Page 10 / 60 Section 2. General description
2.5. Understanding EDID
2.5.1. 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 HDMI source to a HDMI display, the source reads out the EDID to
determine the resolution and refresh rate of the image to be transmitted.
Figure 2-5. 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 which have the extension are HDMI capable.
2.5.2. Common problems related to EDID
Problem: „My system consists of the following: a Blu-Ray player, then a Lightware
HDMI-OPT-TX200R, a WUXGA (1920x1200) LCD as local monitor, then a
HDMI-OPT-RX200R connected to an SXGA (1280x1024) projector and an
UXGA (1600x1200) monitor. I would like to see the same image on the
monitors and the projector. What EDID should I chose on the
HDMI-OPT-TX200R?” See typical application in section 2.4.
Solution: If you want to see the image on all three 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.
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