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Failing to precisely display stimuli: variable duration of ± 1 frame


So I am developing an experiment in Builder that consists in a train of characters displayed on screen for a brief period of time. To do so, I used a Text Component that selects the character to show from an Excel conditions file and also a loop.

The issue is, I have set the duration of the stimulus to 9 frames, however, when I check the .csv generated after the experiment is run, the difference between the rows of the text.start column is sometimes 9 frames and sometimes 10.

I would like to know if this is an expected behaviour due to time spent by Text Component during each iteration or there is something wrong.

PsychoPy 3.2
Windows 10