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DVD (commonly "Digital Versatile Disc", previously "Digital Video Disc") is an optical disc storage media format that can be used for data storage, including movies with high video and sound quality. DVDs resemble compact discs as their physical dimensions are the same (120 mm (4.72 inches) or occasionally 80 mm (3.15 inches) in diameter), but they are encoded in a different format and at a much higher density.
In the early 1990s two high-density optical storage standards were being developed: one was the MultiMedia Compact Disc (MMCD), backed by Philips and Sony, and the other was the Super Density disc (SD), supported by Toshiba, Time-Warner, Matsushita Electric, Hitachi, Mitsubishi Electric, Pioneer, Thomson, and JVC. IBM's president, Lou Gerstner, acting as a matchmaker, led an effort to unite the two camps behind a single standard, anticipating a repeat of the costly format war between VHS and Betamax in the 1980s.
Philips and Sony abandoned their MMCD format (not to be confused with MultiMediaCards) and agreed upon Toshiba's SD format (not to be confused with secure digital cards, although the logo for the SD disc format would be re-used for the SD digital card format) with two modifications that are both related to the servo tracking technology. The first one was the adoption of a pit geometry that allows "push-pull" tracking, a proprietary Philips/Sony technology. The second modification was the adoption of Philips' EFMPlus. EFMPlus, created by Kees Immink, who also designed EFM, is 6% less efficient than Toshiba's SD code, which resulted in a capacity of 4.7 GB as opposed to SD's original 5 GB. The great advantage of EFMPlus is its great resilience against disc damage such as scratches and fingerprints. The result was the DVD specification Version 1.5, announced in 1995 and finalized in September 1996. In May 1997, the DVD Consortium was replaced by the DVD Forum, which is open to all companies.
"DVD" was originally an initialism for "Digital Video Disc."  Some members of the DVD Forum believe that it should stand for "Digital Versatile Disc" to reflect its widespread use for non-video applications. Toshiba, which maintains the official DVD Forum site, adheres to the latter interpretation, and indeed this appeared within the copyright warnings on some of the earliest examples. However, the DVD Forum never reached a consensus on the matter, and so today the official name of the format is simply "DVD"; the letters do not officially stand for anything.
DVD disc capacity
Note: GB here means gigabyte, equal to 109 (or 1,000,000,000) bytes. Many computers will display gibibyte (GiB), equal to 230 (or 1,073,741,824) bytes.
Example: A disc with 8.5 GB capacity is equivalent to: (8.5 x 1,000,000,000) / 1,073,741,824 ≈ 7.92 GiB.
The four basic types of DVD are referred to by their capacity in gigabytes, rounded to the nearest integer.
Another format in use (while remaining quite uncommon) is a double sided DVD with one side comprising a single layer of data while the opposite side comprises two layers of data. This format holds approximately 13.2 GB of data and is therefore known as DVD-14. However this format is limited in availability due to its infrequent use.
DVD recordable and rewriteable
- Main article: DVD recordable
HP initially developed recordable DVD media from the need to store data for back-up and transport.
DVD recordables are now also used for consumer audio and video recording. Three formats were developed: -R/RW (dash), +R/RW (plus), -RAM (random access memory).
Note: in the United Kingdom's British English, "DVD-R/RW" is pronounced "minus", not "dash" (the full sentence being pronounced as: DVD minus R (the 'R' rhyming with car, not the 'ruh' format).
Dual layer recording
Dual Layer recording allows DVD-R and DVD+R discs to store significantly more data, up to 8.5 Gigabytes per disc, compared with 4.7 Gigabytes for single-layer discs. DVD-R DL (dual layer — see figure) was developed for the DVD Forum by Pioneer Corporation, DVD+R DL (double layer — see figure) was developed for the DVD+RW Alliance by Sony.
A Dual Layer disc differs from its usual DVD counterpart by employing a second physical layer within the disc itself. The drive with Dual Layer capability accesses the second layer by shining the laser through the first semi-transparent layer. The layer change mechanism in some DVD players can show a noticeable pause, as long as two seconds by some accounts. More than a few viewers have worried that their dual layer discs were damaged or defective.
DVD recordable discs supporting this technology are backward compatible with some existing DVD players and DVD-ROM drives. Many current DVD recorders support dual-layer technology, and the price point is comparable to that of single-layer drives, though the blank media remains significantly more expensive.
DVD-Video is a standard for storing video content on DVD media. As of 2003, DVD-Video has become the dominant form of consumer video formats in the United States, Europe, and Australia.
Though many resolutions and formats are supported, most consumer DVD-Video disks utilize either 4:3 or 16:9 aspect ratio MPEG-2 video, stored at a resolution of 720x480 (NTSC) or 720x576 (PAL). Audio is commonly stored using the Dolby Digital (AC-3) and/or Digital Theater System (DTS) formats, ranging from monaural to 6.1 channel "Surround Sound" presentations. DVD-Video also supports features like selectable subtitles, multiple camera angles and multiple audio tracks.
DVD-Audio is a format for delivering high-fidelity audio content on a DVD. It offers many channel configuration options (from mono to 5.1 surround sound) at various sampling frequencies and sample rates. Compared with the CD format, the much higher capacity DVD format enables the inclusion of either considerably more music (with respect to total running time and quantity of songs) or far higher audio quality (reflected by higher linear sampling rates and higher vertical bit-rates, and/or additional channels for spatial sound reproduction).
Despite DVD-Audio's superior technical specifications, there is debate as to whether or not the resulting audio enhancements are distinguishable to typical human ears. DVD-Audio currently forms a niche market, probably due to its dependency upon new and relatively expensive equipment.
DVD-Audio discs employ a robust copy prevention mechanism, called Content Protection for Prerecorded Media (CPPM) developed by the 4C group (IBM, Intel, Matsushita, and Toshiba).
CPPM can be circumvented on a PC by capturing decoded audio streams in PCM format, but the underlying protection mechanism, encryption algorithms, and keys have not yet been cracked.
Players and recorders
Modern DVD recorders often support additional formats, including DVD+/-R/RW, CD-R/RW, MP3, WMA, SVCD, JPEG, PNG, SVG, KAR and MPEG-4 (DivX/Xvid). Some also include USB ports or flash memory readers. Many players are priced from under $/€ 25 and recorders from $/€ 50.
DVD drives for computers usually come with one of two kinds of Regional Playback Control (RPC), either RPC-1 or RPC-2. This is used to enforce the publisher's restrictions on what regions of the world the DVD can be played. See Regional lockout.
Windows XP lacks the ability to burn rewritable DVDs, even single layer. Add-on software is required. Newer Mac computers can burn DVD+RW, DVD-RW, and DVD-RAM natively from the OS X operating system.
Competitors and successors
There are several possible successors to DVD being developed by different consortiums: Sony/Panasonic's Blu-ray Disc (BD), Toshiba's HD DVD and Maxell's Holographic Versatile Disc (HVD).
The first generation of holographic media with 300 GB of storage capacity and a 160 Mbit/s transfer rate is scheduled for release in late 2006 by Maxell and its partner, InPhase.
On November 18, 2003, the Chinese news agency Xinhua reported the final standard of the Chinese government-sponsored Enhanced Versatile Disc (EVD), and several patents for it. However, since then the format has generally failed to live up to expectations.
On November 19, 2003, the DVD Forum decided by a vote of eight to six that HD DVD will be its official HDTV successor to DVD. This had no effect on the competing Blu-ray Disc Association's (BDA) determination that its format would succeed DVD, especially since most of the voters belonged to both groups.
On April 15, 2004, in a co-op project with TOPPAN Printing Co., the electronics giant Sony Corp. successfully developed the paper disc, a storage medium that is made out of 51% paper and offers up to 25 GB of storage, about five times more than the standard 4.7 GB DVD. The disc can be easily cut with scissors and recycled, offering foolproof data security and an environment-friendly storage media.
As reported in a mid 2005 issue of Popular Mechanics, it is not yet clear which technology will win the format war over DVD. HD DVD discs have a lower capacity than Blu-ray discs (15 GB vs. 25 GB for single layer, 30 GB vs. 50 GB for dual layer).
In April, 2000, Sonic Solutions and Ravisent announced hDVD, an HDTV extension to DVD that presaged the HD formats that debuted 6 years later. This situation—multiple new formats fighting as the successor to a format approaching purported obsolescence—previously appeared as the "war of the speeds" in the record industry of the 1950s. It is also, of course, similar to the VHS/Betamax war in consumer video recorders in the late 1980s.
The new generations of optical formats have restricted access through various digital rights management schemes; it remains to be seen what impact the limitation of fair use rights has on their adoption in the marketplace.
- Bennett, Hugh (April 2004). Understanding Recordable & Rewritable DVD. Optical Storage Technology Association. Retrieved on 2006-12-17.
- Labarge, Ralph. DVD Authoring and Production. Gilroy, Calif.: CMP Books, 2001. ISBN 1-57820-082-2.
- Taylor, Jim. DVD Demystified, 2nd edition. New York: McGraw-Hill Professional, 2000. ISBN 0-07-135026-8.
- ^ DVD Primer. DVD Forum (2000-09-06). Retrieved on 2006-12-17.
- ^ DVD FAQ. DVD Demystified (2006-09-12). Retrieved on 2006-12-17.
- ^ DVD Discs. DVworkshop (2003). Retrieved on 2006-12-17.
- ^ Bakalis, Anna (2003-06-20). It's unreel: DVD rentals overtake videocassettes. Washington Times. Retrieved on 2006-12-17.
- ^ Sonic Solutions ships New hDVD Format. cdrinfo (2000-04-18). Retrieved on 2006-12-17.
- DVD+RW Alliance
- DVD Copy Control Association and the Content Scramble System (CSS)
- Dual Layer Explained- Informational Guide to the Dual Layer Recording Process
- Understanding Recordable & Rewritable DVD by Hugh Bennett
- DVD Frequently Asked Questions (and Answers)
- DVDs: in the fast lane
- DVD Players Surpass VCRs in U.S. Households