superimposing video signals in real time

Discussion in 'Digital Video' started by dullard, Aug 1, 2006.

  1. dullard macrumors newbie

    Aug 1, 2006

    I have a puzzler for you...

    I have an intel iMac and a G5 (both brand new). Both have external displays. I would like copies of what is shown on those two displays to be superimposed on top of each other (using something like a chroma key), and that composite signal to be added to an audio track and recorded as DV or MPEG on a hard drive. And all this has to happen in real time.

    Here's my solution. The DVI out from each computer is converted to VGA using Apple adaptors. That signal is split. One signal goes to the external display, the other is converted from VGA to s-video. The s-video signals (from both computers) go into a video mixing board (like this one). The mixing board uses a chroma key to superimpose the two signals, and outputs to s-video. That analog signal is converted into firewire DV using a converter. The firewire goes back into the G5 and iMovie records it.

    I *think* that will work, but please let me know if you see any problems. It does, however, seem like a bit of a hackneyed solution, since that poor video signal goes through 5 different conversions/manipulations.

    Why am I doing all this? I'm building an eye tracking lab. The iMac is shoing stuff to people on that external display. The G5 is calculating their gaze position and creating a crosshair that moves with their eyes. I want to put together what the subject sees with where their eyes are into one composite image.

    Any help would be very much appreciated!
  2. Texas04 macrumors 6502a


    Jul 2, 2005
    --- eh i think that sounds about right... lol but you will need that mixing board and stuff that can be costly... lol

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