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Jose
Inspiring
February 28, 2016

Mirror view 60 fps and interpolation for gameplay capture?

Hello.

I know Rift outputs at 75 fps for DK2 and 90 fps for CV1. The mirror view I assume matches the monitor that it is output to. Let's say the monitor is at 60hz. So the original output for CV1 is at 90 fps. How does Rift Runtime convert that 90 fps to 60 fps for the mirror view? Does it simply drop every third frame? Doesn't that cause a kind of microstutter? Is there something that the runtime does that blends the frames? Is it possible that it can use something similar to Time Warp to interpolate the the frames so that the resulting 60 fps monitor view output has no stutter at all?

The reason for this question is I plan to do gameplay capture of the mirror view for possibly YouTube or Twitch purposes and would like to have the smoothest video possible for my viewers.

What are your thoughts?

    5 replies

    owenwp
    Up and Coming
    March 1, 2016
    You are probably accustomed to much worse. If you watch movies on TV, you are usually seeing 24hz expanded to 30 or 60. Same if you watch them on your computer or mobile screen unless you have a display that can output 24hz and your media player is configured to switch to that mode in fullscreen, and I am not aware of any that do so automatically. Certainly youtube and netflix in your browser do not.

    Switching to native 24hz for movies is quite nice, but most people just don't notice because you are not so sensitive to microstutter when its on a stationary screen.
    lamour42
    Inspiring
    March 1, 2016
    Rift display is much slower than displaying in a window. The window FPS will most likely follow the rift - it would not make much sense for any game engine to optimize the windowed display so that it is updated more often than the rift itself.

    In my own engine I usually get several hundred FPS in windowed mode on simple scenes, while when the rift is active it immediately drops to rift FPS (75 for DK2)
    thewhiteambit
    Inspiring
    March 1, 2016
    "lamour42" wrote:
    Rift display is much slower than displaying in a window... In my own engine I usually get several hundred FPS in windowed mode on simple scenes, while when the rift is active it immediately drops to rift FPS (75 for DK2)


    This is called V-Sync dude... :lol:
    lamour42
    Inspiring
    March 1, 2016
    "thewhiteambit" wrote:

    This is called V-Sync dude... :lol:


    Sure it is. But its only happening on the Rift. And to my knowledge it's forced and there is no way to prevent it. Nothing prevents you from updating your application window more often (or less often). But it would be complete waste of time to do that because the effort would be very high and the gain almost zero. In the end, we are not interested in application window frame rate, but in Rift frame rate.

    To the OP: I think you have to live with tearing in the application window because Rift display will be fixed at 75 or 90 fps. While it is no problem to update the window as often as the Rift, if your monitor is on another refresh rate a bit tearing seems unavoidable. Far better to have tearing in the app window than in the Rift.
    Pyronious
    New Participant
    May 12, 2017
    Just checked this on our capture system. We are capturing at 60fps but the game is running at 90fps in the Rift. The mirrored 2D display simply drops every 3rd frame. This results alternating frame times of 1/90th and 1/45 of a second. This manifests in the mirrored 60fps capture as microstutter. To the naked eye it looks like a frame rate drop (although this is an illusion - a new frame is indeed being captured every 1/60th of a second - it's just that the frame times are inconsistent). I don't know of a solution for this problem.
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