Display refresh rate question/oddity

Discussion in 'PC Hardware, Software and Displays' started by Jedi2016, Sep 7, 2014.

  1. Jedi2016

    Veteran

    Joined:
    Aug 23, 2005
    Messages:
    1,021
    Likes Received:
    0
    Hopefully someone here can answer this, I may end up cross-posting to the PC game forum. I think I know what's happening, but I'd like a second opinion.

    Background: Oculus Rift is on the way. Runs at 75Hz, my current monitor runs at 60Hz.

    Problem: This mismatch causes issues with the Rift running in Extended Display mode, since each display is using a different refresh rate. Seems to cause some low-level confusion in the display drivers.

    Solution: Bump up the refresh rate of the current monitor to 75Hz. Once they match, many problems solved.

    So I did it, set up a custom resolution in NVidia control panel. The computer seems to be running fine, and displaying normally. The monitor's not freaking out, even though what it's receiving is technically more than it can handle. I half expected it to.

    I tried a game (Diablo 3), cranked it up to 75fps, and the game runs fine like that. EVGA Precision displays the framerate at 75-76fps. Game runs like ass.. lol. It's smooth, but choppy.. I can tell it's running at a high framerate, but there's a juddering to the movement. Easy to see on a game like D3 because the entire background moves whenever you move your character.

    Now, what I think is happening is a simple frame-pacing issue. The computer is sending a new frame every 13ms, but the monitor is only refreshing every 16ms (rough numbers). Every so often, there's a missed frame, and the result is judder. I think this is more or less what occurs in the opposite direction with the Rift not quite locked into the correct refresh rate, and what Digital Foundry talks about with some games running at a locked framerate, but looking choppy because of frame pacing.

    Of course, the only way for me to confirm this is to shoot it with high-speed video, and I don't really have a reliable way to do that, or to properly analyze the footage afterwards.

    Does that frame-pacing theory seem sound? Anyone have any other ideas what might be going on if that's not it? I'm sure the monitor can handle all of this, but I'd rather not burn it up in the process.. hehe. It's a nice monitor.
     
  2. Alexko

    Veteran Subscriber

    Joined:
    Aug 31, 2009
    Messages:
    4,515
    Likes Received:
    934
    Do you get the same issue if you play at 60Hz on the Rift?
     
  3. Jedi2016

    Veteran

    Joined:
    Aug 23, 2005
    Messages:
    1,021
    Likes Received:
    0
    Don't know yet, the Rift won't be here for another few days. I'm "prepping", as it were.
     
  4. Alexko

    Veteran Subscriber

    Joined:
    Aug 31, 2009
    Messages:
    4,515
    Likes Received:
    934
    Ah, sorry, I read that too quickly and thought you had that problem on the Rift. I suspect that you're right, the GPU is sending a frame every 1/75th of a second but the display is only updating them every 1/60th, even though it is accepting the 75Hz input. I wouldn't expect the same behavior on the Rift.
     
  5. lanek

    Veteran

    Joined:
    Mar 7, 2012
    Messages:
    2,469
    Likes Received:
    315
    Location:
    Switzerland
  6. Jedi2016

    Veteran

    Joined:
    Aug 23, 2005
    Messages:
    1,021
    Likes Received:
    0
    That's weird... according to that test, across multiple takes, there were no skipped frames. It showed both playback and refresh at 75Hz, and all solid. I'll have to run some more tests, but it looks like it actually is running at 75Hz.

    Is that really all you have to do to "overclock" a monitor, is to send it a higher frequency signal?
     
  7. Blazkowicz

    Legend Veteran

    Joined:
    Dec 24, 2004
    Messages:
    5,607
    Likes Received:
    256
    Older monitors at least (i.e. 1280x1024 and 1024x768) would take a 75Hz signal or similar as input fine, but actually displayed 60Hz and dropped frames or parts of frames. That's what I read about back then (never bothered to tried setting a rate above 60 on a LCD monitor ; though VGA text mode at 70Hz is common)

    If so, that would match with your frame pacing feelings and if you can try an old 1280x1024 at 75Hz, it should behave the same. Maybe your monitor is "not really overclocked".
    Overclocked monitors do show the real refresh rate (some IPS models do support somewhat officially 72Hz)

    See your monitor's officially supported refreshes and resolutions? (not sure 1080p at 75Hz would be explicitly supported, but at least for the old VESA resolutions you will see 60-75Hz support, with the frame skipping issue going on)

    ..if V-sync is going on at 75Hz, maybe that gives you a consistent judder. If you set the displays at 72Hz maybe the judder will be more interesting.
     
    #7 Blazkowicz, Sep 8, 2014
    Last edited by a moderator: Sep 8, 2014
  8. lanek

    Veteran

    Joined:
    Mar 7, 2012
    Messages:
    2,469
    Likes Received:
    315
    Location:
    Switzerland
    You have follow the step and take a photo for get the right result ? best way is to use an photo and you will need at least 5 squares who appears without one black in between

    Anyway, many monitor today can oc, at least a little bit ( 60 > 85 > 100hz ) ( my PLS do easely 85hz maybe 100hz, but its not a Korean like the Qnix who can OC to 120hz ) .. Maybe if you have some question, the forum link i have post, there's some guy who know many thing on overclocking monitor. Like Yamasoka ( ).
     
    #8 lanek, Sep 8, 2014
    Last edited by a moderator: Sep 8, 2014
  9. Grall

    Grall Invisible Member
    Legend

    Joined:
    Apr 14, 2002
    Messages:
    10,801
    Likes Received:
    2,175
    Location:
    La-la land
    I tried the NV "display overclocking" thing when I was with the green team, and it was a complete and dismal failure. Even bumping vsynch a single fps on my samsung SA850 would cause skipping and juddering (seemingly even more than just one frame actually).

    This was via displayport; I never tried DVI, but it probably wouldn't have made any difference.

    It's worth noting that many flatpanel displays have historically tolerated higher than 60fps when connected via VGA rather than DVI...
     
  10. snarfbot

    Regular Newcomer

    Joined:
    Apr 23, 2007
    Messages:
    627
    Likes Received:
    197
    what you can do which is annoying but works is set the rift to extended mode in the oculus vr config program, then when you want to play a game with it turn off your other monitor. it automatically becomes the primary display then and at least for my setup windows sets the refresh to 75hz.

    im sure going forward theyll fix the drivers so that it its not necessary to jump through these hoops, but in the mean time.. lol.
     
  11. Jedi2016

    Veteran

    Joined:
    Aug 23, 2005
    Messages:
    1,021
    Likes Received:
    0
    Yes, I can read instructions, and I have a rather good DSLR that I can program in any way I like. Full one-second exposure and zero black boxes.

    Thanks for the info, guys. Still can't quite figure out what's going on. Diablo runs like crap, but other games seem to run okay at the higher framerate and I can't see any odd artifacts or anything. I guess we'll wait a couple days for the Rift to get here and see what I can make of with that. Is there a Rift thread somewhere, or just the ones in the gaming sections?
     
  12. homerdog

    homerdog donator of the year
    Legend Veteran Subscriber

    Joined:
    Jul 25, 2008
    Messages:
    6,282
    Likes Received:
    1,058
    Location:
    still camping with a mauler
    Use MSI Afterburner to cap the framerate at 75fps. Then see if if judders.
     
Loading...

Share This Page

  • About Us

    Beyond3D has been around for over a decade and prides itself on being the best place on the web for in-depth, technically-driven discussion and analysis of 3D graphics hardware. If you love pixels and transistors, you've come to the right place!

    Beyond3D is proudly published by GPU Tools Ltd.
Loading...