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29-589: Universal Disk Format ( UDF ) is an open , vendor-neutral file system for computer data storage for a broad range of media. In practice, it has been most widely used for DVDs and newer optical disc formats, supplanting ISO 9660 . Due to its design, it is very well suited to incremental updates on both write-once and re-writable optical media . UDF was developed and maintained by the Optical Storage Technology Association (OSTA). In engineering terms, Universal Disk Format

58-400: A free format which is not encumbered by any copyrights, patents, trademarks or other restrictions. Open formats (in the royalty-free and free access sense) include: The following formats are open (royalty-free with a one-time fee on the standard): Packet writing Packet writing allows users to create, modify, and delete files and directories on demand without the need to burn

87-415: A UDF partition formatted by Windows cannot be written under macOS. On the other hand, a partition formatted by macOS cannot be directly written by Windows, due to the requirement of a MBR partition table. In addition, Linux only supports writing to UDF 2.01. A script for Linux and macOS called format-udf handles these incompatibilities by using UDF 2.01 and adding a fake MBR; for Windows the best solution

116-711: A disk controller for a hard drive. The tools and drives that do not fully support revision 1.5 of UDF will ignore the sparing table, which would lead them to read the outdated worn-out sectors, leading to retrieval of corrupted data. An overhead that is spread over the entire disc reserves a portion of the data storage space, limiting the usable capacity of a CD-RW with e.g. 650 MB of original capacity to around 500 MB. The UDF specifications allow only one Character Set OSTA CS0 , which can store any Unicode Code point excluding U+FEFF and U+FFFE. Additional character sets defined in ECMA-167 are not used. Since Errata DCN-5157,

145-499: A file is deleted on the disc, the file's data still remains on the disc. It does not appear in the directory any more, but it still occupies the original space where it was stored. Eventually, after using this scheme for some time, the disc will be full, as free space cannot be recovered by deleting files. Special tools can be used to access the previous state of the disc (the state before the delete occurred), making recovery possible. Not all drives fully implement version 1.5 or higher of

174-487: A standards body and are fully documented and publicly available." The Enterprise Technical Reference Model (ETRM) classifies four formats as "Open Formats": Sun Microsystems defined the criteria for open formats as follows: According to The Linux Information Project , the term open format should refer to "any format that is published for anyone to read and study but which may or may not be encumbered by patents, copyrights or other restrictions on use" – as opposed to

203-457: A while, meaning that their data becomes unreliable, through having been rewritten too often (typically after a few hundred rewrites, with CD-RW). The plain and VAT builds of the UDF format can be used on rewriteable media, with some limitations. If the plain build is used on a -RW media, file-system level modification of the data must not be allowed, as this would quickly wear out often-used sectors on

232-424: A whole disc. Packet writing technology achieves this by writing data in incremental blocks rather than in a single block. Deleting files and directories of a CD-R using packet writing technology does not recover the space occupied by these objects but, rather, they are simply marked as being deleted (making them effectively hidden ). Similarly, changes to files cause new instances to be created instead of replacing

261-436: Is a profile of the specifications known as ISO/IEC 13346 and ECMA-167. Normally, authoring software will master a UDF file system in a batch process and write it to optical media in a single pass. But when packet writing to rewritable media, such as CD-RW , UDF allows files to be created, deleted and changed on-disc just as a general-purpose filesystem would on removable media like floppy disks and flash drives . This

290-516: Is also possible on write-once media, such as CD-R , but in that case the space occupied by the deleted files cannot be reclaimed (and instead becomes inaccessible). Multi-session mastering is also possible in UDF, though some implementations may be unable to read disks with multiple sessions. The Optical Storage Technology Association standardized the UDF file system to form a common file system for all optical media: both for read-only media and for re-writable optical media. When first standardized,

319-423: Is functionally equivalent to ISO-8859-1 , and the 16-bit storage is UTF-16 in big endian. 8-bit-per-character file names save space because they only require half the space per character, so they should be used if the file name contains no special characters that can not be represented with 8 bits only. The reference algorithm neither checks for forbidden code points nor interprets surrogate pairs , so like NTFS

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348-473: Is using the command-line tool format /FS:UDF /R:2.01 . Open format An open file format is a file format for storing digital data , defined by an openly published specification usually maintained by a standards organization , and which can be used and implemented by anyone. An open file format is licensed with an open license . For example, an open format can be implemented by both proprietary and free and open-source software , using

377-522: The VAT build to the UDF standard in its revision 1.5. The VAT is an additional structure on the disc that allows packet writing ; that is, remapping physical blocks when files or other data on the disc are modified or deleted. For write-once media, the entire disc is virtualized, making the write-once nature transparent for the user; the disc can be treated the same way one would treat a rewritable disc. The write-once nature of CD-R or DVD-R media means that when

406-644: The VAT build, CD-RW/DVD-RW media effectively appears as CD-R or DVD+/-R media to the computer. However, the media may be erased again at any time. The spared build was added in revision 1.5 to address the particularities of rewriteable media. This build adds an extra Sparing Table in order to manage the defects that will eventually occur on parts of the disc that have been rewritten too many times. This table keeps track of worn-out sectors and remaps them to working ones. UDF defect management does not apply to systems that already implement another form of defect management, such as Mount Rainier (MRW) for optical discs, or

435-601: The plain build and not necessarily either the VAT or Spared UDF builds. Mac OS X 10.4.5 claims to support Revision 1.50 (see man mount_udf ), yet it can only mount disks of the plain build properly and provides no virtualization support at all. It cannot mount UDF disks with VAT, as seen with the Sony Mavica issue. Releases before 10.4.11 mount disks with Sparing Table but does not read its files correctly. Version 10.4.11 fixes this problem. Similarly, Windows XP Service Pack 2 (SP2) cannot read DVD-RW discs that use

464-526: The Open Standards Principles apply to every aspect of government IT and that Government technology must remain open to everyone. They have seven principles for selecting open standards for use in government, following these principals many open formats were adopted, notably Open Document Format (ODF) . The seven principles for selecting open standards for use in the UK government are: Within

493-543: The UDF 2.00 sparing tables as a defect management system. This problem occurs if the UDF defect management system creates a sparing table that spans more than one sector on the DVD-RW disc. Windows XP SP2 can recognize that a DVD is using UDF, but Windows Explorer displays the contents of a DVD as an empty folder. A hotfix is available for this and is included in Service Pack 3. Due to the default UDF versions and options,

522-501: 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 . UDF shares the basic 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

551-471: The UDF part. Multiple revisions of UDF have been released: UDF Revisions are internally encoded as binary-coded decimals ; Revision 2.60, for example, is represented as 0x0260 . 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

580-445: The UDF, and some may therefore be unable to handle VAT builds. Rewriteable media such as DVD-RW and CD-RW have fewer limitations than DVD-R and CD-R media. Sectors can be rewritten at random (though in packets at a time). These media can be erased entirely at any time, making the disc blank again, ready for writing a new UDF or other file system (e.g., ISO 9660 or CD Audio ) to it. However, sectors of -RW media may "wear out" after

609-556: The disc (such as those for directory and block allocation data), which would then go unnoticed and lead to data loss. To allow modification of files on the disc, rewriteable discs can be used like -R media using the VAT build. This ensures that all blocks get written only once (successively), ensuring that there are no blocks that get rewritten more often than others. This way, a RW disc can be erased and reused many times before it should become unreliable. However, it will eventually become unreliable with no easy way of detecting it. When using

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638-669: The first version of the standard, this format can be used on any type of disk that allows random read/write access, such as hard disks , DVD+RW and DVD-RAM media. Metadata (up to v2.50) and file data is addressed more or less directly. In writing to such a disk in this format, any physical block on the disk may be chosen for allocation of new or updated files. Since this is the basic format, practically any operating system or file system driver claiming support for UDF should be able to read this format. Write-once media such as DVD-R and CD-R have limitations when being written to, in that each physical block can only be written to once, and

667-771: The framework of Open Government Initiative , the federal government of the United States adopted the Open Government Directive , according to which: "An open format is one that is platform independent, machine readable, and made available to the public without restrictions that would impede the re-use of that information". The State of Minnesota defines the criteria for open, XML-based file formats as follows: The Commonwealth of Massachusetts "defines open formats as specifications for data file formats that are based on an underlying open standard, developed by an open community, affirmed and maintained by

696-508: The highest UDF support level of all the implementations that has written to this image. 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 0x0201 , the minimum read revision set to 0x0150 , the minimum write to 0x0150 , and the maximum write to 0x0260 . The UDF standard defines three file system variations, called "builds". These are: Introduced in

725-478: The original files. Because of this, the available space on a non-rewritable medium using packet writing technology will decrease every time its content is modified. The most common file system for packet writing systems is UDF . Due to the characteristics of optical rewritable media such as CD-RWs and DVD-RWs , the ability of data sectors to hold their contents diminishes when changing them frequently (since re-crystallized alloy de-crystallizes). To cope with this

754-430: The range of code points was expanded to all code points from Unicode 4.0 (or any newer or older version), which includes Plane 1-16 characters such as Emoji . DCN-5157 also recommends normalizing the strings to Normalization Form C. The OSTA CS0 character set stores a 16-bit Unicode string "compressed" into 8-bit or 16-bit units, preceded by a single-byte "compID" tag to indicate the compression type. The 8-bit storage

783-533: The string may be malformed. (No specific form of storage is specified by DCN-5157, but UTF-16BE is the only well-known method for storing all of Unicode while being mostly backward compatible with UCS-2 .) Many DVD players do not support any UDF revision other than version 1.02. Discs created with a newer revision may still work in these players if the ISO 9660 bridge format is used. Even if an operating system claims to be able to read UDF 1.50, it still may only support

812-492: The typical software licenses used by each. In contrast to open file formats, closed file formats are considered trade secrets. Depending on the definition, the specification of an open format may require a fee to access or, very rarely, contain other restrictions. The range of meanings is similar to that of the term open standard . In 2012 the UK Government created the policy Open Standards Principles, stating that

841-422: The writing must happen incrementally. Thus the plain build of UDF can only be written to CD-Rs by pre-mastering the data and then writing all data in one piece to the media, similar to the way an ISO 9660 file system gets written to CD media. To enable a CD-R to be used virtually like a hard disk, whereby the user can add and modify files on a CD-R at will (so-called "drive letter access" on Windows), OSTA added

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