FFmpeg
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h264dec.c
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1 /*
2  * RAW H.264 video demuxer
3  * Copyright (c) 2008 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 "avformat.h"
23 #include "rawdec.h"
24 
25 static int h264_probe(AVProbeData *p)
26 {
27  uint32_t code = -1;
28  int sps = 0, pps = 0, idr = 0, res = 0, sli = 0;
29  int i;
30 
31  for (i = 0; i < p->buf_size; i++) {
32  code = (code << 8) + p->buf[i];
33  if ((code & 0xffffff00) == 0x100) {
34  int ref_idc = (code >> 5) & 3;
35  int type = code & 0x1F;
36  static const int8_t ref_zero[] = {
37  2, 0, 0, 0, 0, -1, 1, -1,
38  -1, 1, 1, 1, 1, -1, 2, 2,
39  2, 2, 2, 0, 2, 2, 2, 2,
40  2, 2, 2, 2, 2, 2, 2, 2
41  };
42 
43  if (code & 0x80) // forbidden_bit
44  return 0;
45 
46  if (ref_zero[type] == 1 && ref_idc)
47  return 0;
48  if (ref_zero[type] == -1 && !ref_idc)
49  return 0;
50  if (ref_zero[type] == 2)
51  res++;
52 
53  switch (type) {
54  case 1:
55  sli++;
56  break;
57  case 5:
58  idr++;
59  break;
60  case 7:
61  if (p->buf[i + 2] & 0x03)
62  return 0;
63  sps++;
64  break;
65  case 8:
66  pps++;
67  break;
68  }
69  }
70  }
71 
72  if (sps && pps && (idr || sli > 3) && res < (sps + pps + idr))
73  return AVPROBE_SCORE_EXTENSION + 1; // 1 more than .mpg
74 
75  return 0;
76 }
77 
78 FF_DEF_RAWVIDEO_DEMUXER(h264, "raw H.264 video", h264_probe, "h26l,h264,264,avc", AV_CODEC_ID_H264)