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.
Background. RCA home.
DVDThe standard-definition (SD) optical disc format. Introduced in the U.S. in 1997 and developed by the computer and movie industries, the disc has the same 120mm/4.75" diameter as a CD but holds 4.7GB rather than 700MB. Whereas CDs use only one side, DVDs can be recorded on both sides as well as in dual layers. DVDs have 480 lines of resolution in the U.S. (NTSC) and 576 lines elsewhere (PAL). For high-definition (HD) optical discs with 1,080 lines of resolution, see Blu-ray.
DVD first stood for "digital videodisc;" then "digital versatile disc" and finally just "D-V-D." In practice, DVD refers to all the following DVD formats. Modern DVD drives read and write all CD and DVD formats, except for DVD-RAM, which requires its own drive. For DVD speed ratings (1x, 2x, etc.), see DVD drives. See CSS, DVD region codes and optical disc.
DVD-Video - SD Movies
DVD-Video is the movie format, which uses MPEG-2 compression to provide approximately two hours of video per side at 480i resolution. Blu-ray players also play DVD movies. See DVD-Video, DTV and Blu-ray.
DVD-ROM - Read-Only Data
DVD-ROMs hold data permanently, and like CD-ROMs, they are pressed at the factory. See DVD-ROM.
DVD-R/DVD+R - Recordable (burnable)
DVD-R and DVD+R are competing write-once formats for burning movies or data. They function like high-capacity CD-R discs. DVD-R DL and DVD+R DL are dual layer discs with twice the capacity. See DVD-R and DVD+R.
DVD-RW/DVD+RW - Rewritable
DVD-RW and DVD+RW are competing formats that can be rewritten 1,000 times. Aimed at the consumer, 1,000 rewrites are considered adequate. See DVD-RW and DVD+RW.
DVD-RAM - Rewritable
A DVD-RAM functions like a removable hard disk with a similar file structure. Although DVD-RAMs can be rewritten 100,000 times before they are no longer usable, they are not a popular medium. See DVD-RAM.
DVD-Audio - High-Quality Music
DVD-Audio was designed to supersede the music CD, but like its SACD counterpart, never caught on. However, downloable music is available at the same sampling rates as DVD-Audio. See DVD-Audio and high-resolution audio.
Plus and Minus: +R, +RW, -R, -RW
The formats endorsed by the DVD Forum have a hyphen in their names and are verbalized as "DVD Minus" or "DVD Dash." The competing formats from the DVD+RW Alliance use a plus sign. Starting in 2002, drives supporting both formats were introduced. See DVD Forum and DVD+RW Alliance.
For drive specifications (2x, 4x, 8x, etc.), see DVD drives. For DVD storage specifications, see DVD storage capacities.
|Sides and Layers|
|DVDs come in any combination of single or double sided with single or double layers. This shows the laser beam contacting the recorded surface in all of the possibilities.|
|DVD vs. CD-ROM|
|At minimum, the capacity of a DVD is seven times that of a CD-ROM because its tracks, pits and lands are more than twice as dense. It also uses more efficient recording algorithms. Add a second layer or record on both sides of the DVD, and capacity is doubled. (Image courtesy of C-Cube Microsystems.)|