modules/demux/mxpeg_helper.h

   1 /*****************************************************************************
   2  * mxpeg_helper.h: MXPEG helper functions
   3  *****************************************************************************
   4  * Copyright (C) 2012 VLC authors and VideoLAN
   5  * $Id$
   6  *
   7  * Authors: Sébastien Escudier
   8  *
   9  * This program is free software; you can redistribute it and/or modify it
  10  * under the terms of the GNU Lesser General Public License as published by
  11  * the Free Software Foundation; either version 2.1 of the License, or
  12  * (at your option) any later version.
  13  *
  14  * This program is distributed in the hope that it will be useful,
  15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  17  * GNU Lesser General Public License for more details.
  18  *
  19  * You should have received a copy of the GNU Lesser General Public License
  20  * along with this program; if not, write to the Free Software Foundation,
  21  * Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
  22  *****************************************************************************/
  23
  24 /**
  25  * Finds FF XX in the first size byte of data
  26  */
  27 static uint8_t find_jpeg_marker(int *position, const uint8_t *data, int size)
  28 {
  29     for (int i = *position; i + 1 < size; i++) {
  30         if (data[i] != 0xff)
  31             continue;
  32         if (data[i + 1] != 0xff) {
  33             *position = i + 2;
  34             return data[i + 1];
  35         }
  36     }
  37     return 0xff;
  38 }
  39
  40 /*
  41  * Mxpeg frame format : http://developer.mobotix.com/docs/mxpeg_frame.html
  42  * */
  43 static bool IsMxpeg(stream_t *s)
  44 {
  45     const uint8_t *header;
  46     int size = vlc_stream_Peek(s, &header, 256);
  47     int position = 0;
  48
  49     if (find_jpeg_marker(&position, header, size) != 0xd8 || position > size-2)
  50         return false;
  51     if (find_jpeg_marker(&position, header, position + 2) != 0xe0)
  52         return false;
  53
  54     if (position + 2 > size)
  55         return false;
  56
  57     /* Skip this jpeg header */
  58     uint32_t header_size = GetWBE(&header[position]);
  59     position += header_size;
  60
  61     /* Get enough data to analyse the next header */
  62     if (position + 6 > size)
  63     {
  64         size = position + 6;
  65         if( vlc_stream_Peek (s, &header, size) < size )
  66             return false;
  67     }
  68
  69     if ( !(header[position] == 0xFF && header[position+1] == 0xFE) )
  70         return false;
  71     position += 2;
  72     header_size = GetWBE (&header[position]);
  73
  74     /* Check if this is a MXF header. We may have a jpeg comment first */
  75     if (!memcmp (&header[position+2], "MXF\0", 4) )
  76         return true;
  77
  78     /* Skip the jpeg comment and find the MXF header after that */
  79     size = position + header_size + 8; //8 = FF FE 00 00 M X F 00
  80     if (vlc_stream_Peek(s, &header, size ) < size)
  81         return false;
  82
  83     position += header_size;
  84     if ( !(header[position] == 0xFF && header[position+1] == 0xFE) )
  85         return false;
  86
  87     position += 4;
  88
  89     if (memcmp (&header[position], "MXF\0", 4) )
  90         return false;
  91
  92     return true;
  93 }