What is the state of WMV/VC-1 DXVA acceleration in XP?

[davexnet]

Hello, I've got a triple boot system and an 8600GT, this one:
http://www.newegg.com/Product/Product.aspx?Item=N82E16814130297

On my box with Vista Ultimate, after I enabled DXVA in the performance tab of WMP 11,
a 1080p WMV/VC-1 file that was barely playable (48-50% CPU on my dual core)
dropped to 35 % and played smoothly.

On my two installs of XP, one with WMP 10 and the other with WMP 11,
this file plays at 48-50 % CPU no matter what I set in WMP.
Sure looks like VC-1 acceleration is not working.

H.264 DXVA acceleration works fine in XP using MPC home cinema.
There is a note on the MPC-HC page that says its software only accelerates
H.264 if you use Nvidia, but it can accelerate VC-1 & H.264 if you have ATI.

What is the real story with WMV/VC-1 acceleration in XP?
I can't get it to work, but it seems to in Vista.
Thanks for any info.

[roozhou]

8600GT only supports partial acceleration of VC1.
WMP 11's VC1 decoder(wmvdecod.dll) supports single-threaded partial acceleration and multi-threaded software decoding. If only one core is used during playback, it is probably using DXVA.

Try PotPlayer or KMPlayer and use WMV Decoder DMO + Overlay Mixer for best performance.

[davexnet]

Thanks for your response, I'll give KMPlayer a try and report back.

I understand what you said about 8600GT supporting only a flavor of VC-1 acceleration.
The question is, why do I see a noticeable benefit in Vista but not in XP ( I assume that
in Vista some acceleration is taking place, but in XP nothing)

I am using a dual core but in XP it uses 50% CPU,
so its using the whole of one core.