How to mirror (flip horizontally) and image using expression encoder and .net 4.5

Question

I am building a application and it seems that image is wrongly mirrored (if I raise my left finger up, it shows my right finder is raised and vice versa).

Here is some of my code

 <Grid>
   <WindowsFormsHost Name="WinFormsHost" Height="960" Width="1280">
      <forms:Panel x:Name="WebcamPanel" RightToLeft="Yes" />
    </WindowsFormsHost>
 </Grid>

and

_job = new LiveJob();
_deviceSrc = _job.AddDeviceSource(video, audio);
_deviceSrc.PreviewWindow = new PreviewWindow(new HandleRef(WebcamPanel, WebcamPanel.Handle));

How do I mirror the live stream from webcam?