I had the same problems. I didn't notice that the picture flickering (do you get big patches of mostly green garbage?)
No, not at all, always still pictures that was seen before.
was triggered by channel changes, but that could well be the case.
Only with channel changes here, and only with the option "software scaling" set to true in xineliboutput.
I noticed the bad sync too. It seemed to start off slightly out of sync and get worse the longer I left it running, but I haven't confirmed that.
I didn't have the feeling that it get worse, it seems to be stable.
I'm using HDMI audio, you'd think the video and sound clocks would therefore be derived from the same clock on the NVidia chip and it should be easier to avoid loss of sync :-(.
Okay, I don't use HDMI audio, because my receiver is too old for this and I am even not sure currently whether my Plasma supports HDMI Audio, will test next chance.
Yesterday I have switched back to the use of vdpau, because I got now periodically hick ups with xv and xxmc, the last time I had this working correct I had another CPU, mainboard and nvdida driver :(. The loss of sync is less disturbing than this periodically stops of motion.
Will soon try the r167 release of the vdpau patch.
Gerald