Sandy Bridge 2105 DXVA performance flaky?

[velis]

Using MS DTV-DVD codec playing 1080i MPEG2 20mbit / s content I get between 5 and 50% CPU usage. The CPU usage may stay at 5% for a few minutes and then go to 50% for the next few, then 15% for the next timeframe, etc...
I won't say anything about 5%, but 50% is clearly decoding in the CPU and not the GPU. Heck, even ffdshow with Yadif 2x and significant post-processing uses less than that.

I have my bios set to 128MB RAM for the GPU (max setting) - ASUS P8H67-V Rev. 3.0
CPU is i3 2105 with a HD3000 (supposedly)
RAM is set to 1333 (default was 1066), 9-9-9-24, 4GB of it

Using other codecs such as LAFV or MPC-HC MPEG2 decoder doesn't make much of a difference.

so any ideas how to ensure proper DXVA playback on this CPU?

Edit: sorry, forgot to mention I connect 2 displays, one 1080p, the other 1024x768

 

[mnewsham]

according to intel the DVMT (Dynamic video memory technology) is 1720Mb for all HD 3000 CPU's (including yours). so 128Mb RAM sounds like the minimum NOT the maximum. You should be able to allocate up to 1720Mb of RAM for the GPU.

 

[alyarb]

Don't use DXVA on sandy bridge. FFDShow (and all its post processing goodness) unofficially supports the fixed function quicksync decoder .

http://www.avsforum.com/avs-vb/showthread.php?t=1358343

 

[velis]

Wow, thanks for this link. Will be sure to try it out.
However,as far as I can see, this port only introduces decoders for MPEG2,4,AVC and VP1. The resize post-processing filter (that I would love to see accelerated) is left untouched.

 

[alyarb]

dxva was never meant for such filters anyway. it is merely a decoder that uses the CPU less. quicksync isn't perfect either but decoding with quicksync will use the CPU less than dxva would, freeing up cycles for your filters.

 

[velis]

Well, tried the filter with very disappointing results. CPU usage was *the same* as with libavcodec.
Playing 1080i (see post 1) took a very sizeable 50% CPU. To be honest, the same CPU usage turned out with both DXVA and libavcodec (all ffdshow).

Seems I must have my problem somewhere further down the road. Even using kernel deinterlacer in ffdshow drops the CPU usage down to 30% so I guess I'm having issues with "hardware" deinterlacing and postprocessing.

I'll need to drop it down to bare minimums to see where I'm losing cycles.
Then there's the problem of extremely high CPU usage using ffdshow as liveTV decoder in MediaPortal. Playing 1080i takes 80% of my CPU while using MS DTV-DVD only takes 30% ???