Editing VOB (section)

==File format==
Files in VOB format have a <code>.vob</code> filename extension and are typically stored in the [[VIDEO_TS]] directory at the root of a [[DVD]].<ref>{{Cite web
 |url = http://www.fileinfo.com/extension/vob
 |title = .VOB File Extension
 |work = FileInfo.com
 |access-date = 18 April 2012
}}</ref> The VOB format is based on the [[MPEG program stream]] format, but with additional limitations and specifications in the private streams.<ref name="whatisvob">{{Cite web
 |url = http://www.mpucoder.com/DVD/vobov.html
 |title = What is a VOB file
 |work = MPUCoder
 |publisher = SoundWare Associates 
 |access-date = 18 April 2012
}}</ref><ref name="mpeg-dvd">{{Cite web
 |url = http://dvd.sourceforge.net/dvdinfo/dvdmpeg.html
 |title = DVD - MPeg (sic.) differences
 |work = DVD Resources for Open Source Development
 |publisher = [[SourceForge]]
 |access-date = 28 April 2012
}}</ref><ref>{{cite web |url=http://dvdpro.com/dvd.htm |title=Is it easy to understand DVD format? |access-date=2011-02-26 |archive-url=https://web.archive.org/web/20011024182535/http://dvdpro.com/dvd.htm |archive-date=2001-10-24}}</ref> The MPEG program stream has provisions for non-standard data (as used in VOB files) in the form of so-called private streams. VOB files are a very strict subset of the MPEG program stream standard. While all VOB files are MPEG program streams, not all MPEG program streams comply with the definition for a VOB file.<ref name="whatisvob" />

Analogous to the MPEG program stream, a VOB file can contain [[H.262/MPEG-2 Part 2]] or [[MPEG-1#Part 2: Video|MPEG-1 Part 2]] video, [[MPEG-1 Audio Layer II]] or MPEG-2 Audio Layer II audio, but usage of these compression formats in a VOB file has some restrictions in comparison to the MPEG program stream. In addition, a VOB file can contain [[linear PCM]], [[Dolby Digital|AC-3]] or [[Digital Theatre System|DTS]] audio and subpictures (subtitles).<ref name="mpeg-dvd" /><ref>MPEG.org (July 21, 1996) [http://www.mpeg.org/MPEG/DVD/Book_B/Video.html DVD Technical Notes - Video Data Specifications], Retrieved on 2009-07-25</ref><ref name="videohelp-dvd">Videohelp.com [http://www.videohelp.com/dvd#tech What is DVD? Technical Info for DVD-Video], Retrieved on 2009-07-28</ref> VOB files cannot contain [[Advanced Audio Coding|AAC]] audio (MPEG-2 Part 7), [[MPEG-4]] compression formats and others, which are allowed in the MPEG program stream standard.{{CitationNeeded|date=July 2017}}

On the DVD, all of the content for one title set is contiguous, but if necessary is broken up into 1 [[Gigabyte|GB]] VOB files in order to be compatible with all operating systems, as some cannot read files larger than that size.<ref name="whatisvob" /><ref>Doom9.org [http://www.doom9.org/dvd-structure.htm doom9.org What's on a DVD?], Retrieved on 2009-07-26</ref>

=== Companion files{{anchor|IFO}} ===
VOB files may be accompanied with IFO and BUP files. These files respectively have <code>.ifo</code> and <code>.bup</code> filename extensions.

IFO (information) files contain all the information a DVD player needs to know about a DVD so that the user can navigate and play all DVD content properly,<ref>AfterDawn.com (2007-07-31) [http://www.afterdawn.com/guides/archive/how_to_play_vob___ifo___bup_files.cfm How to play VOB / IFO / BUP files], Retrieved on 2009-07-26</ref> such as where a chapter starts, where a certain audio or subtitle stream is located, information about menu functions and navigation. BUP (backup) files are exact [[data redundancy|redundant]] copies of IFO files, supplied to help in case of corruption. Video players may not allow DVD navigation when IFO or BUP files are absent.