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  • 1.  AR Tracking issue

    Posted 02-21-2019 21:29
    Hello all,

    We're doing a quizshow in Augmented Reality where we are using the XPression to generate the augmented graphics.

    This morning when we were testing, everything was fine but this afternoon the graphics started flickering.

    Initially I thought it was the videocard so I restarted the machine but without succes, the flickering stayed.

    When using a non-augmented graphic, everything was fine. So I thought it might have something to do with the tracking-system which was giving wrong data or so. I checked the packet-count in the camera tracking but I don't have any errors or lost packets there.

    When I disable the global tracker inside my perspective camera, the flickering stops. When I enable the lobal tracker again, it starts flickering again. So it seems related to be related to the trackingdata. However, since the guys from the tracking are not in today I can't reboot their kit to test if a reboot of their system would fix the problem.

    I did cross my mind that it might be some sort of "pollution" on the network between my XPression and the trackingsystem of the crane. However we're not passing by any switch, it's basically a direct connection (going through a few patchbays). The XPression is not connected to any other network or internet so there can't be other data interfering with the trackingdata. I did try and removed the networkconnection for a few seconds and then put it back. At that moment the flickering stopped.

    So it seems that there is indeed an issue with the tracking data of some sort. Maybe it gets polluted in some way or XPression stats lagging or misinterpreting the data?

    Just for clarity, the graphic did not change position, it stayed fixed on the same position on the screen, it was just invisible for a few milliseconds and then came back.

    Did anyone else ever encountered a similar issue? If so, did you find a solution and can I know what you did to solve it?

    Thank you,
    "‹Kenneth


  • 2.  RE: AR Tracking issue

    Posted 02-21-2019 21:51
    This is pretty much always because of one of two things:
    - the reference (genlock) connected to XPression and the tracking system are different, missing or too out of sync
    - there is enough delay in the network that packets reaching XPression are coming in too slowly to align them with the rendered output frames

    If you open the XPression Live Log: XPression > Tools > Debug

    You probably will see the message "22-10-18 20:09:53.381: Render line 0 has lost tracking sync, resynchronizing..."

    If you open the XPression tracking monitor: XPression > Tools > Tracking Monitor

    What do you see for the "packet delay" value? If that value is above the time it takes for a frame to be rendered (16ms at 59fps and 32ms at 29fps) then you'll get this issue, and that can be caused by the genlock or network issues.



    #XPression