DVD

In 1995, Philips and Sony introduced the digital video disc (DVD), which had the same dimensions as a standard compact disk (CD), but was able to store up to 4.7 gigabytes of data, such as high-definition digital video files. This is more than three times the capacity of a CD. DVD players use a higher-power laser than that used for CDs, which enables smaller pits (0.4 micrometre) and separation tracks (0.74 micrometre) to be used.

To record a DVD, semiconductor red lasers, with wavelengths of 630 nm, "burn" grooves into the medium. The peaks and valleys created are interpreted as binary numbers by the computer. To increase the amount of information stored, data is compressed using a form of lossy compression such as MPEG-2, an industry standard for audio and video sanctioned by a governing body called the Moving Pictures Experts Group. This technology strips unnecessary or redundant data from videos. The compression allows 135 minutes on a single side of an optical disc. Some DVD discs use two sides of the disc for longer movies, while others put a wide-screen version on one side of the disc and a standard 4:3 version on the other. But this was simply the first incarnation of DVD. Some discs now feature a dual-layer technology, meaning that a single side of the disc actually holds two separate MPEG video streams, like an upstairs/downstairs apartment. This allows a single side of the disc to hold 4-1/2 hours of video. Soon, there will be dual-sided/dual-layer discs, which will double the capacity to nine hours.

Most DVDs are write-once read-only disks. DVDRAMs are now available for home use, allowing the user to record data on the DVD. These DVD-RAM drives can copy 315 megabytes (MB) of data in about 12 minutes; read and write DVD-RAM discs (as large as 5.2 gigabytes [GB]); and can read CD-ROM, CD-R, CD-RW, and DVD-ROM discs.

New technology pioneered by several major companies, such as Pioneer, introduced a rewriting method known as phase-change recording. To re-record, the disk is reheated with a laser at a different phase than the initial recording. The laser light hits the disk at a slightly different angle, changing the shape of the grooves. The data layer does not experience wear and tear because DVDs are read by laser light and never physically touched by mechanics. The data layer is coated with a protective plastic substrate.

The DVD defines the capability to display movies in three different ways. The wide-screen format provides a special anamorphic video signal that, when processed by a wide-screen television set, fills the entire screen and delivers optimum picture quality. Pan and Scan fills the screen of traditional 4:3 television sets with an entire picture, much like watching network movies. The Letterbox mode provides horizontal bands at the top and bottom to, in essence, create a wide-screen picture in a traditional television set.

DVD-Video supports multiple aspect ratios. Video stored on a DVD in 16:9 format is horizontally squeezed to a 4:3 (standard TV) aspect ratio. On wide-screen TVs, the squeezed image is enlarged by the TV to an aspect ratio of 16:9. DVD video players output wide-screen video in three different ways: letterbox (for 4:3 screens), pan and scan (for 4:3 screens), anamorphic or unchanged (for wide screens).

At the moment, DVD players resemble VCRs, however the race is on to make DVD players smaller and less expensive. Several companies developed a DVD player the size of a personal CD player with an integrated liquid crystal display viewing panel and speakers. A Chinese manufacturer incorporated the DVD player with the TV itself. Higher capacity and higher definition is not far off.

At the January 2000 Consumer Electronics Show, Pioneer showed off its high-definition DVD Recorder. Analysts say that high-definition DVD (HD-DVD) will become a reality when blue lasers, emitting wavelengths of 400-430 nm are perfected. The HD-DVD will require a storage capacity of 15 GB per side, more than three times that of current DVDs. A shorter wavelength laser increases the amount of information stored on an optical disk. Each time the wavelength is halved, the corresponding storage media can contain four times more data.

In order to promote the technology and establish a consensus on format standards, ten companies organized the DVD Consortium in 1995. These companies included: Hitachi, Ltd., Matsushita Electronic Industrial Co., Ltd., Mitsubishi Electric Corp., Philips Electronics N.V., Pioneer Electronics Corp., Sony Corp., THOMSON multimedia, Time Warner Inc., Toshiba Corp. and Victor Company of Japan Ltd. Today, the Forum boasts 122 member companies, including electronics manufacturers, software firms, and media companies worldwide.