Image generation for n per minute off a bit

[whyboris]

If you make your hub generate a screenshot "one every 1 minute" and then look at the timestamps, it seems to create a screenshot ever 56 or 57 seconds.

This could be because FFmpeg tries to grab the nearest keyframe or it could be something weird with my code 😅

Glance around to see if there's an easy fix. It would be lovely if the 1st screenshot was at 1:00 and the next at 2:00 rather than 0.56 followed by 1:54 🤷