What is a segmentation fault?
 

When I try and use "ffmpeg" and "transcode" on command line to encode a DVD I've ripped as a .vob file, it stops, and says "Segmentation Fault": no other error messages. GUI dvd ripper programs have all failed, presumably because of this.

Anybody have any idea how can I fix this?

segmentation fault occurs when a programs access an area of memmory that it does not have access to.

Sometime it can occur when you use a program in a way that the authour didn't account for when he designed the software.
Can you post what you parsed to transcode at the command line ?