Christian published a new, lengthy patch-set that adds most of the missing functionality to the VDPAU state tracker. One of the missing items that has been filled in is support for bit-map surfaces.
Additionally, these patches improved video playback by using page-flipping rather than frequently copying the frame content around. The usage of page-flipping by the VDPAU state tracker should allow for full-screen tear-free video playback, even when driving a secondary display.
In total there were 25 new patches published by this open-source AMD engineer for Gallium3D VDPAU. They can currently be found on the Mesa development list. This open-source video playback work should be another thing to look forward to with Mesa 8.1.