Designing Content for a Multi-Screen Video Display
COW Library : Adobe After Effects Tutorials : Matt Hall : Designing Content for a Multi-Screen Video Display
Photo by Greg Martinelli
You've seen multiple screen video presentations. You've seen them at trade shows and behind the counter in clothing stores. They use a number of different screens, usually plasmas, together to form one linked image. You know you want to build them for yourself, so I'll help you get started with a simple example in After Effects.
First, let's differentiate these multi-screen installations from traditional video walls. A traditional video wall splits up a single video source, and displays it on multiple joined screens. This is accomplished using a hardware video wall processor, and it arranges the multiple screens in a grid to make either a 4:3 or 16:9 image.
Multi-screen installations aren't restricted to any traditional aspect ratio. They can be laid out any way you can imagine. How about 5 screens edge to edge to make one long strip? Or 10 LCD screens arranged in an arch over a doorway? Or 4 curved rear projection screens arranged to make one 360 degree screen? Or 20 plasma screens mixed with 10 LCD screens mixed with 2 rear projection screens that all together make the shape of your client's logo? These are all examples of actual projects I've done!
Understand that, without hardware to do the work for you, you've got to do the work yourself. Instead of one source being split onto, say, 12 screens, you have 12 sources going to 12 screens. And each of those 12 sources needs to be synchronized so they all play back at the same time.
That's actually easier than it sounds, especially if you're using DVDs for playback. Industrial DVD players can be connected to pieces of hardware that ensure they play back at the same time.
Computer playback is a little more complicated. Don't forget, in this example you've got 12 computers that need to be synced. Software called Watchout, by Dataton, is one way to manage this.
Next to consider is video format. Maybe by the time you read this there will be industrial-grade DVD players that play back HD media, but for now, for your multiscreen installation, DVD equals SD. If you need HD – often the case if people are going to get close to the video -- computer playback is the way to go.
So after figuring out the format and devices for playback, you're ready to start designing. Which means you're ready for math.
Let's use a very simple project I worked on recently as an example.
We had four plasma screens mounted on top of each other, each fed from a DVD source. Here comes the math. If the digital canvas for one DVD is 864 x 480 (the square pixel equivalent of a 16:9 anamorphic DVD) then 4 plasmas stacked on top of each other is 864 x 1920 (480 x 4 = 1920).
But wait! That assumes that each screen is perfectly stacked on the other. That's never true because of the monitor's frame and the little bit of air that will be in between each monitor. So I added 50 pixels as spacers between the screens to account for that. Now my digital canvas is 864 x 2070 (1920 + (50 x 3).
Whew! Glad the math is over.
So I create a composition in After Effects of 864 x 2070. Next I have to create some solid layers as guides so I know where each of my screens is going to be. I make a new solid at 480 pixels high and 864 pixels wide to serve as a stand-in for each screen. I name the first Screen 1, and put it at the very top of the comp.
Next I use a 50 pixel high solid as a stand in for the spacer. Then another solid for Screen 2, another spacer, and so on. So now, if I hide the visibility of my screen solids, I'm left with the spacer solids. I now know where the gaps (the space between the screens) in my animation are going to be.
This is a very simple example, and as I mentioned earlier, multiscreen installations can get very, very complicated. No matter what kind of project you have, here are a few things to remember as you compose:
• Mind the Gaps! By gaps I mean the mullions of the monitors and the space between them. Try not to make anything important - like a word or a person's face - fall across those spaces.
Now for output. To render the files for your DVDs, make four new compositions at 864 x 480. Following the naming pattern for the original comps, I call them Screen 1 Render Comp, Screen 2 Render Comp, etc). Into each of those comps, drop your master comp and position so it shows the current area for that screen. Use your original guides to make sure this is right.
A CRITICAL ENDING:
Finally, there's one absolutely critical element: when you render each of your screens out, make sure that the length of each of your renders is exactly, to the frame, the same length. If one ends before the others, you'll have major problems with the synchronization.
And now you're ready to build your own multi-screen installation! The only limits are your imagination and the client's budget.
Matt Hall is a New York-based artist and producer whose work has been used at major trade expositions by clients in the pharmaceutical and other fields.
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