libavformat/h263dec.c

   1 /*
   2  * RAW H.263 video demuxer
   3  * Copyright (c) 2009 Michael Niedermayer <michaelni@gmx.at>
   4  *
   5  * This file is part of Libav.
   6  *
   7  * Libav 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  * Libav 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 Libav; 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
  65 FF_DEF_RAWVIDEO_DEMUXER(h263, "raw H.263", h263_probe, NULL, AV_CODEC_ID_H263)