FFmpeg
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h263dec.c
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1 /*
2  * RAW H.263 video demuxer
3  * Copyright (c) 2009 Michael Niedermayer <michaelni@gmx.at>
4  *
5  * This file is part of FFmpeg.
6  *
7  * FFmpeg is free software; you can redistribute it and/or
8  * modify it under the terms of the GNU Lesser General Public
9  * License as published by the Free Software Foundation; either
10  * version 2.1 of the License, or (at your option) any later version.
11  *
12  * FFmpeg is distributed in the hope that it will be useful,
13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15  * Lesser General Public License for more details.
16  *
17  * You should have received a copy of the GNU Lesser General Public
18  * License along with FFmpeg; if not, write to the Free Software
19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20  */
21 
22 #include "avformat.h"
23 #include "rawdec.h"
24 
25 static int h263_probe(AVProbeData *p)
26 {
27  uint64_t code= -1;
28  int i;
29  int valid_psc=0;
30  int invalid_psc=0;
31  int res_change=0;
32  int src_fmt, last_src_fmt=-1;
33  int last_gn=0;
34 
35  for(i=0; i<p->buf_size; i++){
36  code = (code<<8) + p->buf[i];
37  if ((code & 0xfffffc0000) == 0x800000) {
38  src_fmt= (code>>2)&3;
39  if( src_fmt != last_src_fmt
40  && last_src_fmt>0 && last_src_fmt<6
41  && src_fmt<6)
42  res_change++;
43 
44  if((code&0x300)==0x200 && src_fmt){
45  valid_psc++;
46  last_gn=0;
47  }else
48  invalid_psc++;
49  last_src_fmt= src_fmt;
50  } else if((code & 0xffff800000) == 0x800000) {
51  int gn= (code>>(23-5)) & 0x1F;
52  if(gn<last_gn){
53  invalid_psc++;
54  }else
55  last_gn= gn;
56  }
57  }
58  if(valid_psc > 2*invalid_psc + 2*res_change + 3){
59  return 50;
60  }else if(valid_psc > 2*invalid_psc)
61  return 25;
62  return 0;
63 }
64