Hardware Reference
In-Depth Information
DVD+R disc, using the same recording method, laser wavelength, and other specifica-
tions. However, DVD+R DL discs have two recording layers, with the reflective surface
of the top layer being semi-transparent to permit recording on the second layer. Because
ofthelowerreflectivityofthetoplayer,someDVD-ROMdrivescannotreadDVD+RDL
media. DVD+RW DL media is typically rated at 8x recording speeds.
Multiformat Rewritable DVD Drives
The DVD Multi specification from the DVD Forum was developed for drives and players
that are compatible with all DVD Forum standards, including DVD-R/RW, DVD-RAM,
DVD-ROM, DVD-Video, and eventually DVD Audio (DVD+R/RW are not DVD Forum
specifications and are not supported). The original version of DVD Multi was published
inFebruary2001;thecurrentversion,version1.01,wasapprovedbytheDVDForumand
published in December 2001. The first DVD Multi products for computers reached the
market in early 2003.
ToprovidesupportfordifferenttypesofDVDmediainasingledrive,allrewritableDVD
drive vendors now sell drives compatible with both DVD+R/RW and DVD-R/RW discs.
These drives are commonly known as DVD'R/RW. LG's Super Multi Drive series was
the first to also add compatibility with DVD-RAM, and most current DVD'R/RW drives
fromothermakersarealsocompatiblewithDVD-RAM.Many(butnotall)currentdrives
also support DVD-R DL, so you can now buy a single drive that supports all common
formats supported by both the DVD Forum and the DVD+RW Alliance. Lite-On uses the
term Super AllWrite to refer to drives that support all these media types.
BD
In February 2002, the leading optical storage companies formed the Blu-ray Disc
Founders (BDF) and announced the initial specifications for BD, a high-capacity optical
disc format. By May 2002, BD specification 1.0 was released, and in April 2003, Sony
released the BDZ-S77 for the Japanese market, the first commercially available BD re-
corder. In January 2006, the Blu-ray Disc Association also released a 2.0 specification for
BD-RE discs. Blu-ray is a fully rewritable format that enables recording up to 25GB of
data or up to 11.5 hours of standard-definition video on a single-sided, single-layer 12cm
diameter disc (which is the same as existing CDs and DVDs) using a 405nm blue-violet
laser. Dual-layer BD-R DL recorders are also available and can record up to 50GB or 23
hours of standard-definition video. The latest BD specifications, BDXL (recordable) and
BD-RE XL (rewritable), can store up to 100GB or 128GB at 2x or 4x speeds.
Although backward compatibility with DVD and CD is not a requirement of the Blu-ray
specification, it is a feature drive manufacturers have included. One of the main applica-
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