1 /*
2 * RAW H.261 video demuxer
3 * Copyright (c) 2009 Michael Niedermayer <michaelni@gmx.at>
4 *
5 * This file is part of FFmpeg.
6 *
7 * FFmpeg 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 * FFmpeg 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 FFmpeg; 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
h261_probe(AVProbeData * p)26 static int h261_probe(AVProbeData *p)
27 {
28 int i;
29 int valid_psc=0;
30 int invalid_psc=0;
31 int next_gn=0;
32 int src_fmt=0;
33
34 for(i=0; i<p->buf_size; i++){
35 if ((AV_RB16(&p->buf[i]) - 1) < 0xFFU) {
36 int shift = av_log2_16bit(p->buf[i+1]);
37 uint32_t code = AV_RB64(&p->buf[FFMAX(i-1, 0)]) >> (24+shift);
38 if ((code & 0xffff0000) == 0x10000) {
39 int gn= (code>>12)&0xf;
40 if(!gn)
41 src_fmt= code&8;
42 if(gn != next_gn) invalid_psc++;
43 else valid_psc++;
44
45 if(src_fmt){ // CIF
46 static const int lut[16]={1,2,3,4,5,6,7,8,9,10,11,12,0,16,16,16};
47 next_gn = lut[gn];
48 }else{ //QCIF
49 static const int lut[16]={1,3,16,5,16,0,16,16,16,16,16,16,16,16,16,16};
50 next_gn = lut[gn];
51 }
52 }
53 }
54 }
55 if(valid_psc > 2*invalid_psc + 6){
56 return AVPROBE_SCORE_EXTENSION;
57 }else if(valid_psc > 2*invalid_psc + 2)
58 return AVPROBE_SCORE_EXTENSION / 2;
59 return 0;
60 }
61
62 FF_DEF_RAWVIDEO_DEMUXER(h261, "raw H.261", h261_probe, "h261", AV_CODEC_ID_H261)
63