# 3 Different Projectors from same Computer?



## jowens (May 6, 2010)

Hi Everyone,
Thanks in advance for your thoughts!

Next year's drama production (at a high school) is going to require 3 screens framing out the back of the stage. There will need to be different video projections at the same time on each of the screens.

Will Qlab support this? Can my macbook do this?
Is this possible at all from one computer? 

These projections will act as the set for the show, so we're willing to put a decent amount of money towards it.

Any thoughts you might be able to give would be really helpful!
Thanks.

Joe


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## sk8rsdad (May 6, 2010)

QLAB can support up to 8 monitors assuming you have a MAC with multiple GPUs and enough processing power to drive them. Personally, I've done 3 screens with 1 or 2 projectors and a careful combination of image editing and screen placement because it was less expensive than building a custom MAC.


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## MarshallPope (May 6, 2010)

Also, there is a thingamajig available - I will see if I can hunt it down - that can take one VGA and stretch it into 3 side-by-side VGA outputs. If I remember right, it is about $250. if you do something like this, you could just make one "billboard" of projection on the computer, line it up correctly, and send each line to it's respective projector. We use this setup for backgrounds at our theatre.

EDIT: This could be it:
Matrox Graphics eXpansion Module TripleHead2Go DP Edition Video converter
or at least give you a general idea of what I'm talking about. This doesn't look like I remember ours, but the name sounds familiar. Anyway, I can't vouch for this particular product, but this could be something that could help.


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## museav (May 9, 2010)

jowens said:


> Next year's drama production (at a high school) is going to require 3 screens framing out the back of the stage. There will need to be different video projections at the same time on each of the screens.


I'm not sure the Matrox (Matrox Graphics - Products - Graphics eXpansion Module - TripleHead2Go) is what is desired, that is typically used to either stretch an image across three displays or to display three different applications, one per display. So can you clarify what you are wanting? Are you saying that you plan on having three screens each potentially displaying a single different source or are you saying three screens with each displaying multiple sources? What are the potential sources and could they all be computer files?


jowens said:


> These projections will act as the set for the show, so we're willing to put a decent amount of money towards it.


There have been several past discussion regarding using rear projection for sets and the image sizes being considered often require greater brightness and space than expected. You might want to verify that aspect before getting into too many other related details.


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## byrnebox (May 17, 2010)

I do not know your budget here, but a more reliable solution in my mind would be to get a matrix switcher, and then freeze the images on different screens. That would be more reliable I think. But I agree you need to make sure projectors are the right solution first.


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## Footer (May 18, 2010)

museav said:


> I'm not sure the Matrox (Matrox Graphics - Products - Graphics eXpansion Module - TripleHead2Go) is what is desired, that is typically used to either stretch an image across three displays or to display three different applications, one per display. So can you clarify what you are wanting? Are you saying that you plan on having three screens each potentially displaying a single different source or are you saying three screens with each displaying multiple sources? What are the potential sources and could they all be computer files?
> 
> 
> There have been several past discussion regarding using rear projection for sets and the image sizes being considered often require greater brightness and space than expected. You might want to verify that aspect before getting into too many other related details.



I have used the Triple head to go to do a poor mans 3 screen projection. It works rather well. If you want your content stretched across 3 screens it is the way to go on the cheap. You don't get edge blending or anything fancy, but it does work just great.


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## willbb123 (May 18, 2010)

I recently ran projection for an opera production. They have a large budget and love to spend money, so it may be out of your budget. 

The setup was 4 projectors, with their own desktop PC. And a control PC. Software was Dataton WatchOut. We only projected images, but it looked like the software could do video. I was just running the shows, so I didn't play around with the software too much. All media was placed in a timeline with transparency fades, then cues advanced with the space bar. Each projector can be aligned/calibrated from the software, although I didn't need to after the initial setup. I believe it can even be controlled via DMX.


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## HornsOverIthaca (May 20, 2010)

QLab can do this. You could use a rental license for testing. I've done three screens at the same time with QLab on a MacPro quad-core. The cost of the hardware is the issue. Unfortunately the new Macs use the mini-display port connector which will require an adapter. They also do not screw in. They kind of lock into place, but a good tug will pop them out.

I'm unaware of a method for stretching one VGA image across three projectors without using a high end display switcher.


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## NicoDanger (Jun 7, 2010)

I've been driving three projectors across three screens using a triplehead for the last three or four years. The software I use is called VDMX and can be demoed at vidvox.com. There is a steep learning curve but I've become quite proficient at running realtime video in sync across the entire array. 

A bit of time invested on their forum will yield more information about how to do this. It's a common setup for many VJs.


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## NickVon (Dec 7, 2012)

old thread but a question regarding the Matrox Hardware. We are doing a show with 3 discrete projector screens (we are not spanning a space using 3 projectors,as I think the OP was discussing) We are looking to put 3 unique images on the 3 projectors and to do this with Qlab rental license as our software solution. Will the Matrox Hardware show as multiple video outputs with regard to Qlab? or even "Screenmonkey." How do devices like USB to VGA adapters perform, (we'd need 3?)


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## cpf (Dec 7, 2012)

NickVon said:


> old thread but a question regarding the Matrox Hardware. We are doing a show with 3 discrete projector screens (we are not spanning a space using 3 projectors,as I think the OP was discussing) We are looking to put 3 unique images on the 3 projectors and to do this with Qlab rental license as our software solution. Will the Matrox Hardware show as multiple video outputs with regard to Qlab? or even "Screenmonkey." How do devices like USB to VGA adapters perform, (we'd need 3?)




I'd steer clear of USB-to-VGA devices - there's a reason most video cards run on PCI Express with orders of magnitude more bandwidth than even USB 3.

DH2G devices show up as a single, really large monitor. Doesn't mean you can't put separate video on each, just that you'll have to manually position them vs. just pressing "full screen."


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## museav (Dec 8, 2012)

cpf said:


> DH2G devices show up as a single, really large monitor. Doesn't mean you can't put separate video on each, just that you'll have to manually position them vs. just pressing "full screen."


I agree and this seems to be a basic misunderstanding for many people. The Matrox DH2G and TH2G make multiple display devices (projectors, monitors, etc.) appear to the computer as one single very wide format display spanning horizontally across the displays. Whether that single, wide format output is used to display a single image or multiple images is determined by the software.

Also note that all of the displays on the output of the Matrox have to operate at the same resolution and refresh rate and that those have to be one of the combination supported by the Matrox device. You can mix different native format and resolution displays but the signal the Matrox provides to each display will be the same format and resolution and that must be supported by all of the connected displays.

With QLab I believe that all three projectors would appear as one 'screen' and then on the 'video stage' you would have that one screen selected and use custom geometry to create the portion of the overall 'video stage' over which each video will be displayed as part of that cue. It will likely take some tweaking to get the custom geometry for each video to exactly match the portion of the 'video stage' associated with each of the three projectors.

You may also want to consider just how much load running QLab and three simultaneous video files may represent and if your computer can support that.


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## metti (Dec 9, 2012)

In my experience, the easiest way to use a Triple or DualHead2Go with QLab is to throw together a custom Quartz comp for each projector that handles the custom geometry for you and then simply put the proper Quartz file on each cue to assign the file to the proper screen. This also lets you add in any sort of edge blending or geometric compensation you need per projector.


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## NickVon (Feb 14, 2013)

I've run in to a problem where our colleges media deparment has failed to aquire a working Mactower with 2 video cards despite making the request and getting the go confirmation on it 3 months ago.

I have a mac book pro and a license for Qlab Video.
USB32DVIPRO
USB 3.0 to DVI Adapter - Multi-Monitor External Graphics Card | StarTech.com

I realize the USB to VGA/DVI external cards are not ideal but I'm curious if the would work for our simple application. 

We have 3 unique projections of static images, so we aren't talking HiDef video or animation or gaming or anything. Would two of these work connected to a a late 2011 Macbook pro (it's a i5, 4GB Ram) we'd be projecting in no more then 1280x1024

In addition does anyone know of the USB 3.0 versions of the Startek devices are backwards compatible with a USB2.0 port, (with less bandwith/resolution.)

Thoughts and advice appreciated.
I had initially requested our Mac for this Monday but it is still not up and working, and our Tech/loadin begins this Saturday. 2/16/2013


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## metti (Feb 14, 2013)

Those would possibly work if you are only doing still images but they are definitely NOT backwards compatible with USB 2.0 and you may run into issues trying get everything talking properly. A TripleHead2Go is almost certainly going to be your most affordable and most reliable solution. They are widely used in the projection world from the smallest shows up through Broadway. I would guess that a TH2G Digital Edition fed via a MiniDP to VGA adapter is going to be your best bet.


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## NickVon (Feb 14, 2013)

@Metti, A friend had a MacG5 that he just acquired used but hasn't had needed or hooked up yet so the theater gods have heard my prayers. That said. Are there some more detailed instructions about what you where talking about with Quartz Composer functions you where speaking of in the previous post.


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## metti (Feb 14, 2013)

Quartz composer isn't particularly well documented unfortunately beyond the information Apple publishes for developers. You're best bet would be to download the sample comp from Figure 53's website and mess around with that. You could also post on the QLab google group or shoot me an email via my website with specific questions.


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## NickVon (Feb 14, 2013)

thanks for steering me in the right direction!


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## leastlikely (Feb 14, 2013)

QLab (the pro version, not the free version I'm pretty sure) can run three projectors... but you probably don't want to do it on your personal Macbook. You'll want a machine dedicated to running projections. If you have other programs running on your computer, it can cause lag/glitches in the projections (...yes maybe I learned that the hard way).


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