Tobii eye tracker has lots of temporal noise and missing samples #173

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1. dev-jam

   changed the title [-]Tobii eye trackers has lots of temporal noise and missing samples[/-] [+]Tobii eye tracker has lots of temporal noise and missing samples[/+] on Jun 16, 2023
2. dcnieho commented on Jun 21, 2023

   

   dcnieho

   on Jun 21, 2023

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   To add to this, your code has two major problems in libtobii:

   1. You should be getting the timestamps from the sample in https://github.com/esdalmaijer/PyGaze/blob/master/pygaze/_eyetracker/libtobii.py#L1182, not writing data with the timestamp of the moment it is written. Tobii provides good timestamps for each eye tracking sample that are already in eye tracker time, use them.
   2. Bigger issue, but: the way gaze data is received through a callback, https://github.com/esdalmaijer/PyGaze/blob/master/pygaze/_eyetracker/libtobii.py#LL207, can and will be blocked at times, meaning you lose samples. Sometimes even large parts of your data are lost, and in our experience its rather undeterministic. Easy for a programmer to write Python code in such a way that the callback will sometimes be blocked. The ways around this are to not use Python and its fake threading (best!); at least not use python for the gaze callback (aka, the Titta approach with a c++ library) or to put gaze collection in its own process (iohub does this, does make things super complex).
3. dcnieho commented on Jun 21, 2023

   

   dcnieho

   on Jun 21, 2023

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   Regarding point number 1, doing https://github.com/esdalmaijer/PyGaze/blob/master/pygaze/_eyetracker/libtobii.py#L1152 really is a nono for storing the gaze data (and more generally, if users already have an even in the right system time (Screen flip, key press), you'd want them to be able to supply their own timestamp.