MSX's kapi batcher, intended for macOS Terminal (but may work on Linux too). Thanks to hyenatown for the shell basis.
a little ffmpeg batching script. drag your video (or audio) on, enter the selection, and it does its thing. requires the ffmpeg executable in either the same folder or for it to be available via %PATH%. it also has a thumbnail batcher, which requires pngquant and pngout be available the same way.