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ffmpeg / libavformat / h263dec.c @ 2912e87a

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/*
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 * RAW H.263 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 "avformat.h"
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#include "rawdec.h"
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static int h263_probe(AVProbeData *p)
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{
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    uint64_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 res_change=0;
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    int src_fmt, last_src_fmt=-1;
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    int last_gn=0;
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    for(i=0; i<p->buf_size; i++){
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        code = (code<<8) + p->buf[i];
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        if ((code & 0xfffffc0000) == 0x800000) {
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            src_fmt= (code>>2)&3;
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            if(   src_fmt != last_src_fmt
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               && last_src_fmt>0 && last_src_fmt<6
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               && src_fmt<6)
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                res_change++;
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            if((code&0x300)==0x200 && src_fmt){
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                valid_psc++;
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                last_gn=0;
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            }else
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                invalid_psc++;
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            last_src_fmt= src_fmt;
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        } else if((code & 0xffff800000) == 0x800000) {
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            int gn= (code>>(23-5)) & 0x1F;
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            if(gn<last_gn){
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                invalid_psc++;
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            }else
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                last_gn= gn;
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        }
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    }
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//av_log(NULL, AV_LOG_ERROR, "h263_probe: psc:%d invalid:%d res_change:%d\n", valid_psc, invalid_psc, res_change);
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//h263_probe: psc:3 invalid:0 res_change:0 (1588/recent_ffmpeg_parses_mpg_incorrectly.mpg)
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    if(valid_psc > 2*invalid_psc + 2*res_change + 3){
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        return 50;
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    }else if(valid_psc > 2*invalid_psc)
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        return 25;
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    return 0;
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}
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AVInputFormat ff_h263_demuxer = {
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    "h263",
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    NULL_IF_CONFIG_SMALL("raw H.263"),
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    0,
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    h263_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 = "h263", //FIXME remove after writing mpeg4_probe
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    .value = CODEC_ID_H263,
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};