Universal Disk Format
The Universal Disk Format (UDF) is used for so called "packet written" writable CD-ROMs that are not simply copies of ISO 9660 CDROMs. Packet writing allows CDs to be partially written using variable or fixed length records in multiple sessions. Variable length packets written CD-Rs and CD-RWs can (usually) be closed to ISO 9660 format just by writing a table of contents on the CD. Fixed length packet formatting can not be closed to ISO 9660 format, but can be randomly written and overwritten. Fixed length formatting cuts CD capacity by about 20% relative to ISO 9660 or variable length formatting.
Conventional operating systems only provide support for ISO 9660 format unless special drivers are loaded. Thus UDF formatted information can not be used or listened to without closing the file to ISO 9660 format. Once closed, the CDROM can not be reopened.
For the basic user the UDF allows a CD-RW to be used like a floppy disk.
More generally, UDF is a format specification of a file system for storing files on recordable media, mainly media with limited rewriting conditions, such as:
- MO (magneto optical)
- DVD (including DVD-ROM, DVD-R and others)
- CD-R, CD-RW
It is mainly used for DVD-Video discs, but also by software such as DirectCD for Windows by Roxio, or Write UDF by Software Architects.
UDF is practically the successor of ISO 9660, supporting larger files, larger disk and more information about individual files and folders (e.g., it includes support for special file properties, such as Apple's File Types, Resource Forks, and other OS-specific data).
UDF is fully compliant with the ISO 13346 standard.
UDF has been released in multiple revisions:
- Revision 2.50. Added the Metadata Partition facilitating metadata clustering and optional duplication of file system information.
- Revision 2.01. Added support for Real Time Files.
- Revision 2.00. Added support for Stream Files, Access Control lists, and Power Calibration.
- Revision 1.50.
- Revision 1.02. UDF 1.02 is specified for use by DVD drives.
- Revision: 1.0
Modern operating systems understand 1.02 and 2.01 revisions of UDF.
External link
Referenced By
CD-ROM | CD-RW | CD-Rewritable | CDROM | CD ROM | Compact Disc Rewritable | Compact Disk Rewritable | DVD-Audio | DVD drive | DVD movie | DVD ripper | Digital Versatile Disc | Digital Video Disc | File System | File systems | Filesystem | Mount Rainier (disambiguation) | Mount Rainier (packet writing) | UDF Format
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