3 * Copyright (c) 2000 Fabrice Bellard.
5 * This library is free software; you can redistribute it and/or
6 * modify it under the terms of the GNU Lesser General Public
7 * License as published by the Free Software Foundation; either
8 * version 2 of the License, or (at your option) any later version.
10 * This library is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 * Lesser General Public License for more details.
15 * You should have received a copy of the GNU Lesser General Public
16 * License along with this library; if not, write to the Free Software
17 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
21 * First version by Francois Revol revol@free.fr
23 * Features and limitations:
24 * - currently no compression is performed,
25 * in fact the size of the data is 9/8 the size of the image in 8bpp
26 * - uses only a global standard palette
27 * - tested with IE 5.0, Opera for BeOS, NetPositive (BeOS), and Mozilla (BeOS).
29 * Reference documents:
30 * http://www.goice.co.jp/member/mo/formats/gif.html
31 * http://astronomy.swin.edu.au/pbourke/dataformats/gif/
32 * http://www.dcs.ed.ac.uk/home/mxr/gfx/2d/GIF89a.txt
34 * this url claims to have an LZW algorithm not covered by Unisys patent:
35 * http://www.msg.net/utility/whirlgif/gifencod.html
36 * could help reduce the size of the files _a lot_...
37 * some sites mentions an RLE type compression also.
41 #include "bitstream.h"
43 /* bitstream minipacket size */
44 #define GIF_CHUNKS 100
46 /* slows down the decoding (and some browsers don't like it) */
47 /* 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 */
48 #define GIF_ADD_APP_HEADER // required to enable looping of animated gif
56 /* we use the standard 216 color palette */
58 /* this script was used to create the palette:
59 * 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
60 * echo -n "{ 0x$r, 0x$g, 0x$b }, "; done; echo ""; done; done
63 static const rgb_triplet gif_clut[216] = {
64 { 0x00, 0x00, 0x00 }, { 0x00, 0x00, 0x33 }, { 0x00, 0x00, 0x66 }, { 0x00, 0x00, 0x99 }, { 0x00, 0x00, 0xcc }, { 0x00, 0x00, 0xff },
65 { 0x00, 0x33, 0x00 }, { 0x00, 0x33, 0x33 }, { 0x00, 0x33, 0x66 }, { 0x00, 0x33, 0x99 }, { 0x00, 0x33, 0xcc }, { 0x00, 0x33, 0xff },
66 { 0x00, 0x66, 0x00 }, { 0x00, 0x66, 0x33 }, { 0x00, 0x66, 0x66 }, { 0x00, 0x66, 0x99 }, { 0x00, 0x66, 0xcc }, { 0x00, 0x66, 0xff },
67 { 0x00, 0x99, 0x00 }, { 0x00, 0x99, 0x33 }, { 0x00, 0x99, 0x66 }, { 0x00, 0x99, 0x99 }, { 0x00, 0x99, 0xcc }, { 0x00, 0x99, 0xff },
68 { 0x00, 0xcc, 0x00 }, { 0x00, 0xcc, 0x33 }, { 0x00, 0xcc, 0x66 }, { 0x00, 0xcc, 0x99 }, { 0x00, 0xcc, 0xcc }, { 0x00, 0xcc, 0xff },
69 { 0x00, 0xff, 0x00 }, { 0x00, 0xff, 0x33 }, { 0x00, 0xff, 0x66 }, { 0x00, 0xff, 0x99 }, { 0x00, 0xff, 0xcc }, { 0x00, 0xff, 0xff },
70 { 0x33, 0x00, 0x00 }, { 0x33, 0x00, 0x33 }, { 0x33, 0x00, 0x66 }, { 0x33, 0x00, 0x99 }, { 0x33, 0x00, 0xcc }, { 0x33, 0x00, 0xff },
71 { 0x33, 0x33, 0x00 }, { 0x33, 0x33, 0x33 }, { 0x33, 0x33, 0x66 }, { 0x33, 0x33, 0x99 }, { 0x33, 0x33, 0xcc }, { 0x33, 0x33, 0xff },
72 { 0x33, 0x66, 0x00 }, { 0x33, 0x66, 0x33 }, { 0x33, 0x66, 0x66 }, { 0x33, 0x66, 0x99 }, { 0x33, 0x66, 0xcc }, { 0x33, 0x66, 0xff },
73 { 0x33, 0x99, 0x00 }, { 0x33, 0x99, 0x33 }, { 0x33, 0x99, 0x66 }, { 0x33, 0x99, 0x99 }, { 0x33, 0x99, 0xcc }, { 0x33, 0x99, 0xff },
74 { 0x33, 0xcc, 0x00 }, { 0x33, 0xcc, 0x33 }, { 0x33, 0xcc, 0x66 }, { 0x33, 0xcc, 0x99 }, { 0x33, 0xcc, 0xcc }, { 0x33, 0xcc, 0xff },
75 { 0x33, 0xff, 0x00 }, { 0x33, 0xff, 0x33 }, { 0x33, 0xff, 0x66 }, { 0x33, 0xff, 0x99 }, { 0x33, 0xff, 0xcc }, { 0x33, 0xff, 0xff },
76 { 0x66, 0x00, 0x00 }, { 0x66, 0x00, 0x33 }, { 0x66, 0x00, 0x66 }, { 0x66, 0x00, 0x99 }, { 0x66, 0x00, 0xcc }, { 0x66, 0x00, 0xff },
77 { 0x66, 0x33, 0x00 }, { 0x66, 0x33, 0x33 }, { 0x66, 0x33, 0x66 }, { 0x66, 0x33, 0x99 }, { 0x66, 0x33, 0xcc }, { 0x66, 0x33, 0xff },
78 { 0x66, 0x66, 0x00 }, { 0x66, 0x66, 0x33 }, { 0x66, 0x66, 0x66 }, { 0x66, 0x66, 0x99 }, { 0x66, 0x66, 0xcc }, { 0x66, 0x66, 0xff },
79 { 0x66, 0x99, 0x00 }, { 0x66, 0x99, 0x33 }, { 0x66, 0x99, 0x66 }, { 0x66, 0x99, 0x99 }, { 0x66, 0x99, 0xcc }, { 0x66, 0x99, 0xff },
80 { 0x66, 0xcc, 0x00 }, { 0x66, 0xcc, 0x33 }, { 0x66, 0xcc, 0x66 }, { 0x66, 0xcc, 0x99 }, { 0x66, 0xcc, 0xcc }, { 0x66, 0xcc, 0xff },
81 { 0x66, 0xff, 0x00 }, { 0x66, 0xff, 0x33 }, { 0x66, 0xff, 0x66 }, { 0x66, 0xff, 0x99 }, { 0x66, 0xff, 0xcc }, { 0x66, 0xff, 0xff },
82 { 0x99, 0x00, 0x00 }, { 0x99, 0x00, 0x33 }, { 0x99, 0x00, 0x66 }, { 0x99, 0x00, 0x99 }, { 0x99, 0x00, 0xcc }, { 0x99, 0x00, 0xff },
83 { 0x99, 0x33, 0x00 }, { 0x99, 0x33, 0x33 }, { 0x99, 0x33, 0x66 }, { 0x99, 0x33, 0x99 }, { 0x99, 0x33, 0xcc }, { 0x99, 0x33, 0xff },
84 { 0x99, 0x66, 0x00 }, { 0x99, 0x66, 0x33 }, { 0x99, 0x66, 0x66 }, { 0x99, 0x66, 0x99 }, { 0x99, 0x66, 0xcc }, { 0x99, 0x66, 0xff },
85 { 0x99, 0x99, 0x00 }, { 0x99, 0x99, 0x33 }, { 0x99, 0x99, 0x66 }, { 0x99, 0x99, 0x99 }, { 0x99, 0x99, 0xcc }, { 0x99, 0x99, 0xff },
86 { 0x99, 0xcc, 0x00 }, { 0x99, 0xcc, 0x33 }, { 0x99, 0xcc, 0x66 }, { 0x99, 0xcc, 0x99 }, { 0x99, 0xcc, 0xcc }, { 0x99, 0xcc, 0xff },
87 { 0x99, 0xff, 0x00 }, { 0x99, 0xff, 0x33 }, { 0x99, 0xff, 0x66 }, { 0x99, 0xff, 0x99 }, { 0x99, 0xff, 0xcc }, { 0x99, 0xff, 0xff },
88 { 0xcc, 0x00, 0x00 }, { 0xcc, 0x00, 0x33 }, { 0xcc, 0x00, 0x66 }, { 0xcc, 0x00, 0x99 }, { 0xcc, 0x00, 0xcc }, { 0xcc, 0x00, 0xff },
89 { 0xcc, 0x33, 0x00 }, { 0xcc, 0x33, 0x33 }, { 0xcc, 0x33, 0x66 }, { 0xcc, 0x33, 0x99 }, { 0xcc, 0x33, 0xcc }, { 0xcc, 0x33, 0xff },
90 { 0xcc, 0x66, 0x00 }, { 0xcc, 0x66, 0x33 }, { 0xcc, 0x66, 0x66 }, { 0xcc, 0x66, 0x99 }, { 0xcc, 0x66, 0xcc }, { 0xcc, 0x66, 0xff },
91 { 0xcc, 0x99, 0x00 }, { 0xcc, 0x99, 0x33 }, { 0xcc, 0x99, 0x66 }, { 0xcc, 0x99, 0x99 }, { 0xcc, 0x99, 0xcc }, { 0xcc, 0x99, 0xff },
92 { 0xcc, 0xcc, 0x00 }, { 0xcc, 0xcc, 0x33 }, { 0xcc, 0xcc, 0x66 }, { 0xcc, 0xcc, 0x99 }, { 0xcc, 0xcc, 0xcc }, { 0xcc, 0xcc, 0xff },
93 { 0xcc, 0xff, 0x00 }, { 0xcc, 0xff, 0x33 }, { 0xcc, 0xff, 0x66 }, { 0xcc, 0xff, 0x99 }, { 0xcc, 0xff, 0xcc }, { 0xcc, 0xff, 0xff },
94 { 0xff, 0x00, 0x00 }, { 0xff, 0x00, 0x33 }, { 0xff, 0x00, 0x66 }, { 0xff, 0x00, 0x99 }, { 0xff, 0x00, 0xcc }, { 0xff, 0x00, 0xff },
95 { 0xff, 0x33, 0x00 }, { 0xff, 0x33, 0x33 }, { 0xff, 0x33, 0x66 }, { 0xff, 0x33, 0x99 }, { 0xff, 0x33, 0xcc }, { 0xff, 0x33, 0xff },
96 { 0xff, 0x66, 0x00 }, { 0xff, 0x66, 0x33 }, { 0xff, 0x66, 0x66 }, { 0xff, 0x66, 0x99 }, { 0xff, 0x66, 0xcc }, { 0xff, 0x66, 0xff },
97 { 0xff, 0x99, 0x00 }, { 0xff, 0x99, 0x33 }, { 0xff, 0x99, 0x66 }, { 0xff, 0x99, 0x99 }, { 0xff, 0x99, 0xcc }, { 0xff, 0x99, 0xff },
98 { 0xff, 0xcc, 0x00 }, { 0xff, 0xcc, 0x33 }, { 0xff, 0xcc, 0x66 }, { 0xff, 0xcc, 0x99 }, { 0xff, 0xcc, 0xcc }, { 0xff, 0xcc, 0xff },
99 { 0xff, 0xff, 0x00 }, { 0xff, 0xff, 0x33 }, { 0xff, 0xff, 0x66 }, { 0xff, 0xff, 0x99 }, { 0xff, 0xff, 0xcc }, { 0xff, 0xff, 0xff },
102 /* The GIF format uses reversed order for bitstreams... */
103 /* at least they don't use PDP_ENDIAN :) */
104 /* so we 'extend' PutBitContext. hmmm, OOP :) */
105 /* seems this thing changed slightly since I wrote it... */
107 #ifdef ALT_BITSTREAM_WRITER
108 # error no ALT_BITSTREAM_WRITER support for now
111 static void gif_put_bits_rev(PutBitContext *s, int n, unsigned int value)
113 unsigned int bit_buf;
116 // printf("put_bits=%d %x\n", n, value);
117 assert(n == 32 || value < (1U << n));
119 bit_buf = s->bit_buf;
120 bit_cnt = 32 - s->bit_left; /* XXX:lazyness... was = s->bit_cnt; */
122 // printf("n=%d value=%x cnt=%d buf=%x\n", n, value, bit_cnt, bit_buf);
124 if (n < (32-bit_cnt)) {
125 bit_buf |= value << (bit_cnt);
128 bit_buf |= value << (bit_cnt);
130 *s->buf_ptr = bit_buf & 0xff;
131 s->buf_ptr[1] = (bit_buf >> 8) & 0xff;
132 s->buf_ptr[2] = (bit_buf >> 16) & 0xff;
133 s->buf_ptr[3] = (bit_buf >> 24) & 0xff;
135 //printf("bitbuf = %08x\n", bit_buf);
137 if (s->buf_ptr >= s->buf_end)
138 puts("bit buffer overflow !!"); // should never happen ! who got rid of the callback ???
139 // flush_buffer_rev(s);
140 bit_cnt=bit_cnt + n - 32;
144 bit_buf = value >> (n - bit_cnt);
148 s->bit_buf = bit_buf;
149 s->bit_left = 32 - bit_cnt;
152 /* pad the end of the output stream with zeros */
153 static void gif_flush_put_bits_rev(PutBitContext *s)
155 while (s->bit_left < 32) {
156 /* XXX: should test end of buffer */
157 *s->buf_ptr++=s->bit_buf & 0xff;
161 // flush_buffer_rev(s);
166 /* !RevPutBitContext */
169 static int gif_image_write_header(ByteIOContext *pb,
170 int width, int height, int loop_count,
179 put_le16(pb, height);
181 put_byte(pb, 0xf7); /* flags: global clut, 256 entries */
182 put_byte(pb, 0x1f); /* background color index */
183 put_byte(pb, 0); /* aspect ratio */
185 /* the global palette */
187 put_buffer(pb, (const unsigned char *)gif_clut, 216*3);
188 for(i=0;i<((256-216)*3);i++)
193 put_byte(pb, (v >> 16) & 0xff);
194 put_byte(pb, (v >> 8) & 0xff);
195 put_byte(pb, (v) & 0xff);
199 /* update: this is the 'NETSCAPE EXTENSION' that allows for looped animated gif
200 see http://members.aol.com/royalef/gifabout.htm#net-extension
202 byte 1 : 33 (hex 0x21) GIF Extension code
203 byte 2 : 255 (hex 0xFF) Application Extension Label
204 byte 3 : 11 (hex (0x0B) Length of Application Block
205 (eleven bytes of data to follow)
206 bytes 4 to 11 : "NETSCAPE"
207 bytes 12 to 14 : "2.0"
208 byte 15 : 3 (hex 0x03) Length of Data Sub-Block
209 (three bytes of data to follow)
210 byte 16 : 1 (hex 0x01)
211 bytes 17 to 18 : 0 to 65535, an unsigned integer in
212 lo-hi byte format. This indicate the
213 number of iterations the loop should
215 bytes 19 : 0 (hex 0x00) a Data Sub-block Terminator
218 /* application extension header */
219 #ifdef GIF_ADD_APP_HEADER
220 if (loop_count >= 0 && loop_count <= 65535) {
224 put_tag(pb, "NETSCAPE2.0"); // bytes 4 to 14
225 put_byte(pb, 0x03); // byte 15
226 put_byte(pb, 0x01); // byte 16
227 put_le16(pb, (uint16_t)loop_count);
228 put_byte(pb, 0x00); // byte 19
234 /* this is maybe slow, but allows for extensions */
235 static inline unsigned char gif_clut_index(uint8_t r, uint8_t g, uint8_t b)
237 return ((((r)/47)%6)*6*6+(((g)/47)%6)*6+(((b)/47)%6));
241 static int gif_image_write_image(ByteIOContext *pb,
242 int x1, int y1, int width, int height,
243 const uint8_t *buf, int linesize, int pix_fmt)
246 uint8_t buffer[200]; /* 100 * 9 / 8 = 113 */
255 put_le16(pb, height);
256 put_byte(pb, 0x00); /* flags */
261 left= width * height;
263 init_put_bits(&p, buffer, 130);
266 * the thing here is the bitstream is written as little packets, with a size byte before
267 * but it's still the same bitstream between packets (no flush !)
273 gif_put_bits_rev(&p, 9, 0x0100); /* clear code */
275 for(i=(left<GIF_CHUNKS)?left:GIF_CHUNKS;i;i--) {
276 if (pix_fmt == PIX_FMT_RGB24) {
277 v = gif_clut_index(ptr[0], ptr[1], ptr[2]);
282 gif_put_bits_rev(&p, 9, v);
290 if(left<=GIF_CHUNKS) {
291 gif_put_bits_rev(&p, 9, 0x101); /* end of stream */
292 gif_flush_put_bits_rev(&p);
294 if(pbBufPtr(&p) - p.buf > 0) {
295 put_byte(pb, pbBufPtr(&p) - p.buf); /* byte count of the packet */
296 put_buffer(pb, p.buf, pbBufPtr(&p) - p.buf); /* the actual buffer */
297 p.buf_ptr = p.buf; /* dequeue the bytes off the bitstream */
301 put_byte(pb, 0x00); /* end of image block */
307 int64_t time, file_time;
308 uint8_t buffer[100]; /* data chunks */
311 static int gif_write_header(AVFormatContext *s)
313 GIFContext *gif = s->priv_data;
314 ByteIOContext *pb = &s->pb;
315 AVCodecContext *enc, *video_enc;
316 int i, width, height, loop_count /*, rate*/;
318 /* XXX: do we reject audio streams or just ignore them ?
319 if(s->nb_streams > 1)
326 for(i=0;i<s->nb_streams;i++) {
327 enc = s->streams[i]->codec;
328 if (enc->codec_type != CODEC_TYPE_AUDIO)
336 width = video_enc->width;
337 height = video_enc->height;
338 loop_count = s->loop_output;
339 // rate = video_enc->time_base.den;
342 /* XXX: is it allowed ? seems to work so far... */
343 video_enc->pix_fmt = PIX_FMT_RGB24;
345 gif_image_write_header(pb, width, height, loop_count, NULL);
347 put_flush_packet(&s->pb);
351 static int gif_write_video(AVFormatContext *s,
352 AVCodecContext *enc, const uint8_t *buf, int size)
354 ByteIOContext *pb = &s->pb;
355 GIFContext *gif = s->priv_data;
359 /* graphic control extension block */
362 put_byte(pb, 0x04); /* block size */
363 put_byte(pb, 0x04); /* flags */
365 /* 1 jiffy is 1/70 s */
366 /* the delay_time field indicates the number of jiffies - 1 */
367 delay = gif->file_time - gif->time;
369 /* XXX: should use delay, in order to be more accurate */
370 /* instead of using the same rounded value each time */
371 /* XXX: don't even remember if I really use it for now */
372 jiffies = (70*enc->time_base.num/enc->time_base.den) - 1;
374 put_le16(pb, jiffies);
376 put_byte(pb, 0x1f); /* transparent color index */
379 gif_image_write_image(pb, 0, 0, enc->width, enc->height,
380 buf, enc->width * 3, PIX_FMT_RGB24);
382 put_flush_packet(&s->pb);
386 static int gif_write_packet(AVFormatContext *s, AVPacket *pkt)
388 AVCodecContext *codec = s->streams[pkt->stream_index]->codec;
389 if (codec->codec_type == CODEC_TYPE_AUDIO)
390 return 0; /* just ignore audio */
392 return gif_write_video(s, codec, pkt->data, pkt->size);
395 static int gif_write_trailer(AVFormatContext *s)
397 ByteIOContext *pb = &s->pb;
400 put_flush_packet(&s->pb);
404 /* better than nothing gif image writer */
405 int gif_write(ByteIOContext *pb, AVImageInfo *info)
407 gif_image_write_header(pb, info->width, info->height, AVFMT_NOOUTPUTLOOP,
408 (uint32_t *)info->pict.data[1]);
409 gif_image_write_image(pb, 0, 0, info->width, info->height,
410 info->pict.data[0], info->pict.linesize[0],
413 put_flush_packet(pb);
417 AVOutputFormat gif_muxer = {