DVD
DVD, also known as Digital Video Disc or Digital Versatile Disc, is an optical disc storage media format, and was invented and developed by Philips, Sony, Toshiba, and Time Warner in 1995. Its main uses are video and data storage. DVDs are of the same dimensions as compact discs (CDs), but are capable of storing almost seven times as much data.
Variations of the term DVD often indicate 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 (recordable) can record data only once, and then function as a DVD-ROM; DVD-RW (re-writable), DVD+RW, and DVD-RAM (random access memory) can all record and erase data multiple times. The wavelength used by standard DVD lasers is 650 nm;[1] thus, the light has a red color.
DVD-Video and DVD-Audio discs refer to properly formatted and structured video and audio content, respectively. Other types of DVDs, including those with video content, may be referred to as DVD Data discs.
History
In 1993, two optical disc storage formats were being developed. One was the MultiMedia Compact Disc (MMCD) also called CDi, 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 disc as well as seeking support for their format for storing computer data. Alan E. Bell, 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 in 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.[2] 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 Disc Format [UDF]) for use on the new DVDs.
Philips and Sony decided it was in their best interest to avoid another format war over their MultiMedia Compact Disc, and agreed to unify with companies backing the Super Density Disc to release a single format with technologies from both. The specification was 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 because of its great resilience to 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 first introduced by Toshiba in Japan in November 1996, in the United States in March 1997 (test marketed),[3] in Europe in October 1998, and in Australia in February 1999.
In May 1997, the DVD Consortium was replaced by the DVD Forum, which is open to all other companies.[3]
Specifications
DVD specifications created and updated by the DVD Forum are published as so-called DVD Books (e.g. DVD-ROM Book, DVD-Audio Book, DVD-Video Book, DVD-R Book, DVD-RW Book, DVD-RAM Book, DVD-AR Book, DVD-VR Book, etc.).[4][5][6]
Some specifications for mechanical, physical and optical characteristics of DVD optical discs can be downloaded as freely available standards from the ISO website.[7] Also, the DVD+RW Alliance publishes competing DVD specifications such as DVD+R, DVD+R DL, DVD+RW or DVD+RW DL. These DVD formats are also ISO standards.[8][9][10][11]
Some of DVD specifications (e.g. for DVD-Video) are not publicly available and can be obtained only from the DVD Format/Logo Licensing Corporation for a fee of US $5000.[12][13] Every subscriber must sign a non-disclosure agreement as certain information in the DVD Book is proprietary and confidential.[12]
Etymology
The official DVD specification documents have never defined the initialism DVD. Usage in the present day varies, with Digital Versatile Disc,[14] Digital Video Disc, and DVD being the most common.
DVD was originally used as an initialism for the unofficial term digital videodisk.[15]
A newsgroup FAQ written by Jim Taylor (a prominent figure in the industry) claims that four years later, in 1999, the DVD Forum stated that the format name was simply the three letters "DVD" and did not stand for anything.[16]
The DVD Forum website has a section called "DVD Primer" in which the answer to the question, "What does DVD mean?" reads, "The keyword is 'versatile.' Digital Versatile Discs provide superb video, audio and data storage and access—all on one disc."[17]