6.1 EDID

Basics

EDID is an acronym for Extended Display Identification Data. EDID is a standard that lets display devices like monitors, televisions, and projectors communicate their capabilities to the video source. When using HDMI, the EDID from your television tells the video source what the dimensions of the screen are.

You should know the following terms:

  • EDID (Extended Display identification Data)
  • Handshaking

The Handshake Process

EDID works by establishing a connection between the screen and video source in which they exchange data via a “handshaking” process. The cable has channels that are specifically used to facilitate this handshake process, and it happens instantly when the screen and video source are connected and powered on. On a normal basis the EDID Standard is so baked-in to the modern video formats that it's kind of hard for things to go wrong

The EDID handshake process routinely exchanges the following information:

  • The EDID Version and manufacturer information (model, serial number, etc.);

  • The video resolution the screen supports (e.g., 720p, 1080p, 4k, others);

  • Information unique to monitors that can be different from a television screen, for example, ultra-wide monitors; and

  • Hardware-related capabilities (e.g., power management, color gamut, refresh rate).

Troubleshooting EDID

The more pieces of equipment an HDMI signal has to pass through, the more chances there are for problems. Examples of issues and their resolution are 
(Content Credit: https://thehometheaterdiy.com/hdmi-edid/):

  • Video resolution displays incorrectly. Configure the video output manually. You will likely need to do this each time when using this video source.

  • Issues from using a cable extender. There are many inexpensive HDMI extenders on the market today and many of them will cause issues with the handshake. The easiest solution is to purchase a longer cable so the extension is not necessary. It is also possible to configure HDMI over Cat6 cabling.

  • Issues from using a cable adapter. There are also a variety of inexpensive adapters on the market today that may not work well. Depending on your equipment, students and staff may need an HDMI adapter to connect their computer to a display. Be sure they have the correct adapter and a high-quality one.

  • You experience a long delay when switching sources when using a switcher or receiver.  Every step in the process has to take in the EDID signal, adjust, then output the right signal. Be aware that if your video source has to go to a receiver, then a television or monitor,  it takes time to decode and encode the EDID signal. This may mean waiting on a black screen for a few seconds when changing sources.

Complete the following task or self-assessment:

Check to see if anyone is using cable extenders or adapters in your building. If found, develop a plan for replacing extenders over time and ensuring adapters work well.