Alex, Thanks for your kind reply.
I read the Tobii Gaze Overlay Post before asking my question.
It was very beautiful tool but I couldn’t understand how it works minutely.
Because the tool’s source code is not opened.
I think that you’ve confirmed me two important things
1) Gaze data stream doesn’t guarantee fixation coordinate precisely. It needs extra filter.
2) Do not record gaze data officially according to SDK license agreement.
Are these right?
I haven’t understood gaze data stream & license agreement certainly before getting your answer.
Thanks again!