120Hz reduces input lag of 30fps and 60fps!

All newer XBOX consoles supports 120Hz+ & FreeSync. Getting help with getting "Better Than 60Hz" on the XBOX ONE, XBOX Series S, and XBOX Series X, as well as the PlayStation 5.
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120Hz reduces input lag of 30fps and 60fps!

Post by Chief Blur Buster » 23 Apr 2018, 14:19

Everyone.

One important consideration: Input lag

60fps @ 120Hz has much less VSYNC ON input lag than 30fps @ 60Hz on the same display.

Frames refreshed faster onto the screen surface. Instead of a 30fps frame being scanned-out onto the panel in 1/60sec, you now have a 30fps frame scanned-out onto the panel in 1/120sec.

That _really_ makes a big difference.

Also, VRR ranges needs to be huge so that you don't get the VSYNC ON input-lag increase effect at 60 frames per second. You need to run at framerates below VRR maximum, to fully eliminate the backpressure input lag that is common to VSYNC ON or when hitting maximum framerate on a VRR monitor.

As people know from the various GSYNC articles on Blur Busters, we cap a few frames per second below max Hz. We were the world's first to measure the input lag of variable refresh rates back in year 2012 ... (FreeSync is a variable refresh rate tech, similar to GSYNC). So, 60fps would have no VSYNC ON lag due to it never being VRR max. So 60fps FreeSync has much less input lag if the FreeSync monitor is at least approximately ~61Hz or higher (preferably ~65Hz or higher).

So giving consoles 120Hz + VRR is a two-way input-lag fix:
--> Reduction in input lag from faster 120Hz refresh cycles of 30fps or 60fps content; AND
--> Reduction in input lag from no longer hitting VRR maximum.

Just one of the two is a big lag reduction.
Having both is having cake and eating it too.
Low-lag 30fps and low-lag 60fps FTW!
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120Hz reduces input lag of 30fps and 60fps!

Post by Chief Blur Buster » 23 Apr 2018, 14:21

If you enable 60fps FreeSync, you aren't getting lag-saving benefits of capping below FreeSync max Hz.

Instead, Enable FreeSync and enable 120Hz simultaneously.
(Once the 120Hz software upgrade arrives, and you've got a 120Hz+ FreeSync Monitor)

Now you're getting much-lower-lag 60fps because 60fps is no longer the VRR max.

Conclusion:
  • 120 Hz is not useless for 30fps and 60fps games
  • It reduces input lag of 30fps and 60fps
Your controller will respond MUCH faster and MUCH more instantly, even though your frame rate is unchanged.

In addition, with proper variable refresh rate support, the stutters of varying refresh rates can be reduced or eliminated (see TestUFO Simulated animation of FreeSync) so that's a bonus benefit with framerates between 30fps and 60fps. And the bonus framerate swings above 60fps. But you still benefit anyway at 60fps and less.
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Re: 120Hz reduces input lag of 30fps and 60fps!

Post by MrBrown » 24 Apr 2018, 09:41

In best case scenario it would indeed cut a few dozen ms off input lag, we need to wait and see how ms implements this feature.

If the games dont switch the Hz mode once u start them and can be forced to output at 120hz, we might see some input lag reduction.

However 30fps usually gets doubled when using freesync/gsync, i dont know if the input lag doubles in such cases or not.
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Re: 120Hz reduces input lag of 30fps and 60fps!

Post by RealNC » 24 Apr 2018, 10:41

MrBrown wrote:However 30fps usually gets doubled when using freesync/gsync, i dont know if the input lag doubles in such cases or not.
It doesn't.

However, the lag reduction at 30FPS when using VRR is not that big as Chief makes it out to be, since at 30FPS you're not hitting vsync backpressure, like you do at 60FPS/60Hz :mrgreen: But motion consistency is very much improved. At 30FPS, single-frame hiccups (repeats) are 67ms (33.4ms is the frame time at 30FPS, and with vsync you sometimes repeat one frame due to the frame limiter's accuracy, and suddenly the frame stays for twice that long.) That's huge and quite visible and annoying. These cannot be avoided, since frame limiters aren't perfect (they don't sync to the monitor's refresh.) VRR (at least g-sync) completely fixes this though and these stutters go away completely. You can already do that in non-VRR mode by using 1/2 vsync (behaves like 30Hz vsync), but THEN the input lag that wasn't there before appears, since now you do get vsync backpressure. But at 30Hz, vsync backpressure is huge.
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Re: 120Hz reduces input lag of 30fps and 60fps!

Post by Chief Blur Buster » 24 Apr 2018, 13:22

MrBrown wrote:However 30fps usually gets doubled when using freesync/gsync, i dont know if the input lag doubles in such cases or not.
No. Scanout lag gets halved.

This is because the video cable transmits the "30fps" frame in only 1/120sec.

While there is no vsync backpressure, you defintely have a faster frame transmission.
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Re: 120Hz reduces input lag of 30fps and 60fps!

Post by MrBrown » 25 Apr 2018, 07:49

I have tested Wolfenstein 2 on Xbox X yesterday. Theres a Demo of this game, so everyone can test it for free.

In the game settings its possible to disable dynamic resolution. Then the game runs at native 4K with the framerate dropping to low 50s / high 40s.

My Asus VP28UQ which has Freesync 1 support over HDMI wirked fine with 4K @ Freesync on Xbox X. It even has an option to show framerate and it did show the framerate going to low 50s in many areas.

I went to areas with low 50fps and tested a bit- there was no stutter, game was smooth, so Freesync worked. However Ivenoticed massive input lag. Alot higher that enabling dynamic resolution ingame. Not sure if the engine itself causes it, however- so far in Wolfenstein 2 at around 51fps (which is below minitors max. refresh rate which is 60) tha input lag was insane, much higher than with Dynamic Res enabled ingame and Freesync turned off in Xbox settings.

So ppl shouldnt get super excited about reduced input latency with Freesync enabled on Xbox X.

Another Test in COD WW2 with and without Freesync showed that with Freesync disabled the controller input delay was slightly more responsive as opposed to Freesync enabled, which felt a little bit less responsive.

The thing with Freesync is that it might actually force Vsync in some games that by default dont use Vsync.

As of right now I would go as far as claiming- dont enable Freesync on Xbox if you have a 60 Hz monitor. If you have a 120 Hz 1440p/1080p monitor- you can give Freesync a try, other than that it will introduce more lag.

Also according to rtings.com, who have tested several Freesync capable monitors, in their lag tests of 4K 60hz monitors theyve noticed that with Freesync enabled the overall input lag was slightly higher versus 4K 60Hz with Freesync disabled. Not by much though- usually 1-3ms higher.
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Re: 120Hz reduces input lag of 30fps and 60fps!

Post by RealNC » 25 Apr 2018, 08:32

Outch!
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Re: 120Hz reduces input lag of 30fps and 60fps!

Post by MrBrown » 25 Apr 2018, 09:40

I mean its still an early implementation, we may see different results later.

The next console gen will support HDMI 2.1 by default, which goes up to 4K 120 Hz + Freesync. I expect the Freesync feature to mature by then- in 1-2 years.

Again COD ww2 runs 99% at locked 60 fps- with freesync enabled it felt just slightly less responsive, Id say 5 to max 15 ms. Not that big of a disadvantage. Cant tell if its to blame on the monitor or Freesync itself.

In Wilfenstein 2 however at 51-54 fps (4K mode, dynamic resolution OFF, freesync enabled) the input lag is alot higher than Dynamic Resolution ON (which lock the game at pretty consistent 60fps) + Freesync disabled.
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Re: 120Hz reduces input lag of 30fps and 60fps!

Post by Chief Blur Buster » 25 Apr 2018, 09:42

120Hz should make a big difference as GSYNC 101 recommends capping frame rates a few frames oer second below Hz.
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Re: 120Hz reduces input lag of 30fps and 60fps!

Post by MrBrown » 25 Apr 2018, 10:45

But that will only work if games can be forced to output at 120 Hz. We know from the PC side that most games start in 60 Hz mode, then in the settings we can select 120/144 etc.

If the Xbox games ask the monitor to switch to 60 Hz, there will be zero advantages.
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