An optical storage medium with improved capacity and bandwidth compared with the Compact Disc. DVD, like CD, was initially marketed for entertainment and later for computer users.
A DVD can hold a full-length film with up to 133 minutes of high quality video, in MPEG-2 format, and audio.
The first DVD drives for computers were read-only drives ("DVD-ROM"). These provide over seven times the storage capacity of CD-ROM (4.7 GB). DVD-ROM drives read existing CD-ROMs and music CDs and are compatible with installed sound and video boards. Additionally, the DVD-ROM drive can read DVD films using an advanced (MPEG-2) video board, required to decode the high resolution video format.
The first drives, using a single-layer disc of 4.7GB, were expected to be available during the second half of 1996 from Toshiba, Philips, Sony, Hitachi and others. In 1997, dual-layer discs were expected to increase the disc capacity to 8.5 GB. Double-sided, dual-layer discs will eventually increase the capacity to 17 GB.
Write-once DVD-R ("recordable") drives record a 3.9GB DVD-R disc that can be read on a DVD-ROM drive. The first DVD-R drive was expected by mid 1997.
By the end of 1997, the rewritable DVD-RAM (by false analogy with random access memory) drive was expected to become available. DVD-RAM drives read and write to a 2.6 GB DVD-RAM disc, read and write-once to a 3.9GB DVD-R disc, and read a 4.7 GB or 8.5 GB DVD-ROM. Also, it was expected that a DVD-RAM disc would be readable on both the DVD-R and DVD-ROM drives.
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