When NVIDIA had introduced VDPAU they did supply patches that added support for this API to the MPlayer and ffmpeg projects. The open-source community came along and provided VDPAU support for MythTV late last month. This work done entirely outside of NVIDIA ended up working out quite well and now MythTV takes full advantage of this NVIDIA creation.
The Xine community has now come along, however, and created their own VDPAU support. This Xine VDPAU implementation doesn't depend upon ffmpeg and currently supports H.264 and MPEG streams with OSD (On-Screen Displays) and de-interlacing also working.
Currently to take advantage of VDPAU with Xine you'll need to checkout the latest code from their Subversion repository and be using the NVIDIA 180.16 driver or later. Additional information on the Xine video player is available from their web-site.
While VDPAU continues to be adopted by different media players and users have been experiencing great results, AMD's competitor, which will be called X-Video Bitstream Acceleration, still has yet to see the light of day.