Compatibility With Attached Devices; Edid Compatibility - Avocent Emerge MPX Installer/User Manual

Compatibility with Attached Devices

The following sections provide guidelines regarding compatibility with source and display devices.

EDID compatibility

Display devices communicate with source devices using Extended Display Identification Data
(EDID), a Video Electronics Standards Association (VESA) standard data format that contains
basic information about a monitor and its capabilities, including vendor information, maximum
image size, color characteristics, factory pre-set timings, frequency range limits and character
strings for the monitor name and serial number.
EDID information stored in a display device is passed to the MPX receiver across the video cable
through a digital path called the Display Data Channel (DDC). The receiver forwards this
information to the transmitter across the media LAN. The transmitter, in turn, passes the EDID
information to the source device, thus allowing plug-and-play functionality among display and
source devices.
An MPX extender group has a single primary receiver, which has special responsibilities regarding
serial, IR, and video functionality. Regarding video, only the primary receiver passes its EDID
information back to the transmitter. Thus, the display device attached to the primary receiver
should be representative of the devices attached to other receivers.
The MPX transmitter is pre-configured with default EDID information, which indicates support
only for 640x480 resolution at 60Hz. This EDID will be passed to a source device in lieu of
information received from MPX receivers. As the transmitter learns about the attached display
devices through receiver bindings, it uses the information to create a more meaningful EDID string,
referred to as the active EDID string. The process occurs as follows:
• Initially, the active EDID string is blank
• When a receiver binding occurs, if the receiver is not the primary and if the active EDID string
is blank, then the transmitter will merge the received and default EDID strings such that the
resulting string represents the common features supported by both devices. This new string
will be stored as the active EDID and will be reported to the source device.
• When the primary receiver binds with the transmitter for the first time, the merge process will
be repeated using the default and primary EDID strings.
• When bindings are established with subsequent receivers, no action is taken.
• If a different receiver is selected as the primary via the transmitter's web interface, then the
merge process will be repeated when a new primary EDID string is received.
• If the primary display device is replaced with a different model, then the receiver will report
the information to the transmitter and a merge process will take place.
NOTE: A blank screen may occur as EDID changes are being processed.
Chapter 1: Product Overview 9