Sony DADC - Manual (Page 4)

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DVD, which stands for Digital Versatile Disc, is the
next generation of optical disc storage technology.
It is essentially an optical disc that can hold video as
well as audio and computer data. This new optical
disc can reach a capacity of up to 26 times the
capacity of a CD-ROM and encompasses pre-
recorded read only discs like DVD-Video, DVD-ROM,
DVD-Audio, SACD and recordable formats like
DVD-R, DVD-RAM, DVD+RW and DVD-R/W. For
movie applications, a DVD can store full length
movies in a high-quality digital video with surround
sound in several languages and a wide range of
interactivity as well as subtitles. Almost all DVD
players and DVD-ROM drives are equipped with an
additional laser diode or a special lens for playback
capability of existing Audio CDs and CD-ROMs.
Main Features
1.1. Format and Specifications
The DVD standard defines a disc that maintains the
overall dimensions of the current Compact Disc.
Therefore the backwards compatibility with existing
Audio CDs and CD-ROMs was easier to realise. The
table below demonstrates similarities and
differences of CD and DVD.
CD DVD
Disc diameter 120mm 120mm
Disc thickness 1.2mm 1.2mm
Disc structure single substrate two bonded
0.6mm substrates
Laser wavelength 780nm 650 / 635nm
Numerical aperture 0.5 0.6
Track pitch 1.µm 0.74µm
Shortest pit/land 0.83µm 0.4µm
length
Data layers 1 up to 4
Data capacity approx. 650 MB 4.7 GB - 17.1 GB
1. From CD to DVD