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
- 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
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