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/*
* RAW H.261 video demuxer
* Copyright (c) 2009 Michael Niedermayer <michaelni@gmx.at>
*
* This file is part of Libav.
*
* Libav is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* Libav is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with Libav; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "libavcodec/bitstream.h"
#include "avformat.h"
#include "rawdec.h"
static int h261_probe(AVProbeData *p)
{
uint32_t code= -1;
int i;
int valid_psc=0;
int invalid_psc=0;
int next_gn=0;
int src_fmt=0;
BitstreamContext bc;
bitstream_init8(&bc, p->buf, p->buf_size);
for(i=0; i<p->buf_size*8; i++){
if ((code & 0x01ff0000) || !(code & 0xff00)) {
code = (code << 8) + bitstream_read(&bc, 8);
i += 7;
} else
code = (code << 1) + bitstream_read_bit(&bc);
if ((code & 0xffff0000) == 0x10000) {
int gn= (code>>12)&0xf;
if(!gn)
src_fmt= code&8;
if(gn != next_gn) invalid_psc++;
else valid_psc++;
if(src_fmt){ // CIF
next_gn= (gn+1 )%13;
}else{ //QCIF
next_gn= (gn+1+!!gn)% 7;
}
}
}
if(valid_psc > 2*invalid_psc + 6){
return AVPROBE_SCORE_EXTENSION;
}else if(valid_psc > 2*invalid_psc + 2)
return AVPROBE_SCORE_EXTENSION / 2;
return 0;
}
FF_DEF_RAWVIDEO_DEMUXER(h261, "raw H.261", h261_probe, "h261", AV_CODEC_ID_H261)
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