Annex P 120 mm DVD Medium (Normative)

This Annex defines the use of the UDF and ISO 9660 file systems with DVD media in such a manner as to require a reader to be capable of reading all of the physical media types and UDF and ISO 9660 file system versions that are defined in this Annex, and a creator to be able to create at least one of those types of media and file system.

The media types supported are DVD-ROM, DVD-R authoring and general, DVD-RW, DVD+R and DVD+RW.

Notes: 1. Capitalization in this annex may be inconsistent with other DICOM standards in order to be consistent with historical usage for terms in referenced documents.

2. Mandatory support for reading both UDF and ISO 9660 is included to facilitate migration from legacy CD-R implementations, which use ISO 9660, as well as to support the industry standard filesystem for DVD, UDF.

Universal Disk Format (UDF) is a profile of the ECMA 167 3rd edition file system.

Notes: 1. The ECMA 167 3rd edition is more recent than ISO 13346:1995 which is equivalent to ECMA 167 2nd edition.

2. A reader of a UDF 2.01 file system can also read a 2.0, 1.5 or 1.02 file system.

P.1 DICOM mapping to media format

P.1.1 Media Character Set

The character set used in UDF fields shall be the CS0 OSTA Compressed Unicode character set, required by the UDF standard.

Notes: 1. The CS0 OSTA Unicode character set is defined in UDF and is a subset of Unicode 2.0.

2. UDF defines a specific form of compression of 8 and 16 bit Unicode characters that must be supported.

3. The character set defined elsewhere in this section for DICOM File-set fields is a subset of this character set. However other fields in the UDF file system, and other files in the UDF file system not in the DICOM File-set, may use characters beyond those defined by DICOM for File ID Components, including those encoded in 16 bits.

4. The character set for File IDs and File-set IDs (see PS 3.10) is a subset of the ISO 9660 character set, therefore no further restrictions need to be imposed for ISO 9660 filesystems.

P.1.2 DICOM File-set

One and only one DICOM File-set shall be stored on each side of a single piece of media.

A DICOM File-set is defined to be completely contained within one UDF or ISO 9660 File-set.

Only a single UDF or ISO 9660 File-set shall be present in the UDF Volume.

Each side of the media will comprise a single self-contained UDF or ISO 9660 Volume. That is the UDF or ISO 9660 Volume Set shall not consist of more than one UDF or ISO 9660 Volume.

Only a single UDF or ISO 9660 Partition shall be present on each side the media.

Note: Other partitions containing other file systems, possibly sharing the same data, may be present, such as an ISO-9660 bridge disk, a Mac HFS or Unix UFS hybrid disk, etc.

P.1.3 DICOM File ID Mapping

The UDF and ISO 9660 Standards provide a hierarchical structure for directories and files within directories. Each volume has a root directory that may contain references to both files and subdirectories. Subdirectories may contain reference to both files and other subdirectories.

P.1.3.1 File ID

PS 3.10 defines a DICOM File ID Component as a string of 8 characters from a subset of the G0 repertoire of ISO 8859. Each of these File ID Components is mapped to a UDF File Identifier or Path Component in the OSTA CS0 character set.

Note: This mapping is a subset of the MS-DOS mapping specified in UDF.

Filename extensions are not used in DICOM File ID Components, hence an UDF or ISO 9660 File Identifier shall not contain a File Extension or the '.' that would precede such a File Extension.

The maximum number of levels of a Resolved Pathname in a UDF or ISO 9660 file-set shall be at most 8 levels, to comply with the definition of a DICOM File-set in PS 3.10.

The File Version Number is always equal to 1, as specified by UDF or ISO 9660.

Note: This file ID mapping is also compatible with ISO 9660 Level 1.

P.1.3.2 DICOMDIR File

A DICOMDIR file in a DICOM File-set shall reside in the root directory of the directory hierarchy, as specified in PS 3.10.

P.1.4 DICOM File Management Information

No file management information beyond that specified in the UDF or ISO 9660 File Entry is required. In particular no Extended Attributes or Named Streams are required.

Note: Unlike the Annex of this part specifying CD-R media, no restrictions or specifications with respect to ISO 9660 Recording Date and Time, file modification date, file owner identification and permissions, or other Extended Attribute Record values are specified, since these may be beyond the control of the DICOM application.

P.2 Filesystem

The reader shall be able to read a logical format conforming to UDF and ISO 9660 filesystems, as defined below.

The creator shall be able to create a logical format conforming to UDF or ISO 9660 filesystems or both, as defined below.

No requirements are defined for an updater.

Note: The intent of these requirements is to insist that a reader be able to read media created by any creator, but not to require that media created by a particular creator can necessarily be updated by a different updater.

P.2.1 UDF File system

The reader shall be able to read a logical format conforming to UDF 1.02 or 1.5 or 2.0 or 2.01, as required by the UDF 2.01 standard.

The creator shall be able to create a logical format conforming to any one of UDF 1.02 or 1.5 or 2.0 or 2.01.

Options or extensions defined in UDF are required or restricted as specified in the following sub-sections, and in the media specific sub-sections.

Note: Though the names of the files within the DICOM Fileset are restricted by PS 3.10, other files on the media may have longer filenames.

P.2.1.1 Interchange Levels

For the UDF Primary Volume Descriptor, both the Interchange Level and Maximum Interchange Level shall always be set to 2.

Notes: 1. This means that the volume is not and will never be, part of a multi-volume set.

2. The Interchange Level and Maximum Interchange Level in the File Set Descriptor are defined by UDF to always be 3. This is despite the fact that restrictions specified for the DICOM File-set may be very similar to lower Interchange Levels specified in ECMA 167.

P.2.1.2 Virtual Partition Map and Allocation Tables

Creators and updaters may or may not write UDF Virtual Partition Maps and Virtual Allocation Tables depending on the appropriate choice for physical media.

All readers are required to support UDF Virtual Partition Maps and Virtual Allocation Tables.

P.2.1.3 Sparable Partition Maps and Sparing Tables

Creators and updaters may or may not write UDF Sparable Partition Maps and Sparing Tables depending on the appropriate choice for physical media, since defect management may or may not be performed in the drive.

All readers are required to support UDF Sparable Partition Maps and Sparing Tables.

P.2.1.4 System Dependent Requirements

The reader shall not depend on any system dependent requirements as specified in UDF to be able to read the DICOM File-set, and shall not behave differently if they are present. Any unrecognized system dependent requirements shall be gracefully ignored.

Creators and updaters writing to a version of UDF that supports Named Streams shall use the default stream to write each file within the DICOM File-set.

Notes: 1. For example, a particular form of file permissions, particular extended attributes or particular named streams may not be required or affect application behavior.

2. This does not mean that Extended Attributes or Named Streams may not be present and associated with files within the DICOM File-set.

P.2.1.5 Permissions and File Characteristics

Creators and updaters shall always create permissions for files within the DICOM File Set such that all users may read, write and delete all files, and all users may access and delete all directories on all systems.

Notes: 1. These requirements are equivalent to setting a Unix permission of 644 for files and 755 for directories.

2. The intent of these requirements is that for DICOM interchange media, implementation specific access control is not used or required.

The UDF File Identifier Descriptor for files within the DICOM File Set shall not specify a File Characteristic of "hidden.”

P.2.1.6 File Types

The UDF File Types within the DICOM File Set shall only be files (that is a File Type of 0, meaning unspecified interpretation) or symbolic links to files (that is a File Type of 12).

P.2.2 ISO 9660 File system

The reader shall be able to read a logical format conforming to ISO 9660 Level 1, 2 and 3, with or without Rockridge or Joliet Extensions, which may or may not be present.

The creator shall be able to create a logical format conforming to ISO 9660 Level 1, 2 or 3, and may or may not add Rockridge or Joliet Extensions.

Note: Though the files within the DICOM Fileset are restricted to names that conform to a subset of ISO 9660 Level 1, other files on the media may have longer filenames. Unlike the Annex of this part specifying CD-R media, strict Level 1 conformance of the filesystem is not required, since this has proven difficult to constrain in practice.

P.2.2.1 Extended Attributes, Permissions and File Characteristics

File modification data, file owner identification, and permissions are part of the ISO 9660 - Extended Attribute Record. Support of the Extended Attribute Record is not required.

If Extended Attribute Records are present, all files within the DICOM File Set shall have permissions such that all users may read all files, and all users may access all directories on all systems.

Note: The intent of these requirements is that for DICOM interchange media, implementation specific access control is not used or required.

P.3 Media formats

P.3.1 DVD

P.3.1.1 DVD Physical Format

The physical format of DVD media shall comply with one of the following applicable definitions:

P.3.1.1.1 DVD Sector Format

The sector format of DVD media shall comply with one of the following applicable definitions:

No restrictions are placed on the use of disc-at-once, track-at-once, multi-session or packet-written format if applicable to the physical media type, other than that any session should be finalized at the conclusion of writing the media in order to make it readable.

P.3.1.2 DVD Logical Format

There are no requirements, restrictions, options or extensions to the logical format that are specific to this media type, beyond those specified in section P.2.

P.3.1.3 DVD Physical Media

The physical medium shall be the 120 mm DVD-R medium as defined in one of the following: