DVD

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DVD is an optical storage media format that is primarily used for playback of movies with high video and sound quality. The acronym "DVD" does not stand for anything in particular now, but it originally stood for "Digital Video Disc" or "Digital Versatile Disc", depending on which nonauthoritative source you ask.

DVD-Video disks require a DVD-Video player, which is similar to a common VCR, but cannot record onto the discs as standard. Commercial DVD movies are encoded using a combination of MPEG-2 compressed video and Dolby AC-3 audio (often in multi-channel formats.) Typical data rates for DVD movies range from 3-10 Mbps, and the bitrate is usually adaptive. Discs often provide an additional audio format, for example PCM or DTS.The initial DVD launch in Europe included MPEG-2 audio, although Dolby AC-3 quickly replaced it.

Most DVD-Video titles use Content Scrambling System (CSS) encryption to discourage people from making perfect digital copies to another medium, however DVD discs can be duplicated in entirety. Discs can also specify for the player to use Macrovision, an analog anti-copying scheme that prevents the consumer from copying the video onto a VCR tape.

DVD movies can contain a region code, denoting which area of the world it is targeted at, which is completely independent of encryption. The commercial DVD-video player specification dictates that players must only play discs that contain its region code. This allows the film studios, for commercial and logistical reasons, to dictate release schedules and prices around the world. However, many DVD players around the world allow playback of any disc, or can be modified to do so, in violation of the Digital Millennium Copyright Act (in the United States) and its counterparts in other countries. New Zealand is unique in that the courts decided that the DVD region coding system is restrictive and therefore illegal, allowing region-free players to be sold commercially.

Region
code
Area
1United States, Canada, and U.S. territories
2Europe, Greenland, South Africa, Lesotho, Swaziland, Japan, Egypt, and the Middle East
3Southeast Asia, South Korea, Hong Kong, Indonesia, Philippines, Taiwan
4Australia, New Zealand, Mexico, Central America, South America,
5Russia, other former Soviet Union countries, eastern Europe, Indian subcontinent, Mongolia, Africa
6People's Republic of China
7reserved for future use
8International venues such as airplanes, cruise ships, etc.
See the map


DVD-ROM disks are used for data storage, and require a DVD-ROM drive to be read. Each read-only disc holds approximately 4.7 GB of data per layer; some disks are double-layered, holding up to 8.5 GB on one side.

DVD recorders started to become available in Japan during 2000, and the rest of the world soon after, with a familiar battle for format dominance beginning. DVD-RW disks require a DVD-RW Drive, but can record up to 8.5 GB of data per single-sided disk, in a similar fashion to a CD-RW drive. Other formats for recordable DVD include DVD+RW and DVD-RAM.

DVD-Audio is a new format to deliver high-fidelity audio content on a DVD. It offers stereo and surround sound capability, as well as a maximum of 4 hours of stereo audio per disk (2 hours of surround audio).

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