Sorry, but if you want crap images, use ripped movies and free programs. If you want good images, use shareware programs and rip the movies in full quality. That's the only way. If you just want to use the rips then you won't get any decent pictures, I can tell you that. I only use VLC to take really fast snapshots like for an avatar. Since the image is going to be so small, you can't tell it's a crappy picture.
There's no easy way to get good quality snapshots. You need storage space, $, be willing to make the effort, and have the time to make the quality good. If you're missing even one of those components, you can just forget it.
What is VOB by the way?
A piece of crap video format that makes movies that could be 1-2gb into 4-9gb movies.

: It's gotta be the worst format to work with (well....besides RGBM.....)