TroikaTronix Forum: Isadora: General: VIDEO DELAY ACTOR


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VIDEO DELAY ACTOR

carolekim
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Feb 16, 2008, 8:35 PM

Post #1 of 7 (1343 views)
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VIDEO DELAY ACTOR	Can't Post

Hey Izzy Users:

Wanted to inquire about the behavior of Izzy's Video Delay Actor to see if there's an easy way to translate from frames to time, and if it's a constant time delay or if the actual time is determined by the frame rate of the patch, which would be constantly changing.

Thanx. +++CK

william
User

Feb 17, 2008, 6:51 AM

Post #2 of 7 (1327 views)
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Re: [carolekim] VIDEO DELAY ACTOR [In reply to]	Can't Post

My understanding is that Video Delay is specifically a frame delay that translates into time only in a stable framerate situation. I've used this actor to resync video to its own audio, in which case it was always perfect, regardless of the overall system framerate because it was a self-referential task. However, I believe this is a frame delay that is not necessary fixed to the 30frames=1sec model because of the variable nature of Isadora (relating to system and video tasks).

What is it that you are actually trying to do?

carolekim
Novice

Feb 17, 2008, 8:08 AM

Post #3 of 7 (1323 views)
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Re: [william] VIDEO DELAY ACTOR [In reply to]	Can't Post

Hey William.

We are working with a variable delay between two spaces using a figure 8 feedback loop structure ( audio/video is mixed, delayed and sent directly to the other space which is then picked up through the live-feed and mics, delayed, mixed and sent back). The live-feed video will be controlled by Isadora and the audio will be controlled (delay, spatialization, mix) through Max. Wondering how we could maintain sync sound. We were planning on connecting via OSC.

Any suggestions? +++C

william
User

Feb 17, 2008, 3:52 PM

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Re: [carolekim] VIDEO DELAY ACTOR [In reply to]	Can't Post

Sounds very interesting! Where are you presenting this?

My first thought is to use timecode, but I haven't tried anything remotely similar to this, and Isadora doesn't function via timecode or Quicktime tics, but rather scales videos into percent-based format for time. Anyway, with a live feed, if it's a DV camera, you can track the timecode using the DV Device Control Actor, but getting that value out of that actor... I don't know / haven't tried it.

There is a string from a few months back about syncing multiple computers here -

http://forum.troikatronix.com/...;t=search_engine#522

How much mixing is happening live? Are you experiencing greatly fluxating frame rates or is this a fixed environment wherein you can sustain a constant reliable frame rate?

In theory, you could use the Performance Monitor Actor to keep track of FPS fluxations and feed those into a calculator to vary your frame delay to keep things fluid. The calculation could be made using a Pass Value Actor to set limits on (if fps = this) then (video delay = that), and so on... Might take a lot of fiddling to get this right...

Perhaps Mark and the other users on the forum will have suggestions as well...

Matt
Novice

Feb 18, 2008, 1:33 AM

Post #5 of 7 (1293 views)
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Re: [carolekim] VIDEO DELAY ACTOR [In reply to]	Can't Post

I did a time test, 1000 frames = 2 minutes (max amount of frames for the actor) with a frame rate of no more then 10fps, 300f=20s with no really frame drop. To conclude it seems that you can not accurately relate a time to frames for the Video Delay Actor.

Mark Coniglio
TroikaTronix / Moderator

Feb 18, 2008, 2:53 AM

Post #6 of 7 (1291 views)
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Re: [carolekim] VIDEO DELAY ACTOR [In reply to]	Can't Post

Assuming your video camera is running a full frame rate (30 fps NTSC, 25 fps PAL) then the delay can be calculated by dividing the number of frames by 30 or 25 respectively. However, if your patch is not achieving full bandwidth (again 30fps or 25fps) then the delay will not be what you expect.

Theoretically you could use the Performance Monitor actor to adjust the number of frames to the current frame rate... but each time you change the number of frames in the Video Delay actor it will reset, and you'll lose the imagery. So you would only want to do this once and then leave it.

Hope that helps,
Mark

- - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Mark Coniglio / TroikaTronix
Creator of Isadora

carolekim
Novice

Feb 19, 2008, 12:29 PM

Post #7 of 7 (1261 views)
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Re: [Mark Coniglio] VIDEO DELAY ACTOR [In reply to]	Can't Post

Thanks All. Will report back. CK

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