I'm using mencoder to encode a DVD on my computer (reading it is not an issue), and I'm having trouble getting the codec to read a certain library.

My command includes these options:
-ovc lavc
-lavcopts vcodec=libx264 (I also tried with libxvid)
It spat out this error at the end:
Cannot find codec 'libxvid' in libavcodec...
Couldn't open video filter 'lavc'.
Failed to open the encoder.

Unless I can get this working I'll fall back on mpeg4 but I would like these codecs. I've had good experiences with them. I've checked and the libx264-98 package is installed, along with libxvidcore4 and avifile-xvid-plugin

Is this a permission problem? Or do I have to set a conf file?

DO NOT suggest using a different -ovc or vcodec. If you have one that works for you, keep that for yourself. I am going to use lavc.

This isn't really life or death here. I'd just like it to be able to work!