Super Audio CD
China Video Disc
Video Single Disc
(pronounced as DVDR or DVD 'minus' R) is
a DVD recordable format. A DVD-R has more storage capacity than a CD-R,
typically 4.7 GB (or 4.38 GiB) instead of 700 MB, although the capacity of
the original standard developed by Pioneer was 3.95 GB (3.68 GiB). Pioneer
has also developed an 8.54 GB dual layer version, which appeared on the
market in 2005. A DVD-R can be written to only once, whereas a DVD-RW
(DVD-rewritable) can be rewritten multiple
The DVD-R format was developed by Pioneer in autumn
of 1997. It is supported by most DVD players, and is approved by the DVD Forum.
A competing format is
DVD+R (also DVD+RW for the rewritables), causing some people to
refer to DVD-R as DVD 'minus' R unofficially. Hybrid drives that handle both
formats are often labeled DVD±R and Super Multi (which
includes DVD-RAM support) and are very popular.
The larger storage
capacity of a DVD-R compared to a CD-R is achieved through smaller pit
size and smaller track pitch of the groove spiral which guides the laser
beam. Consequently, more pits can be written
on the same physical sized disc. In order to write smaller pits
onto the recording dye layer (see CD-R) a red laser beam
with a wavelength of 650 nm (for general use recordable
DVD) is used in conjunction with a higher numerical aperture lens. Because of
this shorter wavelength, DVD-R and DVD+R use different dyes
from CD-R to properly absorb this wavelength.
DVD-R discs are composed
of two 0.6 mm polycarbonate discs, bonded with an adhesive to each other.
One contains the laser guiding groove and is coated with the recording dye
and a silver alloy or gold reflector. The other one (for single-sided
discs) is an ungrooved 'dummy' disc to assure mechanical stability of the
sandwich structure, and compatibility with the compact disc standard
geometry which requires a total disc thickness of about 1.2 mm.
Double-sided discs have two
grooved, recordable disc sides, and require the user to flip the disc
to access the other side. Compared to a CD's 1.2 mm
of polycarbonate, a DVD's laser beam only has to penetrate
0.6 mm of plastic in order to reach the dye recording layer, which
allows the lens to focus the beam to a
smaller spot size to write smaller pits.
In a DVD-R, the addressing (the determination of location
of the laser beam on the disc) is done with
additional pits and lands (called land pre-pits) in the areas between the grooves.
The groove on a DVD-R disc has a constant
wobble frequency used for motor control etc.
Wikipedia information about
DVD-R. This article is licensed under the GNU Free Documentation License . It uses material
from the Wikipedia article 'DVD-R'
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