As far as what I've understood, here is the content of a VOB file, correct me if I'm wrong:
- A video encoded with the mpeg2 codec. The video is compressed and encrypted.
- An audio track encoded either with the Dolby codec (AC3) or the DTS codec. The audio, is compresed and encrypted too (I'm not sure about that).
- A subtitle track. Subtitles are kind of bitmaps, not encrypted.