Playing back VC-1 (WVC-1) videos with DXVA in Windows Media Centre 7
After a lot of messing around with codecs, I've successfully gotten VC-1 videos to playback using DXVA hardware acceleration in Windows Media Centre on Windows 7. CPU usage is 8%-15% on a 2.13Ghz Core 2 Duo. This is down from around 80%-90%. GPU usage is around 10% on an NVidia GT440.
Don't bother with the Microsoft DMO codecs for VC-1 as they don't use DXVA (at least they don't with my NVidia GT440) and use more CPU time than software based ffdshow.
The ffdshow DXVA enabled codec for VC-1 seems to crash on the VC-1 streams I tried.
Download Media Player Classic MPHC Stand Alone filters from here. Make sure you you download the 64bit version if you're using 64bit Windows Media Centre.
Extract MPCVideoDec.ax from the zip file to a safe location and then register it from the command prompt using "regsvr32 MPCVideoDec.ax".
Use Win7DSFilterTweaker and select "MPCVideoDec" under xx-bit decoders/VC-1.
Everything should work straight after that (no reboot required). If you encounter any problems then you can use the DSFilterTweaker to switch back to the Microsoft decoder and "regsvr32 /u MPCVideoDec.ax" to deregister the MPC codec.