/*
  * 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)
 {
     int i;
     int valid_psc=0;
     int invalid_psc=0;
     int next_gn=0;
     int src_fmt=0;
 

     for(i=0; i<p->buf_size; i++){
         if ((AV_RB16(&p->buf[i]) - 1) < 0xFFU) {
             int shift = av_log2_16bit(p->buf[i+1]);
             uint32_t code = AV_RB64(&p->buf[FFMAX(i-1, 0)]) >> (24+shift);
             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

                     static const int lut[16]={1,2,3,4,5,6,7,8,9,10,11,12,0,16,16,16};

                     next_gn = lut[gn];
                 }else{       //QCIF

                     static const int lut[16]={1,3,16,5,16,0,16,16,16,16,16,16,16,16,16,16};

                     next_gn = lut[gn];
                 }

             }
         }
     }
     if(valid_psc > 2*invalid_psc + 6){

         return AVPROBE_SCORE_EXTENSION;

     }else if(valid_psc > 2*invalid_psc + 2)

         return AVPROBE_SCORE_EXTENSION / 2;

     return 0;
 }
 

 FF_DEF_RAWVIDEO_DEMUXER(h261, "raw H.261", h261_probe, "h261", AV_CODEC_ID_H261)