TroikaTronix Forum: Isadora: Performance: live video delay


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live video delay

eyemag
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Sep 9, 2007, 11:33 AM

Post #1 of 3 (1447 views)
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live video delay	Can't Post

I have been trying in a variety of ways to get live video onto three stages but I am getting quite a delay although not as bad as it was. We have a lot of live speaking to camera and the lipsynch is very noticeably off.

Here are the results so far we have tried both a direct firewire dv source and an s-video thru usb capture. Looking only at the live preview there is virtually no lag and the usb source seems quicker. We have tried various compressions and uncompressed or photojpeg are about the same.

When we place 1 projector to 1 video-in watcher there is virtually no difference on the stage but when we add 2 additional projectors & stages is where we notice a substantial delay - bad enough that lipsynch is totally off.

There is a lot of on camera speaking so it's a difficult situation. Do the basic projector & zoomer functions happen in open GL space on the display card or through the cpu? This is a new fast macpro with 5g ram. But it seems like there must be a bottleneck somwhere but I can't see why. We have also tried this with blackmagic cards with the same effect.

Any ideas

Mark Coniglio
TroikaTronix / Moderator

Sep 10, 2007, 8:27 AM

Post #2 of 3 (1429 views)
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Re: [eyemag] live video delay [In reply to]	Can't Post

I've answered some of these questions to you directly. It is worth saying at this point that I think Eyemag and I have narrowed this problem down to the fact that it is the process of getting the imagery to three Projector actors that is the issue. When they send to only one projector the delay is much much less. So I'm looking into this with them.

Best,
Mark

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Mark Coniglio / TroikaTronix
Creator of Isadora

eyemag
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Sep 11, 2007, 7:07 AM

Post #3 of 3 (1417 views)
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A new wrinkle [In reply to]	Can't Post

As the lighting cues have developed for the show we have encountered a new odd situation. It seems that whenever the image is high contrast/sharp with very little detail (strong blacks) the delay virtually disappears.

When the imagery has a lot of detail. Well lit complicated backgrounds. The delay gets much worse. I know that the more visual content there is the more there is to process but we are only using the zoomer on these live feeds. Nothing complicated.

Does this add anything or just muddy the water?

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