DVD

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,[1] 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).[2][3] However, the trademarked HD DVD discs have been discontinued since Blu-ray absorbed their market share.

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)[5], 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.

In 2006, a new format called Blu-ray Disc (BD), designed by Sony, Philips, and Panasonic, was released as the successor to DVD. Another format, HD DVD, competed unsuccessfully with this format in the format war of 2006 to 2008. A dual layer Blu-ray Disc can store 50 GB.

However, unlike previous format changes (e.g. audio tape to compact disc, VHS videotape to DVD), there is no immediate indication that production of the standard DVD will gradually wind down, as they still dominate with around 87% of video sales and approximately one billion DVD player sales worldwide. Consumers initially were slow to adopt Blu-ray, partly due to the cost. By 2009, 85% of stores that sold DVD sold Blu-ray Discs. Currently, Blu-ray players are selling for $198 USD, while titles retail for as cheap as $9.86 USD (but are usually significantly higher in price than SD DVD releases, at a more common $20–$30 USD price). A high-definition TV and appropriate connection cables are also required to take advantage of Blu-ray disc. Some analysts suggest that the biggest obstacle to replacing DVD is due to its installed base; a large majority of consumers are satisfied with DVDs. The DVD had succeeded because it offered a compelling alternative to VHS. In addition, Blu-ray players are designed to be backwards compatible, allowing older DVDs to be played since the media are physically identical; this differed from the change from vinyl to CD and from tape to DVD, which involved a complete change in physical medium.

This situation can be best compared to the changeover from 78 rpm shellac recordings to 45 rpm and 33 1/3 rpm vinyl recordings; because the medium used for the earlier format was virtually the same as the latter version (a disk on a turntable, played using a needle), phonographs continued to be built to play obsolete 78s for decades after the format was discontinued. Manufacturers have announced standard DVD releases well into 2009, and the format remains the preferred one for the release of older television programs and films, with some programs such as Star Trek: The Original Series requiring reediting and replacement of certain elements such as special effects in order to be better received in high-definition viewing.

The Holographic Versatile Disc (HVD) is an optical disc technology that may one day hold up to 3.9 terabytes (TB) of information, albeit the current maximum is 250GB. It employs a technique known as collinear holography.

DVD-Audio is a format for delivering high-fidelity audio content on a DVD. It offers many channel configuration options (from mono to 7.1 surround sound) at various sampling frequencies (up to 24-bits/192 kHz versus CDDA's 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).

Despite DVD-Audio's superior technical specifications, there is debate as to whether the resulting audio enhancements are distinguishable in typical listening environments. DVD-Audio currently forms a niche market, probably due to the very sort of format war with rival standard SACD that DVD-Video avoided.

DVD-Audio discs employ a DRM mechanism, called Content Protection for Prerecorded Media (CPPM) developed by the 4C group (IBM, Intel, Matsushita, and Toshiba).

To date, CPPM has not been "broken" in the sense that DVD-Video's CSS has been broken, but ways to circumvent it have been developed. By modifying commercial DVD(-Audio) playback software to write the decrypted and decoded audio streams to the hard disk, users can essentially extract content from DVD-Audio discs much in the same way they can from DVD-Video discs.