FFmpeg is wonderful software. Growing up as a Windows user in the early 2000s, devices were far more picky than they are today about which video codecs they'd support. It was a non-trivial task as an 11yo trying to convert DivX .avis into an MP4 my old iPod Video could understand. Discovering ffmpeg and finding that someone was offering for free what I otherwise could only find under mountains of crappy shareware was a real watershed moment.
20 years later it's still a goto. Great tool.