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libavformat/h263dec.c

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00001 /*
00002  * RAW H.263 video demuxer
00003  * Copyright (c) 2009 Michael Niedermayer <michaelni@gmx.at>
00004  *
00005  * This file is part of FFmpeg.
00006  *
00007  * FFmpeg is free software; you can redistribute it and/or
00008  * modify it under the terms of the GNU Lesser General Public
00009  * License as published by the Free Software Foundation; either
00010  * version 2.1 of the License, or (at your option) any later version.
00011  *
00012  * FFmpeg is distributed in the hope that it will be useful,
00013  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00014  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00015  * Lesser General Public License for more details.
00016  *
00017  * You should have received a copy of the GNU Lesser General Public
00018  * License along with FFmpeg; if not, write to the Free Software
00019  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
00020  */
00021 
00022 #include "avformat.h"
00023 #include "rawdec.h"
00024 
00025 static int h263_probe(AVProbeData *p)
00026 {
00027     uint64_t code= -1;
00028     int i;
00029     int valid_psc=0;
00030     int invalid_psc=0;
00031     int res_change=0;
00032     int src_fmt, last_src_fmt=-1;
00033     int last_gn=0;
00034 
00035     for(i=0; i<p->buf_size; i++){
00036         code = (code<<8) + p->buf[i];
00037         if ((code & 0xfffffc0000) == 0x800000) {
00038             src_fmt= (code>>2)&3;
00039             if(   src_fmt != last_src_fmt
00040                && last_src_fmt>0 && last_src_fmt<6
00041                && src_fmt<6)
00042                 res_change++;
00043 
00044             if((code&0x300)==0x200 && src_fmt){
00045                 valid_psc++;
00046                 last_gn=0;
00047             }else
00048                 invalid_psc++;
00049             last_src_fmt= src_fmt;
00050         } else if((code & 0xffff800000) == 0x800000) {
00051             int gn= (code>>(23-5)) & 0x1F;
00052             if(gn<last_gn){
00053                 invalid_psc++;
00054             }else
00055                 last_gn= gn;
00056         }
00057     }
00058 //av_log(NULL, AV_LOG_ERROR, "h263_probe: psc:%d invalid:%d res_change:%d\n", valid_psc, invalid_psc, res_change);
00059 //h263_probe: psc:3 invalid:0 res_change:0 (1588/recent_ffmpeg_parses_mpg_incorrectly.mpg)
00060     if(valid_psc > 2*invalid_psc + 2*res_change + 3){
00061         return 50;
00062     }else if(valid_psc > 2*invalid_psc)
00063         return 25;
00064     return 0;
00065 }
00066 
00067 FF_DEF_RAWVIDEO_DEMUXER(h263, "raw H.263", h263_probe, NULL, CODEC_ID_H263)

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