J UDF on 120 mm DVD-RAM Medium (Normative)
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# J UDF on 120 mm DVD-RAM Medium (Normative)

This Annex defines the use of the UDF 1.5 file system with DVD-RAM media.

### Note

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. DVD-ROM is a pre-mastered medium, that is it is manufactured rather than written on a one-off basis by a medical device. While it is likely that a device conforming to this Annex will be able to read a UDF file system from DVD-ROM, it is not a requirement.

Universal Disk Format (UDF) version 1.5 is a profile of the ECMA 167 3rd edition file system.

### Note

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

2. Though later revisions of UDF such as 2.0 are defined with additional features compared to 1.5, these features are not required to support recording of a DICOM file set.

3. A reader of a UDF 2.0 file system can also read a 1.5 or 1.02 file system.

4. A UDF 1.02 reader cannot read the Virtual Allocation Table (VAT) used to incrementally write a UDF 1.5 or later disk.

5. A UDF 1.5 file system reader can theoretically read those structures of a UDF 2.0 file system that are common to both versions. However, a UDF 1.5 reader cannot read the Named Streams or extended file entries that may be recorded on a UDF 2.0 file system.

   Since a UDF 1.5 reader may completely reject a 2.0 disk based on the version number written on the media, without attempting to read compatible structures of the file system, it is not permitted to write DICOM media with a version greater than 1.5.

6. A writer (FSC or FSU) is not permitted to add structures from a later version of UDF to a file system that has been created with an earlier version of the file system.

## J.1 DICOM Mapping to Media Format

### J.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.

### Note

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.

### J.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 File-set.

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

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

Only a single UDF 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.

### J.1.3 DICOM File ID Mapping

The UDF Standard provides a hierarchical structure for directories and files within directories. Each volume has a root directory that may contain references to both files and sub-directories. Sub-directories may contain reference to both files and other sub-directories.

#### J.1.3.1 File ID

PS3.10 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 a UDF 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 file-set shall be at most 8 levels, to comply with the definition of a DICOM File-set in PS3.10.

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

### Note

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

#### J.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 PS3.10.

### J.1.4 DICOM File Management Information

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

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