DVD
DVD
In 1995, Philips and Sony introduced the digital video disc (DVD, also “digital versatile disc”), which had the same dimensions as a standard compact disk (CD) but could store up to 4.7 gigabytes of data. This is more than six times the capacity of a CD (700 megabytes). DVD players use a higher-power laser than that used for CDs, which enables smaller pits (0.4 micrometer) and separation tracks (0.74 micro-meter) to be used.
To record a DVD, semiconductor red lasers with wavelengths of 630 nm burn pits onto a glass master disc. Pressings of this surface are covered with clear plastic to make mass-produced copies. The peaks and valleys—called “lands” and “pits”—are interpreted as binary numbers by a reading device, whether computer or DVD player. To increase the amount of information stored, video data may be compressed using a form of lossy compression such as MPEG-2, an industry standard for audio and video sanctioned by a governing body called the Moving Pictures Experts Group. This technology strips unnecessary or redundant data from videos. The compression allows 135 minutes on a single side of an optical disc. Some DVD discs use two sides of the disc for longer movies, while others put a wide-screen version on one side of the disc and a standard 4:3 version on the other. But this was simply the first incarnation of DVD. Some discs now feature a dual-layer technology, meaning that a single side of the disc actually holds two separate MPEG video streams, like an upstairs/downstairs apartment. This allows a single side of the disc to hold 4 1/2 hours of video. Soon, there will be dual-sided/dual-layer discs, which will double the capacity to nine hours.
Most DVDs are write-once read-only disks. DVD-RWs are now available for home use, allowing the user to record data on the DVD. These DVD-RW drives can also handle CD-R, CD-RW, and DVD-R discs. DVD-RWs, like CD-RWs, hold slightly less data than their write-once and read-only counterparts.
New technology pioneered by several major companies, such as Pioneer, introduced a rewriting method known as phase-change recording. To re-record, the disk is reheated with a laser at a different phase than the initial recording. The laser light hits the disk at a slightly different angle, changing the shape of the grooves. The data layer does not experience wear and tear because DVDs are read by laser light and never physically touched by mechanics. The data layer is coated with a protective plastic substrate.
The DVD offers the capability to display movies in three different ways. The wide-screen format provides a special anamorphic video signal that, when processed by a wide-screen television set, fills the entire screen and delivers optimum picture quality. Pan and Scan fills the screen of traditional 4:3 television sets with an entire picture, much like watching network movies. The Letterbox mode provides horizontal bands at the top and bottom to, in essence, create a wide-screen picture in a traditional television set.
DVD-Video supports multiple aspect ratios. Video stored on a DVD in 16:9 format is horizontally squeezed to a 4:3 (standard TV) aspect ratio. On wide-screen TVs, the squeezed image is enlarged by the TV to an aspect ratio of 16:9. DVD video players output wide-screen video in three different ways: letterbox (for 4:3 screens), pan and scan (for 4:3 screens), anamorphic or unchanged (for wide screens).
At the moment, DVD players resemble VCRs, however the race is on to make DVD players smaller and less expensive. Several companies developed a DVD player the size of a personal CD player with an integrated liquid crystal display viewing panel and speakers. A Chinese manufacturer incorporated the DVD player with the TV itself. Higher capacity and higher definition is not far off.
At the January, 2000 Consumer Electronics Show, Pioneer showed off its high-definition DVD Recorder. High-definition DVD (HD-DVD), storing 15 GB in two layers for a total storage capacity of 30 GB, became a reality when violet-blue and blue lasers, emitting wavelengths of 400–430 nm, and less, were perfected. A shorter wavelength laser increases the amount of information stored on an optical disk. Each time the wavelength is halved, the corresponding storage media can contain four times more data. The first commercial HD-DVD player was released for sale in the U.S. in March, 2006. A format called the Blu-ray DVD, which stores 50 GB per disc, has also been developed, and machines capable of handling Blu-ray discs were also shipped to the U.S. market starting in 2006. Four-layer Blu-Ray DVDs holding 100 GB have been demonstrated.
In order to promote the technology and establish a consensus on format standards, ten companies organized the DVD Consortium in 1995. These companies included: Hitachi, Ltd., Matsushita Electronic Industrial Co., Ltd., Mitsubishi Electric Corp., Philips Electronics N.V., Pioneer Electronics Corp., Sony Corp., THOMSON multimedia, Time Warner Inc., Toshiba Corp. and Victor Company of Japan Ltd. Today, the Forum boasts 122 member companies, including electronics manufacturers, software firms, and media companies worldwide.
Resources
BOOKS
Barlow, Aaron. The DVD Revolution: Movies, Culture, and Technology. New York: Praeger Publications, 2004.
OTHER
Optical Storage Technology Association. “Understanding Recordable and Rewriteable DVD.” 2004. <http://www.osta.org/technology/dvdqa/> (accessed October 25, 2006).
Laurie Toupin
DVD
DVD
In 1995, Philips and Sony introduced the digital video disc (DVD), which had the same dimensions as a standard compact disk (CD), but was able to store up to 4.7 gigabytes of data, such as high-definition digital video files. This is more than three times the capacity of a CD. DVD players use a higher-power laser than that used for CDs, which enables smaller pits (0.4 micrometre) and separation tracks (0.74 micrometre) to be used.
To record a DVD, semiconductor red lasers, with wavelengths of 630 nm, "burn" grooves into the medium. The peaks and valleys created are interpreted as binary numbers by the computer. To increase the amount of information stored, data is compressed using a form of lossy compression such as MPEG-2, an industry standard for audio and video sanctioned by a governing body called the Moving Pictures Experts Group. This technology strips unnecessary or redundant data from videos. The compression allows 135 minutes on a single side of an optical disc. Some DVD discs use two sides of the disc for longer movies, while others put a wide-screen version on one side of the disc and a standard 4:3 version on the other. But this was simply the first incarnation of DVD. Some discs now feature a dual-layer technology, meaning that a single side of the disc actually holds two separate MPEG video streams, like an upstairs/downstairs apartment. This allows a single side of the disc to hold 4-1/2 hours of video. Soon, there will be dual-sided/dual-layer discs, which will double the capacity to nine hours.
Most DVDs are write-once read-only disks. DVDRAMs are now available for home use, allowing the user to record data on the DVD. These DVD-RAM drives can copy 315 megabytes (MB) of data in about 12 minutes; read and write DVD-RAM discs (as large as 5.2 gigabytes [GB]); and can read CD-ROM, CD-R, CD-RW, and DVD-ROM discs.
New technology pioneered by several major companies, such as Pioneer, introduced a rewriting method known as phase-change recording. To re-record, the disk is reheated with a laser at a different phase than the initial recording. The laser light hits the disk at a slightly different angle, changing the shape of the grooves. The data layer does not experience wear and tear because DVDs are read by laser light and never physically touched by mechanics. The data layer is coated with a protective plastic substrate.
The DVD defines the capability to display movies in three different ways. The wide-screen format provides a special anamorphic video signal that, when processed by a wide-screen television set, fills the entire screen and delivers optimum picture quality. Pan and Scan fills the screen of traditional 4:3 television sets with an entire picture, much like watching network movies. The Letterbox mode provides horizontal bands at the top and bottom to, in essence, create a wide-screen picture in a traditional television set.
DVD-Video supports multiple aspect ratios. Video stored on a DVD in 16:9 format is horizontally squeezed to a 4:3 (standard TV) aspect ratio . On wide-screen TVs, the squeezed image is enlarged by the TV to an aspect ratio of 16:9. DVD video players output wide-screen video in three different ways: letterbox (for 4:3 screens), pan and scan (for 4:3 screens), anamorphic or unchanged (for wide screens).
At the moment, DVD players resemble VCRs, however the race is on to make DVD players smaller and less expensive. Several companies developed a DVD player the size of a personal CD player with an integrated liquid crystal display viewing panel and speakers. A Chinese manufacturer incorporated the DVD player with the TV itself. Higher capacity and higher definition is not far off.
At the January 2000 Consumer Electronics Show, Pioneer showed off its high-definition DVD Recorder. Analysts say that high-definition DVD (HD-DVD) will become a reality when blue lasers, emitting wavelengths of 400-430 nm are perfected. The HD-DVD will require a storage capacity of 15 GB per side, more than three times that of current DVDs. A shorter wavelength laser increases the amount of information stored on an optical disk. Each time the wavelength is halved, the corresponding storage media can contain four times more data.
In order to promote the technology and establish a consensus on format standards, ten companies organized the DVD Consortium in 1995. These companies included: Hitachi, Ltd., Matsushita Electronic Industrial Co., Ltd., Mitsubishi Electric Corp., Philips Electronics N.V., Pioneer Electronics Corp., Sony Corp., THOMSON multimedia, Time Warner Inc., Toshiba Corp. and Victor Company of Japan Ltd. Today, the Forum boasts 122 member companies, including electronics manufacturers, software firms, and media companies worldwide.
Resources
periodicals
Allingham, Philip. "DVDs Not Just Movies Anymore." ZDNetAnchorDesk (January 8, 2000).
Goldberg, Ron. "Digital Video Primer, One Pus Zero Equals a Whole Lot of Fun." Home Theater (September 1997).
Toupin, Laurie. "The Home of the Future." Design News (February 18, 1999).
Laurie Toupin
DVD
DVD
DVD. The Digital Versatile Disc (DVD) is an optical information storage technology with multiple applications. Lasers read pitted digital patterns stamped on DVDs. American, Dutch, and Japanese manufacturers, specifically Philips Electronics, Sony Corporation, Matsushita Electric Industrial Company, and Toshiba Corporation, innovated DVDs simultaneously to surpass compact disc (CD) memory capabilities. Industrial DVD standards were released in 1995 after producers of rival formats, Super Density and Multi Media Compact Disc agreed to coordinate efforts which resulted in the creation of DVDs.
DVDs consist of two extremely thin, round plastic discs known as substrates, which are sealed together. Each DVD can store 4.7 gigabytes of compressed information per side, enough to hold a two-hour movie. If the sides are double-layered, a DVD can contain 17 gigabytes.
American manufacturers first distributed DVD players and introduced DVD-Video for movie storage in 1997. Starting that year, people could also access computer programs stored on DVD-Read-Only Memory (DVD-ROM). In 1998, DVD-Random-Access Memory (DVD-RAM) enabled users to record data on DVDs. By 2000, DVD-Audio provided an alternative to CD players and acoustically supplemented DVD-Video. Consumers eagerly bought several million units of DVD products making them the most quickly adopted technology in the history of electronics.
Most computers manufactured since the late 1990s have incorporated DVD drives. In the early 2000s, engineers had refined DVD technology, issuing new types of recording players and disc polymers. Electronics companies continued to secure patents for innovative DVD designs.
BIBLIOGRAPHY
De Lancie, Philip, and Mark Ely. DVD Production. Boston: Focal Press, 2000.
Purcell, Lee. CD-R/DVD: Disc Recording Demystified. New York: McGraw-Hill, 2000.
Taylor, Jim. DVD Demystified. 2nd ed. New York: McGraw-Hill, 2001.
Elizabeth D.Schafer
See alsoComputers and Computer Industry ; Electricity and Electronics .
DVD
The technology involved in DVD storage is similar to that in compact disks, but more precise. The extra capacity is achieved in a number of ways. The tracks on a DVD are closer and the pits are smaller, allowing more pits per unit area. The key to this was the use of a shorter wavelength laser (typically 635 or 650 nm in the red region for DVDs as opposed to 780 nm in the infrared for CDs). Moreover, a DVD can have two layers on the same side of the disk. The top layer is translucent and the bottom layer opaque. Data can be read from either layer by refocusing the laser. In addition DVDs may be double-sided. DVD formats also have a more efficient error-correction system. The potential capacity of a double-sided double-layer DVD is up to 17 gigabytes.
The early publicity and interest in the DVD format was as a video equivalent of the audio CD – i.e. a medium for distributing films that was cheaper than the VHS tape cassettes used by the film industry (DVD originally stood for digital video disk). There were delays in the introduction of DVD caused partly by disputes about format between large developers, and later by worries in the film industry about piracy.
Since then DVDs have been increasingly used in computing as a higher-capacity version of compact disks. As with compact disks, there are various types. DVD-ROM (DVD read-only memory) is similar to CD-ROM. DVD-R (DVD-recordable) is similar to CD-R. There are also different rewritable formats: DVD-RAM, DVD+RW, and DVD-RW. Unfortunately there are several mutually incompatible standards, each with its own claimed advantages. Philips, Sony, H-P, Ricoh and Yamaha support the DVD+R/DVD+RW formats while Pioneer and ECMA International Standard support the DVD-R/DVD-RW formats. It remains to be seen which format will win, but meanwhile more and more multiformat DVD drives are becoming available.