Uneven frametime graph with V-Sync unless frame limiter is used

Discussion in 'Rivatuner Statistics Server (RTSS) Forum' started by Lendox, Oct 9, 2020.

  1. Lendox

    Lendox Member

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    Recently I noticed that if I set the framelimit to “0” (unlimited) the frametime graph isn’t a straight line anymore in games where it was not long ago (even though V-Sync is on). If I use the limit I use from Blurbusters’ Low Lag V-Sync on method (in my case 59.991), the line is straight again. 2080 Ti
     
  2. AsiJu

    AsiJu Ancient Guru

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    That's the thing, RTSS not only limits framerate but actually frametime so frames are spaced out evenly.

    If you only have Vsync on, you will still get say 60 frames per second but these frames might have varying frametimes between them.

    It's easier to grasp if you think in milliseconds; 1 second = 1000 milliseconds.

    With even frametimes that means between each frame should be 1000 ms / 60 = 16.67 ms
    Uneven frametimes mean this time varies, but with Vsync end result is still 60 frames within 1000 milliseconds.

    Why you previously had flat frametime graphs even without framelimiter I cannot tell, but to have variable frametimes with only Vsync on is normal.
    Changing display drivers, game updates, altering flip queue size etc. could make a difference.
     
  3. RealNC

    RealNC Ancient Guru

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    That's normal. Just because vsync is active doesn't mean the game will present frames at an exact interval. Whether or not this can result in stutter is another question.

    As a rule of thumb, if you get a weird "microstutter" even when the game's FPS is locked to your refresh rate with vsync, then using a frame limiter can often fix that. Witcher 3 for example has that issue on my system (when using vsync without g-sync.) RTSS fixes the frame pacing issue and the game becomes smooth.
     
  4. Lendox

    Lendox Member

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    So if you run a game in V-Sync without the frame limiter, you never get a straight line as well?
    I can’t entirely remember if I had the frame limiter on when I got the straight lines. I turned it off not long ago. What sort of led me on the path of thinking that “something could be wrong” was that while watching video with MPC-HC and MadVR, I’ve been getting 2 or 3 second black screens. I think that it could’ve been a bad driver install, so now I did the Safe Mode DDU thing, but I still have to see whether that fixed the black screens, the uneven frametime graph lines are still there.
     

  5. RealNC

    RealNC Ancient Guru

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    Yep. RTSS measures frame presentation intervals, meaning the interval at which the game itself tries to send each frame to the OS. These will always have some variation, unless you use a very accurate frame limiter.

    Keep in mind that this does not necessarily represent the time interval of when you actually see those frames. With vsync, the actual end result is going to be perfectly flat, because each display scanout is going to display each frame at perfectly equal time intervals. Whether or not those frames represent the correct time in the game's internal state is another question. If not, you're going to see some stutter. Not because of frame duplication or frame skips, but because the frames represent a time in the game that does not actually match the time you got to see those frames. Using a frame limiter can fix this in many cases, because it forces the game's timing intervals to stay closer to the real frame intervals you actually get to see on your display.
     
  6. Lendox

    Lendox Member

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    I tried it in Black Mesa, where I just crouch walked without moving the camera to look for irregularities and without the frame limiter I’m getting two (rather large) “stutters” in this specific example, so there is a huge difference for me.
    I suppose what’s my real question is whether this actually began at some point recently or I just have had the frame limiter always on prior and just can’t remember.
    The thing is I have my 2080 Ti since the end of last year and am running it in a kind of janky way with a universal water block on the GPU, but the rest blank with only two fans at each side of the PCB to cool the VRAM and VRMs and I also have a little bit of liquid metal thermal paste applied to only one shunt, but not enough to make a difference, so I’ve been thinking that maybe this setup has caused the graphics card to go bad and that that caused these issues.
    I hope that once I finally get an RTX 3090 that the issue will either go away, or not.
     
    Last edited: Oct 19, 2020
  7. Lendox

    Lendox Member

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    Update: The black screens are still there, they last happened while on the desktop. It was two ~2 second ones, ~10 seconds apart.
     
    Last edited: Oct 14, 2020
  8. Lendox

    Lendox Member

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    I suppose my real question would be if it’s normal to get stutters in a game (like in my Black Mesa example) with V-Sync activated and without the frame rate limiter (which then dissappear with the frame rate limiter on).
     
  9. AsiJu

    AsiJu Ancient Guru

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    Yes, normal and somewhat common too. Especially if Vsync is enabled in game.
     

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