Outputs on Titan X card not frame locked

Recently we built a 20m x 2m LED screen for an awards presentation. The total pixel count for the screen was 4160 x 416 and the canvas in Millumin was set to the same. Millumin was then setup to use two of the DP outputs on the Titan X card each running 2080 x 416 which were edge-butted to make a seamless image. 


The problem I was having was that the two outputs were not frame locked together. Despite being pixel accurate the seam was clearly visible on fast moving animations and transition (see YouTube video). Luckily the content was all slow moving so for this particular event it was not an issue that was visible. 


I would like to know if this is an issue that can be addressed or is it a hardware limitation of the GFX card? 



vlcsnap-2016-12-13-14h53m32s777.png
1920 x 1090 - 2M
vlcsnap-2016-12-13-14h53m12s398.png
1920 x 1090 - 2M
vlcsnap-2016-12-13-14h53m51s177.png
1920 x 1090 - 2M

Comments

  • Hello @matte,

    Did you monitors/projectors had the same refresh rate (all to 50hz or 60hz) ?

    What is your model of Macintosh ? MacPro 5,1 ? Hackintosh ?
    The Titan X card does not seem to be supported on MacOS, only through custom drivers delivered by Nvidia. Unfortenatly, we don't own this model at our studio.
    For info, Millumin pushes the content to all monitors before calculating the next frame, to avoid such a problem (at least with standard GPU shipped with Macs).

    Best. Philippe
  • edited December 2016
    Hi Philippe, thanks for your reply.

    I was using DVI Parrots on the outputs so both outputs had exactly the same refresh rate (50Hz) and EDID. The LED processors were identical units as well with exactly the same settings. 

    The Macintosh is a MacPro 5,1 currently running the 2.17.k build of Millumin, Nvidia Driver v346.03.15f03 and CUDA driver v8.0.53. All content was encoded with HAP codec which works well on the system. The system was not lagging or dropping any frames on the control monitor. 
  • Hello @matte,

    Wondering if it could come from Nvidia drivers (non-Apple).
    Do you have the issue when moving a small window (such as the Finder) up and own, where your 2 screens are blended ?

    Best. Philippe
  • Hi @Philippe,

    I have tested today with a strobing timecode clip using VLC, PVP and Millumin and recorded the result using a slow motion capture app on my phone. I then reviewed the footage frame by frame. The results were not consistent. 

    At best, the delay between outputs was around half a frame. At worst, there was around 4 frames delay. The worst result was when triggering the video for the first time within Millumin. When it was triggered subsequent times after that there was less delay. It was almost as if Millumin needed to cache the video first.

    As none of the other programs produced perfect results I suspect this is as you said a driver issue. I have tried to contact Nvidia before to provide feedback but they were not interested and simply stated they do not offer support for the Titan X on Mac. This is frustrating as I would like to be able to provide feedback so they are aware of the issues even if they don't get fixed in a prompt matter. After all the Mac driver is written by them and not a third party and does get updated fairly often. 

    I thought a workaround to this might be to use a Datapath X4 and use that to frame lock and split the outputs. In this particular case it wouldn't have worked as the total screen width was over the 4000 pixel width limitation of the X4 but for anything under 4000 pixels I think it would be a viable solution. 


  • Hello @matte,

    I don't know where you bought this Titan X, but you should check this page from MacVidCard. Be sure you Titan X is an official one.
    Also, you should check your setup with simple monitors such as LCD screens (no DVI Parrots), and perform again your testing. This could a problem happening "after" the Mac. At least, you should be sure to check every part of your configuration.

    Best. Philippe
  • Hi @Philippe,

    The cards are genuine. They are branded MSI (there's a few brands, EVGA, Asus, Gigabyte, etc. available) but they all carry Nvidia's chipset.

    The tests I describe above were undertaken with the card's DP outputs going straight into a Marshall Twin M-LYNX-702 LCD rack monitor. No DVI Parrots were used during the test.


  • Was just wondering, are there 2 x LED Wall controllers, or is it all off the same system?
  • Hi @scaryxpuppy,

    In the pictures I was using 2 x LED Wall controllers to be able to map the whole screen as one. Both were the same model and had identical settings. However, since then I have also recreated the problem going from Titan X card to twin LCD rack monitor. Therefore it doesn't seem to be LED controller related. It seems to be a problem with the Titan X card itself running under OS X.
  • TBH this is why you use a Datapath to make this setup work - all outputs are absolutely sync'd as the computer is sending out a single output and the processor does the slicing.
    I don't think you'll ever get this working reliably and would need to look at using a PC as they have more settings for the nVidia card and to even then if you want absolutely top notch multi-output sync feeds you need to use Quadros.
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