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WxTech #1 09/01/2014 - 13h04

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I've been using Freetrack for years. There is a recurrent odd behaviour, whereby in both FT and Il-2 there is a cyclic periodicity if the output data stuttering, or slowing down. It seems to be related to a mismatch between the real camera FPS of 29.75 (?) and the integer setting of 30 in FT.

I have found the smoothest response when doubling the frame rate to 60. At this setting, every ~1.5 seconds, for ~2/3 second there is a stutter, like a mini seizure in my eyes. Sometimes it's so subtle I can hardly tell it's there at all, and at other times it's really annoying.

I can sometimes reduce the intensity by fiddling around, such as changing FPS settings, camera resolution and other settings, etc.

I use a single point model (but with axis mapping that gives me 5dof--no roll.)

Any idea what I can do to get a consistent response?

In FT, FPS fairly regularly cycles between 30 and 29, presumably due the camera's just-under 30fps, and JPS varies mostly between 000 and 001, occasionally 002, always green.
Stormrider #2 11/01/2014 - 13h55

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without using freetrack you don't get  this stuttering?Maybe you can give the Freetrack.exe*32 process and TrackIr.exe*32 process a higher priority.Normal TrackIr.exe*32 process has a low priority, but you can change it in to realtime.

Go to the taskmanager, select processes, select TrackIr.exe*32, click right on your mouse and select priority and change it to realtime.

Did you already try it with antivirus and other software turned off?
Is you pc fast enough and what webcam do you use?
WxTech #3 11/01/2014 - 15h16

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Thanks much for wading in!

My camera is  Live! Cam Vista IM, and is several years old. I seem to recall that its frame rate is stated to just under 30 fps, certainly not exactly 30. I used it on an older XP computer, and now ai'm using a newer XP machine. My IL-2 frame rates are quite high and smooth, and when the head tracking is behaving (and during those intervals between stuttering) the action is glass-smooth.

What confounds me is the variation in the severity of the stutter. Some times you can hardly tell it's there, and at other times it feels like my eyes are suffering seizures every ~1.5 seconds. (Grin)

It's most clear that it's a matter of the mismatch between the camera's non-integer frame rate and FT's expectation of an integer rate. If I fiddle with the fps and multiplier (2, 3 and4) values in FT, the periodicity of the stutter changes to suit. In short, it's a phase difference, like the best frequency between two aircraft engines running at slightly different rpm.

I tried plugging the camera into a different USB port; no real difference.

I'll look at reassigning priority at run-time, which I assume I can do in XP?

Incidentally, when the stutter is even bad, if I hold my head still, the game's frame rates are just fine--as smooth as expected. It's only when there's any head motion, with sufficient movement of the scene between individual frames, that the stutter becomes apparent. This tells me that it's a matter of the rate at which the numbers that FT is sending out is the issue. There are either those periods where the rate is reduced, or the rate is maintained but values are sent out but not different for a frame or two.

I really want to nail this down, for it's very tiring on the eyes, and just not enjoyable in any event.

And it seems to have gotten much more frequent in the past couple of weeks.

Again, thanks for your attention; I very much appreciate it!
WxTech #4 11/01/2014 - 16h39

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I forgot to add... My gaming computer is not connected on-line, and anti-virus is disabled. I also use the utility FSAutostart to disable all unnecessary processes.

I just tried assigning real time priority to both Freetrack.exe and TrackIR.exe; no difference at all.

I also spent a good half hour changing camera resolution and the frame rate multipliers. For each setting, every time I came back to a particular one there was a difference in the severity of the stutter.

The effect is best observed with the game paused, so that the *only* motion is that produced by head tracking. Even with the multiplier set to 3 (to ostensibly give 90 fps) and 4(to ostensibly give 120 fps), the apparent rate is *LESS* than when the multiplier is set to 2 (60 fps). At that latter setting is when I get thee truly smooth rate I want, except of course for those episodic stutters.

From appearances, if at 60 fps, the stutters are at 30 fps. In spite of the render and head motion numbers periodically updated in FT's left display window. That is, render is consistently at 60, with the head motion value changing between 60 and 59, sometimes 58. But with the actual rate dropping to 30 for about 1/5 to 1/4 the time, the *mean* head rate should be closer to 50 fps.

This disparity might be a clue.
Steph #5 11/01/2014 - 16h57

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I observed this behaviour too on an old XP-PC with the Version 2.2.
What you can do is to try the older 2.1 Version of FreeTrack, to see if that change anything. (It does for me, even the 2.1 do not have the multiplier it runs smoother than befor.)
Check out the real FPS-rate in IL-2 too, to see if there isn't any problems on this side. Do you got stuttering only online? Check out for lags.
To see FPS-rate ingame use Shift + Tab to bring up the console, then type fps SHOW START (case sensitive, it has to be in caps). That will bring up your your min, avg, and max fps.
WxTech #6 11/01/2014 - 18h48

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Thanks for the suggestion on v2.1, Steph! That's the one I started with some years ago.

I do not fly online. My frame rates are at least 60, except when things get pretty busy and many effects are being displayed. (The Black Death track runs really smoothly.) I can assure you that the game's fps rate is not the culprit. Besides, this stutter is so incredibly regular in its cyclical timing that you could practically use it as a clock, whether the game is running or paused. This certainly seems to do with a kind of 'beat frequency' resulting from the actual camera's ~29.75 (or whatever it is) fps and the neat integer of 30 fps that FreeTrack seems to want.

Thanks again; I'll download v2.1 and give it a whirl!
WxTech #7 12/01/2014 - 18h07

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Speaking of frame rates... It's been a *long* time since I was at all concerned by this. But I've just done some checking with IL-2's frame rate display. Weirdly, even with vsync turned off I'm constant at 59-60, with occasional *very* brief spikes to ~65 or so. The average is always pretty much 60.

Why would ths be so? This is with 4.08, by the way.

And upon reflection, I doubt I' be happy with FT 2.1. I remember how impressed I was when upgrading to 2.2, with its frame-doubling capability. I really do insist on having 60 fps for head tracking. Why?

Because I use a 40" 1920X1080 monitor. I sit close to it, with reading glasses so as to get comfortable focus, in order to obtain a screen angular width if 90 degrees. This gives a 1 : 1 image scale, which is just like being inside the cockpit. And it eliminates the distortion introduced by the game's gnomonic projection.

Having such an angularly large image on the retina demands faster frame rates. Too slow an update rate results in a larger angular distance between successive images, and this makes the eyes more tired.

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