modules/demux/mxpeg_helper.h

   1 /*****************************************************************************
   2  * mxpeg_helper.h: MXPEG helper functions
   3  *****************************************************************************
   4  * Copyright (C) 2012 VLC authors and VideoLAN
   5  *
   6  * Authors: Sébastien Escudier
   7  *
   8  * This program is free software; you can redistribute it and/or modify it
   9  * under the terms of the GNU Lesser General Public License as published by
  10  * the Free Software Foundation; either version 2.1 of the License, or
  11  * (at your option) any later version.
  12  *
  13  * This program 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
  16  * GNU Lesser General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU Lesser General Public License
  19  * along with this program; if not, write to the Free Software Foundation,
  20  * Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
  21  *****************************************************************************/
  22
  23 /**
  24  * Finds FF XX in the first size byte of data
  25  */
  26 static uint8_t find_jpeg_marker(int *position, const uint8_t *data, int size)
  27 {
  28     for (int i = *position; i + 1 < size; i++) {
  29         if (data[i] != 0xff)
  30             continue;
  31         if (data[i + 1] != 0xff) {
  32             *position = i + 2;
  33             return data[i + 1];
  34         }
  35     }
  36     return 0xff;
  37 }
  38
  39 /*
  40  * Mxpeg frame format : http://developer.mobotix.com/docs/mxpeg_frame.html
  41  * */
  42 static bool IsMxpeg(stream_t *s)
  43 {
  44     const uint8_t *header;
  45     int size = vlc_stream_Peek(s, &header, 256);
  46     int position = 0;
  47
  48     if (find_jpeg_marker(&position, header, size) != 0xd8 || position > size-2)
  49         return false;
  50     if (find_jpeg_marker(&position, header, position + 2) != 0xe0)
  51         return false;
  52
  53     if (position + 2 > size)
  54         return false;
  55
  56     /* Skip this jpeg header */
  57     uint32_t header_size = GetWBE(&header[position]);
  58     position += header_size;
  59
  60     /* Get enough data to analyse the next header */
  61     if (position + 6 > size)
  62     {
  63         size = position + 6;
  64         if( vlc_stream_Peek (s, &header, size) < size )
  65             return false;
  66     }
  67
  68     if ( !(header[position] == 0xFF && header[position+1] == 0xFE) )
  69         return false;
  70     position += 2;
  71     header_size = GetWBE (&header[position]);
  72
  73     /* Check if this is a MXF header. We may have a jpeg comment first */
  74     if (!memcmp (&header[position+2], "MXF\0", 4) )
  75         return true;
  76
  77     /* Skip the jpeg comment and find the MXF header after that */
  78     size = position + header_size + 8; //8 = FF FE 00 00 M X F 00
  79     if (vlc_stream_Peek(s, &header, size ) < size)
  80         return false;
  81
  82     position += header_size;
  83     if ( !(header[position] == 0xFF && header[position+1] == 0xFE) )
  84         return false;
  85
  86     position += 4;
  87
  88     if (memcmp (&header[position], "MXF\0", 4) )
  89         return false;
  90
  91     return true;
  92 }