Why NewVideoSample not work?

Jun 16, 2014 at 6:55 AM
the XAML code :
 <media:VideoCaptureElement x:Name="player" EnableSampleGrabbing="True" NewVideoSample="player_NewVideoSample" 
                                   RenderTransformOrigin="0.5,0.5" >
            <media:VideoCaptureElement.RenderTransform>
                <ScaleTransform ScaleX="-1"/>
            </media:VideoCaptureElement.RenderTransform>
        </media:VideoCaptureElement>
Runs fine on a development machine, but on the other machine, the event(NewVideoSample) is not responding,capture screen is normal.
And,when i set the DesiredPixelWidth,DesiredPixelHeight , the event(NewVideoSample) is not responding any.