Editing Universal Disk Format (section)

== History ==
{{Optical disc authoring}}

The [[Optical Storage Technology Association]] standardized the UDF file system to form a common file system for all optical media: both for [[file system permissions|read-only]] media and for re-writable optical media. When first standardized, the UDF file system aimed to replace [[ISO 9660]], allowing support for both read-only and writable media. After the release of the first version of UDF, the [[DVD Consortium]] adopted it as the official file system for [[DVD-Video]] and [[DVD-Audio]].<ref name="OSTA - UDF Specifications">
{{cite web| url = http://www.osta.org/specs| title = OSTA – UDF Specifications}}</ref>

UDF shares the basic [[ISO 9660#Volume descriptor|volume descriptor]] format with ISO 9660. A "UDF Bridge" format is defined since 1.50 so that a disc can also contain a ISO 9660 file system making references to files on the UDF part.<ref>{{cite web |title=ECMA Technical Report TR/71: DVD Read-Only Disk File System Specifications |url=https://www.ecma-international.org/publications/files/ECMA-TR/ECMA%20TR-071.PDF |date=February 1998}}</ref>

=== Revisions ===

Multiple revisions of UDF have been released:<ref name="OSTA - UDF Specifications"/><ref>{{cite web| url = https://sites.google.com/site/udfintro/| title = Wenguang's Introduction to Universal Disk Format (UDF)}}</ref>
* Revision 1.00{{efn|name="history"|Mentioned only in history of Revision 1.02.}} (24 October 1995). Original Release.
* Revision 1.01{{efn|Not on the OSTA website. See [[#External_links|§ External links]]. Also listed in the history of revision 1.02.}} (3 November 1995). Added DVD Appendix and made a few minor changes.
* Revision 1.02<ref>{{cite web| url = http://www.osta.org/specs/pdf/udf102.pdf| title = OSTA Universal Disk Format Specification Revision 1.02}}</ref> (30 August 1996). This format is used by [[DVD-Video]] discs.
* Revision 1.50<ref>{{cite web| url = http://www.osta.org/specs/pdf/udf150.pdf| title = OSTA Universal Disk Format Specification Revision 1.50}}</ref> (4 February 1997). Added support for CD-R/W Packet Writing and (virtual) rewritability on CD-R/DVD-R media by introducing the Virtual Allocation Table (VAT) structure. Added sparing tables for defect management on rewritable media such as CD-RW, and DVD-RW and DVD+RW. Add UDF bridge.
* Revision 2.00<ref>{{cite web| url = http://www.osta.org/specs/pdf/udf200.pdf| title = OSTA Universal Disk Format Specification Revision 2.00}}</ref> (3 April 1998). Added support for Stream Files, Access Control lists, Power Calibration, real-time files (for [[DVD recording]]) and simplified directory management. VAT support was extended.
* Revision 2.01<ref>{{cite web| url = http://www.osta.org/specs/pdf/udf201.pdf| title = OSTA Universal Disk Format Specification Revision 2.01}}</ref> (15 March 2000) is mainly a bugfix release to UDF 2.00. Many of the UDF standard's ambiguities were resolved in version 2.01.
* Revision 2.50<ref>{{cite web| url = http://www.osta.org/specs/pdf/udf250.pdf| title = OSTA Universal Disk Format Specification Revision 2.50}}</ref> (30 April 2003). Added the Metadata Partition facilitating metadata clustering, easier crash recovery and optional duplication of file system information: All metadata like nodes and directory contents are written on a separate partition which can optionally be mirrored. This format is used by some versions of [[Blu-ray Disc|Blu-rays]] and most [[HD-DVD]] discs.
* Revision 2.60<ref name=udf260p>{{cite web| url = http://www.osta.org/specs/pdf/udf260.pdf| title = OSTA Universal Disk Format Specification Revision 2.60}}</ref> (1 March 2005). Added Pseudo OverWrite method for drives supporting pseudo overwrite capability on sequentially recordable media. Has read-only compatibility with UDF 2.50 implementations.{{rp|10}} (Some [[Blu-ray]]s use this format.)

UDF Revisions are internally encoded as [[binary-coded decimal]]s; Revision 2.60, for example, is represented as {{mono|0x0260}}.<ref name=udf260p/>{{rp|23}} In addition to declaring its own revision, compatibility for each volume is defined by the minimum read and minimum write revisions, each signalling the requirements for these operations to be possible for every structure on this image. A "maximum write" revision additionally records the highest UDF support level of all the implementations that has written to this image.<ref name=udf260p/>{{rp|34}} For example, a UDF 2.01 volume that does not use Stream Files (introduced in UDF 2.00) but uses VAT (UDF 1.50) created by a UDF 2.60-capable implementation may have the revision declared as {{mono|0x0201}}, the minimum read revision set to {{mono|0x0150}}, the minimum write to {{mono|0x0150}}, and the maximum write to {{mono|0x0260}}.