yading@11: /*
yading@11:  * RAW H.261 video demuxer
yading@11:  * Copyright (c) 2009 Michael Niedermayer <michaelni@gmx.at>
yading@11:  *
yading@11:  * This file is part of FFmpeg.
yading@11:  *
yading@11:  * FFmpeg is free software; you can redistribute it and/or
yading@11:  * modify it under the terms of the GNU Lesser General Public
yading@11:  * License as published by the Free Software Foundation; either
yading@11:  * version 2.1 of the License, or (at your option) any later version.
yading@11:  *
yading@11:  * FFmpeg is distributed in the hope that it will be useful,
yading@11:  * but WITHOUT ANY WARRANTY; without even the implied warranty of
yading@11:  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
yading@11:  * Lesser General Public License for more details.
yading@11:  *
yading@11:  * You should have received a copy of the GNU Lesser General Public
yading@11:  * License along with FFmpeg; if not, write to the Free Software
yading@11:  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
yading@11:  */
yading@11: 
yading@11: #include "libavcodec/get_bits.h"
yading@11: #include "avformat.h"
yading@11: #include "rawdec.h"
yading@11: 
yading@11: static int h261_probe(AVProbeData *p)
yading@11: {
yading@11:     uint32_t code= -1;
yading@11:     int i;
yading@11:     int valid_psc=0;
yading@11:     int invalid_psc=0;
yading@11:     int next_gn=0;
yading@11:     int src_fmt=0;
yading@11:     GetBitContext gb;
yading@11: 
yading@11:     init_get_bits(&gb, p->buf, p->buf_size*8);
yading@11: 
yading@11:     for(i=0; i<p->buf_size*8; i++){
yading@11:         if ((code & 0x01ff0000) || !(code & 0xff00)) {
yading@11:             code = (code<<8) + get_bits(&gb, 8);
yading@11:             i += 7;
yading@11:         } else
yading@11:             code = (code<<1) + get_bits1(&gb);
yading@11:         if ((code & 0xffff0000) == 0x10000) {
yading@11:             int gn= (code>>12)&0xf;
yading@11:             if(!gn)
yading@11:                 src_fmt= code&8;
yading@11:             if(gn != next_gn) invalid_psc++;
yading@11:             else              valid_psc++;
yading@11: 
yading@11:             if(src_fmt){ // CIF
yading@11:                 next_gn= (gn+1     )%13;
yading@11:             }else{       //QCIF
yading@11:                 next_gn= (gn+1+!!gn)% 7;
yading@11:             }
yading@11:         }
yading@11:     }
yading@11:     if(valid_psc > 2*invalid_psc + 6){
yading@11:         return 50;
yading@11:     }else if(valid_psc > 2*invalid_psc + 2)
yading@11:         return 25;
yading@11:     return 0;
yading@11: }
yading@11: 
yading@11: FF_DEF_RAWVIDEO_DEMUXER(h261, "raw H.261", h261_probe, "h261", AV_CODEC_ID_H261)