ffdshow broke NPVR (maybe)!

[mikeh49]

Here's the background:

I've been advocating Windows 7 EVR with the Microsoft decoders as the default working setup for North America. So, I thought I'd try it on a old, lower power system (cheapo ECS MB, Sempron 2800, Radeon 9600Pro) to see what it could do. After a clean install of 7 and NPVR, I could play MPEG2 HD (PS or TS or dvr-ms NPVR or GBPVR recordings) smoothly at about 30% CPU with the MS video decoder/EVR and AC3 filter, which I thought was pretty good. (I had ditched this system when we got HD as it could barely handle it with XP and VMR9 FSE.)

I have never had success with ffdshow, but thought I'd try it again on 7 to see how it compared to the MS decoder. So, I installed ffdshow beta 7 and it was terrible - near 100% CPU and choppy video and async audio. (I used the pBS recommended settings - NV12, interlace flag, etc.) I set NPVR back to the MS decoder, and, voila, I now had choppy video with the MS decoder. Uninstalling ffdshow did not help.

Research with Task Manager, Resource Monitor and Process Explorer reveals the following:

NPVR process is using about 20% CPU (same as before the ffdshow fiasco); System process is using about 25%.

System is writing about 1.3 MB/sec to the disk, NPVR is reading about the same! WTF?

The thread/module in System process that is using the CPU is dxgmms1.sys

When I play the same file in WMP, it (WMP) uses about 27% CPU and System uses 1%, so the dxgmms1.sys problem is gone, and it's reasonably smooth.

I've reinstalled the ATI drivers (no help), re-installed the DirectX runtime and finally went back to a restore point before the ffdshow install (still no help).

Thoughts from the assembled experts?