CHAPTER 13

718 Chapter 13 Optical Storage
After you are sure that your drive can read UDF, you must check the OS. Most operating systems can’t
read UDF natively—the support has to be added via a driver. DOS can’t read UDF at all; however, with
Windows 95 and later, UDF-formatted discs can be read by installing a UDF driver. Normally such a
driver is included with the software that is included with most CD-RW drives. If you don’t have a
UDF driver, you can download one for free from Roxio at http://www.roxio.com. The Roxio UDF
Reader is included with DirectCD 3.0 and later. After the UDF driver is installed, you do not need to
take any special steps to read a UDF-formatted disc. The driver will be in the background waiting for
you to insert a UDF-formatted disc.
You can close a DirectCD for Windows disc to make it readable in a normal CD-ROM drive, which
will convert the filenames to Joliet format, causing them to be truncated to 64 characters.
Macintosh HFS
HFS is the file system used by the Macintosh OS. HFS can also be used on CD-ROMs; however if that
is done, they will not be readable on a PC. A hybrid disc can be produced with both Joliet and HFS or
ISO 9660 and HFS file systems, and the disc would then be readable on both PCs and Macs. In that
case, the system will see only the disc that is compatible, which is ISO 9660 or Joliet in the case of
PCs.
Rock Ridge
The Rock Ridge Interchange Protocol (RRIP) was developed by an industry consortium called the Rock
Ridge group. It was officially released in 1994 by the IEEE CD-ROM File System Format Working
Group and specifies an extension to the ISO 9660 standard for CD-ROM that enables the recording of
additional information to support Unix/POSIX file system features. Rock Ridge is not supported by
DOS or Windows. However, because it is based on ISO 9660, the files are still readable on a PC and
the RRIP extensions are simply ignored.
Note
An interesting bit of trivia is that the Rock Ridge name was taken from the fictional Western town in the movie Blazing
Saddles.
DVD
DVD stands for digital versatile disc and in simplest terms is a high-capacity CD. In fact, every DVD-
ROM drive is a CD-ROM drive; that is, they can read CDs as well as DVDs (discs). DVD uses the same
optical technology as CD, with the main difference being higher density. The DVD standard dramatically
increases the storage capacity of, and therefore the useful applications for, CD-ROM–sized discs.
A CD-ROM can hold a maximum of about 737MB (80-minute disc) of data, which might sound like a
lot but is simply not enough for many up-and-coming applications, especially where the use of video
is concerned. DVD discs, on the other hand, can hold up to 4.7GB (single layer) or 8.5GB (dual layer)
on a single side of the disc, which is more than 11 1/2 times greater than a CD. Double-sided DVD
discs can hold up to twice that amount; although currently you must manually flip the disc over to
read the other side.
Up to two layers of information can be recorded to DVD discs, with an initial storage capacity of
4.7GB of digital information on a single-sided, single-layer disc—a disk that is the same overall diameter
and thickness of a current CD-ROM. With Moving Picture Experts Group–standard 2 (MPEG-2)
compression, that’s enough to contain approximately 133 minutes of video, which is enough for a
full-length, full-screen, full-motion feature film—including three channels of CD-quality audio and
four channels of subtitles. Using both layers, a single-sided disc could easily hold 240 minutes of