The Qualiverse - EDID or E-Don't
Buying a car can be challenging due to all the decisions that are required. You have to make the big decisions: size, type, electric, hybrid, or gas-fueled. Then there are the medium decisions: manufacturer, model, color. Then, there are the seemingly endless minor decisions: keyless entry, remote start, heated seats, entertainment system, all which impact your experience as a driver or passenger. You can take the family down to Disney in the family truckster but having that entertainment system for the kids makes the ride so much more tolerable for everyone. Many people geek out on those little details. Although, they don’t impact how well the car drives, fuel efficiency, or safety, but they are still very important facets of the car. You certainly wouldn’t ignore them when buying a car or leave it up to the car dealer to pick which ones are included with your car. They are a minor, but still very significant, aspect of the purchase.
What do EDID and cars have in common?
In my humble opinion, having an EDID prescription or solution for an AV system is the heated seats decision of buying a car. Will the car work without heated seats? Obviously. On early, cold, wintery mornings, are heated seats a gift from God? Most definitely. Would I leave the decision of whether to include heated seats in my car up to the dealer? You done lost your mind, friend.
What is EDID?
EDID, or Extended Display Identification Data, are metadata formats for video destinations to describe their capabilities to video sources, and the sources then use that metadata to determine the optimal video signal outputs for those destinations. (Wait, what?!) Essentially, EDID information allows displays (or other video sinks) to let sources know what video signals they can handle. EDID includes information about supported resolutions, preferred resolutions, supported audio formats, content protection, color space information, etc. When a source is connected to a destination, it goes something like this:
Source: Hey, buddy. I’m a source. What types of video signals can you handle?
Destination: What up, homie. I’m a destination. I can do all these different types of formats. This one is my favorite. Do any of these work?
Source: I picked this one. I know it’s not your favorite, but it is on your list. Is that OK?
Destination: *sigh* It’s fine. I’ll make it work.
Source: Here you go. *sends video signal that should work with the destination*
can EDID go bad?
It’s essentially a video signal negotiation that happens between sources and sinks in the video chain. Sounds easy enough, right? Well...it’s not quite that simple. When a laptop is connecting to a desktop monitor, it usually works our well. However, in a large, complicated system, that video signal negotiation can go sideways quickly. EDID can be managed at several different locations in a system, such as a video transmitter, video scaler or matrix switcher. If the EDID is configured to only allow certain signals, some might not be supported by the sources in the system, which may prevent the video signal from passing. Or, if the EDID negotiation is set to “auto” (which most systems are), that setting may successfully pass a signal, but it might not be the signal the users want.
Allowing Protected content into the system
A common example is whether or not to allow protected content (HDCP sources like TV Tuners or MAC laptops) in the system. On one side, enabling protected content to pass through the system is great. It gives the users the ability to view whatever they want in the system. On the other hand, HDCP sources are not permitted to pass video to recorders or codecs. So, enabling HDCP on system inputs could cause a situation where the laptop is shown on the main display (an HDCP compliant destination), but not shared to the far end (not HDCP compliant) ...and you’re left with confused users. (“Why does it show on the screen, but not the far end?”) It’s typically an easy enough fix: either disable HDCP on the input to work with conferencing equipment or prevent the input from ever being routed to the far end. But this is a significant system setting that requires input from the client. It should not be guessed at by the installation crew.
Setting prioritization for aspect ratios
Another very common example is projector image aspect ratios (or “shape”). Most LCD displays have a 16:9 aspect ratio (1080P, UHD, 4K, etc.). Many projectors have a 16:10 aspect ratio (1920x1200) which is slightly “taller” for the same width. Most laptop sources support 16:9 and 16:10 formats. Which takes the priority in the system for the signal to be optimized for, the displays or the projector? If the projector is the priority, and the system EDID prioritizes 16:10 aspect ratio sources, the sources on the LCD screens may appear squished or cutoff. If 16:9 sources are prioritized, the sources on the projector may look stretched or not take up the whole screen. If the image doesn’t take up the whole screen, the geometry will be maintained (a circle will be a circle instead of an oval) which could be important for military, advertising, and medical users. Other users might freak out about the image not filling the screen. “What did I pay all this money for a large screen if it won’t be filled?!” Again, this is pretty important and requires input from the client. It should be part of the design package, and not left to chance.
To add to this example, let’s say 16:9 sources take priority, but we have a 16:10 projector. What should we do with the screen? Get a 16:10 screen, that might not be filled or stretch the image? Or, get a 16:9 screen, set the projector to 16:9 mode, and maintain the image geometry? BUT! Just because the projector is in 16:9 mode, it’s still putting out some light above and below the edge of the screen. It will project “black” pixels above and below the image, but with front projection systems, “black” pixels are still lit by the projector. It may look like the image is overflowing the screen, instead of stopping at the edge. This EDID stuff is not easy.
Supported Resolutions
Probably the most iconic EDID conversations stem around which resolutions should be supported by the system. If you ask many users what the preferred resolution of the system should be, they say, “4K, of course!” Now don’t get me wrong. 4K images look incredible...from 18” away at my desk. In a boardroom, at the head of the table, the text size on 4K images is incredibly difficult to read. I’ve seen several users forced to move to the front of the table to log in to the system computer because they can’t see the mouse pointer, much less see the text being entered. Would it be better to limit the resolution to 1080P, where the text will be twice as big? Or, dare I say it, 720P where the text would be three times as big? Or, will the users be presenting material that requires the full 2,160 x 3,840 pixels, such as medical images, maps, or other high-resolution content? My preference is typically to recommend using 720P as the preferred resolution, purely for readability in the conference room (and viewing high resolution images is not a system requirement). However, this is too important a decision to make on my own. Again, the client must be brought into the conversation and the EDID solution must be part of the design package.
Is EDID really important?
In my auditing and design review experience, the EDID solution for the system is very often overlooked. Some might say, instead of many designers providing the EDID prescription, they simply E-Don’t. (See what I did there?) However, hopefully, you can see how important it is to the outcome of the system. Could a technician get a system to work without an EDID plan in the design? Probably. Would the system behave exactly how the users want or how the designer intended? Probably not. Having an EDID plan may not impede the functionality of the system, but it will definitely have a large impact on its performance. Similarly, there may be a car out there that absolutely purrs, jumps from 0-60 in 2.5s, and has an absolute baller entertainment system. But I’ll tell you what: at 6am on a below-freezing morning in January, all that stuff matters way less than having those heated seats. It’s the same with EDID. I may be able to present, to collaborate, to be heard clearly...but if the users on the screen look a little shorter and fatter than they are in real life, it may not be considered a successful system. Take the time to communicate exactly how the system should behave during the design phase. Be an EDID designer not an E-Don’t.
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