pos - 2);
 150         } else {
 151             avio_write(pb, pkt->data + off, pkt->size - off);
 152         }
 153     } else {
 154         int delay_pos = gif_parse_packet(s, pkt->data, pkt->size);
 155
 156         if (delay_pos > 0 && delay_pos < pkt->size - 2) {
 157             avio_write(pb, pkt->data, delay_pos);
 158             avio_wl16(pb, gif_get_delay(gif, pkt, new_pkt));
 159             avio_write(pb, pkt->data + delay_pos + 2, pkt->size - delay_pos - 2);
 160         } else {
 161             avio_write(pb, pkt->data, pkt->size);
 162         }
 163     }
 164
 165     av_packet_unref(gif->prev_pkt);
 166     if (new_pkt)
 167         return av_packet_ref(gif->prev_pkt, new_pkt);
 168
 169     return 0;
 170 }
 171
 172 static int gif_write_trailer(AVFormatContext *s)
 173 {
 174     GIFContext *gif = s->priv_data;
 175     AVIOContext *pb = s->pb;
 176
 177     if (!gif->prev_pkt)
 178         return AVERROR(EINVAL);
 179
 180     gif_write_packet(s, NULL);
 181
 182     if (!gif->have_end)
 183         avio_w8(pb, GIF_TRAILER);
 184     av_packet_free(&gif->prev_pkt);
 185
 186     return 0;
 187 }
 188
 189 #define OFFSET(x) offsetof(GIFContext, x)
 190 #define ENC AV_OPT_FLAG_ENCODING_PARAM
 191 static const AVOption options[] = {
 192     { "loop", "Number of times to loop the output: -1 - no loop, 0 - infinite loop", OFFSET(loop),
 193       AV_OPT_TYPE_INT, { .i64 = 0 }, -1, 65535, ENC },
 194     { "final_delay", "Force delay (in centiseconds) after the last frame", OFFSET(last_delay),
 195       AV_OPT_TYPE_INT, { .i64 = -1 }, -1, 65535, ENC },
 196     { NULL },
 197 };
 198
 199 static const AVClass gif_muxer_class = {
 200     .class_name = "GIF muxer",
 201     .item_name  = av_default_item_name,
 202     .version    = LIBAVUTIL_VERSION_INT,
 203     .option     = options,
 204 };
 205
 206 AVOutputFormat ff_gif_muxer = {
 207     .name           = "gif",
 208     .long_name      = NULL_IF_CONFIG_SMALL("CompuServe Graphics Interchange Format (GIF)"),
 209     .mime_type      = "image/gif",
 210     .extensions     = "gif",
 211     .priv_data_size = sizeof(GIFContext),
 212     .audio_codec    = AV_CODEC_ID_NONE,
 213     .video_codec    = AV_CODEC_ID_GIF,
 214     .write_header   = gif_write_header,
 215     .write_packet   = gif_write_packet,
 216     .write_trailer  = gif_write_trailer,
 217     .priv_class     = &gif_muxer_class,
 218     .flags          = AVFMT_VARIABLE_FPS,
 219 };