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Display Computers Out of Sync


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We have a system that's a little cobbled together, and I acknowledge that.  I have 12 LCD displays being driver by three display machines.  Two machines are identical with:

  • Radeon HD7900 with the v17.4.3 of the Radeon driver
  • 3.5 Ghz six core i7

The third machine is unique with:

  • Nvidia Quadro M40000 with v385.69 of the Nvidia driver
  • 3.5 Ghz quad core Xeon E5

The displays are (5) LG 55LS560e's and (7) LG 55LJ5500's

The displays are cabled using HDMI over CAT5 exteneders, (6) Cable Matters, (6) Geffen Toolbox.  We are running Watchout 5.5.2


The issue I'm running into is that the three display machines are noticeably out of sync with each out.  It's slight, but definitely there.  They seem to all go to black in sync, or close enough that I can't see it, but coming back to content there's a definite order of the four screens on the stage display machine, then the four on center, then stage right.  I'm not sure where the best place to start trouble shooting is, but would appreciate any thoughts folks have.



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Most common cause of this is loss of UDP transmissions.


Production mode or cluster mode operation?

Details on the network switch used?

Production mode operation.  (2) Netgear GS108 switches.  One on deck linking the three display machines, one at the tech table linking the production machine with designer laptops.  Then a trunk line between the two.  I did have a bad power supply on one of the switches earlier in the week.  I wonder if the other one is going and causing momentary packet loss...



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Hi Jim,


The best is always to make the setup as simple as possible to start with. This means, take your production computer to the display side and start with the two identical computers. Ideally skip the extenders out for this test too. Are they running in sync? Then add one component at a time and test again.....


The Radeon cards are consumer cards and will never be framelocked (genlocked) which means, you will see a slight variation between the outputs, probably in the range of 2 lines of a 1080p picture.


Are the CAT-5 extenders identical? CAT extenders are one of the main causes for support calls. 



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Sigh...nearly everything in this rig is consumer grade, which is at least half the problem.  There are two different models of extenders in the system, and I would agree they are the most suspicious part of the problem.  I will say that the issue seems to occur per computer, not per display, and the center display computer has two of each type of extender.  I think your point about trying to run a test on a simplified setup is wise.  I'll give some thought about how we can achieve that with the way things are currently rigged and dressed.



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Also check that the displays all have the same settings. Any variance in display mode (specifically between "game" and other modes will change their input latency.

Otherwise, I would definitely swap out or remove completely the Cat5 Extender kits, or at least make them all the same model.


In an ideal world you'd be much better off with decent fibre systems, but I appreciate that this is a more expensive solution.

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