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"Shakey" video via video switcher


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Hi all,

I've tried everything with this, and am properly stumped - I wonder if any of you can help me?

I have some Blackmagic cameras (have tried 3 different ones - URSA Broadcast and PCC6k) connected via SDI cable to a Roland V800-HD switcher and am getting a picture that seems fine when everything in shot is static or moving slowly, but "shakes" from a certain vertical point to the bottom of the frame when something is moving at any sort of pace e.g a person moving their arm.  The picture, including swift movement, seems fine above the vertical line when it starts to be "shakey".

There are 3 short videos at https://www.dropbox.com/sh/4f6rkovql1zlhkh/AACJnN6LUKWnmHh8PXyDYfGIa?dl=0 that show the issue - the 3rd one is probably the easiest to see.

I have ensured that everything is set at 50Hz, with cameras at 25fps, and have also tried multiple inputs on the switcher and SDI cables.

The URSA Broadcast goes direct via SDI, whereas the PCC6k use a Blackmagic HDMI-to-SDI micro convertor, but they all have the same issue.

The "CAM X" input picture on the multiviewer doesn't have the issue (but I think those smaller images are likely to be sampled differently by the switcher); it's only when it goes to preview or program that the problem is evident.

Has anyone got any ideas?  Do we have a problem with the switcher?  Thanks in advance!

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Something isnt in sync. You're getting tearing.

Why have you got the desk at 50 but the cameras at 25? Try setting everything to be the same.

Are the cameras outputting interlaced or progressive? Is the desk set to interlaced or progressive?

Edited by sameness
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As sameness said, set everything to the same frame rate and same scan mode. There's generally no need to be running interlaced anywhere in a live event scenario, so my preference would be either a full 50p or 60p* depending on region. You should then also have a sync generator in your chain and feed that to all cameras, your switcher and any other routing that can accept a genlock signal, and this should also be set to the frame rate your kit is operating at (technically the other way round, but set it all the same).

The videos you shared, that's definitely tearing, but looks rather severe. I'd suggest that you verify the output of the camera on either a field monitor or through a format converter and into a normal screen.

You should also check that anything you're viewing the output on is receiving and reporting the correct signal.

You're right that the atem mixers process the multiviews separately, they can't really be relied upon for critical viewing.


*Exemptions apply

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