How do you convert an entire directory with ffmpeg?

Question

How do you convert an entire directory/folder with ffmpeg via command line or with a batch script?

Answer 1

For anyone who wants to batch convert anything with ffmpeg but would like to have a convenient Windows interface, I developed this front-end:

https://sourceforge.net/projects/ffmpeg-batch

It adds to ffmpeg a window fashion interface, progress bars and time remaining info, features I always missed when using ffmpeg.