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ncdec.c
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1 /*
2  * NC camera feed demuxer
3  * Copyright (c) 2009 Nicolas Martin (martinic at iro dot umontreal dot ca)
4  * Edouard Auvinet
5  *
6  * This file is part of FFmpeg.
7  *
8  * FFmpeg is free software; you can redistribute it and/or
9  * modify it under the terms of the GNU Lesser General Public
10  * License as published by the Free Software Foundation; either
11  * version 2.1 of the License, or (at your option) any later version.
12  *
13  * FFmpeg is distributed in the hope that it will be useful,
14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16  * Lesser General Public License for more details.
17  *
18  * You should have received a copy of the GNU Lesser General Public
19  * License along with FFmpeg; if not, write to the Free Software
20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
21  */
22 
23 #include "libavutil/intreadwrite.h"
24 #include "avformat.h"
25 #include "internal.h"
26 
27 #define NC_VIDEO_FLAG 0x1A5
28 
29 static int nc_probe(AVProbeData *probe_packet)
30 {
31  int size;
32 
33  if (AV_RB32(probe_packet->buf) != NC_VIDEO_FLAG)
34  return 0;
35 
36  size = AV_RL16(probe_packet->buf + 5);
37 
38  if (size + 20 > probe_packet->buf_size)
39  return AVPROBE_SCORE_MAX/4;
40 
41  if (AV_RB32(probe_packet->buf+16+size) == NC_VIDEO_FLAG)
42  return AVPROBE_SCORE_MAX;
43 
44  return 0;
45 }
46 
48 {
49  AVStream *st = avformat_new_stream(s, NULL);
50 
51  if (!st)
52  return AVERROR(ENOMEM);
53 
57 
58  avpriv_set_pts_info(st, 64, 1, 100);
59 
60  return 0;
61 }
62 
64 {
65  int size;
66  int ret;
67 
68  uint32_t state=-1;
69  while (state != NC_VIDEO_FLAG) {
70  if (avio_feof(s->pb))
71  return AVERROR(EIO);
72  state = (state<<8) + avio_r8(s->pb);
73  }
74 
75  avio_r8(s->pb);
76  size = avio_rl16(s->pb);
77  avio_skip(s->pb, 9);
78 
79  if (size == 0) {
80  av_log(s, AV_LOG_DEBUG, "Next packet size is zero\n");
81  return AVERROR(EAGAIN);
82  }
83 
84  ret = av_get_packet(s->pb, pkt, size);
85  if (ret != size) {
86  if (ret > 0) av_free_packet(pkt);
87  return AVERROR(EIO);
88  }
89 
90  pkt->stream_index = 0;
91  return size;
92 }
93 
95  .name = "nc",
96  .long_name = NULL_IF_CONFIG_SMALL("NC camera feed"),
97  .read_probe = nc_probe,
98  .read_header = nc_read_header,
99  .read_packet = nc_read_packet,
100  .extensions = "v",
101 };