I am having a similar problem. On some channels (e.g. the HD channel SVT HD) I get stuttering/pixelation quite often. When watching LiveTV, a severe case of pixelation causes the video and audio to get out sync with up to a couple of seconds in the worst case. If I press the rewind button and watch the timeshift buffer with a few seconds delay after the live feed, a severe case of pixelation doesn't seem to cause the video and audio to get out of sync.I also have a stuttering problem on LiveTV, but only on 2 channels, the rest is fine.
After a reboot these channels work fine, but after a while they begin to stutter. Which suggest a problem with timeshift.
When I pause these channels for a sec and press play again, it runs smoothly.
Using the latest "disaster's build".
It also seems that some codecs are better than other to keep video and audio in sync after a severe case of pixelation. ffdshow H264 codec seem to be better than ATI H264 codec in this respect. I have to test this a bit more though.
I have ReClock installed and it could contribute to the problems but I am quite sure I have managed to deactive ReClock for MediaPortal. But to be on the safe side I will uninstall ReClock.
Yesterday I managed to setup my Dreambox so I can record HD channels and what I have seen so far the quality of the recorded TV seems to be much better when done on the Dreambox compared to my TV card.
Edit, more findings:
The stutter/pixelation problems seem to decrease a lot if I record TV with TV Server in the background without running MediaPortal to watch TV at the same time. When such a recording is played up at a later time with MediaPortal there are much less problems with stutter/pixelation compared to when watching Live TV.
burken