DVD stands for digital versatile disc, although it is also commonly referred to as digital video disc, due to the popularity of DVDs in the video industry. DVD technology allows for the storage of a large amount of data using digital technology. DVDs can store up to 17 gigabytes, compared to the storage capacity of a compact disc (CD), which is approximately 680 megabytes (1 gigabyte is equal to 1,024 megabytes).
Construction of a DVD
A DVD is a thin, circular wafer of clear plastic and metal measuring 4.75 inches (12 centimeters) in diameter with a small hole in its center. In its most basic form, a DVD is one 0.02-inch-thick (0.06-centimeter-thick) disc; at its greatest capacity, a DVD is two such discs, compressed together to create a double-sided disc 0.04 inch (0.12 centimeter) thick.
The digital data (the binary language of ones and zeroes common to all computers) used in DVDs is encoded onto a master disc. This disc is then used to create copies of itself. A laser (a device used to create a narrow, intense beam of very bright light) burns small holes, called pits, into a microscopic layer of metal, usually aluminum. These pits correspond to the binary ones; smooth areas of the disc untouched by the laser, called land, correspond to the binary zeroes. Once the pits have been burned, the metal is coated with a protective, transparent layer.
Origin of the DVD
DVD technology originated in the early 1990s after movie companies saw how successful the digital medium of CDs was to the music consumer. The music industry had seen the CD virtually replace the popular long-playing (LP) vinyl record, a nondigital and, therefore, lower-quality medium. On the motion picture side, the dominant medium of choice for the home consumer was the VHS (video home system) tape, also a nondigital medium. In an attempt to develop a product that would result in improved visual and audio quality, movie companies worked on various digital video formats for the home consumer. The result was the development of the DVD.
By the mid-1990s, such entertainment giants as Time-Warner and Sony agreed that it was in the entertainment industry's best interest to work together as a group. By 1996, this new group helped create a standard for digitized movies and, thereby, promote the new high-quality technology. Introduced to the market in March 1997, DVD has become the most popular electronics consumer item to date.
In contrast to a VHS videotape, a DVD provides better visual and audio quality. In the case of a motion picture, for instance, a DVD provides much sharper images than a VHS videotape due to the use of MPEG-2 compression. (MPEG stands for Moving Pictures Experts Group, an organization of people that meets several times a year to establish standards for audio and video encoding. The term "MPEG," however, has become a nickname for the technology itself. Compression refers to the process of condensing various audio and video signals into less space while improving the quality.)
A DVD also has great storage capacity. In addition to being able to store an entire movie itself, a DVD can also hold a number of additional features as well: these include alternate endings, audio and subtitles in different languages, cast biographies, deleted scenes, documentary footage on how the film was made, and a variety of camera angles, as well as the capacity for surround sound (four microphones, four amplifiers, and four loudspeakers that together provide remarkably realistic sound reproduction though appropriate sound equipment is needed). Additionally, a two-layered DVD allows a movie to be presented in both the more square-shaped television screen size as well as the more rectangular-shaped theater screen size, commonly called letterbox (so-called because its rectangular image resembles a mailbox or letterbox).
DVD and computers
Although DVD is most popularly thought of as a movie-viewing medium, its ability to enhance the computer industry is incredible. DVDROM (read-only memory) drives hook up to a computer and read DVDs. This allows a consumer to watch movies and play games with enhanced graphics on a computer. Four variations of DVD-ROMs have the ability to record data: DVD-R (recordable) can be rewritten only once; DVD-RAM (random access memory) and DVD-RW and DVD+RW (two types of rewritable discs) can be rewritten thousands of times. The three types of rewritable discs have compatibility differences and also vary in the amount of information they can contain. All three are in competition with each other.
The future of DVD technology
As of the beginning of the twenty-first century, DVD technology had yet to significantly impact videocassette recorder (VCR) sales, due primarily to the lack of standards for DVD recording technology and the expensive prices of DVD recorders. Because different manufacturers are offering their own recording technology, market forces have yet to determine which technology will lead the way. Currently, the music industry is studying the viability of DVDs as a consumer-friendly media option.
[See also Compact disc; Video recording ]