tobii-E-prime no.3

The followings are the conversation between E-prime web support and me.
These info is surely useful for some people (though a few...) using Tobii with E-prime!
Now we can see the position of the participant's head and do recalibration at least
during the experimental session if we use Tobii X50 with a good monitor
(which has two cable sockets.
I may need a good switch for Tobii1750)

From Nobuyuki on 5/10/2006 8:24:00 PM
Hi.
Recently, I am wondering how I can do "Re-calibration" during experiment with Tobii eye tracker.
I am doing reading study in which sometimes re-calibration is required during the session to keep the accuracy of the
eye tracking.
First, I tried "DeviceManager.Suspend" & "DeviceManager.Resume" command with In-line object.
(Basically I used Suspend/Resume sample in webpage.)

Then during suspend, I've tried to call ClearView.exe somehow.
However, I couldn't succeed for two reasons.

1. I couldn't call ClearView.exe with "shell" command or "Delare ShellExecute".
(I could call "excel" or "powerpoint" properly in above ways.)

2. After "DeviceManage.Resume", I could not get
signal from tobii eye-tracker. It seems that I have to
resume tobii device as well.

In sum, we want re-calibration module but "suspend-Resume" may not be useful for that.
Do you have any good idea to get re-calibration procedure?

Thank you very much for your support!!

Nobuyuki
From Michael Hout on 5/12/2006 4:02:00 PM
Nobuyuki,

There is actually a good work around for this type of procedure. First, please note that we do not recommend the use of Suspend/Resume for this task. It is also recommended that you calibrate the subject via the Tobii computer (the computer not running E-Prime). The general method is as follows:

I would recommend placing an Infinite Duration object at a location in your experiment in which you'd like to do a recalibration, and where you are not currently tracking eye gaze. For example, it is common to call the TETStartTracking package call at the beginning of a trial procedure. I would recommend that prior to the StartTracking call place an object that will remain on screen until you press a specific key (ie - a TextDisplay stating "Press the 1 key when you would like to begin a trial"). In this way, you can perform a recalibration without collecting unnecessary gaze data.

Once you've reached that designated point in the experiment (ie - at the beginning of the trial, or after a block, etc.), switch over to the computer NOT running E-Prime (via a KVM switch for instance). Recalibrate your subject, and then switch back to the E-Prime computer. The new calibration (or improved calibration) will then be used when the TETStartTrack call is implemented.

I hope this has been helpful. If you need anything further please let me know.

Sincerely,
Michael Hout
Technical Consultant
From Nobuyuki on 5/15/2006 12:01:00 AM
Dear Dr. Hout,

Thank you very much for your help!!
Your recommendation is a big help for us.
However, before trying to your idea, I want to confirm how to calibrate
eye position during Tobii-Eprime experiment.
your recommendation is that I should use ClearView for recalibration via
"tobii(tracking) PC" instead of "E-prime(stim) PC".
BUT
I used to do the calibration in E-prime PC before starting experiment.
This procedure seems to have no problem until now.

so my question is how we should do calibration before and during an experiement. I am thinking the two alternative as follows,
1. always do calibration in Tobii PC because calibrating with E-prime PC have no sense for the setting of Tobii device.

2. before experiment, we can do calibration whichever we want(Tobii PC or
E-prime PC). During experiment, we should do it with Tobii PC because
we should not suspend E-prime during experiment.

If 2 is true, how the calibration can be done? Does Tobii eyetracker device
can save the setting of a calibration internally?

Thanks in advance,

From Michael Hout on 5/16/2006 2:48:00 PM
Nobuyuki,

You can call me Mike or Michael. I'm not actually a doctor :) .

First please verify that you are using a two computer setup. One computer runs E-Prime, and the other computer houses the TET Server. The two computers communicate via a cross-over cable, or a network hub. Is this correct?

Basically what happens is that the TET Server will use the most recent calibration from either machine. So, you can do your initial calibration from either the E-Prime or the Tobii machine (through Clearview of course).

However, for your mid-experiment recalibration, you will need to use the Tobii machine to recalibrate so that the E-Prime experiment does not have to be suspended. When you resume eye tracking (ie - you call StartTracking at the beginning of the trial), this new calibration will be used regardless of which machine the calibration was done on. This is because the TET Server is able to communicate with both machines. If the calibration is done on the E-Prime machine prior to the beginning of the experiment, the TET Server will still have the calibration info. When you recalibrate mid-experiment, the TET Server will receive the new information and use it when processing future eye gaze.

In general, I would recommend calibrating the subject on the Tobii machine both at the beginning and mid-experiment to avoid confusion. This will also enable you to have Clearview installed and open on only one machine.

I hope this is clear. Please let me know if you have any questions.

Sincerely,
Michael Hout
Technical Consultant