Dvd, Dvd

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.

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 was first available commercially in Japan in 1996. IT came out in 1997 in the United States, and 1998 in Australia.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.

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.

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. Sony first introduced the DVD-Video format in Japan in November 1996, in the United States in March 1997 (test marketed) , in Europe and Brazil in 1998 and in Australia in 1999. In May 1997, the DVD Consortium was replaced by the DVD Forum, which is open to all other companies.

Three formats were developed: DVD-R/RW (hyphen/dash), DVD+R/RW (plus), and DVD-RAM.

With parallel track path (PTP), used on DVD-ROM, both layers start at the inside diameter (ID) and end at the outside diameter (OD) with the lead-out. With Opposite Track Path (OTP), used on many DVD-Video discs, the lower layer starts at the ID and the upper layer starts at the OD, where the other layer ends; they share one lead-in and one lead-out. However, some DVD-Video discs also use a parallel track - such as those authored episodically, such as a disc with several separate episodes of a TV series, where more often than not, the layer change is in-between titles and therefore would not need to be authored in the opposite track path fashion.

In the U.S., mass retailer sales of DVD-Video titles and players began in late 1997.

Audio is commonly stored using the Dolby Digital (AC-3) or Digital Theater System (DTS) formats, ranging from 16-bits/48 kHz to 24-bits/96 kHz format with monaural to 7.1 channel "Surround Sound" presentation, and/or MPEG-1 Layer 2. 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 such as menus, selectable subtitles, multiple camera angles, and multiple audio tracks.

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 sample resolution, and/or additional channels for spatial sound reproduction).

DVD-Audio currently forms a niche market, probably due to the very sort of format war with rival standard SACD that DVD-Video avoided.

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.

By 2009, 85% of stores that sold DVD sold Blu-ray Discs. Currently, Blu-ray players are selling for $198 USD, Magnavox Blu-ray Disc Player NB500MG9 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).

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.

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 The Original Series requiring remastering and replacement of certain elements such as special effects in order to be better received in high-definition viewing.

The rise of filesharing and "piracy" has prompted many copyright owners to display notices on DVD packaging or displayed on screen when the content is played that warn consumers of the illegality of certain uses of the DVD.

Arrangements for renting and lending differ more by geography. In the US, the right to rent or lend out bought DVDs is protected by the first-sale doctrine under the United States Copyright Act. In Europe, rental and lending rights are more limited, under a 1992 European Directive that gives copyright holders broader powers to restrict the commercial renting and public lending of DVD copies of their work.

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