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Scanline sync

Discussion in 'MSI AfterBurner Overclock Application Discussion' started by CalinTM, Sep 18, 2018.

  1. CalinTM

    CalinTM Ancient Guru

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    Can anyone explain how scanline sync works? I need to use both frame cap and scanline sync to exact fps to make scanline sync work?
     
  2. RealNC

    RealNC Ancient Guru

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    No. When you enable scanline sync, the frame cap is synced to your monitor's refresh rate. The value you enter is recommended to be negative, in order to push the tear line upwards and make it invisible.

    Also make sure vsync is OFF when using this. Scanline sync is a replacement for vsync, it will glitch out if you forget to disable vsync.
     
  3. CalinTM

    CalinTM Ancient Guru

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    Negative ? Like what ? If i use fps cap of 70, scanline should be -70 ?
     
  4. RealNC

    RealNC Ancient Guru

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    No. The number you enter there is the scanline RTSS should try and sync against. This of course changes depending on the resolution you use. But usually, you want about 30 to 80 scanlines above the bottom. If your current resolution is, say 1440p, then you might have 1500 total scanlines or so (it's always higher than the actual amount of visible pixel lines, because... reasons.) So you'd want to sync against scanline number 1470, for example. So you'd need to enter "1470".

    However, you can just specify a negative value to achieve the same result. In this case, -30 will also sync to scanline 1470, because it means "30 scanlines above the last scanline, whatever that last scanline is." A negative value also means you don't need to care about how many scanlines there are in total. You only care about the distance from the bottom scanline.
     
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  5. CalinTM

    CalinTM Ancient Guru

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    Can you please tell me the number for my 70 fps cap ? And for 65 fps cap?
    Using 1080p and 144hz.
     
  6. RealNC

    RealNC Ancient Guru

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    Scanline sync, as the name suggests, syncs the frame limiter to a specific scanline on every monitor refresh. If you run 60Hz, it means you get 60FPS. If you want 70FPS, then don't use scanline sync. Use the normal FPS cap mode.

    The number you enter is the scanline you want to sync against. It will be the scanline where you see the tearline. Start with -1. You'll see a tearline at the top. Go to -10, then -20, and so on, to push the tearline upwards, until the tealine is hidden.
     
  7. CalinTM

    CalinTM Ancient Guru

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    Thanks for the info! Much appreciated
     
  8. Andy_K

    Andy_K Master Guru

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    I get this, but... isn't it contradictory to your next post?
    If -1 is one line above last scan line it can't be on top, right?
     
  9. RealNC

    RealNC Ancient Guru

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    It takes 30 to 80 scanlines for the GPU to actually sync. If you use 1, for the first scanline, the GPU will most probably sync 30 to 80 scanlines later than that. If you use the last scanline, then the sync will actually happen at the top 30 to 80 scanlines of the next frame. If you use 1, don't you get tearing at the top of the screen, somewhere between 30 and 80 lines from the top?

    You need to target -30 to -80 above the wanted scanline. It's system specific. Very fast GPUs will probably have a smaller delta.
     
  10. khanmein

    khanmein Ancient Guru

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    @RealNC If I enable V-Sync through NvCpl, then the Scanline sync should be 0 right? Any changes from your previous guide? Thanks.
     

  11. CalinTM

    CalinTM Ancient Guru

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    What previous guide?
     
  12. khanmein

    khanmein Ancient Guru

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    Here
     
  13. CalinTM

    CalinTM Ancient Guru

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    Thanks I've set the scanline to - 10 and seems to be working.
     
  14. RealNC

    RealNC Ancient Guru

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    Yes. Scanline sync should not be used together with vsync.
     
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