CHAPTER 13

Writable CDs Chapter 13
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wavelength 650nm (red) laser. Although the shorter wavelength laser works well for reading commercial
CD-ROM discs because the aluminum reflective layer they use is equally reflective at the shorter
DVD laser wavelength, it doesn’t work well at all for reading CD-R or RW discs.
Fortunately, a solution was first introduced by Sony and then similarly by all the other DVD drive
manufacturers. This solution consists of a dual-laser pickup that incorporates both a 650nm (DVD)
and 780nm (CD) laser. Some of these used two discrete pickup units with separate optics mounted to
the same assembly, but they eventually changed to dual-laser units that use the same optics for both,
making the pickup smaller and less expensive. Because most manufacturers wanted to make a variety
of drives—including cheaper ones without the dual-laser pickup—a standard needed to be created so
that someone purchasing a drive would know the drive’s capabilities.
So, how can you tell whether your drive is compatible with CD-R and RW discs? To demonstrate the
compatibility of a particular drive, OSTA created industry standard tests and logos that would guarantee
specific levels of compatibility. These are called the MultiRead specifications. Currently there are
two levels, as follows:
■ MultiRead. For CD-ROM drives
■ MultiRead2. For DVD-ROM drives
In addition, a similar MultiPlay standard exists that is for consumer DVD-Video and CD-DA devices.
Table 13.25 shows the two levels of MultiRead capability that can be assigned to drives and the types
of media guaranteed to be readable in such drives.
Table 13.25 MultiRead and MultiRead2 Compatibility Standards for CD/DVD Drives
Media MultiRead MultiRead2
CD-DA X X
CD-ROM X X
CD-R X X
CD-RW X X
DVD-ROM - X
DVD-Video - X
DVD-Audio - X
DVD-RAM - X
X = Compatible; drive will read this media - = Incompatible; drive won’t read
Note that MultiRead also indicates that the drive is capabile of reading discs written in packet writing
mode because this mode is now being used more commonly with both CD-R and RW media.
To determine whether your drive meets either of these standards, merely look for the MultiRead or
MultiRead2 logo on the drive. These logos are shown in Figure 13.13.
The presence of these logos guarantees that particular level of compatibility. If you are purchasing a
CD-ROM or DVD drive and want to be able to read recordable or rewritable discs, be sure to look for
the MultiRead or MultiRead2 logo on your drive. Especially in the case of DVD drives, MultiRead2
versions generally are more expensive because of the extra cost of the dual-mode laser pickup
required. Virtually all DVD-ROM drives for computers have the dual pickup mechanism, enabling
them to properly read CD-R or CD-RW discs. However, most DVD video players used in entertainment
systems do not have the dual pickups.