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Section
2
.
General
description
2.4.
Understanding EDID
2.4.1. Basics
EDID stands for Extended Display Identification Data. Simply put, EDID is the passport of
display devices (monitors, TV sets, projectors). It contains information about the display’s
capabilities, such as supported resolutions, refresh rates (these are called Detailed
Timings), the type and manufacturer of the display device, etc.
After connecting a DVI source to a DVI display, the source reads out the EDID to determine
the resolution and refresh rate of the image to be transmitted.
Figure 2-2. EDID communication
Most DVI computer displays have 128-byte long EDID structure. However, Digital
Televisions and HDMI capable displays may have another 128 bytes, which is called E-
EDID and defined by CEA (Consumer Electronics Association). This extension contains
information about additional Detailed Timings, audio capabilities, speaker allocation and
HDMI capabilities. It is important to know, that all HDMI capable devices must have CEA
extension, but not all devices are HDMI capable which have the extension.
2.4.2. Common problems related to EDID
Problem:
„My system consists of the following: a computer, a Lightware UMX4x4-Pro
matrix, a WUXGA (1920x1200) LCD monitor, and an SXGA (1280x1024)
projector. I would like to see the same image on the monitors and the projector.
What EDID should I chose on the monitor and the projector?
”
Solution: If you want to see the image on both displays, you need to select the resolution
of the smallest display (in this case SXGA), otherwise the smaller display may
not show the higher resolution image.
Problem:
„I have changed to a different EDID on an input port of the matrix to have a
different
resolution but nothing happens.”
Solution: Some graphics cards and video sources read out the EDID only after power-up
and later th
ey don’t sense that EDID has been changed. You need to restart
your source to make it read out the EDID again.
