private void SwitchStream(bool KeyDown)
 {
     if (client != null && KeyDown)
     {
         if (client.IsStreamOn)
         {
             if (client.StreamOff())
             {
                 img_stream_gray.Visibility = Visibility.Visible;
             }
         }
         else
         {
             if (client.StreamOn())
             {
                 if (!videoReceiverStarted)
                 {
                     // Must start on new thread otherwise wrong keyevent is raised!
                     new Thread(() =>
                     {
                         if (StartVideoReceiver(640, 480))
                         {
                             videoReceiverStarted = true;
                         }
                     }).Start();
                 }
                 img_stream_gray.Visibility = Visibility.Collapsed;
             }
         }
     }
 }