NVIDIA's VDPAU Implemented Over OpenGL/VA-API
Over on GitHub is a new project for providing a "VDPAU driver with OpenGL/VAAPI backend." The project is basically for providing VDPAU support for OpenGL and separately VA-API.
The aim is to allow Adobe Flash and MPlayer to take advantage of modern hardware for those systems not supporting VDPAU but just OpenGL / VA-API. It's quite straight forward and worth checking out if your driver doesn't support VDPAU and your preferred video applications don't have native OpenGL / VA-API / XvMC support.