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Digital Video Disc, a DefinitionDigital Video Disc (DVD) is a new media for the distribution of from 4.7 to 17 billion bytes of digital data on a 120mm (4.75 inch) disk. This huge volume of data (today's CD can store 680 million bytes of data) can be used to store up to nine hours of studio quality video and multi-channel surround-sound audio, highly interactive multimedia computer programs, 30 hours of CD-quality audio, or anything else that can be represented as digital data. The Digital Video Disc Media A digital video disk is made up of a reflective aluminum foil encased in a clear plastic. Data is stored on the foil as a series of tiny pits formed in a tight spiral on the disk. The pits are formed in the foil by stamping it with a glass master. In the case of a single-sided DVD, the stamped disk is backed by a dummy, which may contain graphics advertising the contents of the disk. For a double-sided disk, two halves, each with their foil full of data, are bonded back to back. A combination of the techniques used to make today's audio CDs and laser disks (also a double-sided medium), this process is well understood. Disc replicators estimate that the cost of a single-sided single layer DVD will be comparable to an audio CD, or about £1.30, including the packaging. This cost model, in addition to the lower transportation, warehousing, and retail shelf space requirements, is one of the key attractions of DVD. This low-cost model (a VHS tape costs about £4.90 to make and distribute) may also make new distribution models possible, such as pay-per-view. Overview From its inception, video has been recorded and transmitted as analog electrical signals. While analog video transmitters and receivers can be built inexpensively, analog video is very expensive to transmit and to store. Further, today's powerful digital computers cannot process analog signals, so analog information cannot be easily sorted, searched or edited. The transition of video from the analog to the digital domain changes everything. Digital video can be stored and distributed more cheaply than analog video, and digital video can be stored on randomly accessible media such as magnetic disk drives (hard disks) and optical disk media (CDs). Once stored on a randomly accessible media, video becomes an interactive media, allowing video to be used in games, catalogs, training, education, and other applications. Even movies ( to date a linear media ( can become interactive, allowing viewers to select their point of view, a plot path and the ending. Digital video also dramatically increases transmission efficiency, which means that communications networks, from the public telephone system to coaxial cable television systems to telecommunications satellites, will be able to carry from six to ten times more channels of video programming than was possible before, dramatically increasing consumer choice. The ability to transmit video over the public switched telephone network will also allow video conferencing, accelerating the work-at-home movement that is changing the way we are all employed. One of the first products to be based on digital video technology will be the Digital Video Disc or DVD. These disks are the size of today's audio CD, yet hold up to 17 billion bytes of data, 26 times the data on an audio CD. Convergence and DVD As can been seen from the discussion of DVD players, the DVD decoder chip is the heart of a DVD player. And DVD is based on the MPEG-2 standard for digital video distribution, as are most direct to home satellite systems and wireless cable systems. In fact, the DVD decoder chip is a super set of the video and audio decoder chips required to build a home satellite receiver or a wireless cable set-top box. Because DVD players have much in common with satellite receivers and cable set top boxes, it is likely that one or more of these devices may converge in a single unit, a so called convergence box. In fact, the PC is a kind of convergence box as well. DVD and the InternetA DVD player also contains almost all of the circuitry required to support an Internet browser, making a "full" PC unnecessary. While at first the synergy between the browser and DVD player may not be obvious, the combination offers a wealth of opportunities. For example, it would be possible to showcase all of the clothes in all of the departments in a department store, complete with video of much of the merchandise on a DVD. The connection to the Internet would allow the customer to get current prices, order merchandise, communicate (via email) with a personal shopper or pay their bill. Such a service via the Internet alone is not practical: the low bandwidth available to users would make the "catalog" intolerably slow and limit the audio and image quality that the catalog could deliver. A DVD-based catalog would deliver great interactive performance with a rich audio and video experience, but at £1.60 to duplicate and deliver, a DVD catalog would be far cheaper than today's print media. This combination of DVD and Internet can be extended to other applications as well, including education, training and on-line games. DVD and game platforms DVD versions of today's gaming platforms will also likely appear. Today's Sega Saturn, Sony and 3D0 platforms use CD technology as the delivery platform for their games. However, the single-speed CD drives used in these machines limit interactive performance, which in the twitch game world is everything. DVD provides access and data transfer rates that are 10 times faster than single-speed CD-ROM, and the video experience DVD brings can significantly expand the scope and quality of the games, not to mention the utility of the game machine itself. It is not known if any of these merged devices will become popular. Certainly devices with decidedly different applications are likely to remain separate. Take the PC for example. While a PC can be made into a perfectly good DVD viewing system with the addition of a DVD-ROM drive and a DVD decoder chip, the PC is likely to remain in the study or den because of its other applications ( word processing, tax return preparation, electronic mail and the like ( and the need for a desk-bound keyboard. On the other hand, stand-alone DVD players and satellite receivers will be attached to the TV in the family room, making these two devices good candidates for convergence, especially in Europe where the Digital Video Broadcast (DVB) standard is guaranteeing compatibility between satellite receivers from various manufacturers. DVD is to VHS tape what audio CD was to the long-playing record. Consumers were motivated to switch from LP to audio CD by the superior sound quality and durability of the new medium. DVD offers a similar increase in quality and durability for video, and much more: parental control, interactivity, wide-screen support, multiple-camera angles, multiple languages, just to name a few. Further, Hollywood is committed to DVD, both for the increased revenue it represents and the greater control over distribution it provides. And personal computer makers need DVD for its larger capacity and enhanced video and audio. ( C-Cube Microsystems Inc June 1999 Compiled by Will Garside 2