DVD..

DVD also known as "Digital Versatile Disc" or "Digital Video Disc" is a popular optical disc storage media format. Its main uses are video and data storage. Most DVDs are of the same dimensions as compact discs (CDs) but store more than six times as much data. Variations of the term DVD often describe the way data is stored on the discs: DVD-ROM has data which can only be read and not written, DVD-R and DVD+R can only record data once and then function as a DVD-ROM. DVD-RW and DVD+RW can both record and erase data multiple times. The wavelength used by standard DVD lasers is 650 nm, and thus has a red color. DVD-Video and DVD-Audio discs respectively refer to properly formatted and structured video and audio content. Other types of DVDs, including those with video content, may be referred to as DVD-Data discs. As next generation High definition optical formats also use a disc identical in some aspects yet more advanced than a DVD, such as Blu-ray Disc, the original DVD is occasionally given the retronym SD DVD (for standard definition).

In 1993, two high-density optical storage formats were being developed; one was the Multi Media Compact Disc (MMCD), backed by Philips and Sony, and the other was the Super Density (SD) disc, supported by Toshiba, Time Warner, Matsushita Electric, Hitachi, Mitsubishi Electric, Pioneer, Thomson, and JVC. DVD uses 650nm wavelength laser diode light as opposed to 780 nm for CD or 405 nm for HD-DVD or Blu-ray Disc. This permits a smaller pit to be etched on the media surface (1.32 µm for DVD versus 1.6 µm for CD) compared to CDs. HP initially developed recordable DVD media from the need to store data for back-up and transport. DVD recordable are now also used for consumer audio and video recording. Three formats were developed: DVD-R/RW (minus/dash), DVD+R/RW (plus), DVD-RAM. Dual Layer recording allows DVD-R and DVD+R discs to store significantly more data, up to 8.5 gigabytes per side, per disc, compared with 4.7 gigabytes for single-layer discs. DVD-R DL was developed for the DVD Forum by Pioneer Corporation, DVD+R DL was developed for the DVD+RW Alliance by Philips and Mitsubishi Kagaku Media (MKM).

DVD-Video is a standard for storing video content on DVD media. In the U.S., mass retailer sales of DVD-Video titles and players began in late 1997. By June 2003, weekly DVD-Video rentals began out-numbering weekly VHS cassette rentals, reflecting the rapid adoption rate of the technology in the U.S. marketplace. Currently DVD-Video is the dominant form of home video distribution worldwide. Although the specifications for video and audio requirements vary by global region and television system, many DVD players support all possible formats. DVD-Video also supports features like menus, selectable subtitles, multiple camera angles, and multiple audio tracks. Manufacturers of commercial DVD-Video disks have a rather perverse sense of what is appropriate to getting copyright and company logo messages across, often extending for minutes for a movie that may only last for 90 minutes. A book equivalent may be a printing company forcing readers to sit through many pages of copyright text, before being able to access the books, and without an ability to skip those pages.

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 (up to 24-bits/192 kHz versus CDDAs 16-bits/44.1 kHz).Compared with the CD format, the much higher capacity DVD format enables the inclusion of considerably more music (with respect to total running time and quantity of songs) and/or far higher audio quality (reflected by higher sampling rates and greater bit-depth, and/or additional channels for spatial sound reproduction). DVD-Audio discs employ a copy prevention mechanism, called Content Protection for Prerecorded Media (CPPM) developed by the 4C group (IBM, Intel, Matsushita, and Toshiba).

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.