Blackmagic Decklink Quad 2 Visually out of sync

Hey folks,

I suspect this is an easy answer but i’ve been crawling the net for some time and haven’t managed to find anything clear.

I’ve got 8 Projectors hooked up via SDI from a Blackmagic Decklink Quad2, everything running through Touchdesigner. The Projectors are mapped to seamlessly cover a large sculpture that’s then populated with various video. The system is running plenty of other features but performance remains solid and consistent (frame time <16ms).

However, after a few hours of run time, the projections appear to be out of sync. For example, a video of a vertical line becomes “unmapped” when it is run up the projection raster. The video is not lagging, it is just playing a few frames behind at various moments.
The input video is a single 4k Frame cropped to the different sources via touch.

Restarting the server fixes the problem until the drift sets back in a few hours later.

My question is: would a Sync Generator (Mini Converters – Tech Specs | Blackmagic Design)
Hooked up to the Decklink’s Reference port potentially lock the sync?
(This also assumes the problem is the Decklink)

Other Specs:
Quadro RTX 5000,
128gb of RAM,
Some Flavor of Intel (iSeries) Processor clocked at 4.5Ghz.
Touch version: 2021.14360

I would attach .TOX but I am unfortunately under NDA until Mid September.

Unfortunately not. The only thing the sync generator would do is ensure the refresh interval of the projectors is in-sync, not the content. That is, it’ll sync when things are shown, not what is shown.
Each output is essentially it’s own device with it’s own queue of frames, and those queues can be read from and filled at different times within a frame.
The only way to get this somewhat better is to use a quad-link 4k quadrant output mode so that you have 4 outputs that are in sync together.
We are working on a solution using Deltacast FLEX, however that is far more expensive.

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Ah bummer. There’s no chance that the new Timecode CHOP Input on the Video Device In Op might be able to clock them together? (Reaching at straws now).

Otherwise, the signal splitter would probably be the way to go. Two Datapath FX4s I suppose.

Thanks so much!

Along the lines of a quad-link solution, you might look at the AJA HA5-4K. It converts a single HDMI 2.0 input to four 3G SDI outputs, and can be configured for quadrant (square division) mode. It does not support external genlock and has fewer features than the FX4, but is much cheaper.

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Brilliant recommendation, thanks! Was hoping a more straight forward quadrant splitter might be around and this may just be it*