VOB stands for DVD Video OBject.

The VOB file is amongst the core files found on DVD-Video discs and has multiplexed Dolby Digital audio (normally AC3 format) and MPEG-2 video. VOB files with a DVD are numbered as follows: vts_XX_y.vob where XX represents the title and Y fault the title. There is 99 titles and 10 parts, although vts_XX_0.vob will not contain any video, usually just menu or navigational information. You will find them on a DVD video disc in the subdirectory labelled VIDEO_TS.

 

A VOB file (Video Object) can be a container format in DVD-Video media. VOB can contain video, audio, subtitle and menu contents multiplexed together in a stream form. VOB will be based upon the MPEG program stream format, but with additional limitations and specifications within the private streams. The MPEG program stream has provisions for non-standard data (as found in VOB files) available as so-called private streams. VOB files can be a very strict subset with the MPEG program stream standard. While all VOB files are MPEG program streams, not every MPEG program streams conform to the definition for just a VOB file.

 

Around the DVD, all the content for starters title set (VTS) is contiguous, but cracked into 1 GiB VOB files inside computer compatible file systems for that simplicity of various systems. Each VOB file must be below or corresponding to one GiB. Analogous towards MPEG program stream, VOB file can contain H.262/MPEG-2 Part 2 or MPEG-1 Part 2 video, MPEG-1 Audio Layer II or MPEG-2 Audio Layer II audio, but use of these compression formats within a VOB file has some restrictions with regards to the MPEG program stream. Moreover, VOB can contain Linear PCM, AC-3 or DTS audio and subpictures (subtitles). VOB file cannot contain AAC audio (MPEG-2 Part 7), MPEG-4 compression formats among others, that happen to be allowed in MPEG program stream standard.

 

Copy protection

Virtually all commercially produced DVD-Video titles apply certain restriction or copy protection method, which also affects VOB files. Copy protection is usually useful for copyrighted content. Many DVD-Video titles are encrypted with Content Scramble System (CSS). This is a data encryption and communications authentication method designed to prevent copying video and audio data completely from the DVD-Video discs. Decryption and authentication keys essential for playing back encrypted VOB files are trapped in the normally inaccessible lead-in section of the DVD disc and therefore are used only by CSS decryption software.

 

If people is wanting to repeat the belongings in an encrypted DVD-Video into a disk drive, an oversight can occur, as the DVD disc was not authenticated inside the drive by CSS decryption software. Authentication from the disc allows the copying of individual VOB files without error, but the encryption keys will never be copied. If the copied undecrypted VOB files are opened within a player, they're going to request the keys on the DVD-ROM drive and can fail.