void mediaElement_MediaOpened(object sender, RoutedEventArgs e)
 {
     lastMarkerCheckTime = null;
     markers.Clear();
     // add all markers embedded in the stream.
     foreach (var marker in mediaElement.Markers)
     {
         markers.Add(marker);
     }
 }
 void SmoothStreamingMediaElementWrapper_MediaOpened(object sender, System.Windows.RoutedEventArgs e)
 {
     lastMarkerCheckTime = null;
     markers.Clear();
 }