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h261dec.c
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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 
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){
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)
static int shift(int a, int b)
Definition: sonic.c:82
#define FF_DEF_RAWVIDEO_DEMUXER(shortname, longname, probe, ext, id)
Definition: rawdec.h:69
#define xf(width, name, var, subs,...)
Definition: cbs_vp9.c:342
uint64_t_TMPL AV_WL64 unsigned int_TMPL AV_WL32 unsigned int_TMPL AV_WL24 unsigned int_TMPL AV_WL16 uint64_t_TMPL AV_WB64 unsigned int_TMPL AV_WB32 unsigned int_TMPL AV_WB24 unsigned int_TMPL AV_RB16
Definition: bytestream.h:87
int av_log2_16bit(unsigned v)
Definition: intmath.c:31
bitstream reader API header.
#define FFMAX(a, b)
Definition: common.h:94
int buf_size
Size of buf except extra allocated bytes.
Definition: avformat.h:451
unsigned char * buf
Buffer must have AVPROBE_PADDING_SIZE of extra allocated bytes filled with zero.
Definition: avformat.h:450
static int h261_probe(AVProbeData *p)
Definition: h261dec.c:26
#define AVPROBE_SCORE_EXTENSION
score for file extension
Definition: avformat.h:458
This structure contains the data a format has to probe a file.
Definition: avformat.h:448
uint64_t_TMPL AV_WL64 unsigned int_TMPL AV_WL32 unsigned int_TMPL AV_WL24 unsigned int_TMPL AV_WL16 uint64_t_TMPL AV_RB64
Definition: bytestream.h:87
Main libavformat public API header.