[Solved] Number of "begin" and "end" fixation inconsistant

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    Romain GROSSE

    Hi there,

    I am currently trying to work on the use of fixations but I encounter a problem :

    The number of Begin-tagged and the number of end-tagged fixation is not the same, it is possible to have several “begin” in a row, or with “data” tagged between them.
    I have already let appart cases where the repetition is due to having the same timestamp.

    To summarize :
    Begin – Begin – Data …
    Begin – Data*n – Begin – Data*n …
    Begin – Data – End – End

    Is there a way to prevent this ?

    Grant [Tobii]

    Hi @romaingrosse, we are looking at this issue and trying to reproduce.

    Could you kindly be more explicit with reference to the language bindings being used, SDK Version, system info, etc.


    Romain GROSSE


    Thank you to try to help me, I will do my best to list everything i can :

    – First I’m working with Unity (I thought i mentionned it before but apparently I didn’t…) using the “TobiiEyeXSdk-Unity-1.7.480”
    – The Eye X controller Drivers were from the version
    – The system i’m using is en EyeX controller marked “EYEX2-030105901334
    – My code look like this :

    _eyeXHost = EyeXHost.GetInstance ();
    _fixationProvider = _eyeXHost.GetFixationDataProvider (FixationDataMode.Slow); // or sensitive
    _fixationProvider.Start ();
    eyeFixationPoint = _fixationProvider.Last;
    if (eyeFixationPoint.IsValid) {
    	if (eyeFixationPoint.Timestamp - lastEyeFixationPoint.Timestamp != 0)   // avoiding doublons
    		Debug.Log (eyeFixationPoint.EventType);

    – The version of Uniti is 5.4.0f3 if that matters and I set up the update delay at 0.02 s so I should not miss some of the tracker state

    Tell me if i’m not precise enough or if you need more informations
    Thank you again for your work.


    edit : tried with the latest version of the drivers too (

    Jenny [Tobii]

    Hi @romaingrosse,

    Thanks for clarifying the specs and SDK you are using, along with the code sample and the fact that you have a short update delay to not miss any of the events from the eye tracking engine.

    I believe the EyeX Controller can deliver eye tracking data up to 60 Hz, and that is once per 0.017 seconds, so it could actually still be a problem of missing some of the events from the eye tracker if your update delay is set at 0.02 seconds. Would it be possible for you to test with an ever shorter update delay?

    There might also be a bug in the Slow version of the data stream – the symptoms seemed similar to an old known bug when I talked to the guy who has implemented the data stream algorithm in the eye tracking engine. Have you seen the issue also with the Sensitive filtering?

    Romain GROSSE

    Hi jenny,

    no problem doing my best to help you helping me 😉

    I actually forgot that the sample rate was up to 60 Hz, unfortunately, even setting the framerate down to 0.005s (200 Hz) the problem persists.

    I already tried switching between slow and sensitive, both are giving me inconsistent results but i’m quite confident on the number and the veracity of the Begin-tagged fixations when I use the “slow” mode. Getting the time between two Begins should work for me by now (subtracting the saccadic mean time and expecting the user isn’t doing any smooth pursuit). But I am still here if you want me to try something or if you need more infos.

    I have downloaded the v2.0 beta of the Unity SDK but didn’t have the time to test it yet. I’ll provide infos when I can.

    Grant [Tobii]

    Hi @romaingrosse, may I ask how you got on following the latest 2.0 Beta? Thanks for the update.

    Romain GROSSE


    I’m sorry, almost two weeks without any feedback from me.
    So I started looking at the 2.0 Beta. Some good things there! But eh… not on fixation points :

    The Fixations data stream has been removed because of expected future changes to what is provided from the underlying system.

    from the transition guide to beta 2.0

    I will stick on the older version by now.


    Grant [Tobii]

    Okay, thanks for the update.

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