1/*
2 * RAW H.261 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 "libavcodec/get_bits.h"
23#include "avformat.h"
24#include "rawdec.h"
25
26static int h261_probe(AVProbeData *p)
27{
28    uint32_t code= -1;
29    int i;
30    int valid_psc=0;
31    int invalid_psc=0;
32    int next_gn=0;
33    int src_fmt=0;
34    GetBitContext gb;
35
36    init_get_bits(&gb, p->buf, p->buf_size*8);
37
38    for(i=0; i<p->buf_size*8; i++){
39        if ((code & 0x01ff0000) || !(code & 0xff00)) {
40            code = (code<<8) + get_bits(&gb, 8);
41            i += 7;
42        } else
43            code = (code<<1) + get_bits1(&gb);
44        if ((code & 0xffff0000) == 0x10000) {
45            int gn= (code>>12)&0xf;
46            if(!gn)
47                src_fmt= code&8;
48            if(gn != next_gn) invalid_psc++;
49            else              valid_psc++;
50
51            if(src_fmt){ // CIF
52                next_gn= (gn+1     )%13;
53            }else{       //QCIF
54                next_gn= (gn+1+!!gn)% 7;
55            }
56        }
57    }
58    if(valid_psc > 2*invalid_psc + 6){
59        return 50;
60    }else if(valid_psc > 2*invalid_psc + 2)
61        return 25;
62    return 0;
63}
64
65FF_DEF_RAWVIDEO_DEMUXER(h261, "raw H.261", h261_probe, "h261", CODEC_ID_H261)
66