hidden .gallery folder in movies

This looks like some cache files that some application might have created, but I have no idea which one. For sure, not something that Apple applications dealing with video, like iMovie, Final Cut Pro or Quicktime Player would have created.

Do you recall using any particular video application that might have created these?

Note: it’s almost certainly safe to trash this folder, but in case of doubt you can copy this off to an external drive, delete it and see if anything happens.

I have never seen this folder, and I do not have one on either of the macs I have access to.

Can you tell us what the contents of that folder are? Anything you recognize in there?