Hello,
sorry to resurrect an older post, but I think my question best fits here, and I hope this is o.k.?
I’m still not quite sure whether I fully understood how time stamp precision in TOBII Eyex gaze data has to be considered:
1) Accuracy
According to the “Timing Guide for Tobii Eye Trackers and Eye Tracking Software”
the variance of the timestamp generated in the eye tracker at the middle of the capturing period is primarily linked
to how well the experiment setup complies with the optimal conditions the eye tracker is designed for to deliver optimal performance.
In the worst of experiment setup conditions, it may be up to +/-3ms.
But that is an issue distinct from the aspect of “latency” which solely affects the availability of the gaze data for the subscribing application once it is recorded by the scanner.
Therefore the timestamp contained in the data frame still describes the recording time accurately (within that range of max. +/-3ms
as cited in the “Timing Guide for Tobii Eye Trackers and Eye Tracking Software”), unaffected by these latencies?
Latency then primarily affects the availability of recorded data?
Put differently: as soon as one obtains the gaze data frame in the client application, one still can determine the point in time of it’s recording with the cited accuracy and in reference to the starting point of the time stamp count up (as arbitrarily initiated by TOBII software stack internals) by using it’s bundled time stamp?
2) Measurement unit
As [ms] often refers to “milliseconds”, i think here and in the context of that whitepaper “Timing Guide for Tobii Eye Trackers and Eye Tracking Software”,
still refers to “microseconds”, as often indicated, and this unit [ms] actually means “micro”?
I am trying to understand this right as I want to draw conclusions for subsequent data frames in the situation when frames/samples have been dropped,
which depends on the time stamp information bundled in their frames representing their true recording time accurately.
If someone could kindly confirm or correct my assumptions, that would be great!