When you plug your laptop into a projector how does it know which resolutions to allow you to select?  You’ll often see that the slider in the display properties page changes the available resolutions to use when plugged into a projector.  When you connect your laptop to a display, a small package of information is handed off from the display/projector to the computer’s video card.  This package is called EDID, or Extended display identification data.  Essentially, it lets the video card know what kind of display it is, who makes it, what resolution is its “favorite,” that is, the native resolution, the list of other resolutions it supports, etc.  Your video card then updates the available resolutions you can choose from and output.

This usually works great at your desk, however, in a presentation room, classroom or auditorium where there may be numerous splitters, switchers, and video extenders between your laptop and the display, this information can get lost, or even “hijacked” by a component.

This can cause issues like:

• Their laptop image is blurry on the projector.
• Black borders show up around the image and it’s too small on the big screen
• The image looks crummy on their local screen.
• The user is left to guess at what the resolution of the projector is supposed to be.  Unless they are an A/V engineer, I doubt they’ll know the native resolution of each projector model out there!
• Or worst of all, their laptop may not have a compatible resolution.  Then the A/V support team gets a call and the presentation grinds to a halt.

Most users won’t understand why these problems are happening and will just get frustrated with the system that’s “broken”.

Potential gottchas include:

• Virtually all systems that send video over Cat5 cable block EDID information.
• These same video extenders often reinsert their own table of supported resolutions, and guess what… they might not match the resolutions of your display!  A major headache.
• Often, video splitters (aka distribution amplifiers) only pass back the EDID from the display hooked up to output #1.  Usually, this is not explained in the documentation.

So what can you do?

Software solutions exist.  If you control the pool of laptops you can load software on the system that unlocks extra resolutions for your projectors.  Still, this means the users has to know what they are doing, plus there are licensing costs for this software on each PC.  One such example is from EnTech and is called PowerStrip (http://entechtaiwan.com/util/ps.shtm).  It is very powerful, but not very easy to use.

In my opinion, this is a hardware problem and not surprisingly, hardware solutions are the better answer.  DVN often uses EDID emulators to restore the EDID information so that it is handed off to the laptop properly.  One of our favorites switching and video distribution companies, Kramer Electronics, makes just such a product.  They are available for both DVI and VGA connections.  You’ll probably find that VGA is still the most common connection that laptop users utilize so I recommend tackling this first.

They are a snap to use when compared to deploying software on dozens of laptops:

1)      Hook EDID emulator box up directly to projector or display using a short VGA or DVI cable (make sure nothing is between unit and projector)

2)      Plug in power and put it in “capture” mode

3)      Allow unit to capture the EDID information and store it internally

4)      Replug the unit in as the first component that the laptop sees on the route to your projector.

Hardware EDID “problem fixers” are typically more affordable than software solutions since one device works for all laptops that will be used within the room.