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7. Advanced EDID Management
Each DVI and HDMI sink (e.g. monitors, projectors, plasma displays, and switcher
inputs) 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 is supported. DVI standard makes use of EDID data structure for the
identification of the monitor type and capabilities. Most DVI and HDMI sources
(VGA cards, set top boxes, etc) will output video signal only after accepting the
connected sink’s EDID information. In case of EDID readout failure or missing
EDID the source will output no signal.
7.1. Why is EDID management necessary?
All DVI and HDMI sources must read attached sink’s EDID data (switcher input,
monitor input, etc.) before starting the video signal transmission. If no EDID is
available, most sources will not output the signal. Unlike in standard analog VGA
graphics cards, DVI graphics cards do not allow to be forced from Windows
desktop/properties/settings tab to different pixel resolutions. Only those resolutions
and refresh rates are allowed, which are defined in EDID data.
To provide proper EDID data for the sources, Lightware matrices have an
Advanced EDID Manager, which can manage the emulated EDID on all of its
inputs independently. The EDID management can be done from the front panel,
from the control software, from the webpage or from any other software, which
implements the protocol described in the Programmer’s reference. Emulating the
right EDID information helps the user and installation engineer to control overall
system signal properties
EDID emulating options are:
Memory EDID emulation: static EDID emulation from factory preset
memory (50 EDID from 01 to 50). The selected EDID is emulated
at the desired (or all) inputs.
User memory EDID emulation: static EDID emulation from user preset
memory (50 memory locations from 51 to 100) The selected EDID
is emulated at the desired (or all) inputs.
Dynamic EDID emulation: copying and emulating EDID from one of
attached display devices. The EDID of the attached display device
(projector, monitor, etc) is emulated on the desired input. If the
display is changed, and new device is attached, the EDID on
selected inputs will automatically be changed according to the new
display.
With EDID Router function, the user is able to store EDID from any attached
monitor to one of the user programmable memories, to download EDID from file to
user memory, and to upload EDID from the router to file.
Info: The user does not have to disconnect DVI cables to change an EDID opposite to
other manufacturer’s products. EDID can be changed even if source is connected
to the input and powered ON.
Info: When EDID has been changed, the router toggles the HOTPUG signal for 200
msec. Some graphic cards or DVD players do not sense the hotplug signal, and it
may happen, that even if EDID has been changed, the newly set resolution is not
applied. In this case the source device must be restarted or powered OFF and ON
again.
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