text: /*
   * RAW H.261 video demuxer
   * Copyright (c) 2009 Michael Niedermayer <michaelni@gmx.at>
   *
   * This file is part of FFmpeg.
   *
   * FFmpeg is free software; you can redistribute it and/or
   * modify it under the terms of the GNU Lesser General Public
   * License as published by the Free Software Foundation; either
   * version 2.1 of the License, or (at your option) any later version.
   *
   * FFmpeg is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   * Lesser General Public License for more details.
   *
   * You should have received a copy of the GNU Lesser General Public
   * License along with FFmpeg; if not, write to the Free Software
   * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
   */
  
  #include "libavcodec/get_bits.h"
  #include "avformat.h"
  #include "rawdec.h"
  
  static int h261_probe(AVProbeData *p)
  {
      uint32_t code= -1;
      int i;
      int valid_psc=0;
      int invalid_psc=0;
      int next_gn=0;
      int src_fmt=0;
      GetBitContext gb;
  
      init_get_bits(&gb, p->buf, p->buf_size*8);
  
      for(i=0; i<p->buf_size*8; i++){
          if ((code & 0x01ff0000) || !(code & 0xff00)) {
              code = (code<<8) + get_bits(&gb, 8);
              i += 7;
          } else
              code = (code<<1) + get_bits1(&gb);
          if ((code & 0xffff0000) == 0x10000) {
              int gn= (code>>12)&0xf;
              if(!gn)
                  src_fmt= code&8;
              if(gn != next_gn) invalid_psc++;
              else              valid_psc++;
  
              if(src_fmt){ // CIF
                  next_gn= (gn+1     )%13;
              }else{       //QCIF
                  next_gn= (gn+1+!!gn)% 7;
              }
          }
      }
      if(valid_psc > 2*invalid_psc + 6){
          return 50;
      }else if(valid_psc > 2*invalid_psc + 2)
          return 25;
      return 0;
  }
  
  FF_DEF_RAWVIDEO_DEMUXER(h261, "raw H.261", h261_probe, "h261", CODEC_ID_H261)
  