FFmpeg: libavformat/gif.c Source File

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 "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 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, const 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  const FFOutputFormat ff_gif_muxer = {
207  .p.name = "gif",
208  .p.long_name = NULL_IF_CONFIG_SMALL("CompuServe Graphics Interchange Format (GIF)"),
209  .p.mime_type = "image/gif",
210  .p.extensions = "gif",
211  .priv_data_size = sizeof(GIFContext),
212  .p.audio_codec = AV_CODEC_ID_NONE,
213  .p.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  .p.priv_class = &gif_muxer_class,
218  .p.flags = AVFMT_VARIABLE_FPS,
219 };
av_packet_unref
void av_packet_unref(AVPacket *pkt)
Wipe the packet.
Definition: avpacket.c:422
GIFContext::last_pos
int64_t last_pos
Definition: gif.c:38
AVOutputFormat::name
const char * name
Definition: avformat.h:508
AVERROR
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
gif_write_header
static int gif_write_header(AVFormatContext *s)
Definition: gif.c:43
opt.h
GetByteContext
Definition: bytestream.h:33
AVFMT_VARIABLE_FPS
#define AVFMT_VARIABLE_FPS
Format allows variable fps.
Definition: avformat.h:482
GIF_TRAILER
#define GIF_TRAILER
Definition: gif.h:42
gif_get_delay
static int gif_get_delay(GIFContext *gif, AVPacket *prev, AVPacket *new)
Definition: gif.c:85
AVPacket::data
uint8_t * data
Definition: packet.h:374
AVOption
AVOption.
Definition: opt.h:251
data
const char data[16]
Definition: mxf.c:146
GIF_GCE_EXT_LABEL
#define GIF_GCE_EXT_LABEL
Definition: gif.h:45
ENC
#define ENC
Definition: gif.c:190
av_packet_free
void av_packet_free(AVPacket **pkt)
Free the packet, if the packet is reference counted, it will be unreferenced first.
Definition: avpacket.c:73
GIFContext::loop
int loop
Definition: gif.c:35
FFOutputFormat::p
AVOutputFormat p
The public AVOutputFormat.
Definition: mux.h:34
avio_wl16
void avio_wl16(AVIOContext *s, unsigned int val)
Definition: aviobuf.c:458
bytestream2_skip
static av_always_inline void bytestream2_skip(GetByteContext *g, unsigned int size)
Definition: bytestream.h:168
avpriv_set_pts_info
void avpriv_set_pts_info(AVStream *st, int pts_wrap_bits, unsigned int pts_num, unsigned int pts_den)
Set the time base and wrapping info for a given stream.
Definition: avformat.c:771
ff_gif_muxer
const FFOutputFormat ff_gif_muxer
Definition: gif.c:206
avio_tell
static av_always_inline int64_t avio_tell(AVIOContext *s)
ftell() equivalent for AVIOContext.
Definition: avio.h:500
loop
static int loop
Definition: ffplay.c:340
GIFContext::prev_pkt
AVPacket * prev_pkt
Definition: gif.c:40
GIFContext::have_end
int have_end
Definition: gif.c:39
GIFContext::last_delay
int last_delay
Definition: gif.c:36
gif_muxer_class
static const AVClass gif_muxer_class
Definition: gif.c:199
pkt
AVPacket * pkt
Definition: movenc.c:59
AV_LOG_ERROR
#define AV_LOG_ERROR
Something went wrong and cannot losslessly be recovered.
Definition: log.h:180
GIFContext::duration
int duration
Definition: gif.c:37
s
#define s(width, name)
Definition: cbs_vp9.c:256
AVFormatContext
Format I/O context.
Definition: avformat.h:1104
internal.h
LIBAVUTIL_VERSION_INT
#define LIBAVUTIL_VERSION_INT
Definition: version.h:85
AVClass
Describe the class of an AVClass context structure.
Definition: log.h:66
NULL
#define NULL
Definition: coverity.c:32
av_default_item_name
const char * av_default_item_name(void *ptr)
Return the context name.
Definition: log.c:237
FFOutputFormat
Definition: mux.h:30
avio_w8
void avio_w8(AVIOContext *s, int b)
Definition: aviobuf.c:200
av_packet_ref
int av_packet_ref(AVPacket *dst, const AVPacket *src)
Setup a new reference to the data described by a given packet.
Definition: avpacket.c:430
bytestream2_get_bytes_left
static av_always_inline int bytestream2_get_bytes_left(GetByteContext *g)
Definition: bytestream.h:158
bytestream2_tell
static av_always_inline int bytestream2_tell(GetByteContext *g)
Definition: bytestream.h:192
AVIOContext
Bytestream IO Context.
Definition: avio.h:166
AVPacket::size
int size
Definition: packet.h:375
NULL_IF_CONFIG_SMALL
#define NULL_IF_CONFIG_SMALL(x)
Return NULL if CONFIG_SMALL is true, otherwise the argument without modification.
Definition: internal.h:115
gif.h
size
int size
Definition: twinvq_data.h:10344
AV_NOPTS_VALUE
#define AV_NOPTS_VALUE
Undefined timestamp value.
Definition: avutil.h:248
GIFContext
Definition: gif.c:43
gif_write_trailer
static int gif_write_trailer(AVFormatContext *s)
Definition: gif.c:172
avio_write
void avio_write(AVIOContext *s, const unsigned char *buf, int size)
Definition: aviobuf.c:222
av_packet_alloc
AVPacket * av_packet_alloc(void)
Allocate an AVPacket and set its fields to default values.
Definition: avpacket.c:62
AV_CODEC_ID_GIF
@ AV_CODEC_ID_GIF
Definition: codec_id.h:149
gif_parse_packet
static int gif_parse_packet(AVFormatContext *s, const uint8_t *data, int size)
Definition: gif.c:58
log.h
AV_CODEC_ID_NONE
@ AV_CODEC_ID_NONE
Definition: codec_id.h:50
AVPacket::pts
int64_t pts
Presentation timestamp in AVStream->time_base units; the time at which the decompressed packet will b...
Definition: packet.h:367
GIF_EXTENSION_INTRODUCER
#define GIF_EXTENSION_INTRODUCER
Definition: gif.h:43
options
static const AVOption options[]
Definition: gif.c:191
AVClass::class_name
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:71
avformat.h
AV_OPT_TYPE_INT
@ AV_OPT_TYPE_INT
Definition: opt.h:225
av_clip_uint16
#define av_clip_uint16
Definition: common.h:107
AVMEDIA_TYPE_VIDEO
@ AVMEDIA_TYPE_VIDEO
Definition: avutil.h:201
GIF_APP_EXT_LABEL
#define GIF_APP_EXT_LABEL
Definition: gif.h:47
gif_write_packet
static int gif_write_packet(AVFormatContext *s, AVPacket *new_pkt)
Definition: gif.c:95
AVPacket
This structure stores compressed data.
Definition: packet.h:351
bytestream.h
imgutils.h
bytestream2_init
static av_always_inline void bytestream2_init(GetByteContext *g, const uint8_t *buf, int buf_size)
Definition: bytestream.h:137
av_log
#define av_log(a,...)
Definition: tableprint_vlc.h:27
OFFSET
#define OFFSET(x)
Definition: gif.c:189
mux.h
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