User talk:BioNaresh/sandbox

DVD TECHNIQUES :
1.jpg|Caption1 Example.jpg|Caption2 DVD, in full digital video disc or digital versatile disc, type of optical disc used for data storage and as a platform for multimedia. Its most prominent commercial application is for playing back recorded motion pictures and television programs (hence the designation “digital video disc”), though read-only, recordable, and even erasable and rewritable versions can be used on personal computers to store large quantities of almost any kind of data (hence “digital versatile disc”). The DVD represents the second generation of compact disc (CD) technology, and, in fact, soon after the release of the first audio CDs by the Sony Corporation and Philips Electronics NV in 1982, research was under way on storing high-quality video on the same 120-mm (4.75-inch) disc. In 1994–95 two competing formats were introduced, the Multimedia CD (MMCD) of Sony and Philips and the Super Density (SD) disc of a group led by the Toshiba Corporation and Time Warner Inc. By the end of 1995 the competing groups had agreed on a common format, to be known as DVD, that combined elements of both proposals, and in 1996 the first DVD players went on sale in Japan.

Like a CD drive, a DVD drive uses a laser to read digitized (binary) data that have been encoded onto the disc in the form of tiny pits tracing a spiral track between the centre of the disc and its outer edge. However, because the DVD laser emits red light at shorter wavelengths than the red light of the CD laser (635 or 650 nanometres for the DVD as opposed to 780 nanometres for the CD), it is able to resolve shorter pits on more narrowly spaced tracks, thereby allowing for greater storage density. In addition, DVDs are available in single- and double-sided versions, with one or two layers of information per side. A double-sided, dual-layer DVD can hold more than 16 gigabytes of data, more than 10 times the capacity of a CD-ROM, but even a single-sided, single-layer DVD can hold more than four gigabytes—more than enough capacity for a two-hour movie that has been digitized in the highly efficient MPEG-2 compression format. Indeed, soon after the first DVD players were introduced, single-sided DVDs became the standard media for watching movies at home, almost completely replacing videotape. Consumers quickly appreciated the convenience of the discs as well as the higher quality of the video images, the interactivity of the digital controls, and the presence of numerous extra features packed into the discs’ capacious storage.