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RSS >  Software FAQ, Read this first
Kestrel #1 02/01/2008 - 03h34

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What is FreeTrack?

See the FreeTrack Wikipedia page for a general overview.

What does '2dof' and '6dof' mean?

2dof : Two degrees of freedom [Yaw, Pitch]
6dof : Six degrees of freedom [Yaw, Pitch, Roll, X, Y, Z], only available using 3 or 4 point tracking.

Yaw: Rotate left-right
Pitch: Rotate up-down
Roll: Tilt left-right
X: Move left-right
Y: Move up-down
Z: Move forward-back

A 'degree of freedom' describes an axis about which motion can be tracked.

How do I get FreeTrack working on Microsoft Vista?

FreeTrack needs administrator privileges on its first run so that it can register its DirectShow filter in the registry. To do this, right click on the executable and select 'Execute as admin'

FreeTrack crashes when I press start!

*Make sure your webcam is not already in use by another application.
*Reduce your webcam's exposure and increase the threshold setting in FreeTrack before pressing start otherwise, if too much light is seen, the point finding algorithm can crash. I420 video is less likely to crash than RGB24.
* FreeTrack only supports I420, RGB24 and RGB32 video. Driverless webcams use USB Video Class (UVC) which only supports YUYV (YUY2) and NV12 which currently aren't supported but you may still be able to get them to work with FreeTrack using SplitCam.

I'm using 3 point cap tracking and sometimes tracking fails for some axes and 'NAN' appears in the data readout, FreeTrack may also crash.

The model's front points cannot be allowed to move behind the middle point, relative to the camera plane. This could happen for downward pitching and extreme yawing. To avoid this, make your model deeper, with the middle point further back than the distance between the two front points.

Also make sure that only the tracking points are being tracked at all times and that there is only one tracking cross per point.

The video is completely red when I use I420!

The video background is red and light appears as white when using I420 video.

Webcam frame rate is lower than advertised.

*Turn off auto-exposure and manually reduce exposure (this is essential).
*Make sure your USB port is not less than a USB 2.0 port.
*Use a different USB port.  Sharing ports or hubs with other devices can cause bandwidth bottleneck and lower fps.
*Disable anti-flicker/enable outdoors mode in your camera properties.
*Reduce video quality in the Stream property page if your webcam supports it.

My webcam's Auto-Exposure (AE) is on and the option is greyed out so I can't turn it off!

Try to enable the option by using Enable Button or WindowsEnabler for XP or VistaEnabler for Vista.

In the case of Microsoft VX-1000:
1. Set auto exposure on (default) and exposure value to 0 (or a little higher).
2. Place a bright light source, like a lamp, in the field of view of the camera so that it reaches 30fps.
3. Disable auto exposure with one of the enable button apps.
4. Switch the light off,  the camera should still be producing 30fps and will continue to do so while the exposure settings are not changed.

Make sure your webcam is not listed as incompatible.

View panning stutters.

It is important to ensure that the setting Global -> Interpolation -> Average webcam fps is set to the actual webcam frame rate reported in the Cam section.

Make sure Jitter isn't too high and FreeTrack is minimized. When FreeTrack is not minimized the webcam frame rate is not controlled so some stuttering is to be expected.

What does the 'jitter' measurement mean?

Jitter counts the number of frames that deviate more than +/-15% of the average frame rate in a second. It indicates frame rate instability which can potentially cause a reduction in panning smoothness. If the deviation is small FreeTrack, when minimized, may be able to neutralise it, so a high jitter number does not necessarily mean there will be high jitter in the output.

High jitter can be caused by anti-flicker being enabled or equivalently, outdoors mode being disabled.

CPU usage is too high.

FreeTrack CPU usage should only be measured when there are fewer than 5 visible points in the video stream and the program itself is minimized to the system tray.

Steps to reducing CPU usage:
*Reduce webcam resolution.
*Use a more CPU efficient webcam.
*Use a dual-core CPU.

My webcam doesn't remember exposure settings between video streams.

This is a known problem with many Logitech webcams, some new models use a standardized driver (UVC) which doesn't have this problem. Use the Force Exposure option in FreeTrack to automatically apply your desired exposure settings every time a video stream is started.
Edited by Kestrel on 10/06/2008 at 04h58.
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