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 "mux.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 av_cold int gif_init(AVFormatContext *s)
  44 {
  45     avpriv_set_pts_info(s->streams[0], 64, 1, 100);
  46
  47     return 0;
  48 }
  49
  50 static int gif_parse_packet(AVFormatContext *s, const uint8_t *data, int size)
  51 {
  52     GetByteContext gb;
  53     int x;
  54
  55     bytestream2_init(&gb, data, size);
  56
  57     while (bytestream2_get_bytes_left(&gb) > 0) {
  58         x = bytestream2_get_byte(&gb);
  59         if (x != GIF_EXTENSION_INTRODUCER)
  60             return 0;
  61
  62         x = bytestream2_get_byte(&gb);
  63         while (x != GIF_GCE_EXT_LABEL && bytestream2_get_bytes_left(&gb) > 0) {
  64             int block_size = bytestream2_get_byte(&gb);
  65             if (!block_size)
  66                 break;
  67             bytestream2_skip(&gb, block_size);
  68         }
  69
  70         if (x == GIF_GCE_EXT_LABEL)
  71             return bytestream2_tell(&gb) + 2;
  72     }
  73
  74     return 0;
  75 }
  76
  77 static int gif_get_delay(GIFContext *gif, AVPacket *prev, AVPacket *new)
  78 {
  79     if (new && new->pts != AV_NOPTS_VALUE)
  80         gif->duration = av_clip_uint16(new->pts - prev->pts);
  81     else if (!new && gif->last_delay >= 0)
  82         gif->duration = gif->last_delay;
  83     else if (prev->duration)
  84         gif->duration = prev->duration;
  85
  86     return gif->duration;
  87 }
  88
  89 static int gif_write_packet(AVFormatContext *s, AVPacket *new_pkt)
  90 {
  91     GIFContext *gif = s->priv_data;
  92     AVIOContext *pb = s->pb;
  93     AVPacket *pkt = gif->prev_pkt;
  94
  95     if (!gif->prev_pkt) {
  96         gif->prev_pkt = av_packet_alloc();
  97         if (!gif->prev_pkt)
  98             return AVERROR(ENOMEM);
  99         return av_packet_ref(gif->prev_pkt, new_pkt);
 100     }
 101
 102     gif->last_pos = avio_tell(pb);
 103     if (pkt->size > 0)
 104         gif->have_end = pkt->data[pkt->size - 1] == GIF_TRAILER;
 105
 106     if (!gif->last_pos) {
 107         int delay_pos;
 108         int off = 13;
 109
 110         if (pkt->size < 13)
 111             return AVERROR(EINVAL);
 112
 113         if (pkt->data[10] & 0x80)
 114             off += 3 * (1 << ((pkt->data[10] & 0x07) + 1));
 115
 116         if (pkt->size < off + 2)
 117             return AVERROR(EINVAL);
 118
 119         avio_write(pb, pkt->data, off);
 120
 121         if (pkt->data[off] == GIF_EXTENSION_INTRODUCER && pkt->data[off + 1] == 0xff)
 122             off += 19;
 123
 124         if (pkt->size <= off)
 125             return AVERROR(EINVAL);
 126
 127         /* "NETSCAPE EXTENSION" for looped animation GIF */
 128         if (gif->loop >= 0) {
 129             avio_w8(pb, GIF_EXTENSION_INTRODUCER); /* GIF Extension code */
 130             avio_w8(pb, GIF_APP_EXT_LABEL); /* Application Extension Label */
 131             avio_w8(pb, 0x0b); /* Length of Application Block */
 132             avio_write(pb, "NETSCAPE2.0", sizeof("NETSCAPE2.0") - 1);
 133             avio_w8(pb, 0x03); /* Length of Data Sub-Block */
 134             avio_w8(pb, 0x01);
 135             avio_wl16(pb, (uint16_t)gif->loop);
 136             avio_w8(pb, 0x00); /* Data Sub-block Terminator */
 137         }
 138
 139         delay_pos = gif_parse_packet(s, pkt->data + off, pkt->size - off);
 140         if (delay_pos > 0 && delay_pos < pkt->size - off - 2) {
 141             avio_write(pb, pkt->data + off, delay_pos);
 142             avio_wl16(pb, gif_get_delay(gif, pkt, new_pkt));
 143             avio_write(pb, pkt->data + off + delay_pos + 2, pkt->size - off - delay_pos - 2);
 144         } else {
 145             avio_write(pb, pkt->data + off, pkt->size - off);
 146         }
 147     } else {
 148         int delay_pos = gif_parse_packet(s, pkt->data, pkt->size);
 149
 150         if (delay_pos > 0 && delay_pos < pkt->size - 2) {
 151             avio_write(pb, pkt->data, delay_pos);
 152             avio_wl16(pb, gif_get_delay(gif, pkt, new_pkt));
 153             avio_write(pb, pkt->data + delay_pos + 2, pkt->size - delay_pos - 2);
 154         } else {
 155             avio_write(pb, pkt->data, pkt->size);
 156         }
 157     }
 158
 159     av_packet_unref(gif->prev_pkt);
 160     if (new_pkt)
 161         return av_packet_ref(gif->prev_pkt, new_pkt);
 162
 163     return 0;
 164 }
 165
 166 static int gif_write_trailer(AVFormatContext *s)
 167 {
 168     GIFContext *gif = s->priv_data;
 169     AVIOContext *pb = s->pb;
 170
 171     if (!gif->prev_pkt)
 172         return AVERROR(EINVAL);
 173
 174     gif_write_packet(s, NULL);
 175
 176     if (!gif->have_end)
 177         avio_w8(pb, GIF_TRAILER);
 178     av_packet_free(&gif->prev_pkt);
 179
 180     return 0;
 181 }
 182
 183 #define OFFSET(x) offsetof(GIFContext, x)
 184 #define ENC AV_OPT_FLAG_ENCODING_PARAM
 185 static const AVOption options[] = {
 186     { "loop", "Number of times to loop the output: -1 - no loop, 0 - infinite loop", OFFSET(loop),
 187       AV_OPT_TYPE_INT, { .i64 = 0 }, -1, 65535, ENC },
 188     { "final_delay", "Force delay (in centiseconds) after the last frame", OFFSET(last_delay),
 189       AV_OPT_TYPE_INT, { .i64 = -1 }, -1, 65535, ENC },
 190     { NULL },
 191 };
 192
 193 static const AVClass gif_muxer_class = {
 194     .class_name = "GIF muxer",
 195     .item_name  = av_default_item_name,
 196     .version    = LIBAVUTIL_VERSION_INT,
 197     .option     = options,
 198 };
 199
 200 const FFOutputFormat ff_gif_muxer = {
 201     .p.name         = "gif",
 202     .p.long_name    = NULL_IF_CONFIG_SMALL("CompuServe Graphics Interchange Format (GIF)"),
 203     .p.mime_type    = "image/gif",
 204     .p.extensions   = "gif",
 205     .priv_data_size = sizeof(GIFContext),
 206     .p.audio_codec  = AV_CODEC_ID_NONE,
 207     .p.video_codec  = AV_CODEC_ID_GIF,
 208     .p.subtitle_codec = AV_CODEC_ID_NONE,
 209     .flags_internal   = FF_OFMT_FLAG_MAX_ONE_OF_EACH |
 210                         FF_OFMT_FLAG_ONLY_DEFAULT_CODECS,
 211     .init             = gif_init,
 212     .write_packet   = gif_write_packet,
 213     .write_trailer  = gif_write_trailer,
 214     .p.priv_class   = &gif_muxer_class,
 215     .p.flags        = AVFMT_VARIABLE_FPS,
 216 };