I keep going on and on about performance of the VideoRendererElement...well because I think it's important that peeps know.
As you can see in this video that the webcam is indeed in WPF space (reflection). It is doing 640x480x30FPS live from the camera. I show the Task Manager running about about 4 - 6% CPU. Playing the webcam in regular graphedt.exe (not in WPF) yields about 4% CPU usage. So most of the CPU tax is on the webcam driver itself, making VideoRendererElement almost nothing in the big picture!
(BTW, youtube might still be processing the file!)