libavformat/ncdec.c

   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 Libav.
   7  *
   8  * Libav 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  * Libav 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 Libav; 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
  47 static int nc_read_header(AVFormatContext *s)
  48 {
  49     AVStream *st = avformat_new_stream(s, NULL);
  50
  51     if (!st)
  52         return AVERROR(ENOMEM);
  53
  54     st->codec->codec_type = AVMEDIA_TYPE_VIDEO;
  55     st->codec->codec_id   = AV_CODEC_ID_MPEG4;
  56     st->need_parsing      = AVSTREAM_PARSE_FULL;
  57
  58     avpriv_set_pts_info(st, 64, 1, 100);
  59
  60     return 0;
  61 }
  62
  63 static int nc_read_packet(AVFormatContext *s, AVPacket *pkt)
  64 {
  65     int size;
  66     int ret;
  67
  68     uint32_t state=-1;
  69     while (state != NC_VIDEO_FLAG) {
  70         if (s->pb->eof_reached)
  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
  94 AVInputFormat ff_nc_demuxer = {
  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 };