How to change framerate of an XviD file

You would need to re-encode the audio. As such this really should be in the audio forum I guess. Either way it really has nothing to do with XviD. First you need to extract/demux the audio. This would depend on the container. Re-encode the audio whilst changing the duration with say BeSweet. Remux with original video with framerate changed.

Also in case you didn't know besweet has an "change framerate from" option which may help you out here, I've never used it but I suppose this is what it's for.

Thanks, I found all the options and it worked. However, I came to realize, that the source material must be somehow faulty. With either 23,976fps or 25fps I get a jerky motion at the exact same position - both on TV and on PC screen. Those are scenes with motion, i.e. zoom-in a pass-by-the camera, moving people and so on. Is it possible that this behaviour was produced by encoding... ???

Encoding more or less doesn't cause jerkyness. It sounds like the problem is interlacing or a framerate conversion of some sort and how it was processed before it was published to dvd or whatever. However to make sure check your cpu usage % during the part where the jerkyness ensues, if it's at 100% it could be your system isn't fast enough.

No, 10% usage of my 2,8GHz cpu ;) I will go rent a DVD and see what it looks like. But that is the PAL version... ah, we'll see...