digital versatile disc
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digital versatile discor
digital video disc(DVD), a small plastic disc used for the storage of digital data. The successor media to the compact disccompact disc
(CD), a small plastic disc used for the storage of digital data. As originally developed for audio systems, the sound signal is sampled at a rate of 44,100 times a second, then each sample is measured and digitally encoded on the 4 3-4 in (12 cm) disc as a series of
..... Click the link for more information. (CD), a DVD can have more than 100 times the storage capacity of a CD. When compared to CD technology, DVD also allows for better graphics and greater resolution. In the case of an audio recording, where the data to be stored is in analog rather than digital form, the sound signal is sampled at a rate of 48,000 or 96,000 times a second, then each sample is measured and digitally encoded on the 4 3-4-in. (12-cm) disc as a series of microscopic pits on an otherwise polished surface. The disc is covered with a protective, transparent coating so that it can be read by a laser beam. As with other optical disksoptical disk,
any of a variety of information storage disks that are played or read using a laser. Optical disks include compact discs (CDs and CD-ROMs), laser discs (see videodisc), and digital versatile discs (or digital video discs; DVDs and DVD-ROMs).
..... Click the link for more information. nothing touches the encoded portion, and the DVD is not worn out by the playing process. Because DVD players are backward compatible to existing technologies, they can play CD and CD-ROM discs; however, CD players cannot play DVD and DVD-ROM discs.
DVD formats include DVD-Video (often simply called DVD), DVD-ROM, and DVD-Audio. DVD-Video discs hold digitized movies or video programs and are played using a DVD player hooked up to a standard television receiver. In a sense, DVD-Video players are the successors to the videocasette recordersvideocassette recorder
(VCR), device that can record television programs or the images from a video camera on magnetic tape (see tape recorder); it can also play prerecorded tapes.
..... Click the link for more information. (VCRs) that play VHS tapes. DVD-ROM [Read Only Memory] discs hold computer data and are read by a DVD-ROM drive hooked up to a computer. These disks can only be read—the disks are impressed with data at the factory but once written cannot be erased and rewritten with new data. DVD-ROM also includes recordable variations. DVD-R and DVD+R[Recordable] discs can be written to sequentially but only once. DVD-RAM [Random Access Memory], DVD-RW, and DVD+RW [ReWritable] discs can be written to thousands of times; they differ in their technical standards and, as a result, in the amount of information they can hold. Dual layer disks, such as DVD-R DL, record data on two different layers within the disk. Many DVD recorders can record in several different recordable DVD formats. Some recorders include computer hard drives that allow the user to record tens to hundreds of hours of material temporarily; the user can then select the material that will be transferred to a DVD. When DVD was released in 1996 there was no DVD-Audio format, although the audio capabilities of DVD-Video far surpassed those available from a CD; the DVD-Audio format was introduced in 1999.
Digital Versatile Disc(storage)
The first DVD drives for computers were read-only drives ("DVD-ROM"). These can store 4.7 GBytes - over seven times the storage capacity of CD-ROM. DVD-ROM drives read existing CD-ROMs and music CDs and are compatible with installed sound and video boards. Additionally, the DVD-ROM drive can read DVD films and modern computers can decode them in software in real-time.
The DVD video standard was announced in November 1995. Matshusita did much of the early development but Philips made the first DVD player, which appeared in Japan in November 1996. In May 2004, Sony released the first dual-layer drive, which increased the disc capacity to 8.5 GB. Double-sided, dual-layer discs will eventually increase the capacity to 17 GB.
Write-once DVD-R ("recordable") drives record a 3.9GB DVD-R disc that can be read on a DVD-ROM drive. Pioneer released the first DVD-R drive on 1997-09-29.
By March 1997, Hitachi had released a rewritable DVD-RAM drive (by false analogy with random-access memory). DVD-RAM drives read and write to a 2.6 GB DVD-RAM disc, read and write-once to a 3.9GB DVD-R disc, and read a 4.7 GB or 8.5 GB DVD-ROM. Later, DVD-RAM discs could be read on DVD-R and DVD-ROM drives.
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