Sometimes images don’t behave the way you want them to. For example you can take the output of one device, perhaps a BluRay player, connect it to a distribution amplifier and then to two monitors.

The picture appears on the one monitor but not the other. Even more weirdly if you disconnect the monitor that is working, then the picture appears on the other screen.

What is going on? Did I hear you say Enid? Not quite.

EDID – Extended Display Identification Data. Whenever you connect an image source to a display there is a dialogue over the HDMI cable. The display says its resolution and other details to the source, the source says OK, I can do that and sends the correct signal to the display. So far so simple.

Once you try to connect two or more different display screens then things get more complicated. The source can only send out one format at any time so if the displays ask for different specifications the source will only get one of them right.

At the time of writing the MS Teams Room app has a maximum resolution of 1920×1080. So if you use a PC connected to a 4k resolution screen, the PC may try to send a 4k image. This is most often an issue when there are two screens and it can even be intermittent making it a difficult problem to trace.

How can you fix it?

Sometimes you can go into the PC settings and tell it what resolution to use on the output. This can fail if the PC has to be reset or reconfigured in some way. The most robust solution is to use a little hardware device called an EDID manager or EDID emulator. This sits in the cable connection between the PC and the display screen and forces the PC to output a 1080p image.