UDF Product and Support Overview

“UDF” stands for “Univeral Disk Format” and file system. Originally specified for DVD, the UDF format is fast becoming the new international format standard for all types of storage devices because it ensures that disks can be properly used on all types of computer systems, on large storage devices and consumer digital appliances.

UDF was the file system selected by the computer and entertainment industries to enable complete data interchange between computer-based and entertainment-based media ("digital convergence"). The initial goal is to enable disc interchange between different vendors' computer, video players and home entertainment systems. The overall goal of UDF is to facilitate data interchange independent of hardware, software and operating system by standardizing on the way the information is stored and organized on the disk.

UDF is based upon the International Standards Organization's (ISO) ISO-13346 standard and the implementation guidelines are published by the Optical Storage Technology Association (www.osta.org).

UDF represents a key element to developing, mastering and playing the future family of optical discs such as DVD-RAM, DVD-ROM, CD-RW and CD-ROM. For example, with the initial deliveries of DVD discs in one of two basic formats: DVD-Video and DVD-ROM, strict adherence to international standards is necessary to provide broad-based compatibility and accessibility to the content provided.

The effectiveness of adhering to international standards is best illustrated with CD-ROMs and ISO-9660. Developed to ensure first generation CD-ROM interchange across multiple operating systems, the ISO-9660 file system was fundamental in establishing an installed based of conventional CD-ROM drives estimated to exceed 40 million. Yet ISO-9660 was based upon audio CD-ROMs is inadequate for larger and more complicated files and for the higher capacity, recordable and erasable discs. As a result, UDF was chosen as the file system of choice for the coming generation of DVD and other devices and media.

Advantages of the UDF file format include:

  • Supports very large capacity disks.
    UDF can store and manage data at the terabyte level on a single volume. UDF is the ONLY way to ensure proper use of high capacity disks. For example, Windows file system FAT 16 does not allow for larger than 2gbyte volumes in legacy operating systems and only 4gbytes on newer ones. The OSTA UDF specification allows for 1 terabyte and above volume sizes in UDF. UDF was designed for high capacity storage and for interchangability between operating systems. UDF is the ONLY way to ensure proper use of high capacity disks and the new large hard disk drives.
  • UDF supports the Unicode character set for compatibility with foreign language files and systems.
  • UDF is a standard format controlled by an industry organization (OSTA) that, with the appropriate software, can be applied for use on any proprietary operating system. This format is suitable for data archival purposes where the recovery of data may be in the future when operating systems have changed.
  • UDF File transfer rates can be optimized for large files, such as digital video.
  • UDF supports file "extended attributes", that are used by some operating systems
  • UDF supports long file names beyond the limits of most operating systems
  • UDF provides an international standard for read only, recordable and re-writable disks to be formatted to, to enable disk interchange between a large variety of computer systems and digital consumer devices, such as DVD devices.
SAI - Leader in UDF Solutions

SAI has been working on UDF longer than any other software developer. We started before it was called UDF. We helped co-author the standard and continue to be a leading member of the Optical Storage Trade Association.

SAI has the world's first and most comprehensive line of UDF file system support for personal computer storage devices. Products are available in English, Japanese, French, German, Spanish & Italian language versions. The UDF Developer Toolkit is available in an English version only.

All SAI products are OSTA UDF compliant. This means that SAI follows the spirit, intent and goal of UDF, which is troublefree interchange of disks. Some other companies may produce UDF products, but they may not be 100% compliant (meaning that you have to buy their other products and are not automatically readable by Microsoft and Apple readers).

SAI's UDF products are compatible with the built in UDF reader support in MS Windows 98, Me & 2000, XP and Windows Server 2003; and Mac OS 8, 9 and X. Furthermore SAI is the only company to support all versions of UDF.
  • V1.0.2 - Basic file system as used by DVD video players (ie rental movies)
  • V1.5.0 - Support for CD-R and CD-RW drives and media
  • V2.0.0 - Support for NT streaming.
  • V2.0.1 - Support for Video Recording Files (ability to copy, read and delete VOR files)
  • V2.5 and 2.6 are pending release

    Click here for PDF document to learn more about UDF

An Overview of the UDF File System

Advantages of UDF 

Large Capacity: A UDF-compliant file system will be able to store more data (exceeding the terabyte level), and a larger number of files than current operating systems. 

More Efficient Space Allocation: UDF supports volume sizes grater than the size allowed by the original operating system.  Small files written to a UDF disk would not take up extra space (e.g. a 512 byte file on a 2 GB Macintosh HFS volume takes up 32KB of space.  The same file on an optical disk formatted with UDF would only take up 512 bytes. 

Use of the Unicode Character Set:  The most commonly used character set today is ASCII which has a limit of 256 characters.  By comparison, UDF supports the Unicode character set which comprises 65,536 possible characters.  UDF supports characters from multiple languages including double-byte character sets like Japanese. 

File Names Up to 255 Characters:  UDF supports all current naming conventions.  File names will not have to be truncated when accessed out side their native operating system. 

Retention of Extended File System Attributes:  This feature permits flexible multiple Operating System mastering capabilities without compromising the integrity of the originating Operating System. 

Multiple Volume Set Support:  The UDF file system can handle multiple volume sets allowing users to take advantage of the performance gains and increased storage space obtained through spanning multiple disks. 

System-Independence:  System independence means UDF is the optimal archival medium.  Adherence to the UDF specification ensures data access regardless of future operating system implementations. 

OSTA UDF Details
[Source: OSTA Website]

This specification describes the Universal Disk Format, a file system defined by OSTA (www.osta.org). This specification, fully compliant with the ISO 13346 standard, is intended for developers who intend to implement UDF to enable file interchange among different operating systems. 

The OSTA Universal Disk Format Specification
OSTA has developed a file system format specification to address these problems of complexity and full data interchange. The goal of the OSTA Universal Disk Format (UDF) specification was to develop a practical subset of the NSR standard that would be much easier to bring to market, while also addressing how data is to be interchanged between systems. OSTA specifically defines what information shall be recorded on disk for a particular operating system and how other systems are to treat this information.

UDF was developed by an industry consortium of leading companies in the optical storage industry. Numerous experts have invested significant time in developing a document that would meet the above objectives. As an industry consortium OSTA is not hampered by the restrictions placed on ISO standards. This fact has allowed OSTA to develop a specification that is a significant advancement towards the goal of data interchange between operating systems.

UDF is:

Built on the foundation of the ISO/IEC 13346 standard: A practical subset of the ISO/IEC 13346 standard; Fully compliant with ISO/IEC 13346.

Simple and universal, defining support for multiple operating systems:

Defines what information must be stored on disk by all operating systems;
Defines what information must be stored on disk for each particular operating system;
Defines how information stored on the disk by one operating system is to be processed by another operating system;  
Provides support of, and data interchange among, the major commercial operating systems, including:
 DOS
 OS/2
 Macintosh
 POSIX [UNIX]

Expandable to include support for future operating systems.

UDF has been selected as the file system for 2nd generation high capacity CD-ROM, CD Recordable and CD Erasable disks. This includes Digital Video Disc (DVD), the first consumer application use of 2nd generation CD-ROM. Through the use of UDF, DVD entertainment based and computer based content can reside on the same disk and be accessed by a wide variety of computer systems as well as the consumer DVD player in the home.

UDF was designed to meet the mass storage needs of a global community well into the future.

Application Level Interchange
Once you have sector and file interchange you can move data among different optical drives on different computers with different operating systems. File interchange allows you to see the same directories and files on the different computers. The next level of data interchange is Application Interchange which deals with the file formats supported by the individual application.

For example, assume that you have sector and file interchange between a PC running DOS, and a Macintosh running MacOS. You can copy files to an optical disk on the Macintosh, bring that disk over to the PC and see the Macintosh files when listing the appropriate directories. Assume further that you used a database application called ALPHA on the Macintosh to create the files on the disk, and you wish to read access those files on the PC using a database application called BETA. Unless ALPHA and BETA use the same file format, you will not be able to read the data written by ALPHA with the BETA program. To have interchange between applications, they must use the same application standards and the same file format.

There currently exists a wide variety of file format standards that allow application interchange. There are database file format standards such as DBF, DIF and RTF. There are image file format standards such as TIFF, PCX, GIF and JPEG. There are audio file format standards such as WAV and VOC. Applications that support standard file formats will be able to interchange data at the application level.

Conclusion -- Ask yourself these questions:

What operating system will I be using 10 or 20 years from now?
What hardware platform will I be on?    
If I store massive amounts of data today, what will I do if I can't read it on my machine of tomorrow?

ISO standard optical media gives the assurance that you can access your data in a wide variety of different optical drives. The ISO standard NSR file system gives the assurance that you can have data interchange among today's wide variety of different operating systems and the operating systems of tomorrow. Optical storage standards provide assurance that today's data will be available beyond tomorrow. 

[Source: OSTA Website]