TrackIR5 Stutter at framerates other than 60 or 120 fps in DCS 2.8

[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 (using the AutoExec) Alt+Enter does not fix the issue anymore, it is prevalent in in both exclusive fullscreen and fullscreen in the ST Open Beta.

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 the NaturalPoint 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.

Their assistance is ongoing, and I will update this post if troubleshooting resolves the issue.

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. The experience is very jarring to my eyes, looking something akin to 30fps, irrespective of the high framerate.

Edited August 22, 2023 by hughlb
Added detail

[SharpeXB]

I’m using TrackIR along with a 120Hz G-Sync monitor. I don’t experience any trouble with this. I can’t detect any improvement locking the refresh to 60 (actually seems worse) nor using a 1000Hz gaming mouse to look around. You may just have performance trouble with DCS unrelated to TrackIR which is just more noticeable in 6DoF 

[hughlb]

If you have a 120Hz monitor, and are gaming at 120 FPS, then you are perfectly matched with TrackIR's native 120Hz polling rate. 60fps will seem "worse" because it is low enough that you will see some ghosting or trailing of the image as you look around, but it will look smoother than 61-119 FPS, because it is a perfect division of 120 (2x 60 = 120).

There is absolutely no performance trouble in DCS. You can see I am running a 100Hz monitor, and can easily maintain 100 FPS or greater with a 4090 and 7800X3D. I have also tested with a completely different machine running a 1080TI and 4790K, on a different OS, and the issue is the same. I have tested with different TrackIR's also.

[SharpeXB]

On 8/22/2023 at 7:53 PM, hughlb said:

If you have a 120Hz monitor, and are gaming at 120 FPS, then you are perfectly matched with TrackIR's native 120Hz polling rate. 60fps will seem "worse" because it is low enough that you will see some ghosting or trailing of the image as you look around, but it will look smoother than 61-119 FPS, because it is a perfect division of 120 (2x 60 = 120).

There is absolutely no performance trouble in DCS. You can see I am running a 100Hz monitor, and can easily maintain 100 FPS or greater with a 4090 and 7800X3D. I have also tested with a completely different machine running a 1080TI and 4790K, on a different OS, and the issue is the same. I have tested with different TrackIR's also.

I’m usually running DCS anywhere between 58 and 120fps on a 120Hz display, not always at exactly 120 fps. I’ve seen this topic mentioned before and like is said, tested out out for myself. I can’t really see any difference between all these methods and settings. Except that higher frame relates simply look better. Locking the frame rate to 60 looked the worst of all. Not that 60fps is actually bad but still higher looks better. 

[Lange_666]

This has been an issue since the early days of TrackIR.  When the FPS is not in sync with the TrackIR pull rate, slight microstutter is visible when not looking into the direction of motion.
When looking straight ahead, i don't notice it, when looking sideways it's noticable, even when the FPS dips or jumps 1 frame below or above the pull rate (or a division of it). It gets worse the more frames it diverts from the optimal value. And it becomes more noticeable the faster the image is moving.
That's why i VSync and cap to 60 (120 isn't reachable all the time in every situation) since i run TrackIR.
Without TrackIR, fluctuating FPS values are no problem, with TrackIR it's a no go (for me at least, not everybody's perception of stutter is the same).

PS: Same goes for VR, fluctuating FPS is never smooth for me.

Edited August 24, 2023 by Lange_666

[Bosun]

I know exactly the phenomena you speak of. 

When I zoom into the landscape or a target, I can absolutely tell.  What this means is that distant contacts get washed or stutter'd out when looking around.  Not until my head is stationary, will they reliably remain on the screen.  Close up, it can cause issues with tracking movement of moving objects accurately and breaks the immersion, as well as blurs the contact moving, so that it is difficult to ascertain its aspect, velocity or ID.

This is present in every simulation I play with TrackIR, including IL2 and others.  

1. It only happens when I look around, not when head is stationary
2. It does not occur when I pan with mouse, keyboard or other control

I've long attributed it to the refresh rate of TrackIR itself, being not synced or otherwise not tuned well.  TrackIR hasn't had any significant updates in, what? A decade?  The software and hardware work - yes - but it amazes me that they no longer support it. I think it would be well worth a more modern company to buy them out and update it.  They don't even offer a wireless version of the trackclip pro, which is ridiculous because you can get home made versions of it on Ebay or Etsy and they work great.  Why on earth would they not carry one? 

All in all, I love TrackIR but it is an outdated, un-updated system that deserves better from NaturalPoint, perhaps better than NaturalPoint, and the day someone makes a competing system for it that has the fidelity and feel of its interface and tracking reliability, I'm buying it. 

[SharpeXB]

6 hours ago, Bosun said:

The software and hardware work - yes - but it amazes me that they no longer support it.

What do you mean? The OP actually received a response from NP to this very same question today on their support forum. 
https://forums.naturalpoint.com/viewtopic.php?t=25141

[hughlb]

Yes, part of the reason I have looked into this issue again is -

A) It has returned to DCS since the release of 2.8 for me, and is too jarring to unlock my frame rate above 60 fps. The image resembles 20-30 apparent FPS when looking around, despite a locked 100 FPS.
B) NaturalPoint are answering forum threads, and troubleshooting issues, and so are Eagle Dynamics. Both communities are in a better state than they were in 2016 when I first raised this issue, and seem very receptive to helping. I have had at least three ED employees try to assist in this problem thus far.

What we don't have yet, is a clear explanation for what is happening. We know the issue exists, I just provided a video analysis of it, many users have arrived at the same conclusion independently that for whatever reason 60Hz (or 120Hz if you can maintain it), provide a 'fix' to this issue. I am optimistic that a software solution is viable, be it the TrackIR itself, or how the game interfaces with TrackIR (or possibly 6DoF in general). This is because the experience is different game to game. I just fired up IL2 GB and its butter smooth at a locked 100 FPS when looking around with TrackIR, go figure.

 

[Hiob]

On 8/23/2023 at 4:53 AM, hughlb said:

If you have a 120Hz monitor, and are gaming at 120 FPS, then you are perfectly matched with TrackIR's native 120Hz polling rate. 60fps will seem "worse" because it is low enough that you will see some ghosting or trailing of the image as you look around, but it will look smoother than 61-119 FPS, because it is a perfect division of 120 (2x 60 = 120).

There is absolutely no performance trouble in DCS. You can see I am running a 100Hz monitor, and can easily maintain 100 FPS or greater with a 4090 and 7800X3D. I have also tested with a completely different machine running a 1080TI and 4790K, on a different OS, and the issue is the same. I have tested with different TrackIR's also.

Whatever the underlaying issue is, that is solved by having a fix 60 or 120 framerate....

It is NOT a given, that other framerates (61-119) will cause issues. I use a 120Hz G-sync capable TV and my fps fluctuate wildly between ~80 and 120, but I don't experience any issues with TrackIR.

I have experiences TrackIR stuttering in the past however. Unfortunately I was never able to pinpoint the root cause. (My personal suspect is windows/windows-settings or USB)

Edited August 25, 2023 by Hiob

[Loukuins]

With OpenTrack sometimes the tracking goes to 64Hz (I have the PS3 Eye camera) and I need to restart OpenTrack to have the full 187Hz to have a smooth movement, if it changes to 64 the movement is not smooth at all... Maybe DCS need a higher Refresh rate of you camera than your FPS ? Idk... 

[hughlb]

That's great data Loukuins, it'll be interesting to see if someone more knowledgeable than me can shed light on why that is occurring, maybe as you say, DCS needs a specific ratio of refresh rate to camera input. Thanks.

[hughlb]

Quote

(My personal suspect is windows/windows-settings or USB)

Possibly Hiob, but I really doubt it. If it were, you would see it in all applications equally I would have thought. I can go play IL2 GB right now and its smooth, MSFS is somewhere in between, and DCS is just horrible for whatever reason.

Also I have my USB devices connected via two powered hubs for everything except keyboard and mouse, and I have turned those hubs off for testing to remove an possible conflicts. I even have  a new mouse and keyboard in my latest PC of different brand, so that rules out those causing an issue. Windows 10 and 11 same problem.

I think it is something to do with the polling rate of the TrackIR, that's the only suspect presently, because of that 120Hz polling rate. But as others have pointed out, it shouldn't really matter, it's just spitting out position data at pretty high rate. Such a strange issue.

Vsync seems to have an impact on it, not in DCS, but in other titles, so perhaps we are seeing something akin to screen tearing, but in this instance motion induced stutter.

[Loukuins]

To add some info, I have a 175Hz G-Sync monitor and I run at 150-175fps (forced V-Sync on my Nvidia control panel. also V-Sync doesn't affect the movement of the camera, maybe made them more smooth?).

But before I changed GPU I was running at 110-150fps and I still had the same "issue". 
When I found out that the weird stuttery movement came from Opentrack going at 64Hz I was so happy to have a very stable and fluid experience in DCS haha.

Edited August 25, 2023 by Loukuins

[hughlb]

4 minutes ago, Loukuins said:

To add some info, I have a 175Hz G-Sync monitor and I run at 150-175fps (forced V-Sync on my Nvidia control panel. also V-Sync doesn't affect the movement of the camera, maybe made them more smooth?).

But before I changed GPU I was running at 110-150fps and I still had the same "issue". 
When I found out that the weird stuttery movement came from Opentrack going at 64Hz I was so happy to have a very stable and fluid experience in DCS haha.

Again good data. I have had this issue occur with a 100 Hz and 144 Hz monitor, but never had a monitor that could go any higher. I recall with the 144 Hz monitor, I found dropping it to 120 Hz fixed the issue, but I never went into that 150-175 Hz range.

One thing for people to know, if you try to look for this issue with a 60Hz monitor or with a framerate below 60 FPS, don't bother. Any stutter gets lost in the trailing/ghosting and inherently less smooth image at that framerate. There weren't many people running 144Hz monitors back in 2016, which is maybe why I didn't find much help back then.

 

[Loukuins]

5 minutes ago, hughlb said:

Again good data. I have had this issue occur with a 100 Hz and 144 Hz monitor, but never had a monitor that could go any higher. I recall with the 144 Hz monitor, I found dropping it to 120 Hz fixed the issue, but I never went into that 150-175 Hz range.

One thing for people to know, if you try to look for this issue with a 60Hz monitor or with a framerate below 60 FPS, don't bother. Any stutter gets lost in the trailing/ghosting and inherently less smooth image at that framerate. There weren't many people running 144Hz monitors back in 2016, which is maybe why I didn't find much help back then.

 

Yeah this explain a lot indeed. And I agree that on a 60Hz monitor you won't feel having less Hz on the tracking, maybe just a tad more latency? I don't know to be honnest haha.

[Hiob]

@hughlb

Did the recommendations of the NP-Staff in the other forum make any difference?

[hughlb]

39 minutes ago, Hiob said:

@hughlb

Did the recommendations of the NP-Staff in the other forum make any difference?

No unfortunately. I have posted a response there, but it takes a while to clear moderation. The smoothing options in the TrackIR, which were a good idea to test, made no difference.

[boerdi]

On 8/24/2023 at 8:00 AM, Lange_666 said:

This has been an issue since the early days of TrackIR.  When the FPS is not in sync with the TrackIR pull rate, slight microstutter is visible when not looking into the direction of motion.
When looking straight ahead, i don't notice it, when looking sideways it's noticable, even when the FPS dips or jumps 1 frame below or above the pull rate (or a division of it). It gets worse the more frames it diverts from the optimal value. And it becomes more noticeable the faster the image is moving.
That's why i VSync and cap to 60 (120 isn't reachable all the time in every situation) since i run TrackIR.
Without TrackIR, fluctuating FPS values are no problem, with TrackIR it's a no go (for me at least, not everybody's perception of stutter is the same).

PS: Same goes for VR, fluctuating FPS is never smooth for me.

 

In two years of using TrackIR I never had any issues with "mismatching" FPS
And I am sensible to micro stutters of any kind, so I would know when something "feels off"
Currently it is DCS itself that's occasionally producing stutters and longer freezes sometimes

My FPS range from 60 to 100+ depending on the map and how busy the multiplayer server is but never have i witnessed any TrackIR micro stutters
Playing in 1440p on a 144 Hz G-Sync Monitor with G-Sync enabled and V-Sync disabled

I apologize if this is no help for OPs problem

[edit]

But now as I am writing this down, this issue I had comes to mind: How is your Track IR connected to your PC? Directly via the USB ports on the front or back of the PC?
I had problems with my whole HOTAS, Streamdeck and Track IR setup (total of 5-6 USB devices) due to the simple lack of USB power provided by the motherboard
If you don't have tried it yet, maybe attach all your USB devices to a powered USB hub?
For example something like this one: https://sabrent.com/collections/usb-3-0-hubs/products/hb-bup7

Worked flawlessly for over a year now

Edited August 25, 2023 by boerdi

[hughlb]

23 hours ago, boerdi said:

am writing this down, this issue I had comes to mind: How is your Track IR connected to your PC? Directly via the USB ports on the front or back of the PC?

I had problems with my whole HOTAS, Streamdeck and Track IR setup (total of 5-6 USB devices) due to the simple lack of USB power provided by the motherboard
If you don't have tried it yet, maybe attach all your USB devices to a powered USB hub?
For example something like this one: https://sabrent.com/collections/usb-3-0-hubs/products/hb-bup7

A very good point indeed boerdi. I do run two powered hubs for peripherals, but have been running my TrackIR directly into the rear IO. I will test your suggestion. 

Another point worth raising for people reading this thread - over on the Natural Point forum, I was asked to check what my TrackIR framerate is running at. It is 30 FPS in the Track IR  window. When I move my mouse around in the window it jumps up to 100 FPS to match my monitor output. Odd... perhaps nothing, I mean the Track IR window may be running at 30 FPS displayed, but the sensor running at 120 Hz, but worth noting. I will see what Natural Point say in response.

[PinkCube]

In my experimentation of finding out how to improve the smoothness of TrackIR and make it feel less stuttery I found a file called view.lua. Going by "feeling" changing these values to 0 made trackIR feel much more responsive in DCS. However didn't quite mitigate the stuttering (lower framerate feeling when looking around) I was trying to solve.

Edited August 26, 2023 by PinkCube

[silverdevil]

@hughlb i did see in the NP post the helper mentioned "Does minimizing the TrackIR software while the game is running make any difference in how the smooth the image is?" 

interesting. i am going to try to see if there is a difference. 

[hughlb]

1 hour ago, silverdevil said:

@hughlb i did see in the NP post the helper mentioned "Does minimizing the TrackIR software while the game is running make any difference in how the smooth the image is?" 

interesting. i am going to try to see if there is a difference. 

I have responded to their post, but it hasn't cleared moderation yet. Essentially though, minimizing didn't make any difference (or any of the other suggestions). The only strange thing was the 30 FPS of the TrackIR software, but it may be a red herring.

[silverdevil]

48 minutes ago, hughlb said:

I have responded to their post, but it hasn't cleared moderation yet. Essentially though, minimizing didn't make any difference (or any of the other suggestions). The only strange thing was the 30 FPS of the TrackIR software, but it may be a red herring.

understood.

i looked at my trackIR and do not see the fps. where is that found?

[boerdi]

No issues with Track IR here and I'm also getting 30 FPS in the desktop window

Using the app FPS Monitor

 

[hughlb]

8 hours ago, silverdevil said:

understood.

i looked at my trackIR and do not see the fps. where is that found?

As boerdi shows, use FPS Monitor or Fraps, and open the TrackIR software. It should have a counter in the top right or left corner of the screen. I believe they run the app at 30 FPS to minimize pressure on the CPU, as the software is just a monitor to ensure its tracking properly. The sensor itself would still be running at 120 Hz, I would have thought.