Another big thank you to Stephen for taking the time and effort to reproduce what looks like a very hardware specific issue.
I'm another M2N68-VM owner who has been fighting with these "Block Artifacts" during MythTV VDPAU playback of MPEG2 TV recordings. As others have said, Mplayer plays perfectly via VDPAU so I'd originally concentrated on MythTV settings to try and resolve the issue. After trying every MythTV tweak I could think of, I assumed that my 8400GT may have been under powered for what I was asking (High Quality VDPAU @1920x1080). Last week I invested in a new 9800GT with 1GB RAM and was horrified to find that the Artifacts survived the upgrade.
I will watch with great interest to see how Stephen gets on with the bug that's been filed and offer my time (and excess NVidia hardware) if I can help with any testing that needs to be done along the way.
Originally Posted by Stephen Warren
Interesting. I tracked down an nForce 630a and a similar GPU and managed to reproduce the problem with the "curious george" clip. I'll file a bug and see if we can find out what's going wrong.