VOB files and MPEG 2 videos aren't able to be decoded for playback in Video-SL. DVD-Video discs are encoded in a format which Video-SL does not currently support.

If your DVD isn't copy protected (made with a DVD recorder for instance), it's possible to convert the content into a file or files able to be played back by Video-SL.

For information on converting files check out these Video-SL articles:

MAC: Converting a DVD or VOB file using Handbrake

PC: Converting a DVD or VOB file using Handbrake