Computer Dictionary Online

video adapter definition

graphics adaptor

video card definition

graphics adaptor

Video Compact Disc definition

<storage> (VCD) A storage format used for film distribution.

[Details? Relationship to audio CD?]

(2004-02-15)

video compression definition

Compression of sequences of images. Video compression algorithms use the fact that there are usually only small changes from one "frame" to the next so they only need to encode the starting frame and a sequence of differences between frames. This is known as "inter-frame coding" or "3D coding".

MPEG is a committee producing standards in this area and also the name of their standard algorithm. H.261 is another standard.

See also Integrated Information Technology, 3DO, full-motion video, Online Media.

video conference definition

An instance of video conferencing.

video conferencing definition

<communications> A discussion between two or more groups of people who are in different places but can see and hear each other using electronic communications. Pictures and sound are carried by the telecommunication network and such conferences can take place across the world.

To overcome the bandwidth and latency limitations of current networks (especially the PSTN), some form of video compression is often used.

(1995-05-01)

video dial tone definition

<communications> A means by which telephone companies can deliver "television" programs on a common carrier basis and, by law, provide equal access to all.

[What does this mean?]

(1996-12-01)

video display terminal definition

visual display unit

Video Electronics Standards Association definition

<body, standard> (VESA) An industry standards organisation created in 1989 or 1990 mostly(?) concerned with IBM compatible personal computers. The first standard it created was the 800 x 600 pixel Super VGA (SVGA) display and its software interface. It also defined the VESA Local Bus (VLB).

See also PCI.

Home.

(1995-11-16)

Video Graphics Adapter definition

Video Graphics Array

Video Graphics Adaptor definition

Video Graphics Array

Video Graphics Array definition

<hardware> (VGA) A display standard for IBM PCs, with 640 x 480 pixels in 16 colours and a 4:3 aspect ratio. There is also a text mode with 720 x 400 pixels.

IBM technical references define the *product name* of their original VGA display board as "Video Graphics Array", in contrast to the preceding boards, the "Color Graphics Adapter" (CGA) and "Enhanced Graphics Adapter" (EGA).

See also Super Video Graphics Adapter.

(1995-01-12)

video memory definition

<storage> The memory in a computer's graphics adaptor, used to store the image displayed on a bitmap display. Often this is built using VRAM chips. There is normally a simple correspondence between groups of bits in video memory and the dots or "pixels" on the screen, such that writing to a given group of bits will alter the appearance of a single dot. If each pixel corresponds to eight bits then it can have any of 256 colours (or shades of grey on a monochrome display).

The video display electronics is responsible for reading the data from video memory and converting it into the necessary signals to drive the display. Often this includes a colour palette which converts pixel values into RGB triplets.

(1996-11-01)

Video on Demand definition

<communications> (VoD) A planned system using video compression to supply programs to viewers when requested, via ISDN or cable.

(1994-11-02)

video RAM definition

video random access memory

video random access memory definition

<hardware> (VRAM) Fast memory designed for storing the image to be displayed on a computer's monitor. VRAM may be built from special memory integrated circuits designed to be accessed sequentially.

VRAM must be fast enough to supply data to the display electronics at the speed at which the screen is scanned. Thus for example, for a resolution of 1280x1024 eight-bit pixels at a refresh rate of 70 Hz, the video memory would need to supply 1280x1024x70 = 90 Mbyte/s or one byte every 11 ns. The VRAM may be dual ported in order to allow the display electronics and the CPU to access it at the same time.

In an IBM PC the VRAM is located on the display interface card and 0.5 - 2 MB is typical.

A VRAM Song!

(2001-02-14)

video terminal definition

visual display unit

videotex definition

An obsolete electronic service offering people the privilege of paying to read the weather on their television screens instead of having somebody read it to them for free while they brush their teeth. The idea bombed everywhere it wasn't government-subsidised, because by the time videotex was practical the installed base of personal computers could hook up to time-sharing services and do the things for which videotex might have been worthwhile better and cheaper. Videotex planners badly overestimated both the appeal of getting information from a computer and the cost of local intelligence at the user's end. Like the gorilla arm effect, this has been a cautionary tale to hackers ever since. See also vannevar.

[Jargon File]