FFmpeg
gif.c
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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;
37  int duration;
38  int64_t last_pos;
39  int have_end;
41 } GIFContext;
42 
44 {
45  if (s->nb_streams != 1 ||
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 
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 
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 
166  if (new_pkt)
167  return av_packet_ref(gif->prev_pkt, new_pkt);
168 
169  return 0;
170 }
171 
173 {
174  GIFContext *gif = s->priv_data;
175  AVIOContext *pb = s->pb;
176 
177  if (!gif->prev_pkt)
178  return AVERROR(EINVAL);
179 
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 
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,
217  .priv_class = &gif_muxer_class,
219 };
static void write_packet(OutputFile *of, AVPacket *pkt, OutputStream *ost, int unqueue)
Definition: ffmpeg.c:689
#define NULL
Definition: coverity.c:32
int64_t last_pos
Definition: gif.c:38
void avio_wl16(AVIOContext *s, unsigned int val)
Definition: aviobuf.c:469
Bytestream IO Context.
Definition: avio.h:161
AVOption.
Definition: opt.h:246
ptrdiff_t const GLvoid * data
Definition: opengl_enc.c:100
#define OFFSET(x)
Definition: gif.c:189
misc image utilities
#define LIBAVUTIL_VERSION_INT
Definition: version.h:85
void avpriv_set_pts_info(AVStream *s, int pts_wrap_bits, unsigned int pts_num, unsigned int pts_den)
Set the time base and wrapping info for a given stream.
Definition: utils.c:4882
enum AVCodecID codec_id
Specific type of the encoded data (the codec used).
Definition: avcodec.h:3953
int have_end
Definition: gif.c:39
int size
Definition: avcodec.h:1478
const char * av_default_item_name(void *ptr)
Return the context name.
Definition: log.c:191
#define GIF_GCE_EXT_LABEL
Definition: gif.h:45
static av_always_inline void bytestream2_init(GetByteContext *g, const uint8_t *buf, int buf_size)
Definition: bytestream.h:133
static int gif_write_header(AVFormatContext *s)
Definition: gif.c:43
static const AVClass gif_muxer_class
Definition: gif.c:199
#define ENC
Definition: gif.c:190
static AVPacket pkt
AVOutputFormat ff_gif_muxer
Definition: gif.c:206
Format I/O context.
Definition: avformat.h:1358
const char * class_name
The name of the class; usually it is the same name as the context structure type to which the AVClass...
Definition: log.h:72
void av_packet_free(AVPacket **pkt)
Free the packet, if the packet is reference counted, it will be unreferenced first.
Definition: avpacket.c:62
uint8_t
AVOptions.
AVStream ** streams
A list of all streams in the file.
Definition: avformat.h:1426
uint8_t * data
Definition: avcodec.h:1477
ptrdiff_t size
Definition: opengl_enc.c:100
static av_always_inline int64_t avio_tell(AVIOContext *s)
ftell() equivalent for AVIOContext.
Definition: avio.h:557
void avio_write(AVIOContext *s, const unsigned char *buf, int size)
Definition: aviobuf.c:218
int flags
Definition: gif.c:52
#define av_log(a,...)
int av_packet_ref(AVPacket *dst, const AVPacket *src)
Setup a new reference to the data described by a given packet.
Definition: avpacket.c:608
int loop
Definition: gif.c:35
#define AV_LOG_ERROR
Something went wrong and cannot losslessly be recovered.
Definition: log.h:176
static av_always_inline void bytestream2_skip(GetByteContext *g, unsigned int size)
Definition: bytestream.h:164
#define NULL_IF_CONFIG_SMALL(x)
Return NULL if CONFIG_SMALL is true, otherwise the argument without modification. ...
Definition: internal.h:186
Definition: gif.c:46
enum AVMediaType codec_type
General type of the encoded data.
Definition: avcodec.h:3949
static av_always_inline unsigned int bytestream2_get_bytes_left(GetByteContext *g)
Definition: bytestream.h:154
simple assert() macros that are a bit more flexible than ISO C assert().
AVPacket * prev_pkt
Definition: gif.c:40
unsigned int nb_streams
Number of elements in AVFormatContext.streams.
Definition: avformat.h:1414
static int write_trailer(AVFormatContext *s1)
Definition: v4l2enc.c:94
#define GIF_APP_EXT_LABEL
Definition: gif.h:47
const char * name
Definition: avformat.h:505
#define s(width, name)
Definition: cbs_vp9.c:257
int duration
Definition: gif.c:37
#define GIF_EXTENSION_INTRODUCER
Definition: gif.h:43
static av_always_inline int bytestream2_tell(GetByteContext *g)
Definition: bytestream.h:188
static int gif_write_trailer(AVFormatContext *s)
Definition: gif.c:172
AVIOContext * pb
I/O context.
Definition: avformat.h:1400
static int gif_get_delay(GIFContext *gif, AVPacket *prev, AVPacket *new)
Definition: gif.c:85
static const AVOption options[]
Definition: gif.c:191
void avio_w8(AVIOContext *s, int b)
Definition: aviobuf.c:196
GIF format definitions.
void av_packet_unref(AVPacket *pkt)
Wipe the packet.
Definition: avpacket.c:599
int last_delay
Definition: gif.c:36
Describe the class of an AVClass context structure.
Definition: log.h:67
static int gif_parse_packet(AVFormatContext *s, uint8_t *data, int size)
Definition: gif.c:58
#define GIF_TRAILER
Definition: gif.h:42
Main libavformat public API header.
#define AVFMT_VARIABLE_FPS
Format allows variable fps.
Definition: avformat.h:470
void * priv_data
Format private data.
Definition: avformat.h:1386
AVPacket * av_packet_alloc(void)
Allocate an AVPacket and set its fields to default values.
Definition: avpacket.c:51
static void write_header(FFV1Context *f)
Definition: ffv1enc.c:337
static int gif_write_packet(AVFormatContext *s, AVPacket *new_pkt)
Definition: gif.c:95
AVCodecParameters * codecpar
Codec parameters associated with this stream.
Definition: avformat.h:1028
Filter the word “frame” indicates either a video frame or a group of audio as stored in an AVFrame structure Format for each input and each output the list of supported formats For video that means pixel format For audio that means channel sample they are references to shared objects When the negotiation mechanism computes the intersection of the formats supported at each end of a all references to both lists are replaced with a reference to the intersection And when a single format is eventually chosen for a link amongst the remaining all references to the list are updated That means that if a filter requires that its input and output have the same format amongst a supported all it has to do is use a reference to the same list of formats query_formats can leave some formats unset and return AVERROR(EAGAIN) to cause the negotiation mechanism toagain later.That can be used by filters with complex requirements to use the format negotiated on one link to set the formats supported on another.Frame references ownership and permissions
This structure stores compressed data.
Definition: avcodec.h:1454
int64_t pts
Presentation timestamp in AVStream->time_base units; the time at which the decompressed packet will b...
Definition: avcodec.h:1470
#define AV_NOPTS_VALUE
Undefined timestamp value.
Definition: avutil.h:248