A VOB file is a specialized container format based on the . It acts as a wrapper that "multiplexes" several streams of data so they can be played back in perfect synchronization: Video: Typically encoded in MPEG-2 format.
Identifies this as the first title set on the disc (usually the main movie).
This specific zero-index file is reserved for the menu of that title set, rather than the movie itself. 3. Usage and Playback
Because VOB files are designed for hardware DVD players, they often require specific software to open on modern computers. A Guide to VOB Files - Adobe