[4.2.0] Random 1-tic stutters every few seconds

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[4.2.0] Random 1-tic stutters every few seconds

Postby Cedric Blythedock » Mon Aug 12, 2019 2:17 pm

Easily reproduced (I hope) by starting a new game and pressing the strafing keys randomly. That seems to be the quickest way to make it stutter. Easier to notice if you're not looking around. The vid_fps counter also flickers when this happens. I definitely don't recall noticing this in the 4.1.x versions. Not present when using OpenGL.

Win 10, GTX 1080. Updated drivers prior to making this post.
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Re: [4.2.0] Random 1-tic stutters every few seconds

Postby Graf Zahl » Mon Aug 12, 2019 2:30 pm

Can you check your INI what value it has for the 'norawinput' CVAR. That's no longer doing anything but I'd like to know what setting it had in 4.1.3.
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Re: [4.2.0] Random 1-tic stutters every few seconds

Postby Cedric Blythedock » Mon Aug 12, 2019 2:50 pm

Yep.

[GlobalSettings.Unknown]
norawinput=false
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Re: [4.2.0] Random 1-tic stutters every few seconds

Postby Graf Zahl » Mon Aug 12, 2019 3:55 pm

Hm, so it was using RawInput before, too. That means it's not the cause.
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Re: [4.2.0] Random 1-tic stutters every few seconds

Postby Player701 » Mon Aug 12, 2019 3:59 pm

I can't reproduce this on either my desktop or laptop. Both have Windows 10, NVIDIA GPU, latest drivers. The game seems to run very smoothly, and the FPS counter is definitely not flickering. Yes, Vulkan is enabled, of course. "norawinput" is false on both machines.
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Re: [4.2.0] Random 1-tic stutters every few seconds

Postby Cedric Blythedock » Mon Aug 12, 2019 4:21 pm

Here's something interesting: I can reproduce this on regular Doom 2 maps, but I can't seem to reproduce it on TUTNT: Supportive Edition. I can also reproduce this if I start a game (MAP01 of D2), open the main menu, and the hold up/down arrow. I also have vid_fps set to true so I can monitor the delay. It occasionally flickers as described in the OP. This seems to stop happening if I turn VSync off. Tried with a fresh INI, but the problem persisted.

It's like in the video in this thread, but the delay is much smaller: viewtopic.php?f=50&t=65552

Also, I did some tests while I was writing this post and it turns out this does happen on 4.1.3, but I reported it as "not happening" because I haven't played Doom 2 to notice it. My bad. I checked my Nvidia control panel, but most settings are "Application-controlled" or "Off". Only "Shader cache" and "Texture filtering - trilinear optimization" are set to "On".
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Re: [4.2.0] Random 1-tic stutters every few seconds

Postby Graf Zahl » Tue Aug 13, 2019 1:06 am

Ok. I moved this to "Technical issues", since you seem to be the only one having this problem. For me both render backends also work flawlessly.
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Re: [4.2.0] Random 1-tic stutters every few seconds

Postby De-M-oN » Tue Aug 13, 2019 11:53 am

This seems to stop happening if I turn VSync off

Because it is actually just Adaptive Vsync.
A terrible vsync method which switches vsync on and off depending on fps rate.
That back and forth switching can lead to stutter.

Please rename it to adaptive vsync and add permanent vsync as the 2nd option of the vsync setting and not a hidden cvar I already forgot again :(

Adaptive Vsync is horrible :/
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Re: [4.2.0] Random 1-tic stutters every few seconds

Postby Cedric Blythedock » Wed Aug 14, 2019 1:08 am

VSync becomes somewhat "broken" later in the game, too. Might be the effect of adaptive vsync. As in, even if I have it enabled, it doesn't seem to do anything once I progress enough through a map, and sometimes the tearing is absolutely horrendous if the map has tall, bright textures. It always works just fine when I first start a level, though. I did ask about this a long time ago on ZDoom's Discord to see if it's a bug and report it as such, but nothing came out of it IIRC. Guess I'll just play with VSync disabled all the time.
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Re: [4.2.0] Random 1-tic stutters every few seconds

Postby De-M-oN » Wed Aug 14, 2019 12:27 pm

It is because of it being Adaptive Vsync.
If your fps wants to be higher than refreshrate it uses vsync
If your fps gets lower than refreshrate it uses no vsync and thus you will get tearing.
Due to the fps limiting by vsync its quickly possible, due to fps never being constant, to drop some fps below refreshrate and adaptive may kick in and a back and forth switching may occur and that causes stuttering.
I had a whole capture card capture full of teared frames, because I didnt know that they changed vsync to adaptive vsync in gzdoom, because that back and forth switching of vsync occured the whole capture because of the mentioned fps variances.
I really would try to turn vsync in GZDoom off and either try to find the permanent vsync cvar of gzdoom which was somewhere written in this forum, or force vsync on in nvidia control panel
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Re: [4.2.0] Random 1-tic stutters every few seconds

Postby Cedric Blythedock » Wed Aug 14, 2019 12:49 pm

Well this doesn't seem to happen anymore. Even with GZDoom's VSync set to "on" I still can't get it to stutter. What in the... Oh well, better enjoy the smooth FPS while it lasts. God I hate issues that automagically fix themselves when you aren't looking.
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Re: [4.2.0] Random 1-tic stutters every few seconds

Postby dpJudas » Wed Aug 14, 2019 2:34 pm

Are you running it windowed by any chance? In windowed mode the DWM unfortunately affects frame presentation and it has moody days where it stutters and other days where it doesn't.

Windows updates of .net crap and other things can also short time affect things with background CPU usage as some geniuses in the late 90's decided it would be a great idea to compile .net assemblies 1 billion times (one for each Windows machine out there) after an update rather than ahead of time.
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Re: [4.2.0] Random 1-tic stutters every few seconds

Postby Cedric Blythedock » Wed Aug 14, 2019 2:57 pm

Nope, fullscreen. Now that you mention it, I think I remember Windows saying something about downloading updates in the background. Not sure if that was yesterday or the day before that, though. Definitely recently.
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