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Thread: Multithreaded Texture downloading issue

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  1. #1
    Junior Member Newbie
    Join Date
    Feb 2018

    Multithreaded Texture downloading issue


    I am writing video composing application that use several video sources (SDI, NDI, CEF3 Browser, libmpv player and etc) as textures and compose final image in another texture that displayed on screen and downloaded to send as NDI. All textures uploaded and downloaded asynchronously via PBO. Everything works fine in single threaded OPENGL renderer. But now I trying to download final textures in dedicated thread. Every frame rendered in round-robin textures list (3 textures) then I make glFenceSync and signal download thread. Download thread insert glWaitSync and initiate downloading for current texture. Then it create another glFenceSync and map PBO from previous frame to send via NDI. The problem is that sometimes it download not finished image that have just background color or just one layer of video. It depends on GPU utilization and happening about once per several seconds (1080p60). On the screen everything is ok and problem exist only in downloaded image. Looks like it miss synchronization.
    Under VMWare everything works fine in both modes (single threaded and mulithreaded).
    Could you help me to fix the issue? because I don't have any ideas. My system is Ubuntu 16.04, NVidia 1050 ti video card, 384.11 driver.
    Also see attached opengl log for one of frames in

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