In computing, an optical disc drive (ODD) is a disk drive that uses laser light or electromagnetic
waves within or near the visible light spectrum as part of the process of reading or writing data to or from optical discs. Some drives can only read from discs, but recent drives are commonly both readers and recorders, also called burners or writers. Compact discs, DVDs, and Blu-ray discs are common types of optical media which can be read and recorded by such drives. Optical drive is the generic name; drives are usually described as "CD" "DVD", or "Blu-ray", followed by "drive", "writer", etc.
Optical disc drives are an integral part of stand-alone consumer appliances such as CD players, DVD players and DVD recorders. They are also very commonly used in computers to read software and consumer media distributed on disc, and to record discs for archival and data exchange purposes. Floppy disk drives, with capacity of 1.44 MB, have been made obsolete: optical media are cheap and have vastly higher capacity to handle the large files used since the days of floppy discs, and the vast majority of computers and much consumer entertainment hardware have optical writers. USB flash drives, high-capacity, small, and inexpensive, are suitable where read/write capability is required.
Disc recording is restricted to storing files playable on consumer appliances (films, music, etc.), relatively small volumes of data (e.g., a standard DVD holds 4.7 gigabytes) for local use, and data for distribution, but only on a small-scale; mass-producing large numbers of identical discs is cheaper and faster than individual recording.
DVD ( "digital versatile disc") is a digital optical disc storage format, invented and developed by Philips, Sony, Toshiba, andPanasonic in 1995. DVDs can be played in multiple types of players, including DVD players. DVDs offer higher storage capacity thancompact discs while having the same dimensions.
Pre-recorded DVDs are mass-produced using molding machines that physically stamp data onto the DVD. Such discs are known as DVD-ROM, because data can only be read and not written or erased. Blank recordable DVD discs (DVD-R and DVD+R) can be recorded once using a DVD recorder and then function as a DVD-ROM. Rewritable DVDs (DVD-RW, DVD+RW, and DVD-RAM) can be recorded and erased many times.
DVDs are used in DVD-Video consumer digital video format and in DVD-Audio consumer digital audio format, as well as for authoring DVD discs written in a special AVCHD format to hold high definition material (often in conjunction with AVCHD format camcorders). DVDs containing other types of information may be referred to as DVD data discs.
Etymology
The Oxford English Dictionary comments that, "In 1995 rival manufacturers of the product initially named digital video disc agreed that, in order to emphasize the flexibility of the format for multimedia applications, the preferred abbreviation DVD would be understood to denote digital versatile disc" The OED also states that in 1995, "The companies said the official name of the format will simply be DVD. Toshiba had been using the name ‘digital video disk’, but that was switched to ‘digital versatile disk’ after computer companies complained that it left out their applications."
"Digital versatile disc" is the explanation provided in a DVD Forum Primer from 2000[7] and in the DVD Forum's mission statement.
History
Development
Before the advent of DVD in 1995, Video CD (VCD) became one of the first formats for distributing digitally encoded films on standard 120 mm (4.7 in) optical discs. (Its predecessor, CD Video, used analog video encoding.) VCD was on the market in 1993. In the same year, two new optical disc storage formats were being developed. One was the Multimedia Compact Disc(MMCD), backed by Philips and Sony, and the other was the Super Density (SD) disc, supported by Toshiba, Time Warner,Matsushita Electric, Hitachi, Mitsubishi Electric, Pioneer, Thomson, and JVC. A much earlier consumer optical disc data storage device, known as LaserDisc, was developed in the United States. Optical recording technology was invented by David Paul Gregg and James Russell in 1958 and first patented in 1961. LaserDisc first came to market in Atlanta, Georgia, in 1978, but used much larger discs than the later formats. Due to the high cost of players and discs, consumer adoption of LaserDisc was very low in both North America and Europe, and was not widely used anywhere outside Japan and the more affluent areas of Southeast Asia, such as Hong-Kong, Singapore, Malaysia and Taiwan.
Representatives from the SD camp asked IBM for advice on the file system to use for their disc, and sought support for their format for storing computer data. Alan E. Bell, a researcher from IBM's Almaden Research Center, got that request, and also learned of the MMCD development project. Wary of being caught in a repeat of the costly videotape format war between VHSand Betamax in the 1980s, he convened a group of computer industry experts, including representatives from Apple,Microsoft, Sun Microsystems, 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. They recruitedLou Gerstner, president of IBM, to pressure the executives of the warring factions. In one significant compromise, the MMCD and SD groups agreed to adopt proposal SD 9, which specified that both layers of the dual-layered disc be read from the same side—instead of proposal SD 10, which would have created a two-sided disc that users would have to turn over.[11] As a result, the DVD specification provided a storage capacity of 4.7 GB for a single-layered, single-sided disc and 8.5 GB for a dual-layered, single-sided disc. The DVD specification ended up similar to Toshiba and Matsushita's Super Density Disc, except for the dual-layer option (MMCD was single-sided and optionally dual-layer—whereas SD was single-layer, but optionally double-sided) and EFMPlus modulation designed by Kees Schouhamer Immink.
Philips and Sony decided that it was in their best interests to avoid another format war over their Multimedia Compact Disc, and agreed to unify with companies backing the Super Density Disc to release a single format, with technologies from both. After other compromises between MMCD and SD, the computer companies through TWG 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) for use on the new DVDs.
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