What is EDID and why is it important?

With all the technology associated with HDMI, lots of elusive terms come into play. One term that comes up pretty frequently is EDID.

What is EDID?

This question comes up a lot when troubleshooting unusual video setting issues with customers. EDID is an acronym for “Extended Display Identification Data”.It might seem a little simplistic, but it actually refers to the method your devices use to “talk to each other”. This short set of letters can be the source of a major headache when it comes to HDMI. When establishing an HDMI connection, the source device must be able to communicate with the display (known as the Sink) and find out what capabilities it has. The communication between these two devices is what is known as the “HDMI handshake”.During this process, the source is attempting to find out what the Sink’s maximum capabilities are so it can transmit the best possible signal.

My usual basic description is that 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.
TV_EDID_with_laptop

Of course if you really get into it, EDID is far more complicated. It includes vendor and product id, serial number, manufacture date, size of the display, resolution and frequencies supported, and detailed signal timings for native resolutions. Plus, often when we speak of EDID we are actually referring to E-EDID, or Enhanced Extended Display Identification Data. This allows the devices to handle additional data, including vendor-specific specifications, as it opens up the data strings to 32 Kilobytes. It’s just another way for your electronics to get a conversation going, but with a little more information.

When EDID was first introduced in 1994 it was short and sweet at just 128 bytes. It had vendor and product information, EDID revision, display capabilities (size, resolution, sync, etc), colour space, and detailed resolution/timing information. In 2000, E-EDID expanded this, allowing multiple 128 byte chunks. Today’s HDMI devices most often use E-EDID and include information to also specify audio capabilities including codecs, sampling rates, and channels.

In conclusion, here are the types of information that might be communicated:

  • EDID version
  • Manufacturer ID
  • Model Number
  • Serial Number
  • Video Resolutions
  • Video Timing Bitmaps and Descriptors
  • Chromaticity Coordinates
  • Video Field Rates
  • White Point Descriptors
  • Display Power Management Info

I’m not going to get too low level or technical here, as this information is already available online and is just a quick Google search away. However I do want to address the practical concerns of EDIDs when using our products.

When you connect your video source (e.g. camera, laptop, scientific instrument, etc) to any VVdeals (HDMI or capture and streaming) device, our device acts as the “monitor” for your video source.

EDID_TV-with_laptop-2

This default EDID is generally good and works with a broad range of video sources. Sometimes, though there may be some troubleshooting.

Why so sad?

On the surface, this seems like it should be a simple process, right?

Not so fast. As long as you are connecting a single source to a single display, it’s usually smooth sailing.

However, throw in another device like a switch, extender or a splitter and chances are your devices might stop talking to one another. On occasion, the source device might have its EDID ROM coded incorrectly, which will cause issues from the outset.

In these cases, you might have trouble reaching the correct resolution or color issues. It might just fail to produce audio and/or video all together.

EDID Troubleshooting

The first step when you’re having issues you believe are related to EDID is to determine if it is the source device causing the issue.

Step 1

Connect the device directly to the TV with nothing in between to see if this solves the problem. If it does, then it’s the middle man causing issues.

Step 2

If it still fails to work, try connecting the source to a different TV that you know to be reliable. If this also fails, then your problem most likely lies with the source.

Step 3

Try updating the manufacturer firmware for whichever device you believe to be the troublemaker. This often takes care of the problems quickly and easily.

Step 4

Check the length of the cables you are using. The HDMI signal depends largely on the power of the device to which it is connected. Typically, HDMI can be transmitted up to 50 feet without issue (check How far your HDMI cable can be run), but some devices just don’t output enough power to make it past 30 feet or less (computers and gaming systems).

If the device isn’t producing enough power, the signal isn’t going to make it to its destination and the source will never get its EDID from the display. Splitters, switches, and of course, extenders, give that signal a boost to carry it further, but these also come with limitations. Check the device’s manual to ensure your cables are not too long for the run.

Step 5

Is your source a computer? Many TVs only accept specific computer resolutions. Make sure the resolution you are attempting to achieve is supported by your TV.

There are a number of different reasons your HDMI compliant devices might have trouble communicating, but hopefully this will get this you started if you’re experiencing issues! Remember, it may not always be the case that you’re working with defective devices. It could just be a missed communication.

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