ATEM & LED Wall Sync

Questions about ATEM Switchers, Camera Converter and everything live!
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greenleaf547

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  • Joined: Sun Jun 16, 2019 4:47 pm
  • Real Name: Zach S Banks

ATEM & LED Wall Sync

PostWed Feb 21, 2024 9:41 pm

We have an ATEM Television Studio Pro 4K, two Studio 6Ks, and an Ursa 4.6K that we’re trying to get synced with our LED wall.
Currently, we get some horizontal line artifacts when tilting up and down, but when sitting still or panning side to side, we don’t get any artifacts.
So we got a Blackmagic Sync Generator and plugged it into our wall processor and our ATEM. Our ATEM program is set to 1080p24, the Sync Generator is set to 1080psf24, the wall is genlocked to the Sync Generator at 48HZ, and our cameras (which are plugged into two SDIs: one in, one out) are set to 1/48 shutter, Program reference, and -10 lines.
But we’re still getting exactly the same artifacts on the cameras.

Any ideas on what we’re doing wrong?
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Mike Ambrose

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Re: ATEM & LED Wall Sync

PostThu Feb 22, 2024 4:18 am

Are the artifacts actually moving or are they stationary? Also, do they appear / disappear while zooming? You might be experiencing the moire effect and not be having a sync issue.
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greenleaf547

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Re: ATEM & LED Wall Sync

PostThu Feb 22, 2024 4:21 am

They’re stationary in the frame of the camera and they appear basically identical on all the cameras, which are at several different zoom levels. And they appear even when the wall is slightly out of focus, when other moire effects aren't present.
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Howard Roll

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Re: ATEM & LED Wall Sync

PostThu Feb 22, 2024 1:53 pm

Are the artifacts the same frequency on all cameras? Id expect the 4.6K to have the least and the Studio 6Ks to have the most.

On the display side there are two refresh rates of concern when shooting LED walls. The first is the frame rate of the content, the second is the physical refresh of the LED tiles. The first is mostly obvious, the second less so. Generally you want a wall with a higher refresh rate than the camera's exposure time. Ideally this is several magnitudes greater. Roe's latest stuff has a refresh rate of over 4000hz specifically to meet the needs of virtual production.

If you can't change the frequency of the LED, one solution may be to render out the graphics at a faster refresh rate. 120 fps would probably be ideal but 60 or 48 are worth a shot. A certain amount of artifacts or vertical distortion are inevitable with rolling shutter cams, the trick is to mitigate them. It may even be helpful to disable genlock. Crazy? With genlock the artifacts will likely appear at the same spot as the cams are sync'd. Without genlock there is drift, the artifacts will happen at seemingly random positions making it less noticeable.

A loop of black and white frames at the intended playback rate will create a stress test that makes it easier to identify rolling shutter, refresh, and sync issues without necessitating the wild camera panning.

Good Luck

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