2 * RAW H.261 video demuxer
3 * Copyright (c) 2009 Michael Niedermayer <michaelni@gmx.at>
5 * This file is part of Libav.
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.
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.
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
22 #include "libavcodec/bitstream.h"
27 static int h261_probe(AVProbeData *p)
37 bitstream_init(&bc, p->buf, p->buf_size * 8);
39 for(i=0; i<p->buf_size*8; i++){
40 if ((code & 0x01ff0000) || !(code & 0xff00)) {
41 code = (code << 8) + bitstream_read(&bc, 8);
44 code = (code << 1) + bitstream_read_bit(&bc);
45 if ((code & 0xffff0000) == 0x10000) {
46 int gn= (code>>12)&0xf;
49 if(gn != next_gn) invalid_psc++;
55 next_gn= (gn+1+!!gn)% 7;
59 if(valid_psc > 2*invalid_psc + 6){
60 return AVPROBE_SCORE_EXTENSION;
61 }else if(valid_psc > 2*invalid_psc + 2)
62 return AVPROBE_SCORE_EXTENSION / 2;
66 FF_DEF_RAWVIDEO_DEMUXER(h261, "raw H.261", h261_probe, "h261", AV_CODEC_ID_H261)