10. Technologies
UMX-HDMI-140 series– User's Manual
112
Applied firmware package: v1.2.0 | LDC software: v2.4.1b7
10.1.
EDID Management
10.1.1.
Understanding the EDID
The Extended Display Identification Data (EDID) is the passport of display devices (monitors, TV sets,
projectors). It contains information about the capabilities of the display, such as supported resolutions,
refresh rates (these are called Detailed Timings), the type and manufacturer of the display device, etc.
After connecting a source to a display (DVI, HDMI, DP), the source reads out the EDID to determine the
resolution and refresh rate of the image to be transmitted.
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 with CEA extension are HDMI capable.
Common Problems Related to EDID
Problem:
“My system consists of the following: a computer, a Lightware device, a WUXGA (1920x1200)
LCD monitor, and an SXGA (1280x1024) projector. I would like to see the same image on the
monitor and the projector. What EDID should I choose on the Lightware device?”
Solution:
If you want to see the image on both displays, you need to select the resolution of the smaller
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 Lightware device 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 they do
not sense that EDID has been changed. You need to restart your source to make it read out the
EDID again.
10.1.2.
Advanced EDID Management
Each DVI sink (e.g. monitors, projectors, plasma displays, etc...) must support the EDID data
structure. Source BIOS and operating systems are likely to query the sink using DDC2B protocol to
determine what pixel formats and interface are supported. DVI standard uses EDID data structure
to identify the monitor type and capabilities. Most DVI sources (VGA cards, set top boxes, etc.)
will output DVI signal after accepting the connected sink’s EDID information. In the case of EDID
readout failure or missing EDID, the source will not output DVI video signal.
Lightware devices provide the Advanced EDID Management function that helps system integration.
The built-in EDID Router can store and emulate factory pre-programmed- and User programmable
EDIDs. The EDID of the attached monitors or projectors for each output are stored in a non-volatile
memory. This way the EDID of a monitor is available when the monitor is unplugged or switched
off.
Any EDID can be emulated on any input. An emulated EDID can be copied from the EDID router’s
memory (static EDID emulation), or from the last attached monitor’s memory (dynamic EDID
emulation). For example, the Lightware device can be set up to emulate a sink device, which is
connected to one of the outputs. In this case, the EDID automatically changes, if the monitor is
replaced with another display device (as long as it has a valid EDID).
EDID is independently programmable for all inputs without affecting each other. All inputs have
their own EDID circuit.
INFO:
The user is not required to disconnect the video cable to change an EDID as opposed to
other manufacturer’s products. EDID can be changed even if a source is connected to the input
and powered ON.
INFO:
When EDID has been changed, the router toggles the HOTPLUG signal for 2 seconds.
Some sources do not sense this signal. In such cases, the source device must be restarted or
powered OFF and ON again.
