File System Formats Definitions, DVD Capacity

LaCie d2 DL DVD±RW Drive – Toast 7 Titanium	5. Tech Tips
User’s Manual	page 25

5.2. File System Formats - Definitions

When writing DVD-R DL, DVD+R DL, DVD±R/RW and CD-R/RW discs, you will have the option to assign the disc a particular file format (the way in which a computer names and organizes files for storage and retrieval). There are essentially three file system formats to be concerned with when using a LaCie DVD or CD Drive:

•Universal Disk Format (UDF)

•ISO 9660

•Mac OS Extended

UDF –

This file system was developed to ensure consistency between various optical media, compatibility across platforms and among various CD and DVD applications. UDF is used by DVD to contain MPEG audio and video streams, and is required by DVD-ROMs.

ISO 9660 –

This is the standard file system for CD-ROMs, which allows them to be read on a Mac, PC or other major computer platform. Microsoft created an extension to the format, called Joliet, which allows for Unicode file character names and file names up to 64 characters in length (twice as many as the ISO 9660 Level 2 and 3 specifications).

Mac OS Extended –

Also known as HFS+, this is the file system used by Mac OS 8.1 and higher. If you will be using your disc only on Macs, this is the preferred file format.

5.3. DVD Capacity

There are important factors to consider when recording video, audio or data to DVD. The DVD media specification provides for two physical sizes: 4.7” (12cm) and 3.1” (8cm) (both are .47” (1.2cm) thick). DVD discs can also be single-sided (SS) or double-sided (DS), and each side can have one (SL) or two (DL) layers of data.

The amount of data or video that a disc can hold are dependent upon factors such as the amount of audio and the degree of compression of the data, video or audio. For example, a single-layer DVD±R disc typically will store just over two hours of MPEG-II video, but it is possible to put up to eight hours of VHS-quality video or one hundred sixty hours of audio on a single-layer disc.

When media companies reference the amount of data that a disc can hold, they represent the total amount in terms of gigabytes (GB), or a billion bytes (1000 x 1000 x 1000 bytes). This number, though, is not the way in which a computer addresses the data; to a computer the value is binary and larger than a billion bytes – 1,073,741,824 (1024 x 1024 x 1024 bytes). Therefore, when you put in a 4.7GB DVD disc, the actual available capacity is 4.38GB; and a 8.5GB Double Layer disc has an actual available capacity of 7.95GB.