What is EDID?
EDID is the information provided by a monitor to the video source describing the monitor’s capabilities. This allows the video source to then send out a video signal that is supported by the monitor. EDIDs are important for DVI and HDMI video sources and occasionally used for VGA sources. It also includes vendor and product id, serial number, manufacture date, size of the display, resolution and frequencies supported, and detailed signal timings for native resolutions.
Take the situation where you may want to send your DVD signal to two locations. In this example you would use a HDMI splitter to allow such connection. This is where things start to become interesting as you now have two lots of manufacturer and capability information going back to the source and they may be different. Which set of information should the source use to set up its signal? You may well have a 1080p capable screen in the main lounge but only a 720p capable screen in the second location. If the main lounge capability information is used by the source then the source will send a 1080p resolution signal but the second location display will not be able to handle this and will show a messaging saying "Out of Range" or something similar.
Another example may be where you want to send your HD signal to multiple locations and one location is a surround sound zone with a 5.1 surround sound amplifier and the other zones are TV's that can only handle 2 channel stereo. If the source sets up the audio format based on the EDID from the surround sound zone then the 2 channel TV displays will typically have a picture but a nasty buzzing noise for the audio as they cannot handle the digital 5.1 channel audio signal.
Our products come pre-loaded with a default EDID that lists a large number of supported resolutions, colour spaces, timing information, audio formats etc. This default EDID is generally good and works with a broad range of video sources. Sometimes, though, it’s useful to copy/upload a specific EDID to the device, telling your video source to provide the video/audio information you want to capture, or adding a custom resolution or timing that isn’t in the default EDID.
Knowledge Base Articles:
- Why EDID Management In HDMI Is So Important by Jason Aldous
- What is EDID and why is it important? by Adam Frame
- Extended Display Identification Data - Wikipedia