TrackIR Stutter in DCS 2.8 at framerates other than 60 and 120 fps

[hughlb]

The issue:

At framerates other than 60 or 120 fps, there is rhythmic stuttering when looking around with TrackIR in DCS World 2.8. When not looking around using TrackIR, and instead looking around with hat switches, or mouse look, the image is perfectly smooth.

The cause:

Unknown. TrackIR has a polling rate of 120hz, which is a likely contributor to this issue, but does not explain why some titles are affected and others are not, or to varying degrees. For instance, Enabling vsync in Microsoft Flight Simulator or IL2 Great Battles, resolves this issue, or minimizes its effect to a point where it is unnoticeable. In DCS, prior to version 2.8, there was no need to enable vsync, or limit framerate, but the user could Alt+Enter to enter apparent "Exclusive Fullscreen", resolving this issue. I can confirm Alt+Enter does not fix the issue anymore, it is prevalent in both exclusive fullscreen and fullscreen.

This is a camera position issue as far as I can tell, in that the position of the camera is not updating linearly on each frame, there is a jump on certain frames and those certain frames appear to be in sequence - e.g. frame 5, 10, 15, 20. I have a video later in this post displaying this. I could deduce that some games are using a form of smoothing to predict the camera position, and bypass any erroneous position data, but I am speculating.

Research:

I first reported on this issue in 2016, in the following thread on this forum:
https://forums.naturalpoint.com/viewtopic.php?t=13991

There have been many more forum discussions since then, here are two recent ones:
https://forum.dcs.world/topic/267346-tr ... tc-solved/
https://forum.dcs.world/topic/325383-tr ... servation/

This is a difficult issue to reproduce - it requires testers run a monitor at a refresh rate greater than 60hz (more common today), and of course, capturing a video will not show the issue clearly, more often than not because the clip has been recorded at less than the in-game framerate, or framerate has been restricted by the upload platform. The only way to see it is frame-by-frame. Below is a video I have captured showing the issue, frame-by-frame.

https://youtu.be/AWHxhHa4ejI

What is noticeable, is the fact there are no real hitches or pauses in the game, but rather every five frames there is a jump or acceleration in the camera position, evident in the relative motion of the P-51 when moving from frames 4-5, 9-10, 14-15, and 19-20, respectively. Then, the very next frame (6, 11, 16, 21) shows less acceleration than all other frames. So the result is quite interesting. If we focus on one instance of stutter (frame 5), we see accelerated movement on frame 5, reduced movement on frame 6, and by frame 7 we see the expected position of the camera, which is to say, the acceleration on frame 5 and deceleration on frame 6 nullifies any gain in camera movement. This makes sense, because if the camera position simply accelerated every 5 frames, we would see a divergence of the input (head tracking) and output (camera movement), so the two must cancel out. But why is there a 'spike' in camera position every five frames?! That is the question, as removing the acceleration and deceleration between frame 5 and 6 would create linearity of movement through the frames, and stutter would be resolved.



Troubleshooting:

There is no apparent hardware issue, all indicator lights are working on the device, and there is nothing to suggest an IR issue. I have also been fortunate to borrow a friend's TrackIR5 and reproduce the issue with their device, and in multiple environments / lighting conditions.

I have lodged a ticket with Eagle Dynamics who provide the following analysis:

Your problem is not related to the fact that enter exclusive full screen was removed from DCS, since other users and our testers do not experience problems with TrackIR stuttering.This may be due to some third party software or TrackIR settings.

They expanded on troublshooting, asking me to cull a considerable number of background processes, as well as establish a new admin account on Windows. Neither of those provided any change to the issue, which isn't surprising, because I don't believe this is a 'stuttering' issue in the traditional sense. The game itself is not stuttering, it is the camera movement, or the camera movement is inducing stuttering.

I have been fortunate to build a new computer, and have been able to reproduce this issue on both old and new systems indicated below:

System 1: 4790k, 1080Ti, 16GB DDR3 1600, Windows 10 19045.3086, Nvidia Driver Version 536.23
System 2: 7800X3D, 4090, 32GB DDR5 6000, Windows 11 22621.2134, Nvidia Driver Version 536.23

I would love a solution to this. I don't wish to be dramatic, but it is preventing me from playing DCS at framerates greater than 60. There experience is very jarring to my eyes, looking something akin to 30fps, irrespective of the high framerate.

Happy to troubleshoot with you.

Regards,

Hugh

[jillian.smythe]

Hello Hugh,

Have you tried adjusting the Motion Control > Smooth setting? Does that have an effect on the stutter? On the camera tab, check to see which Video Processing Mode you are using, Standard or Precision. If you are using Precision Mode, there is also a Precision Mode Smoothing value that can be adjusted.

Kind Regards,

[hughlb]

Hello Hugh,

Have you tried adjusting the Motion Control > Smooth setting? Does that have an effect on the stutter? On the camera tab, check to see which Video Processing Mode you are using, Standard or Precision. If you are using Precision Mode, there is also a Precision Mode Smoothing value that can be adjusted.

Kind Regards,

Hi Jillian, I appreciate you reaching out to me and troubleshooting the issue.

Smoothing, both of the precision setting and motion control seem a great place to start, however I have tested many combinations tonight with no change in the smoothness of the image at 100 Hz. I have tried precision smoothing 0-100 and motion smooth 0-50, with different combinations of each, but the result is exactly the same. Smoothing does add the expected latency in output movement, and removes jitters from over-sensitivity, but the rhythmic stuttering is unaffected

Just further information, to my original post. 'Stuttering' isn't a great term as there can be so many kinds of stuttering, so let me just further elaborate on what I am seeing. The frame-by-frame video above shows a spike or acceleration every 5th frame, which at 100 FPS is 20 spikes per second, if my elementary level math is correct! So that is essentially what it appears like - an image that resembles 20-30 FPS when looking around, but 100 FPS when my head is still, or TrackIR is turned off and I use hat switches. The in-game framerate always reads a locked 100 FPS.

Then, for whatever reason, when the framerate is exactly 60 FPS, the image is smooth when looking around. When I had a 144 Hz monitor, same thing, if I locked the framerate to 120 FPS or 60 FPS, perfectly smooth image. Any other FPS value outside of those two values would lead to this rapid, rhythmic stuttering.

Do you have a hypothesis?

[jillian.smythe]

Hello hughlb,

I have some more questions to see if we can figure out what's going on.

Does the stuttering happen when you are only running the TrackIR software? Or only when you are running any game or a particular game with TrackIR?

Are any other 3rd party game enhancers/software running? Make sure only TrackIR is running.

What frame rate is the TrackIR reporting?

Is your graphics card drivers up to date?

Do you have any anti-virus/security software running? If so, try disabling it.

Do you have any other peripherals plugged into your computer? Try only having a keyboard, mouse, and TrackIR plugged in.

Are you running TrackIR as an administrator? Are you running your game as an administrator?

After restarting your computer and before you open the TrackIR software, can you try deleting this file and see if the stuttering occurs upon TrackIR startup? C:\Users\<USERNAME>\AppData\Roaming\NaturalPoint\TrackIR 5\Settings.xml

Does minimizing the TrackIR software while the game is running make any difference in how the smooth the image is?

Kind Regards,

[hughlb]

Does the stuttering happen when you are only running the TrackIR software? Or only when you are running any game or a particular game with TrackIR?

TrackIR software is running at 30 FPS in its window, and the image doesn't look smooth - it looks like 30 FPS. None of the games themselves are stuttering. Even with TrackIR software running the games are not stuttering. It is only when I move my head using TrackIR that the game stutters as the in-game camera moves around. The stutter looks like the game is suddenly running at 20-30 FPS, despite the game framerate being 100 FPS. Some games appear worse than others.

Are any other 3rd party game enhancers/software running? Make sure only TrackIR is running.

No, I have ensured I have tested with just TrackIR software running. I have also culled the following processes:

AdobeUpdateService.exe
AggregatorHost.exe
amd3dvcacheSvc.exe
amdfendrsr.exe
atieclxx.exe
AUEPDU.exe
AUEPMaster.exe
cmd.exe
dasHost.exe
EasyTuneEngineService.exe
GigabyteUpdateService.exe
GraphicsCardEngine.exe
Navigraph Hub.exe
NavigraphSimlink.exe
NisSrv.exe
NVIDIA Web Helper.exe
OpenConsole.exe
RtkAudUService64.exe
RtkAudUService64.exe
SearchHost.exe
SearchIndexer.exe
SecurityHealthService.exe

What frame rate is the TrackIR reporting?

The TrackIR software window is running at 30 FPS according to Fraps. When I move my mouse around in the window it jumps up to 100 FPS.

Is your graphics card drivers up to date?

I am currently running NVidia's 536.23 on a 4090. I have tried several different versions of drivers without any change, including the most recent 537.13. I have also tried different drivers on two separate PC's, one Windows 11 with the 4090, and one Windows 10 with a 1080Ti

Do you have any anti-virus/security software running? If so, try disabling it.

I only run Windows Defender, and have disabled for testing, it makes no difference.

Do you have any other peripherals plugged into your computer? Try only having a keyboard, mouse, and TrackIR plugged in.

I do run a number of flight sim peripherals, connected to two powered USB hubs. Both hubs are turned off for testing, leaving only my mouse and keyboard plugged in. I have also tried an entirely different make and model of keyboard and mouse, on an entirely different PC, and no difference.

Are you running TrackIR as an administrator? Are you running your game as an administrator?

I don't by default, as TrackIR starts on boot, but I have tried starting both DCS and TrackIR as an admin, and see no difference.

After restarting your computer and before you open the TrackIR software, can you try deleting this file and see if the stuttering occurs upon TrackIR startup? C:\Users\<USERNAME>\AppData\Roaming\NaturalPoint\TrackIR 5\Settings.xml

I tried this, but no difference.

Does minimizing the TrackIR software while the game is running make any difference in how the smooth the image is?

It doesn't make any difference, it starts minimised by default, but whether the windows is maximised or minimised to tray, there is no difference.

[hughlb]

Hi Jillian, did you have any more thoughts about what could be causing this issue?

[jillian.smythe]

Hello hughlb,

I am reaching out to other team members to see if they have any advice. In the meantime, I did find a forum post from a TrackIR user running a different flight sim who was able to improve the performance of their TrackIR by cleaning up the registry as well as uninstalling and reinstalling the TrackIR software: https://www.aerofly.com/community/forum ... #post57489.

Please let me know if this helps.

Kind Regards,

[hughlb]

cleaning up the registry as well as uninstalling and reinstalling the TrackIR software: https://www.aerofly.com/community/forum ... #post57489.

Hi Jillian,

I followed the advice from the user in the aerofly community thread. I note that they appeared to have multiple instances of TrackIR registry entries. I have checked my registry and found only one, which I have included in the screenshot attached (VID_131D&PID_0158). I have also tried uninstalling and reinstalling the TrackIR software, but have not noticed any change.

[jillian.smythe]

Hello hughlb,

I came across a forum post that had some suggestions that might be worth trying (https://forum.dcs.world/topic/257643-if ... -problems/):

Using task manager I set the Track IR priority to High

Disabled any power saving features for USB's. In Device Manager and Power Settings.

Plugged the Track IR into a powered USB hub

You may want to try these steps to see if it helps at all.

Kind Regards,

[hughlb]

Hi Jillian,

I have disabled power saving features for USB in Device Manager and Power Settings.

I have plugged trackir into a powered hub.

I cannot see any difference.