This is the sort of thing you can't help but run into when looking up ffmpeg incantations over the course of building a solution.
Just look how easily you ran into it when you weren't even looking for it.
For such a complex tool, the internet (like StackOverflow answers) ends up becoming a recipe book of practical solutions that would be hard to derive even if you sat down with the documentation and read it front to back. Nothing wrong with embracing that.
