gif.c
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1 /*
2  * Animated GIF muxer
3  * Copyright (c) 2000 Fabrice Bellard
4  *
5  * This file is part of Libav.
6  *
7  * Libav is free software; you can redistribute it and/or
8  * modify it under the terms of the GNU Lesser General Public
9  * License as published by the Free Software Foundation; either
10  * version 2.1 of the License, or (at your option) any later version.
11  *
12  * Libav is distributed in the hope that it will be useful,
13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15  * Lesser General Public License for more details.
16  *
17  * You should have received a copy of the GNU Lesser General Public
18  * License along with Libav; if not, write to the Free Software
19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20  */
21 
22 /*
23  * First version by Francois Revol revol@free.fr
24  *
25  * Features and limitations:
26  * - currently no compression is performed,
27  * in fact the size of the data is 9/8 the size of the image in 8bpp
28  * - uses only a global standard palette
29  * - tested with IE 5.0, Opera for BeOS, NetPositive (BeOS), and Mozilla (BeOS).
30  *
31  * Reference documents:
32  * http://www.goice.co.jp/member/mo/formats/gif.html
33  * http://astronomy.swin.edu.au/pbourke/dataformats/gif/
34  * http://www.dcs.ed.ac.uk/home/mxr/gfx/2d/GIF89a.txt
35  *
36  * this url claims to have an LZW algorithm not covered by Unisys patent:
37  * http://www.msg.net/utility/whirlgif/gifencod.html
38  * could help reduce the size of the files _a lot_...
39  * some sites mentions an RLE type compression also.
40  */
41 
42 #include "avformat.h"
43 #include "libavutil/log.h"
44 #include "libavutil/opt.h"
45 
46 /* The GIF format uses reversed order for bitstreams... */
47 /* at least they don't use PDP_ENDIAN :) */
48 #define BITSTREAM_WRITER_LE
49 
50 #include "libavcodec/put_bits.h"
51 
52 /* bitstream minipacket size */
53 #define GIF_CHUNKS 100
54 
55 /* slows down the decoding (and some browsers don't like it) */
56 /* update on the 'some browsers don't like it issue from above: this was probably due to missing 'Data Sub-block Terminator' (byte 19) in the app_header */
57 #define GIF_ADD_APP_HEADER // required to enable looping of animated gif
58 
59 typedef struct {
60  unsigned char r;
61  unsigned char g;
62  unsigned char b;
63 } rgb_triplet;
64 
65 /* we use the standard 216 color palette */
66 
67 /* this script was used to create the palette:
68  * for r in 00 33 66 99 cc ff; do for g in 00 33 66 99 cc ff; do echo -n " "; for b in 00 33 66 99 cc ff; do
69  * echo -n "{ 0x$r, 0x$g, 0x$b }, "; done; echo ""; done; done
70  */
71 
72 static const rgb_triplet gif_clut[216] = {
73  { 0x00, 0x00, 0x00 }, { 0x00, 0x00, 0x33 }, { 0x00, 0x00, 0x66 }, { 0x00, 0x00, 0x99 }, { 0x00, 0x00, 0xcc }, { 0x00, 0x00, 0xff },
74  { 0x00, 0x33, 0x00 }, { 0x00, 0x33, 0x33 }, { 0x00, 0x33, 0x66 }, { 0x00, 0x33, 0x99 }, { 0x00, 0x33, 0xcc }, { 0x00, 0x33, 0xff },
75  { 0x00, 0x66, 0x00 }, { 0x00, 0x66, 0x33 }, { 0x00, 0x66, 0x66 }, { 0x00, 0x66, 0x99 }, { 0x00, 0x66, 0xcc }, { 0x00, 0x66, 0xff },
76  { 0x00, 0x99, 0x00 }, { 0x00, 0x99, 0x33 }, { 0x00, 0x99, 0x66 }, { 0x00, 0x99, 0x99 }, { 0x00, 0x99, 0xcc }, { 0x00, 0x99, 0xff },
77  { 0x00, 0xcc, 0x00 }, { 0x00, 0xcc, 0x33 }, { 0x00, 0xcc, 0x66 }, { 0x00, 0xcc, 0x99 }, { 0x00, 0xcc, 0xcc }, { 0x00, 0xcc, 0xff },
78  { 0x00, 0xff, 0x00 }, { 0x00, 0xff, 0x33 }, { 0x00, 0xff, 0x66 }, { 0x00, 0xff, 0x99 }, { 0x00, 0xff, 0xcc }, { 0x00, 0xff, 0xff },
79  { 0x33, 0x00, 0x00 }, { 0x33, 0x00, 0x33 }, { 0x33, 0x00, 0x66 }, { 0x33, 0x00, 0x99 }, { 0x33, 0x00, 0xcc }, { 0x33, 0x00, 0xff },
80  { 0x33, 0x33, 0x00 }, { 0x33, 0x33, 0x33 }, { 0x33, 0x33, 0x66 }, { 0x33, 0x33, 0x99 }, { 0x33, 0x33, 0xcc }, { 0x33, 0x33, 0xff },
81  { 0x33, 0x66, 0x00 }, { 0x33, 0x66, 0x33 }, { 0x33, 0x66, 0x66 }, { 0x33, 0x66, 0x99 }, { 0x33, 0x66, 0xcc }, { 0x33, 0x66, 0xff },
82  { 0x33, 0x99, 0x00 }, { 0x33, 0x99, 0x33 }, { 0x33, 0x99, 0x66 }, { 0x33, 0x99, 0x99 }, { 0x33, 0x99, 0xcc }, { 0x33, 0x99, 0xff },
83  { 0x33, 0xcc, 0x00 }, { 0x33, 0xcc, 0x33 }, { 0x33, 0xcc, 0x66 }, { 0x33, 0xcc, 0x99 }, { 0x33, 0xcc, 0xcc }, { 0x33, 0xcc, 0xff },
84  { 0x33, 0xff, 0x00 }, { 0x33, 0xff, 0x33 }, { 0x33, 0xff, 0x66 }, { 0x33, 0xff, 0x99 }, { 0x33, 0xff, 0xcc }, { 0x33, 0xff, 0xff },
85  { 0x66, 0x00, 0x00 }, { 0x66, 0x00, 0x33 }, { 0x66, 0x00, 0x66 }, { 0x66, 0x00, 0x99 }, { 0x66, 0x00, 0xcc }, { 0x66, 0x00, 0xff },
86  { 0x66, 0x33, 0x00 }, { 0x66, 0x33, 0x33 }, { 0x66, 0x33, 0x66 }, { 0x66, 0x33, 0x99 }, { 0x66, 0x33, 0xcc }, { 0x66, 0x33, 0xff },
87  { 0x66, 0x66, 0x00 }, { 0x66, 0x66, 0x33 }, { 0x66, 0x66, 0x66 }, { 0x66, 0x66, 0x99 }, { 0x66, 0x66, 0xcc }, { 0x66, 0x66, 0xff },
88  { 0x66, 0x99, 0x00 }, { 0x66, 0x99, 0x33 }, { 0x66, 0x99, 0x66 }, { 0x66, 0x99, 0x99 }, { 0x66, 0x99, 0xcc }, { 0x66, 0x99, 0xff },
89  { 0x66, 0xcc, 0x00 }, { 0x66, 0xcc, 0x33 }, { 0x66, 0xcc, 0x66 }, { 0x66, 0xcc, 0x99 }, { 0x66, 0xcc, 0xcc }, { 0x66, 0xcc, 0xff },
90  { 0x66, 0xff, 0x00 }, { 0x66, 0xff, 0x33 }, { 0x66, 0xff, 0x66 }, { 0x66, 0xff, 0x99 }, { 0x66, 0xff, 0xcc }, { 0x66, 0xff, 0xff },
91  { 0x99, 0x00, 0x00 }, { 0x99, 0x00, 0x33 }, { 0x99, 0x00, 0x66 }, { 0x99, 0x00, 0x99 }, { 0x99, 0x00, 0xcc }, { 0x99, 0x00, 0xff },
92  { 0x99, 0x33, 0x00 }, { 0x99, 0x33, 0x33 }, { 0x99, 0x33, 0x66 }, { 0x99, 0x33, 0x99 }, { 0x99, 0x33, 0xcc }, { 0x99, 0x33, 0xff },
93  { 0x99, 0x66, 0x00 }, { 0x99, 0x66, 0x33 }, { 0x99, 0x66, 0x66 }, { 0x99, 0x66, 0x99 }, { 0x99, 0x66, 0xcc }, { 0x99, 0x66, 0xff },
94  { 0x99, 0x99, 0x00 }, { 0x99, 0x99, 0x33 }, { 0x99, 0x99, 0x66 }, { 0x99, 0x99, 0x99 }, { 0x99, 0x99, 0xcc }, { 0x99, 0x99, 0xff },
95  { 0x99, 0xcc, 0x00 }, { 0x99, 0xcc, 0x33 }, { 0x99, 0xcc, 0x66 }, { 0x99, 0xcc, 0x99 }, { 0x99, 0xcc, 0xcc }, { 0x99, 0xcc, 0xff },
96  { 0x99, 0xff, 0x00 }, { 0x99, 0xff, 0x33 }, { 0x99, 0xff, 0x66 }, { 0x99, 0xff, 0x99 }, { 0x99, 0xff, 0xcc }, { 0x99, 0xff, 0xff },
97  { 0xcc, 0x00, 0x00 }, { 0xcc, 0x00, 0x33 }, { 0xcc, 0x00, 0x66 }, { 0xcc, 0x00, 0x99 }, { 0xcc, 0x00, 0xcc }, { 0xcc, 0x00, 0xff },
98  { 0xcc, 0x33, 0x00 }, { 0xcc, 0x33, 0x33 }, { 0xcc, 0x33, 0x66 }, { 0xcc, 0x33, 0x99 }, { 0xcc, 0x33, 0xcc }, { 0xcc, 0x33, 0xff },
99  { 0xcc, 0x66, 0x00 }, { 0xcc, 0x66, 0x33 }, { 0xcc, 0x66, 0x66 }, { 0xcc, 0x66, 0x99 }, { 0xcc, 0x66, 0xcc }, { 0xcc, 0x66, 0xff },
100  { 0xcc, 0x99, 0x00 }, { 0xcc, 0x99, 0x33 }, { 0xcc, 0x99, 0x66 }, { 0xcc, 0x99, 0x99 }, { 0xcc, 0x99, 0xcc }, { 0xcc, 0x99, 0xff },
101  { 0xcc, 0xcc, 0x00 }, { 0xcc, 0xcc, 0x33 }, { 0xcc, 0xcc, 0x66 }, { 0xcc, 0xcc, 0x99 }, { 0xcc, 0xcc, 0xcc }, { 0xcc, 0xcc, 0xff },
102  { 0xcc, 0xff, 0x00 }, { 0xcc, 0xff, 0x33 }, { 0xcc, 0xff, 0x66 }, { 0xcc, 0xff, 0x99 }, { 0xcc, 0xff, 0xcc }, { 0xcc, 0xff, 0xff },
103  { 0xff, 0x00, 0x00 }, { 0xff, 0x00, 0x33 }, { 0xff, 0x00, 0x66 }, { 0xff, 0x00, 0x99 }, { 0xff, 0x00, 0xcc }, { 0xff, 0x00, 0xff },
104  { 0xff, 0x33, 0x00 }, { 0xff, 0x33, 0x33 }, { 0xff, 0x33, 0x66 }, { 0xff, 0x33, 0x99 }, { 0xff, 0x33, 0xcc }, { 0xff, 0x33, 0xff },
105  { 0xff, 0x66, 0x00 }, { 0xff, 0x66, 0x33 }, { 0xff, 0x66, 0x66 }, { 0xff, 0x66, 0x99 }, { 0xff, 0x66, 0xcc }, { 0xff, 0x66, 0xff },
106  { 0xff, 0x99, 0x00 }, { 0xff, 0x99, 0x33 }, { 0xff, 0x99, 0x66 }, { 0xff, 0x99, 0x99 }, { 0xff, 0x99, 0xcc }, { 0xff, 0x99, 0xff },
107  { 0xff, 0xcc, 0x00 }, { 0xff, 0xcc, 0x33 }, { 0xff, 0xcc, 0x66 }, { 0xff, 0xcc, 0x99 }, { 0xff, 0xcc, 0xcc }, { 0xff, 0xcc, 0xff },
108  { 0xff, 0xff, 0x00 }, { 0xff, 0xff, 0x33 }, { 0xff, 0xff, 0x66 }, { 0xff, 0xff, 0x99 }, { 0xff, 0xff, 0xcc }, { 0xff, 0xff, 0xff },
109 };
110 
111 /* GIF header */
113  int width, int height, int loop_count,
114  uint32_t *palette)
115 {
116  int i;
117  unsigned int v;
118 
119  avio_write(pb, "GIF", 3);
120  avio_write(pb, "89a", 3);
121  avio_wl16(pb, width);
122  avio_wl16(pb, height);
123 
124  avio_w8(pb, 0xf7); /* flags: global clut, 256 entries */
125  avio_w8(pb, 0x1f); /* background color index */
126  avio_w8(pb, 0); /* aspect ratio */
127 
128  /* the global palette */
129  if (!palette) {
130  avio_write(pb, (const unsigned char *)gif_clut, 216*3);
131  for(i=0;i<((256-216)*3);i++)
132  avio_w8(pb, 0);
133  } else {
134  for(i=0;i<256;i++) {
135  v = palette[i];
136  avio_w8(pb, (v >> 16) & 0xff);
137  avio_w8(pb, (v >> 8) & 0xff);
138  avio_w8(pb, (v) & 0xff);
139  }
140  }
141 
142  /* update: this is the 'NETSCAPE EXTENSION' that allows for looped animated gif
143  see http://members.aol.com/royalef/gifabout.htm#net-extension
144 
145  byte 1 : 33 (hex 0x21) GIF Extension code
146  byte 2 : 255 (hex 0xFF) Application Extension Label
147  byte 3 : 11 (hex (0x0B) Length of Application Block
148  (eleven bytes of data to follow)
149  bytes 4 to 11 : "NETSCAPE"
150  bytes 12 to 14 : "2.0"
151  byte 15 : 3 (hex 0x03) Length of Data Sub-Block
152  (three bytes of data to follow)
153  byte 16 : 1 (hex 0x01)
154  bytes 17 to 18 : 0 to 65535, an unsigned integer in
155  lo-hi byte format. This indicate the
156  number of iterations the loop should
157  be executed.
158  bytes 19 : 0 (hex 0x00) a Data Sub-block Terminator
159  */
160 
161  /* application extension header */
162 #ifdef GIF_ADD_APP_HEADER
163  if (loop_count >= 0 && loop_count <= 65535) {
164  avio_w8(pb, 0x21);
165  avio_w8(pb, 0xff);
166  avio_w8(pb, 0x0b);
167  avio_write(pb, "NETSCAPE2.0", sizeof("NETSCAPE2.0") - 1); // bytes 4 to 14
168  avio_w8(pb, 0x03); // byte 15
169  avio_w8(pb, 0x01); // byte 16
170  avio_wl16(pb, (uint16_t)loop_count);
171  avio_w8(pb, 0x00); // byte 19
172  }
173 #endif
174  return 0;
175 }
176 
177 /* this is maybe slow, but allows for extensions */
178 static inline unsigned char gif_clut_index(uint8_t r, uint8_t g, uint8_t b)
179 {
180  return (((r) / 47) % 6) * 6 * 6 + (((g) / 47) % 6) * 6 + (((b) / 47) % 6);
181 }
182 
183 
185  int x1, int y1, int width, int height,
186  const uint8_t *buf, int linesize, int pix_fmt)
187 {
188  PutBitContext p;
189  uint8_t buffer[200]; /* 100 * 9 / 8 = 113 */
190  int i, left, w, v;
191  const uint8_t *ptr;
192  /* image block */
193 
194  avio_w8(pb, 0x2c);
195  avio_wl16(pb, x1);
196  avio_wl16(pb, y1);
197  avio_wl16(pb, width);
198  avio_wl16(pb, height);
199  avio_w8(pb, 0x00); /* flags */
200  /* no local clut */
201 
202  avio_w8(pb, 0x08);
203 
204  left= width * height;
205 
206  init_put_bits(&p, buffer, 130);
207 
208 /*
209  * the thing here is the bitstream is written as little packets, with a size byte before
210  * but it's still the same bitstream between packets (no flush !)
211  */
212  ptr = buf;
213  w = width;
214  while(left>0) {
215 
216  put_bits(&p, 9, 0x0100); /* clear code */
217 
218  for(i=(left<GIF_CHUNKS)?left:GIF_CHUNKS;i;i--) {
219  if (pix_fmt == PIX_FMT_RGB24) {
220  v = gif_clut_index(ptr[0], ptr[1], ptr[2]);
221  ptr+=3;
222  } else {
223  v = *ptr++;
224  }
225  put_bits(&p, 9, v);
226  if (--w == 0) {
227  w = width;
228  buf += linesize;
229  ptr = buf;
230  }
231  }
232 
233  if(left<=GIF_CHUNKS) {
234  put_bits(&p, 9, 0x101); /* end of stream */
235  flush_put_bits(&p);
236  }
237  if(put_bits_ptr(&p) - p.buf > 0) {
238  avio_w8(pb, put_bits_ptr(&p) - p.buf); /* byte count of the packet */
239  avio_write(pb, p.buf, put_bits_ptr(&p) - p.buf); /* the actual buffer */
240  p.buf_ptr = p.buf; /* dequeue the bytes off the bitstream */
241  }
242  left-=GIF_CHUNKS;
243  }
244  avio_w8(pb, 0x00); /* end of image block */
245 
246  return 0;
247 }
248 
249 typedef struct {
250  AVClass *class;
251  int64_t time, file_time;
252  uint8_t buffer[100]; /* data chunks */
253  int loop;
254 } GIFContext;
255 
257 {
258  GIFContext *gif = s->priv_data;
259  AVIOContext *pb = s->pb;
260  AVCodecContext *enc, *video_enc;
261  int i, width, height /*, rate*/;
262 
263 /* XXX: do we reject audio streams or just ignore them ?
264  if(s->nb_streams > 1)
265  return -1;
266 */
267  gif->time = 0;
268  gif->file_time = 0;
269 
270  video_enc = NULL;
271  for(i=0;i<s->nb_streams;i++) {
272  enc = s->streams[i]->codec;
273  if (enc->codec_type != AVMEDIA_TYPE_AUDIO)
274  video_enc = enc;
275  }
276 
277  if (!video_enc) {
278  av_free(gif);
279  return -1;
280  } else {
281  width = video_enc->width;
282  height = video_enc->height;
283 // rate = video_enc->time_base.den;
284  }
285 
286  if (video_enc->pix_fmt != PIX_FMT_RGB24) {
287  av_log(s, AV_LOG_ERROR, "ERROR: gif only handles the rgb24 pixel format. Use -pix_fmt rgb24.\n");
288  return AVERROR(EIO);
289  }
290 
291 #if FF_API_LOOP_OUTPUT
292  if (s->loop_output)
293  gif->loop = s->loop_output;
294 #endif
295 
296  gif_image_write_header(pb, width, height, gif->loop, NULL);
297 
298  avio_flush(s->pb);
299  return 0;
300 }
301 
303  AVCodecContext *enc, const uint8_t *buf, int size)
304 {
305  AVIOContext *pb = s->pb;
306  int jiffies;
307 
308  /* graphic control extension block */
309  avio_w8(pb, 0x21);
310  avio_w8(pb, 0xf9);
311  avio_w8(pb, 0x04); /* block size */
312  avio_w8(pb, 0x04); /* flags */
313 
314  /* 1 jiffy is 1/70 s */
315  /* the delay_time field indicates the number of jiffies - 1 */
316  /* XXX: should use delay, in order to be more accurate */
317  /* instead of using the same rounded value each time */
318  /* XXX: don't even remember if I really use it for now */
319  jiffies = (70*enc->time_base.num/enc->time_base.den) - 1;
320 
321  avio_wl16(pb, jiffies);
322 
323  avio_w8(pb, 0x1f); /* transparent color index */
324  avio_w8(pb, 0x00);
325 
326  gif_image_write_image(pb, 0, 0, enc->width, enc->height,
327  buf, enc->width * 3, PIX_FMT_RGB24);
328 
329  avio_flush(s->pb);
330  return 0;
331 }
332 
334 {
335  AVCodecContext *codec = s->streams[pkt->stream_index]->codec;
336  if (codec->codec_type == AVMEDIA_TYPE_AUDIO)
337  return 0; /* just ignore audio */
338  else
339  return gif_write_video(s, codec, pkt->data, pkt->size);
340 }
341 
343 {
344  AVIOContext *pb = s->pb;
345 
346  avio_w8(pb, 0x3b);
347  avio_flush(s->pb);
348  return 0;
349 }
350 
351 #define OFFSET(x) offsetof(GIFContext, x)
352 #define ENC AV_OPT_FLAG_ENCODING_PARAM
353 static const AVOption options[] = {
354  { "loop", "Number of times to loop the output.", OFFSET(loop), AV_OPT_TYPE_INT, {0}, 0, 65535, ENC },
355  { NULL },
356 };
357 
358 static const AVClass gif_muxer_class = {
359  .class_name = "GIF muxer",
360  .item_name = av_default_item_name,
361  .version = LIBAVUTIL_VERSION_INT,
362  .option = options,
363 };
364 
366  .name = "gif",
367  .long_name = NULL_IF_CONFIG_SMALL("GIF Animation"),
368  .mime_type = "image/gif",
369  .extensions = "gif",
370  .priv_data_size = sizeof(GIFContext),
371  .audio_codec = CODEC_ID_NONE,
372  .video_codec = CODEC_ID_RAWVIDEO,
376  .priv_class = &gif_muxer_class,
377 };