mpv doesn't run on iPad so it's better for my situation to just burn the blackout into a new video. I actually do a lot more stuff than drawvg (also rescale, pts, framerate,etc) in filter_complex but left the rest of it out for the HN comment so the example is more readable.

I suppose it might be possible to use mpv with a custom shader mask glsl code to blackout circular areas of the screen.

>you sure can crop the video

Cropping the video is straightforward with no information loss when the geometry of presentation and the speaker is laid out like these: https://www.youtube.com/@MeetingCPP/videos

But cropping the following video by shrinking the boundaries of the rectangle until the circle overlay is not visible would result in too much of the text being cut off: https://www.youtube.com/watch?v=nUxuCoqJzlA

Scrub that video timeline to see the information that would be chopped off. For that, it's better to cover up only the circle overlay with a blacked out disc.