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DVD, also known as "Digital Versatile Disc" or "Digital Video Disc,"

is an optical disc storage media format. Its main uses are video and data storage. 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 (Read Only Memory), has data that can only be read and not written, DVD-R and DVD+R can record data only once and then function as a DVD-ROM. DVD-RW, DVD+RW and DVD-RAM can both record and erase data multiple times. The wavelength used by standard DVD lasers is 650 nm, and thus the light 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 more advanced optical formats such as Blu-ray Disc also use a disc identical in some aspects, the original DVD is occasionally given the retronym SD DVD (for standard definition). However, the trademarked HD DVD discs have been discontinued since Blu-ray absorbed their market share.

History

In 1993, two high-density optical storage formats were being developed; one was the MultiMedia 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.

Representatives of the SD camp approached IBM, asking for advice on the file system to use for their disk as well as looking for support for their format for storing computer data. A researcher from IBM's Almaden Research Center received that request and also learned of the MMCD development project. Wary of being caught in a repeat of the costly videotape format war between VHS and Betamax of the 1980s, he convened a group of computer industry experts (including representatives from Apple, Microsoft, Sun, Dell, and many others), this group was referred to as the Technical Working Group, or TWG. The TWG voted to boycott both formats unless the two camps agreed on a single, converged standard. Lou Gerstner, president of IBM, was recruited to apply pressure on the executives of the warring factions. Eventually, the computer companies won the day, and a single format, now called DVD, was agreed upon. The TWG also collaborated with the Optical Storage Technology Association (OSTA) on the use of their implementation of the ISO-13346 file system, known as Universal Disk Format (UDF), for use on the new DVDs.

Philips and Sony abandoned their MultiMedia Compact Disc and agreed upon a specification mostly similar to Toshiba and Matsushita's Super Density Disc except for the dual-layer option (MMCD was single-sided and optionally dual-layer whereas SD was single-layer but optionally double-sided) and EFMPlus modulation. EFMPlus was chosen due to its great resilience against disc damage such as scratches and fingerprints. EFMPlus, created by Kees Immink, who also designed EFM, is 6% less efficient than the modulation technique originally used by Toshiba, which resulted in a capacity of 4.7 GB as opposed to the original 5 GB. The result was the DVD specification, finalized for the DVD movie player and DVD-ROM computer applications in December 1995. The DVD-Video format was introduced first, in 1996, in Japan, to the United States in March 1997 (Test Marketed) , and mid-late 1998 in Europe, Australia and Brazil. In May 1997, the DVD Consortium was replaced by the DVD Forum, which is open to all other companies.