DVD
DVD is an optical disc storage media format, invented and developed by Philips, Sony, Toshiba, and Panasonic in 1995. DVDs offer higher storage capacity than compact 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 nor erased. Blank recordable DVDs (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 multiple times.
DVDs are used in DVD-Video consumer digital video format and in DVD-Audio consumer digital audio format, as well as for authoring AVCHD discs. DVDs containing other types of information may be referred to as DVD data discs.
Design
As a movie delivery medium
DVD was adopted by movie and home entertainment distributors to replace the ubiquitous VHS tape as the primary means of distributing films to consumers in the home entertainment marketplace. DVD was chosen for its superior ability to reproduce moving pictures and sound, for its superior durability, and for its interactivity. Interactivity had proven to be a feature which consumers, especially collectors, favored when the movie studios had released their films on laser disk. When the price point for a laser disk at approximately $100 per disk moved to $20 per disk at retail, this luxury feature became available for mass consumption. Simultaneously, the movie studios decided to change their home entertainment release model from a rental model to a for purchase model, and large numbers of dvds were sold.
As an interactive medium
DVD as a format had two qualities at the time that were not available in any other interactive medium: 1. Enough capacity and speed to provide high quality, full motion video and sound, and 2. low cost delivery mechanism provided by consumer products retailers who quickly moved to sell their players for under $200 and eventually for under $50 at retail. In addition, the medium itself was small enough and light enough to mail using general first class postage. Almost over night, this created a new business opportunity and model for business innovators like Netflix to re-invent the home entertainment distribution model. It also opened up the opportunity for business and product information to be inexpensively provided on full motion video through direct mail.
Capacity
The basic types of DVD (12 cm diameter, single-sided or homogeneous double-sided) are referred to by a rough approximation of their capacity in gigabytes. In draft versions of the specification, DVD-5 indeed held five gigabytes, but some parameters were changed later on as explained above, so the capacity decreased. Other formats, those with 8 cm diameter and hybrid variants, acquired similar numeric names with even larger deviation.
The 12 cm type is a standard DVD, and the 8 cm variety is known as a MiniDVD. These are the same sizes as a standard CD and a mini-CD, respectively. The capacity by surface (MiB/cm2) varies from 6.92 MiB/cm2 in the DVD-1 to 18.0 MiB/cm2 in the DVD-18.
As with hard disk drives, in the DVD realm, gigabyte and the symbol GB are usually used in the SI sense (i.e., 109, or 1,000,000,000 bytes). For distinction, gibibyte (with symbol GiB) is used (i.e., 10243 (230), or 1,073,741,824 bytes).
Technology
DVD uses 650 nm wavelength laser diode light as opposed to 780 nm for CD. This permits a smaller pit to be etched on the media surface compared to CDs (0.74 µm for DVD versus 1.6 µm for CD), allowing in part for DVD's increased storage capacity.
Writing speeds for DVD were 1×, that is, 1,385 kB/s (1,353 KiB/s), in the first drives and media models. More recent models, at 18× or 20×, have 18 or 20 times that speed. Note that for CD drives, 1× means 153.6 kB/s (150 KiB/s), about one-ninth as swift.
DVD-Video
DVD-Video is a standard for storing and distributing video/audio content on DVD media. The format went on sale in Japan on November 1, 1996, in the United States on March 1, 1997, in Europe on October 1, 1998 and in Australia on February 1, 1999. DVD-Video became the dominant form of home video distribution in Japan when it first went on sale in 1996, but did not become the dominant form of home video distribution in the United States until June 15, 2003, when weekly DVD-Video in the United States rentals began outnumbering weekly VHS cassette rentals, reflecting the rapid adoption rate of the technology in the U.S. marketplace. Currently, DVD-Video is the dominant form of home video distribution worldwide, although in Japan it was surpassed by Blu-ray Disc when Blu-ray first went on sale in Japan on March 31, 2006.
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