Video Display Terms

The Video Electronics Standard Association, VESA was formed in 1989. The main goal of this organisation is to establish and support standards that benefit manufacturers of personal computers, workstations and associated hardware and software. With membership of over 300 companies, both consumers and members ultimately benefit by:

• Creation of unbiased standards
• Availability of accurate information
• Fostering a team atmosphere
• Increasing product interpretability

There are, however, manufacturers that do not follow established standards. This does create confusion and incompatibility of various products. Listed below are some associated common terms and definitions:

Analogue Signals: Both video and audio signals that are continuously varying in level are said to be analogue.

Attenuation: A reduction in the strength of a signal.

Bandwidth: The difference between the upper and lower usable limits of a band of frequencies.

Baseband: Unmodulated video or audio signals with an exclusive transmission path.

Chroma: The colour portion of a video signal "C".

Composite Sync: is another standard often used by workstation monitors. The most common example would be a SUN Microsystems monitor. To make composite sync, the horizontal and vertical sync pulses are combined onto one wire.

dB: A logarithmic unit of measure where 3db represents a doubling or halving the power level from a given starting point.

DDC: (Data Display Channel) is a standard that defines communication between a monitor and a host system.

Digital Signals: Data presented as discrete values i.e. On/Off or Binary.

Luma: The brightness portion of a video signal ("Y").

Pixel: A single point on a display.

Resolution: The density of pixels in a given area typically expressed as the horizontal x vertical values, (ex. 640x480).

Refresh Rate: Also referred to as scan rate. It is the number of times in one second (Hz) that the electron beam travels across the screen horizontally from one scan line to the next.

RGB: Red, Green and Blue signals.

SVGA: Super Video Graphics Array.

S-Video: A video signal that separates the "Y" or Luma and "C" or chroma information.

Separate Sync: is a standard PC sync signal type. The horizontal and vertical sync pulse are set on separate wires. The most common problem attaching a workstation monitor to PCs is to convert this combined signal to a sync on green or composite sync signal.

Sync on Green: is a standard usually used by workstations where the horizontal and vertical sync pulses are sent on the green wire.