Is there are know problem of encoding using the x264 encoder? (for default n900 profile for example).

I get about half the screen (the top half) in very good quality. But from there on video quality gets really really bad (very blocky). The line between good and bad is not stable during play it always jumps up and down a little.

I tried to play around with the settings, but it didn't help. Does anyone else have that?

It's version Version : 20100607 of x264 lib. (As shipped in archlinux )