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https://github.com/FFmpeg/FFmpeg.git
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76 lines
2.1 KiB
C
76 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 Libav.
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*
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* Libav 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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* Libav 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 Libav; 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(AVProbeData *p)
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{
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uint32_t code= -1;
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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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GetBitContext gb;
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init_get_bits(&gb, p->buf, p->buf_size*8);
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for(i=0; i<p->buf_size*8; i++){
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if ((code & 0x01ff0000) || !(code & 0xff00)) {
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code = (code<<8) + get_bits(&gb, 8);
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i += 7;
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} else
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code = (code<<1) + get_bits1(&gb);
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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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next_gn= (gn+1 )%13;
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}else{ //QCIF
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next_gn= (gn+1+!!gn)% 7;
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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 50;
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}else if(valid_psc > 2*invalid_psc + 2)
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return 25;
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return 0;
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}
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AVInputFormat ff_h261_demuxer = {
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"h261",
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NULL_IF_CONFIG_SMALL("raw H.261"),
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0,
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h261_probe,
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ff_raw_video_read_header,
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ff_raw_read_partial_packet,
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.flags= AVFMT_GENERIC_INDEX,
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.extensions = "h261",
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.value = CODEC_ID_H261,
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};
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