Hardware Reference
In-Depth Information
pared to the Red Book standard of 1.1mm. To compensate for spherical aberration caused
by a thinner CD layer, one method used is to increase the size of the pits on the CD side
ofaDualDisc,reducingplayingtimeto60minutes.(SomelaterDualDiscmediausesdif-
ferent methods to increase playtime.)
ThetotalthicknessofaDualDiscis1.5mm,comparedto1.2mmforstandardCDorDVD
media, causing DualDiscs to be incompatible with slot-loading drives in car stereos, PCs,
and mega-disc changers. Because DualDisc media is thicker than normal CD media and
because the internal structure of the CD side is not compatible with Red Book standards,
Philips and Sony (the co-creators of the CD format) do not use the CD logo on DualDisc
media, and most DualDisc albums include warning labels that the disc will not work in
slot-loaded drives and mega-disc changers and might not play in other types of players.
DualDisc albums are typically packaged in CD-style jewel cases.
Caution
Some music vendors use the term
DualDisc
to refer to SA-CD as well as actual DualDisc
albums. Be sure to check details of the media carefully to ensure that you can play the disc
in your equipment.
Although DualDisc media, unlike SA-CD media, supports two standard formats, it is not
nearly as popular as SA-CD media. Thousands of albums are available in SA-CD format,
but only a few hundred are available in DualDisc format (virtually none after 2006). SA-
CD provides far better audio quality than DualDisc (which provides only CD quality mu-
sic), making it a better format for the serious audiophile.
DVD Formats and Standards
As with the CD standards, the DVD standards are published in reference topics produced
mainly by the DVD Forum, but also by other companies, such as the DVD+RW Alliance.
The DVD Forum's DVD-Video and DVD-ROM standards are well established and are
supported by virtually every DVD drive, regardless of age. However, rival recordable and
rewritable DVD standards have been developed by both organizations. The DVD Forum
developed the following standards:
• DVD-RAM (drag-and-drop file storage and erasure without any add-on software re-
quired)
• DVD-R (recordable DVD)
• DVD-RW (rewritable DVD)
After the development of DVD-RAM and DVD-R, the rival DVD+RW Alliance deve-
loped these standards:
