Stopping and starting VJ programs during a set
Some time ago, I bounced a thought off of Eric and Anton. I asked them, can you pause a running program? I’d like to be able to pause one VJ program and start another, so I can switch quickly between them during a set with no lag time, no splash windows and such spoiling the illusion of seamless visuals. Anton’s found out how to do it using SIGSTOP and SIGCONT messages in the kill command. Read his post to learn how. Thanks, Anton!
One caveat: if you want to use a live camera with both programs, you’ll probably have to release the camera from the first program, send that program SIGSTOP, send the 2nd program SIGCONT, then open the camera in the 2nd prog. Let us know if you experience any crashes or other problems with this method.
I’m not sure whether it’s worth it to write a program or even an Applescript to do this when you can just keep a Terminal window open. Hmmm…. Depends on how quickly you want to switch programs. If you want to do a set that’s switching frequently between apps then an Applescript with hotkeys would help. If you’re performing for a long time — a half-hour of brush then a half-hour of vade, Modul8 — then a Terminal window’s probably fine. Right? Anton says:
> I think it should be like this: have two drag wells, one and two
> drag app a to 1
> drag app b to 2
> have a global hotkey to turrn one off and the other on
> simple
> now do it 
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January 9th, 2006 at 2:23 am
heya dan.. nice idea – tho the more processor i can keep on my 1ghz machine the better….
i have found that i can play a vj app like grid pro, then open up weird codec videos in quicktime and play them full screen…
then whichever app icon i choose via the dock ( or apple-tab) switches the 2nd screen output to that app…
January 9th, 2006 at 3:05 am
nice idea – tho the more processor i can keep on my 1ghz machine the better….
Yeah, the point is that by pausing the program, it’s not hitting the processor at all. Send it SIGSTOP and it’s %CPU goes to zero. Though it’s probably still using virtual memory and RAM…I’ll have to check that.
January 9th, 2006 at 1:04 pm
Yeah, it definitely is using ram and swap, since the program is technically launched and running – SIGSTOP simply tells the scheduler, DO NOT WASTE ANY TIME SCHEDULING ANY THREADS for that app. So, ram is wired, but no cycles being spent on its execution.
January 13th, 2006 at 9:17 pm
thanks for the explainings…
and look fwd to yr VADE app, vade… 
It’s weird how the auvi objects are built using other building blocks, but auvi tend to not allow anyone else distribute something using the building blokcs they’ve made ( even with licencing deals ) … something about the limited life span of FX i suspect…