XOverlay lost after setting playbin state to Null

[Hoyt, David]

> Cheers, Dave, I will give it a try as soon as I solve my problem with
> signals.  My software is going to display 1-4 videos simultaneously and will
> be run on netbooks and tablets which are pretty slow and even tiniest
> performance gains are very important to me.

If it's any comfort, I've been running d3dvideosink in software that runs 16+ videos simultaneously. Most running it don't use that many at once, but the software supports it. Most do 5-10. But again, it's been running for months with no problems. But you should probably be using autovideosink so gstreamer can choose the best sink to use. If you use autovideosink and d3dvideosink isn't able to initialize for some reason, it should fall back to dshowvideosink.