DVD -- Originally Digital Video Disk, sometimes Digital Versatile Disk, sometimes just DVD. DVD is first and foremost a medium for distributing full length motion pictures on CDROM type optical disks. DVD can also be used to store and read digital data -- including, but not limited to, digitized audio. DVD is thus suitable for a number of entertainment and computer applications. The drawback is that non-technical constraints such as copyright constraints, copy protection and media release control affect the capability and availability of computer DVD hardware.

DVD can store up to 4.7GByte per surface stored to be read at 11.08 Megabits/second constant linear velocity. After overhead, the data rate is about 9.8 Megabits/Second -- roughly equivalent to a 7X or 8X CDROM. Some DVD recording formats are designed for intermittent reading skipping one or more revolutions between reads. This is specifically intended to ease playing of full length movies from one recording surface.

DVD uses a shorter wavelength laser frequency than do CDROMs. DVD drives can, in principle, read standard CDROMs although some problems are reported reading user writable CDROMs. In practice, many DVD drives use a second set of optics to read CDROMs. DVD also permits two layers of data per side by focusing at two different depths. Thus a single DVD disk can have 4 recorded surfaces for a total of 17.08GByte of data. DVD drives can also, in principle read VCD disks -- an alternate recording technology widely available outside the US. DVD-RAM is a technology for user writable/rewritable DVD disks.

As of early 1999, Writable DVD drives 2.6Gb per surface, double sided, are being shipped.

DVD-Video ISO 13818-2 MPEG-2 (subset), ISO 11172-2 MPEG-1
DVD-Audio ISO 13818-3 MPEG-2 (ISO 11172-2 Layer II MPEG-1)
DVD-ROM Micro UDF/ISO 9660 Bridge


Return To Index Copyright 1994-2002 by Donald Kenney.