Variable frame durations detected by win.recordFrameIntervals

OS Win10
PsychoPy version 2023.1.3
Standard Standalone? Yes
What are you trying to achieve?

Hi everyone,

I have recently used win.recordFrameIntervals to track the frame durations and detect dropped frames when presenting alternating white & black squares on an external monitor, set as primary.

  • Monitor refresh rate 60 Hz
  • Graphics card NVIDIA GeForce GTX 1070

Through more than 8 min of recording, only one dropped frame was detected (probably due to system initialization) and the average frame duration was 16.681 (0.354) ms. However, there seems to be a great variability in frame durations, spanning from 15 to 18.5 ms.
The distribution and progression of frame durations (after removal of outlier dropped frame) was:


Since I am having latency issues with the LSL markers and hardware triggers tied to stimulus presentation (see my question here), I was wondering if such variability in frame durations might affect the timing with such markers/triggers.

Have you suggestions on what might be causing these inconsistencies in frame durations?
Any help is greatly appreciated, thanks!