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What
is DVD?
An Overview of DVD
Technology
DVD is a high-density
optical disc format designed for the playback of large amounts of data. DVD
originally stood for digital versatile disc or digital videodisc, but is now
just known as DVD. At first glance, a DVD disc looks much like its CD-ROM
counterpart, and in fact there are several similarities. Both share the same
120mm-diameter dimension, are 1.2mm thick plastic discs and rely on lasers to
read data, but that's where the similarities end. A CD can hold 650MB, while a
single-layer DVD disc can hold 4.7GB - the equivalent of a two-hour digital
movie or seven times the capacity of today's CD-ROMs. Double-sided, double-layer
DVD discs can store up to 17GB of data, or the equivalent of 25 CD-ROMs.
Because DVD is a digital technology, users also can be assured of little or
no degeneration of their data - unlike a well-worn VHS tape or vinyl record.
Consumers can depend on a high degree of investment protection and backward
compatibility.
DVD: Fulfilling the Needs of Two Different Industries
In developing the new standard, it was extremely important to satisfy two key
business sectors: the computer industry and Hollywood movie studios. Both wanted
a small-disc solution that guaranteed CD compatibility. In addition, Hollywood
also had its heart set on 135 minutes of storage, enough for a whole movie to be
viewed without changing to a second disc. DVD also had to meet the following
requirements outlined by these two groups:
- A single, interchangeable standard for both TV and PC-based applications
- Forward compatibility with future read/write and write-once DVD discs
- A low-cost format
- No mandatory container
- Reliable data storage and retrieval
- High online capacity (133 minutes of MPEG-2 video on a single side)
- High performance for sequential and non-sequential data
- Superior picture quality comparable to laser discs
- Exceptional digital surround sound for dynamic ambiance
- Dubbing in at least three languages and subtitling in four languages
There are currently six DVD format books published by the DVD Forum that
include specifications for the following formats:
DVD-ROM: DVD-ROM drives playback DVD read-only media for
desktop, notebook and ultraportable PCs. DVD-ROM drives are being incorporated
into most PCs purchased today, but can also be added as a peripheral via an
upgrade kit.
With MPEG-2 and Dolby Digital Surround Sound playback capabilities, DVD-ROM
drives are ideal for full-length feature films and computer games with advanced
graphics. DVD is one of the most important components of emerging "living
room" computers, or PC-TVs, with large, TV-like monitors and game
console-style remote control devices.
Because of its high capacity and throughput, DVD-ROM is also ideal for
environments needing access to large amounts of data.
DVD-RAM: DVD-RAM drives provide all the benefits of DVD-ROM
with the added advantage of rewritability. DVD-RAM is perfectly suited for
applications such as data back up, document archiving, multimedia titles and
presentations. It allows users to record and re-record from 2.6GB to 5.2GB
and 4.7GB to 9.4GB on one disc. DVD-RAM utilizes phase change technology, in
which a laser heats the inner surface of the disc for a magnetic charge,
allowing data stored on DVD-RAM discs to be written and re-written hundreds of
thousands of times. DVD-RAM is currently shipping and is projected to be the
storage medium of the future because of its storage capacity, low-cost per MB
and compatibility with other DVD formats.
DVD-R: DVD-R is a high capacity, high throughput, write-once
optical disc. It is analogous to CD-R, and is used primarily for authoring and
testing DVD titles, as well as limited distribution DVD publishing. Single-sided
DVD-R discs store 3.9GB and 4.7GB of data.
DVD-RW: Also known as DVD-Rewritable, DVD-RW is a rewritable
version of DVD-R. Offering 4.7GB capacity per disc, it is designed as an
authoring tool as well as for archiving data. DVD-RW uses DVD-R media, but is
rewriteable up to 1,000 times. DVD-RW differs from DVD-RAM in that it records
data sequentially, whereas DVD-RAM provides random access to recorded data.
DVD-Audio: DVD-Audio defines a read-only optical disc designed
for the playback of high-quality audio. Supporting a wide range of digital audio
options, DVD-Audio products offer consumers a superior listening experience.
DVD-Video: DVD-Video offers a high capacity, read-only format
for the interactive playback of high quality video, audio and graphics ideal for
set-top box applications.
In addition to the six formats supported by the DVD Forum, DVD+RW, also known
as DVD rewritable, is another rewritable standard endorsed by the members of the
Yokohama Group. DVD+RW discs hold 3GB per side, and are designed for the same
applications as DVD-RW. Proponents of the DVD+RW format have promised the first
products will be available at the end of 1999.
Conclusion
DVD is the first standard
designed specifically with the consumer and computer electronics industries in
mind. Simply put, DVD enables consumers for the first time to enjoy enhanced
video, audio and increased data storage that allow PC users to turn their PC
into true entertainment devices.
The DVD Forum membership, which included content
developers and other interested parties, established several working groups to
attack a broad range of issues, including recordable (write-once, read-many) and
rewriteable media requirements. These requirements included:
| A
single format for computer, TV-based applications |
| Backward
read compatibility with current CD technology |
| Forward
read compatibility with future R/W and WORM discs |
| Single
file system for all content and disc media types |
| Low
cost |
| No
mandatory container |
| Reliable
data storage and retrieval |
| High
on-line capacity |
| High
performance for sequential, non-sequential data |
Following a three-month evaluation of drive and
media compatibility by more than 20 personal computer and storage media
manufacturers from around the world, the DVD Forum unveiled the DVD-R and DVD-RAM
standards in 1997. Since then, the DVD-RAM standard has been adopted by the
Japanese Industrial Standard (JIS) and the European Computer Manufacturer's
Association (ECMA) and is being reviewed by ISO (International Standards
Organization).
The present DVD-RAM standard provides 2.6GB and
4.7GB of single-sided storage capacity; read compatibility with DVD-ROM, DVD-R,
CD-ROM, CD-R and CD-RW media and a road map for regular capacity increase
milestones. In addition to providing fast data access, the initial products
already provide very low-cost storage solutions (2.6GB single-sided media
provides a storage cost of only .009˘/MB and double-sided 5.2GB media provides
a storage cost of only .008˘/MB).
| 5.2GB
DVD-RAM |
2.6GB
DVD-RAM |
Compact
Disc |
 |
 |
 |
