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https://github.com/FFmpeg/FFmpeg.git
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63 lines
2.1 KiB
C
63 lines
2.1 KiB
C
/*
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* RAW H.261 video demuxer
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* Copyright (c) 2009 Michael Niedermayer <michaelni@gmx.at>
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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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#include "libavcodec/get_bits.h"
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#include "avformat.h"
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#include "rawdec.h"
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static int h261_probe(const AVProbeData *p)
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{
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int i;
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int valid_psc=0;
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int invalid_psc=0;
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int next_gn=0;
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int src_fmt=0;
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for(i=0; i<p->buf_size; i++){
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if ((AV_RB16(&p->buf[i]) - 1) < 0xFFU) {
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int shift = av_log2_16bit(p->buf[i+1]);
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uint32_t code = AV_RB64(&p->buf[FFMAX(i-1, 0)]) >> (24+shift);
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if ((code & 0xffff0000) == 0x10000) {
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int gn= (code>>12)&0xf;
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if(!gn)
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src_fmt= code&8;
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if(gn != next_gn) invalid_psc++;
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else valid_psc++;
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if(src_fmt){ // CIF
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static const int lut[16]={1,2,3,4,5,6,7,8,9,10,11,12,0,16,16,16};
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next_gn = lut[gn];
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}else{ //QCIF
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static const int lut[16]={1,3,16,5,16,0,16,16,16,16,16,16,16,16,16,16};
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next_gn = lut[gn];
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}
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}
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}
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}
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if(valid_psc > 2*invalid_psc + 6){
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return AVPROBE_SCORE_EXTENSION;
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}else if(valid_psc > 2*invalid_psc + 2)
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return AVPROBE_SCORE_EXTENSION / 2;
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return 0;
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}
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FF_DEF_RAWVIDEO_DEMUXER(h261, "raw H.261", h261_probe, "h261", AV_CODEC_ID_H261)
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