Guide to Cataloging DVD and Blu-ray Discs Using AACR2r ... - OLAC

DVD vs. CD
Visually, the DVD is indistinguishable from an audio CD or CD-ROM. Both the DVD and
CD consist of 12 cm (4 ¾ in.) diameter discs containing billions of tiny pits (nonreflective
holes) and lands (reflective bumps) arranged in one long spiral track. These
pits and lands represent the zeros and ones of digital information and are read by a
laser. The main differences are that a DVD’s pits and lands are shorter and narrower
than those of a CD and that the DVD’s laser also has a shorter wavelength. In terms of
storage, this means that a DVD can hold 4.7 billion bytes of information -- seven times
the informational capacity of a standard CD. A DVD can also hold two information layers
on one side which roughly increases its storage to 9 gigabytes. Unlike the CD, a DVD
can also hold information on both sides of a single disc. A DVD is essentially a bigger,
faster CD that can hold cinema-like video and better-than-CD audio as well as still
photos and computer data.
CDs and DVDs consist of the same basic materials and layers but are manufactured
differently. A DVD is actually like two thin CDs glued together. A CD is read from and
written to (by laser) on one side only; a DVD can be read from or written to on one or
both sides. A DVD currently has a disc capacity anywhere from 4.7 GB (single sided
single layer) to 17 GB (double sided dual layer).
New Formats
The Blu-ray Disc (BD) developed by Sony/Philips in February 2002, and the HD DVD
developed by Toshiba in March 2003 are high density optical discs using a blue laser to
record data. According to Jim Taylor in the 3 rd ed. of DVD DeMystified, the HD DVD is
“an extension of the original DVD format” while the Blu-ray Disc “is a significantly
changed version of DVD.” Both high density discs use the blue laser for smaller pits
and tighter tracks to increase capacity. The HD DVD does not change the data layer
depth but the Blu-ray Disc achieves the higher density by “using a 0.1-mm cover layer
to move the data closer to the lens (standard DVD uses a 0.6-mm cover, CD uses a
1.2-mm cover). These discs are considered the next generation optical disc formats
providing greater storage capacity than the DVD and offering high-definition video and
superior audio quality.
Toshiba announced in February 2008 that it “will no longer develop, manufacture and
market HD DVD players and recorders. This decision has been made following recent
major changes in the market.” (Businesswire.com). After this decision by Toshiba, it
was apparent that the Blu-ray Disc had emerged as the industry standard for high
density discs and what had been considered a format war between the two companies
ended.
Maxell added another format to disc development and announced plans to feature its
Holographic Versatile Storage Disc (HVD) at the National Association of Broadcasters
Convention in October 2006. This holographic disc, developed in collaboration with
InPhase Technologies, is designed to hold “800 GB and 1.6 TB of data respectively.”
. The HVD
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