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read real time video from two seperate cameras connected to two computers

Dec 20 2010 | 6:00 pm

I connected one camera to each of the two computers.
I tried to used jit.qt.grab to read both real time videos from each camera and project to two different projectors.
The question is: How can I read both real time videos and display it in one computer? (assuming using jit.glue or videoplane).
If the video is not real time but a recording, I understand how to do this.(simply send a message to "read")
But jit.qt.grab is not saving the real time video anywhere in the computer hard drive. Is there another object I can use, or it there a way to read the real time videos from the cache in the computer? Any suggestions?
Attached an image of what I am trying to do if there is any confusion.


  1. Untitled1copy.jpg


Dec 20 2010 | 10:50 pm

What I understand from your drawing is that the output on both computers is the same, right? In that case, why not attach both cameras to one computer and get a cheap VGA-splitter to put it on 2 beamers (or use two VGA/DVI-out with mirroring on if you have it).

Another solution might be to send the video over the network with for instance. You will get a lot of traffic on your local network.

Dec 20 2010 | 11:18 pm

sylvain, thanks for your fast response. I thought about using VGA splitter but the two projectors are more than 40 feet apart. The two cameras are also more than 40 feet apart. Getting 40 feet VGA cable plus two Unibrain Cameras plus 40 feet fireware cable plus two video cards are just tooo expensive.
The set up in the sketch I drew is the most cost effective since I have two mac computers.

Dec 21 2010 | 2:29 am

You mean like this? Same patch on both computers;

-- Pasted Max Patch, click to expand. --

Dec 25 2010 | 8:22 pm

I would strongly advise you to not use two computers and a network for this if you can avoid it- you can easily make it work as long as both have gigabit cards, but a good rule of thumb is to use as little complicated machines that can fail as possible… so I second sylvain’s suggestion:
– 40 feet of vga cable are actually very cheap from places like
– As for cameras, if you’re using unibrains then it means image quality is not the most important issue- in that case you have a few options (in any case placing the computer near one of the cameras narrows your problem down to just the further cam)
>> use any kind of usb camera, with usb extension cords, also cheap, and for a few bucks more you can get a powered extension cord if you need it.
>> use any kind of analog video camera, and capture via any kind of cheap frame grabber, think 30$ external usb dongle (or even an old minidv cam with av-in will do) –
All this is unless you must have very low latency- then you can use a blackmagic intensity card or a dfg1394. Or if you must use both unibrains, get a firewire repeater for the further cam, and plug both into your computer.
– I’m not sure what you meant by two video cards- for capturing you would not need two grabbers as you’d be using your computer’s firewire port for at least one. If you use usb or any of the other solutions i mentioned except the blackmagic card, you won’t need a grabber card at all.
– for output you may not need a splitter if you’re using a desktop computer with a standard dual output card- most pc’s these days have it, and you can get pretty cheap older cards if all you need i the dual output. If it’s a laptop then dualhead2go would be your solution, though I would just change it for an ideally small form factor desktop, that would help both your input and output problems.
(to put this in context, I’ve installed setups with 4+ live feeds over longer distances using one computer, and it really wasn’t very expensive to set up. It still usually beats dealing with multiple computers and software installations).

Jan 08 2011 | 3:43 am

Thank you Nadav Assor for your insightful advice. So much help!

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