View source for VOB

{{Short description|Container format in DVD-Video media}}
{{other uses}}
{{Infobox file format
| name = VOB
| icon = 
| logo =
| extension = .vob, .ifo, .bup
| mime = video/dvd, video/mpeg,<ref name="vob-whatis" /><ref name="vob-uniblue"/> video/x-ms-vob{{Citation needed|date=April 2012}}
| type code = 
| uniform type = 
| magic = 
| owner = [[DVD Forum]]
| type = [[Container format (digital)|Container format]]
| container for = [[Digital audio|Audio]], [[Digital video|video]], [[Subtitle (captioning)|subtitles]]
| contained by = [[DVD-Video]]
| extended from = [[MPEG program stream]] (ISO/IEC 13818-1)
| extended to = 
| standard = DVD-Video Book<ref name="dvd-book">DVD FLLC (2009-02) [http://www.dvdfllc.co.jp/format/f_bconst.html DVD Book Construction - list of all available DVD Books], Retrieved on 2009-07-24</ref><ref name="dvd-books">DVD FLLC [http://www.dvdfllc.co.jp/format/f_histry.html DVD Format Book - History of Supplements for DVD Books], Retrieved on 2009-07-24</ref>
| open = No
| free = No
}}

'''VOB''' (for '''video object''') is the [[container format]] in [[DVD-Video]] media. VOB can contain [[digital video]], [[digital audio]], [[Subtitle (captioning)|subtitles]], DVD menus and navigation contents [[multiplexed]] together into a stream form. Files in VOB format may be encrypted.

==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 = https://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.<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] {{Webarchive|url=https://web.archive.org/web/20150621150928/http://www.mpeg.org/MPEG/DVD/Book_B/Video.html |date=2015-06-21 }}, 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&nbsp;[[Gibibyte|GiB]] 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.

==Copy protection==
Almost all commercially produced DVD-Video titles use some [[DVD Video#Restrictions|restriction]] or [[copy protection]] method, which also affects VOB files.<ref>DVD Demystified (July 13, 2009) [http://dvddemystified.com/dvdfaq.html#1.11 What are the copy protection issues?], Retrieved on 2009-07-28</ref>  Copy protection is usually used for [[copyright]]ed 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 directly from the DVD-Video discs. Decryption and authentication keys needed for playing back encrypted VOB files are stored in the normally inaccessible lead-in area of the DVD and are used only by CSS decryption software (e.g., in a [[DVD player]] or software player). If someone is trying to copy the contents of an encrypted DVD-Video (e.g., VOB files) to a hard drive, an error can occur, because the DVD was not authenticated in the drive by CSS decryption software. Authentication of the disc allows the copying of individual VOB files without error, but the encryption keys will not be copied. If the copied undecrypted VOB files are opened in a player, they will request the keys from the DVD-ROM drive and will fail.<ref name="dvdemystified">DVD Demystified (July 13, 2009) [http://dvddemystified.com/dvdfaq.html#4.5 DVD Frequently Asked Questions (and Answers) - Why can't I play movies copied to my hard drive?], Retrieved on 2009-07-28</ref><ref name="dvdreplica">[http://www.dvd-replica.com/DVD/dvdprimer-7.php What are the copy protection schemes used in DVD ? What is CSS ?], Retrieved on 2009-07-28</ref>  There are many CSS-decrypting programs, or [[ripping]] software, such as [[libdvdcss]], [[DeCSS]], [[DVD Decrypter]], [[AnyDVD]] or [[DVD Shrink]] which allow a protected DVD-Video disc to be played without access to the original key or copied to hard disk unscrambled. In some countries, their usage can be a violation of law (e.g. for non-personal use).<ref name="dvdreplica" />

==Playback==
A player of generic MPEG-2 files can usually play unencrypted VOB files, which contain MPEG-1 Audio Layer II audio. Other audio compression formats such as AC-3 or DTS are less widely supported.{{Citation needed|date=December 2008}}

[[KMPlayer]], [[VLC media player]], [[GOM player]], [[Media Player Classic]] and more platform-specific [[Media player (application software)|players]] like [[ALLPlayer]] play VOB files.

==Other DVD containers==
{{main|Enhanced VOB|DVD-VR#VRO file format}}
Some [[DVD Recorder]]s use [[DVD-VR]] format and store multiplexed audiovisual content in VRO containers.<ref name="VRO">DVD Demystified (July 13, 2009) [http://dvddemystified.com/dvdfaq.html#4.10 What are .IFO, .VOB, .AOB, and .VRO files? How can I play them?], Retrieved on 2009-07-28</ref><ref>Doom9's forum (2002-2005) [http://forum.doom9.org/showthread.php?t=15908 DVD-RAM *.VRO File Conversion], Retrieved on 2009-07-28</ref> A VRO file is equivalent to a collection of DVD-Video VOB files. The VRO files can be played directly like a VOB if no editing is intended.<ref>[http://www.pixelbeat.org/docs/DVD-VR/ DVD-VR Application format notes], Retrieved on 2009-07-28</ref>  Fragmented VRO files are not widely supported by software players and video editing software.<ref name="VRO" />

[[Enhanced VOB]] (EVO) is also an extension to VOB, originally meant for the now-discontinued [[HD DVD]] video. It can contain additional video and audio formats such [[H.264]] and [[Advanced Audio Coding|AAC]].

==See also==
* [[Comparison of video container formats]]
* [[List of video editing software]]

==References==
{{reflist|refs=
<ref name="vob-whatis">{{Cite web
 |url = http://whatis.techtarget.com/file-extension/VOB-FileFormat.html
 |title = VOB File Format
 |work = WhatIs.com
 |publisher = TechTarget
 |access-date = 18 April 2012
 |archive-date = 7 March 2012
 |archive-url = https://web.archive.org/web/20120307215142/http://whatis.techtarget.com/file-extension/VOB-FileFormat.html
 |url-status = dead
 }}</ref>
<ref name="vob-uniblue">{{Cite web
 |url = http://filext.com/file-extension/vob
 |title = .VOB File
 |work = FileExt
 |publisher = UniBlue
 |access-date = 18 April 2012
  }}</ref>
}}

==External links==
* [http://www.doom9.org/dvd-structure.htm doom9.org - What is on a DVD?]

{{Compression formats}}

{{DEFAULTSORT:Vob}}
[[Category:DVD]]
[[Category:Digital container formats]]
[[Category:Filename extensions]]