Live TV sometimes not smooth

Hey,
i don't know if this is an known issue:

I am using Openelec with TVHeadend (and OSCam) to watch Live TV.
Most of the time, this works great, but sometimes, the HD-Channels begin to stutter. The image holds and then fast forwards to the actual point, you understand?
The Videoinformation shows, that the fps rate ranges between 28 and 31, while both CPU cores show a load around 12%.
(If Playback is smooth, the fps rate is 50 and both CPU loads around 60%)

After rebooting, it works fine again.

I am using the Zotac ND22 which normally hasn't any problems with HD-Content at all.

Do you have any ideas?

That's an issue with vdpau that has always been around.
I have re-written the interface to vdpau but changes have not been integrated into mainline yet. You might want to try a test build:
http://openelec.tv/forum/131-vdpau-nvidi...=600#41558