Doom can record game sessions to LMP file format, which is a recording of the inputs on every frame. That's usually how people share runs in the Doom speedrun community. So yeah a LMP-to-video converter could be legitimately useful to some people.
“LMP-to-video converter” is any Doom port which output you can record by common (or less common) means. PrBoom+ has a built-in demo playback recording (if you consider running the console encoders and feeding them sound and image data “built-in”).
https://doom.fandom.com/wiki/Demo#Custom_demos