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Camera to projector latency with key

PostPosted: Tue Sep 12, 2017 7:51 pm
by Chad Capeland
I have a need to do a live key at an event.

So camera will shoot presenter on a retroreflective BG, some device will composite that over a new background, and the result will be sent to a projector.

If I wanted to minimize the latency from the CMOS sensor to the camera output and minimize the latency of the keying process, what camera and keying system should I use?

Are BMD studio cameras using SDI the best option? Or is HDMI better? Because I'm keying, I'd prefer a 4:4:4 output, but BMD doesn't make that right? Would outputting UHD 4:2:2 to use for a HD projector add latency from the camera?

Would an Ultimatte have less latency than a Decklink and software key? There's no UHD Ultimatte, right? Are there known good solutions for live keying other than Ultimatte?

Re: Camera to projector latency with key

PostPosted: Wed Sep 13, 2017 2:06 am
by rogersuski
BMD Cameras are not the answer - too much internal latency before it even gets to your processor for keying.

Unless the projector is UHD, no sense in acquiring at that level. Conversion will introduce latency.

If the venue is large, you can/should be able to get away with delaying audio to match your processing delay.

CrystalVision is a great chromakeyer, just like Ultimatte.

Re: Camera to projector latency with key

PostPosted: Wed Sep 13, 2017 4:11 am
by Chad Capeland
What are some compact low-latency camera options?

If we use a software keyer, the UHD shouldn't be an issue as long as the actual keying is fast. We're not planning on doing a conversion in the projector or elsewhere in the process, only in the key.

Re: Camera to projector latency with key

PostPosted: Wed Sep 13, 2017 11:52 am
by Howard Roll
UHD camera that outputs 4:4:4? The only ones I can think of are the IO Flare and the Sony f35/65. 4:4:4 output from a 1:1 cmos sensor is kind of pointless, no more information just a bigger pipeline.

Why not just use a BM studio 4K or micro? You can rent them from lensrentals along with the production studio 4K to pull the key, it will show up on your doorstep in 2 days All hardware, low latency, no hassles.

I'd agree about keeping it HD. If latency is a concern then any scaling process is going to introduce it as is a capture card solution.

Good Luck

Re: Camera to projector latency with key

PostPosted: Fri Sep 15, 2017 12:53 pm
by Chad Capeland
Sorry, I meant HD 4:4:4. Using UHD 4:2:2 resized to HD was just a way to get the effect of 4:4:4 in an HD signal.