Continuously buffered desktop capture software for Mac?

I capture a lot of video clips for reference/analysis, and am looking for a program that would buffer a set number of minutes of desktop video, which can be saved at any point.

So it would continuously watch my desktop (or part of it), and by clicking a button, the past few minutes of it would be saved to disk.

Does anyone know of software or hardware that can do this?

Thanks!! I’ve been searching for this for a while, but haven’t found anything..