Black flash/flicker (black rectangle) at onset of MovieStim playback

[TParsons]

I think this is the same bug as in another thread so here’s my reply to that one:

A buffer in the beginning of a video

We made some changes to how movies are buffered and rendered in 2025.2.0 ( Release PsychoPy 2025.2.0 · psychopy/psychopy · GitHub ) so I think this is a result of those. The key difference is that movie frames are now buffered asynchronously, which allows for easier seeking to timestamps and is generally better for stability and speed, but it looks like there’s sometimes a frame at the beginning which is allocated for before any data has arrived (so displays as black), hence what you’re seeing. …