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			420 lines
		
	
	
		
			16 KiB
		
	
	
	
		
			C
		
	
	
	
	
	
			
		
		
	
	
			420 lines
		
	
	
		
			16 KiB
		
	
	
	
		
			C
		
	
	
	
	
	
| /*
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|  * Animated GIF muxer
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|  * Copyright (c) 2000 Fabrice Bellard.
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|  *
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|  * This file is part of FFmpeg.
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|  *
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|  * FFmpeg is free software; you can redistribute it and/or
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|  * modify it under the terms of the GNU Lesser General Public
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|  * License as published by the Free Software Foundation; either
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|  * version 2.1 of the License, or (at your option) any later version.
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|  *
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|  * FFmpeg is distributed in the hope that it will be useful,
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|  * but WITHOUT ANY WARRANTY; without even the implied warranty of
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|  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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|  * Lesser General Public License for more details.
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|  *
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|  * You should have received a copy of the GNU Lesser General Public
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|  * License along with FFmpeg; if not, write to the Free Software
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|  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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|  */
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| 
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| /*
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|  * First version by Francois Revol revol@free.fr
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|  *
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|  * Features and limitations:
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|  * - currently no compression is performed,
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|  *   in fact the size of the data is 9/8 the size of the image in 8bpp
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|  * - uses only a global standard palette
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|  * - tested with IE 5.0, Opera for BeOS, NetPositive (BeOS), and Mozilla (BeOS).
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|  *
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|  * Reference documents:
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|  * http://www.goice.co.jp/member/mo/formats/gif.html
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|  * http://astronomy.swin.edu.au/pbourke/dataformats/gif/
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|  * http://www.dcs.ed.ac.uk/home/mxr/gfx/2d/GIF89a.txt
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|  *
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|  * this url claims to have an LZW algorithm not covered by Unisys patent:
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|  * http://www.msg.net/utility/whirlgif/gifencod.html
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|  * could help reduce the size of the files _a lot_...
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|  * some sites mentions an RLE type compression also.
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|  */
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| 
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| #include "avformat.h"
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| #include "bitstream.h"
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| 
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| /* bitstream minipacket size */
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| #define GIF_CHUNKS 100
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| 
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| /* slows down the decoding (and some browsers don't like it) */
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| /* 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 */
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| #define GIF_ADD_APP_HEADER // required to enable looping of animated gif
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| 
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| typedef struct {
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|     unsigned char r;
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|     unsigned char g;
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|     unsigned char b;
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| } rgb_triplet;
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| 
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| /* we use the standard 216 color palette */
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| 
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| /* this script was used to create the palette:
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|  * 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
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|  *   echo -n "{ 0x$r, 0x$g, 0x$b }, "; done; echo ""; done; done
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|  */
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| 
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| static const rgb_triplet gif_clut[216] = {
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|     { 0x00, 0x00, 0x00 }, { 0x00, 0x00, 0x33 }, { 0x00, 0x00, 0x66 }, { 0x00, 0x00, 0x99 }, { 0x00, 0x00, 0xcc }, { 0x00, 0x00, 0xff },
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|     { 0x00, 0x33, 0x00 }, { 0x00, 0x33, 0x33 }, { 0x00, 0x33, 0x66 }, { 0x00, 0x33, 0x99 }, { 0x00, 0x33, 0xcc }, { 0x00, 0x33, 0xff },
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|     { 0x00, 0x66, 0x00 }, { 0x00, 0x66, 0x33 }, { 0x00, 0x66, 0x66 }, { 0x00, 0x66, 0x99 }, { 0x00, 0x66, 0xcc }, { 0x00, 0x66, 0xff },
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|     { 0x00, 0x99, 0x00 }, { 0x00, 0x99, 0x33 }, { 0x00, 0x99, 0x66 }, { 0x00, 0x99, 0x99 }, { 0x00, 0x99, 0xcc }, { 0x00, 0x99, 0xff },
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|     { 0x00, 0xcc, 0x00 }, { 0x00, 0xcc, 0x33 }, { 0x00, 0xcc, 0x66 }, { 0x00, 0xcc, 0x99 }, { 0x00, 0xcc, 0xcc }, { 0x00, 0xcc, 0xff },
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|     { 0x00, 0xff, 0x00 }, { 0x00, 0xff, 0x33 }, { 0x00, 0xff, 0x66 }, { 0x00, 0xff, 0x99 }, { 0x00, 0xff, 0xcc }, { 0x00, 0xff, 0xff },
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|     { 0x33, 0x00, 0x00 }, { 0x33, 0x00, 0x33 }, { 0x33, 0x00, 0x66 }, { 0x33, 0x00, 0x99 }, { 0x33, 0x00, 0xcc }, { 0x33, 0x00, 0xff },
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|     { 0x33, 0x33, 0x00 }, { 0x33, 0x33, 0x33 }, { 0x33, 0x33, 0x66 }, { 0x33, 0x33, 0x99 }, { 0x33, 0x33, 0xcc }, { 0x33, 0x33, 0xff },
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|     { 0x33, 0x66, 0x00 }, { 0x33, 0x66, 0x33 }, { 0x33, 0x66, 0x66 }, { 0x33, 0x66, 0x99 }, { 0x33, 0x66, 0xcc }, { 0x33, 0x66, 0xff },
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|     { 0x33, 0x99, 0x00 }, { 0x33, 0x99, 0x33 }, { 0x33, 0x99, 0x66 }, { 0x33, 0x99, 0x99 }, { 0x33, 0x99, 0xcc }, { 0x33, 0x99, 0xff },
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|     { 0x33, 0xcc, 0x00 }, { 0x33, 0xcc, 0x33 }, { 0x33, 0xcc, 0x66 }, { 0x33, 0xcc, 0x99 }, { 0x33, 0xcc, 0xcc }, { 0x33, 0xcc, 0xff },
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|     { 0x33, 0xff, 0x00 }, { 0x33, 0xff, 0x33 }, { 0x33, 0xff, 0x66 }, { 0x33, 0xff, 0x99 }, { 0x33, 0xff, 0xcc }, { 0x33, 0xff, 0xff },
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|     { 0x66, 0x00, 0x00 }, { 0x66, 0x00, 0x33 }, { 0x66, 0x00, 0x66 }, { 0x66, 0x00, 0x99 }, { 0x66, 0x00, 0xcc }, { 0x66, 0x00, 0xff },
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|     { 0x66, 0x33, 0x00 }, { 0x66, 0x33, 0x33 }, { 0x66, 0x33, 0x66 }, { 0x66, 0x33, 0x99 }, { 0x66, 0x33, 0xcc }, { 0x66, 0x33, 0xff },
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|     { 0x66, 0x66, 0x00 }, { 0x66, 0x66, 0x33 }, { 0x66, 0x66, 0x66 }, { 0x66, 0x66, 0x99 }, { 0x66, 0x66, 0xcc }, { 0x66, 0x66, 0xff },
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|     { 0x66, 0x99, 0x00 }, { 0x66, 0x99, 0x33 }, { 0x66, 0x99, 0x66 }, { 0x66, 0x99, 0x99 }, { 0x66, 0x99, 0xcc }, { 0x66, 0x99, 0xff },
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|     { 0x66, 0xcc, 0x00 }, { 0x66, 0xcc, 0x33 }, { 0x66, 0xcc, 0x66 }, { 0x66, 0xcc, 0x99 }, { 0x66, 0xcc, 0xcc }, { 0x66, 0xcc, 0xff },
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|     { 0x66, 0xff, 0x00 }, { 0x66, 0xff, 0x33 }, { 0x66, 0xff, 0x66 }, { 0x66, 0xff, 0x99 }, { 0x66, 0xff, 0xcc }, { 0x66, 0xff, 0xff },
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|     { 0x99, 0x00, 0x00 }, { 0x99, 0x00, 0x33 }, { 0x99, 0x00, 0x66 }, { 0x99, 0x00, 0x99 }, { 0x99, 0x00, 0xcc }, { 0x99, 0x00, 0xff },
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|     { 0x99, 0x33, 0x00 }, { 0x99, 0x33, 0x33 }, { 0x99, 0x33, 0x66 }, { 0x99, 0x33, 0x99 }, { 0x99, 0x33, 0xcc }, { 0x99, 0x33, 0xff },
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|     { 0x99, 0x66, 0x00 }, { 0x99, 0x66, 0x33 }, { 0x99, 0x66, 0x66 }, { 0x99, 0x66, 0x99 }, { 0x99, 0x66, 0xcc }, { 0x99, 0x66, 0xff },
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|     { 0x99, 0x99, 0x00 }, { 0x99, 0x99, 0x33 }, { 0x99, 0x99, 0x66 }, { 0x99, 0x99, 0x99 }, { 0x99, 0x99, 0xcc }, { 0x99, 0x99, 0xff },
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|     { 0x99, 0xcc, 0x00 }, { 0x99, 0xcc, 0x33 }, { 0x99, 0xcc, 0x66 }, { 0x99, 0xcc, 0x99 }, { 0x99, 0xcc, 0xcc }, { 0x99, 0xcc, 0xff },
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|     { 0x99, 0xff, 0x00 }, { 0x99, 0xff, 0x33 }, { 0x99, 0xff, 0x66 }, { 0x99, 0xff, 0x99 }, { 0x99, 0xff, 0xcc }, { 0x99, 0xff, 0xff },
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|     { 0xcc, 0x00, 0x00 }, { 0xcc, 0x00, 0x33 }, { 0xcc, 0x00, 0x66 }, { 0xcc, 0x00, 0x99 }, { 0xcc, 0x00, 0xcc }, { 0xcc, 0x00, 0xff },
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|     { 0xcc, 0x33, 0x00 }, { 0xcc, 0x33, 0x33 }, { 0xcc, 0x33, 0x66 }, { 0xcc, 0x33, 0x99 }, { 0xcc, 0x33, 0xcc }, { 0xcc, 0x33, 0xff },
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|     { 0xcc, 0x66, 0x00 }, { 0xcc, 0x66, 0x33 }, { 0xcc, 0x66, 0x66 }, { 0xcc, 0x66, 0x99 }, { 0xcc, 0x66, 0xcc }, { 0xcc, 0x66, 0xff },
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|     { 0xcc, 0x99, 0x00 }, { 0xcc, 0x99, 0x33 }, { 0xcc, 0x99, 0x66 }, { 0xcc, 0x99, 0x99 }, { 0xcc, 0x99, 0xcc }, { 0xcc, 0x99, 0xff },
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|     { 0xcc, 0xcc, 0x00 }, { 0xcc, 0xcc, 0x33 }, { 0xcc, 0xcc, 0x66 }, { 0xcc, 0xcc, 0x99 }, { 0xcc, 0xcc, 0xcc }, { 0xcc, 0xcc, 0xff },
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|     { 0xcc, 0xff, 0x00 }, { 0xcc, 0xff, 0x33 }, { 0xcc, 0xff, 0x66 }, { 0xcc, 0xff, 0x99 }, { 0xcc, 0xff, 0xcc }, { 0xcc, 0xff, 0xff },
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|     { 0xff, 0x00, 0x00 }, { 0xff, 0x00, 0x33 }, { 0xff, 0x00, 0x66 }, { 0xff, 0x00, 0x99 }, { 0xff, 0x00, 0xcc }, { 0xff, 0x00, 0xff },
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|     { 0xff, 0x33, 0x00 }, { 0xff, 0x33, 0x33 }, { 0xff, 0x33, 0x66 }, { 0xff, 0x33, 0x99 }, { 0xff, 0x33, 0xcc }, { 0xff, 0x33, 0xff },
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|     { 0xff, 0x66, 0x00 }, { 0xff, 0x66, 0x33 }, { 0xff, 0x66, 0x66 }, { 0xff, 0x66, 0x99 }, { 0xff, 0x66, 0xcc }, { 0xff, 0x66, 0xff },
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|     { 0xff, 0x99, 0x00 }, { 0xff, 0x99, 0x33 }, { 0xff, 0x99, 0x66 }, { 0xff, 0x99, 0x99 }, { 0xff, 0x99, 0xcc }, { 0xff, 0x99, 0xff },
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|     { 0xff, 0xcc, 0x00 }, { 0xff, 0xcc, 0x33 }, { 0xff, 0xcc, 0x66 }, { 0xff, 0xcc, 0x99 }, { 0xff, 0xcc, 0xcc }, { 0xff, 0xcc, 0xff },
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|     { 0xff, 0xff, 0x00 }, { 0xff, 0xff, 0x33 }, { 0xff, 0xff, 0x66 }, { 0xff, 0xff, 0x99 }, { 0xff, 0xff, 0xcc }, { 0xff, 0xff, 0xff },
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| };
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| 
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| /* The GIF format uses reversed order for bitstreams... */
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| /* at least they don't use PDP_ENDIAN :) */
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| /* so we 'extend' PutBitContext. hmmm, OOP :) */
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| /* seems this thing changed slightly since I wrote it... */
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| 
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| #ifdef ALT_BITSTREAM_WRITER
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| # error no ALT_BITSTREAM_WRITER support for now
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| #endif
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| 
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| static void gif_put_bits_rev(PutBitContext *s, int n, unsigned int value)
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| {
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|     unsigned int bit_buf;
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|     int bit_cnt;
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| 
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|     //    printf("put_bits=%d %x\n", n, value);
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|     assert(n == 32 || value < (1U << n));
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| 
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|     bit_buf = s->bit_buf;
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|     bit_cnt = 32 - s->bit_left; /* XXX:lazyness... was = s->bit_cnt; */
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| 
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|     //    printf("n=%d value=%x cnt=%d buf=%x\n", n, value, bit_cnt, bit_buf);
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|     /* XXX: optimize */
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|     if (n < (32-bit_cnt)) {
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|         bit_buf |= value << (bit_cnt);
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|         bit_cnt+=n;
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|     } else {
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|         bit_buf |= value << (bit_cnt);
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| 
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|         *s->buf_ptr = bit_buf & 0xff;
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|         s->buf_ptr[1] = (bit_buf >> 8) & 0xff;
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|         s->buf_ptr[2] = (bit_buf >> 16) & 0xff;
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|         s->buf_ptr[3] = (bit_buf >> 24) & 0xff;
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| 
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|         //printf("bitbuf = %08x\n", bit_buf);
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|         s->buf_ptr+=4;
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|         if (s->buf_ptr >= s->buf_end)
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|             puts("bit buffer overflow !!"); // should never happen ! who got rid of the callback ???
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| //            flush_buffer_rev(s);
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|         bit_cnt=bit_cnt + n - 32;
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|         if (bit_cnt == 0) {
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|             bit_buf = 0;
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|         } else {
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|             bit_buf = value >> (n - bit_cnt);
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|         }
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|     }
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| 
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|     s->bit_buf = bit_buf;
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|     s->bit_left = 32 - bit_cnt;
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| }
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| 
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| /* pad the end of the output stream with zeros */
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| static void gif_flush_put_bits_rev(PutBitContext *s)
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| {
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|     while (s->bit_left < 32) {
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|         /* XXX: should test end of buffer */
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|         *s->buf_ptr++=s->bit_buf & 0xff;
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|         s->bit_buf>>=8;
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|         s->bit_left+=8;
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|     }
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| //    flush_buffer_rev(s);
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|     s->bit_left=32;
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|     s->bit_buf=0;
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| }
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| 
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| /* !RevPutBitContext */
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| 
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| /* GIF header */
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| static int gif_image_write_header(ByteIOContext *pb,
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|                                   int width, int height, int loop_count,
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|                                   uint32_t *palette)
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| {
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|     int i;
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|     unsigned int v;
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| 
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|     put_tag(pb, "GIF");
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|     put_tag(pb, "89a");
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|     put_le16(pb, width);
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|     put_le16(pb, height);
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| 
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|     put_byte(pb, 0xf7); /* flags: global clut, 256 entries */
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|     put_byte(pb, 0x1f); /* background color index */
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|     put_byte(pb, 0); /* aspect ratio */
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| 
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|     /* the global palette */
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|     if (!palette) {
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|         put_buffer(pb, (const unsigned char *)gif_clut, 216*3);
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|         for(i=0;i<((256-216)*3);i++)
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|             put_byte(pb, 0);
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|     } else {
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|         for(i=0;i<256;i++) {
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|             v = palette[i];
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|             put_byte(pb, (v >> 16) & 0xff);
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|             put_byte(pb, (v >> 8) & 0xff);
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|             put_byte(pb, (v) & 0xff);
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|         }
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|     }
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| 
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|         /*        update: this is the 'NETSCAPE EXTENSION' that allows for looped animated gif
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|                 see http://members.aol.com/royalef/gifabout.htm#net-extension
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| 
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|                 byte   1       : 33 (hex 0x21) GIF Extension code
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|                 byte   2       : 255 (hex 0xFF) Application Extension Label
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|                 byte   3       : 11 (hex (0x0B) Length of Application Block
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|                                          (eleven bytes of data to follow)
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|                 bytes  4 to 11 : "NETSCAPE"
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|                 bytes 12 to 14 : "2.0"
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|                 byte  15       : 3 (hex 0x03) Length of Data Sub-Block
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|                                          (three bytes of data to follow)
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|                 byte  16       : 1 (hex 0x01)
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|                 bytes 17 to 18 : 0 to 65535, an unsigned integer in
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|                                          lo-hi byte format. This indicate the
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|                                          number of iterations the loop should
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|                                          be executed.
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|                 bytes 19       : 0 (hex 0x00) a Data Sub-block Terminator
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|         */
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| 
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|     /* application extension header */
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| #ifdef GIF_ADD_APP_HEADER
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|     if (loop_count >= 0 && loop_count <= 65535) {
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|     put_byte(pb, 0x21);
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|     put_byte(pb, 0xff);
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|     put_byte(pb, 0x0b);
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|         put_tag(pb, "NETSCAPE2.0");  // bytes 4 to 14
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|         put_byte(pb, 0x03); // byte 15
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|         put_byte(pb, 0x01); // byte 16
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|         put_le16(pb, (uint16_t)loop_count);
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|         put_byte(pb, 0x00); // byte 19
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|     }
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| #endif
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|     return 0;
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| }
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| 
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| /* this is maybe slow, but allows for extensions */
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| static inline unsigned char gif_clut_index(uint8_t r, uint8_t g, uint8_t b)
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| {
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|     return ((((r)/47)%6)*6*6+(((g)/47)%6)*6+(((b)/47)%6));
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| }
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| 
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| 
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| static int gif_image_write_image(ByteIOContext *pb,
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|                                  int x1, int y1, int width, int height,
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|                                  const uint8_t *buf, int linesize, int pix_fmt)
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| {
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|     PutBitContext p;
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|     uint8_t buffer[200]; /* 100 * 9 / 8 = 113 */
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|     int i, left, w, v;
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|     const uint8_t *ptr;
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|     /* image block */
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| 
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|     put_byte(pb, 0x2c);
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|     put_le16(pb, x1);
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|     put_le16(pb, y1);
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|     put_le16(pb, width);
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|     put_le16(pb, height);
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|     put_byte(pb, 0x00); /* flags */
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|     /* no local clut */
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| 
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|     put_byte(pb, 0x08);
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| 
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|     left= width * height;
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| 
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|     init_put_bits(&p, buffer, 130);
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| 
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| /*
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|  * the thing here is the bitstream is written as little packets, with a size byte before
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|  * but it's still the same bitstream between packets (no flush !)
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|  */
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|     ptr = buf;
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|     w = width;
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|     while(left>0) {
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| 
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|         gif_put_bits_rev(&p, 9, 0x0100); /* clear code */
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| 
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|         for(i=(left<GIF_CHUNKS)?left:GIF_CHUNKS;i;i--) {
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|             if (pix_fmt == PIX_FMT_RGB24) {
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|                 v = gif_clut_index(ptr[0], ptr[1], ptr[2]);
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|                 ptr+=3;
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|             } else {
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|                 v = *ptr++;
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|             }
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|             gif_put_bits_rev(&p, 9, v);
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|             if (--w == 0) {
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|                 w = width;
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|                 buf += linesize;
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|                 ptr = buf;
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|             }
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|         }
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| 
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|         if(left<=GIF_CHUNKS) {
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|             gif_put_bits_rev(&p, 9, 0x101); /* end of stream */
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|             gif_flush_put_bits_rev(&p);
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|         }
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|         if(pbBufPtr(&p) - p.buf > 0) {
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|             put_byte(pb, pbBufPtr(&p) - p.buf); /* byte count of the packet */
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|             put_buffer(pb, p.buf, pbBufPtr(&p) - p.buf); /* the actual buffer */
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|             p.buf_ptr = p.buf; /* dequeue the bytes off the bitstream */
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|         }
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|         left-=GIF_CHUNKS;
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|     }
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|     put_byte(pb, 0x00); /* end of image block */
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| 
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|     return 0;
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| }
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| 
 | |
| typedef struct {
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|     int64_t time, file_time;
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|     uint8_t buffer[100]; /* data chunks */
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| } GIFContext;
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| 
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| static int gif_write_header(AVFormatContext *s)
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| {
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|     GIFContext *gif = s->priv_data;
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|     ByteIOContext *pb = &s->pb;
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|     AVCodecContext *enc, *video_enc;
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|     int i, width, height, loop_count /*, rate*/;
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| 
 | |
| /* XXX: do we reject audio streams or just ignore them ?
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|     if(s->nb_streams > 1)
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|         return -1;
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| */
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|     gif->time = 0;
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|     gif->file_time = 0;
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| 
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|     video_enc = NULL;
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|     for(i=0;i<s->nb_streams;i++) {
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|         enc = s->streams[i]->codec;
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|         if (enc->codec_type != CODEC_TYPE_AUDIO)
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|             video_enc = enc;
 | |
|     }
 | |
| 
 | |
|     if (!video_enc) {
 | |
|         av_free(gif);
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|         return -1;
 | |
|     } else {
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|         width = video_enc->width;
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|         height = video_enc->height;
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|         loop_count = s->loop_output;
 | |
| //        rate = video_enc->time_base.den;
 | |
|     }
 | |
| 
 | |
|     if (video_enc->pix_fmt != PIX_FMT_RGB24) {
 | |
|         av_log(s, AV_LOG_ERROR, "ERROR: gif only handles the rgb24 pixel format. Use -pix_fmt rgb24.\n");
 | |
|         return AVERROR_IO;
 | |
|     }
 | |
| 
 | |
|     gif_image_write_header(pb, width, height, loop_count, NULL);
 | |
| 
 | |
|     put_flush_packet(&s->pb);
 | |
|     return 0;
 | |
| }
 | |
| 
 | |
| static int gif_write_video(AVFormatContext *s,
 | |
|                            AVCodecContext *enc, const uint8_t *buf, int size)
 | |
| {
 | |
|     ByteIOContext *pb = &s->pb;
 | |
|     GIFContext *gif = s->priv_data;
 | |
|     int jiffies;
 | |
|     int64_t delay;
 | |
| 
 | |
|     /* graphic control extension block */
 | |
|     put_byte(pb, 0x21);
 | |
|     put_byte(pb, 0xf9);
 | |
|     put_byte(pb, 0x04); /* block size */
 | |
|     put_byte(pb, 0x04); /* flags */
 | |
| 
 | |
|     /* 1 jiffy is 1/70 s */
 | |
|     /* the delay_time field indicates the number of jiffies - 1 */
 | |
|     delay = gif->file_time - gif->time;
 | |
| 
 | |
|     /* XXX: should use delay, in order to be more accurate */
 | |
|     /* instead of using the same rounded value each time */
 | |
|     /* XXX: don't even remember if I really use it for now */
 | |
|     jiffies = (70*enc->time_base.num/enc->time_base.den) - 1;
 | |
| 
 | |
|     put_le16(pb, jiffies);
 | |
| 
 | |
|     put_byte(pb, 0x1f); /* transparent color index */
 | |
|     put_byte(pb, 0x00);
 | |
| 
 | |
|     gif_image_write_image(pb, 0, 0, enc->width, enc->height,
 | |
|                           buf, enc->width * 3, PIX_FMT_RGB24);
 | |
| 
 | |
|     put_flush_packet(&s->pb);
 | |
|     return 0;
 | |
| }
 | |
| 
 | |
| static int gif_write_packet(AVFormatContext *s, AVPacket *pkt)
 | |
| {
 | |
|     AVCodecContext *codec = s->streams[pkt->stream_index]->codec;
 | |
|     if (codec->codec_type == CODEC_TYPE_AUDIO)
 | |
|         return 0; /* just ignore audio */
 | |
|     else
 | |
|         return gif_write_video(s, codec, pkt->data, pkt->size);
 | |
| }
 | |
| 
 | |
| static int gif_write_trailer(AVFormatContext *s)
 | |
| {
 | |
|     ByteIOContext *pb = &s->pb;
 | |
| 
 | |
|     put_byte(pb, 0x3b);
 | |
|     put_flush_packet(&s->pb);
 | |
|     return 0;
 | |
| }
 | |
| 
 | |
| AVOutputFormat gif_muxer = {
 | |
|     "gif",
 | |
|     "GIF Animation",
 | |
|     "image/gif",
 | |
|     "gif",
 | |
|     sizeof(GIFContext),
 | |
|     CODEC_ID_NONE,
 | |
|     CODEC_ID_RAWVIDEO,
 | |
|     gif_write_header,
 | |
|     gif_write_packet,
 | |
|     gif_write_trailer,
 | |
| };
 | 
