XOverlay lost after setting playbin state to Null

[Hoyt, David]

> This is how I bind the window handle to the video sink:
>       Gst.Interfaces.XOverlayAdapter overlayAdapter = new
> Gst.Interfaces.XOverlayAdapter(videoSink.Handle);
>       overlayAdapter.XwindowId = (ulong)window.Handle;
> I think that's the standard way of doing this, are ther any others? 
> Avoiding to lock the videosink would solve lots of problems.

WPF itself uses direct 3d, I believe (http://stackoverflow.com/questions/1373195/does-wpf-rely-on-direct3d-calls-even-for-standard-controls). So you may be experiencing issues as a result of that -- it may be trying to initialize and use a different version of direct 3d or the interaction between 2 differently managed direct 3d stacks, so to speak, could be giving rise to the problems you're seeing.

You might want to look at how to mix external direct 3d code with WPF. That might require changes to d3dvideosink or perhaps necessitate a WPF video sink.