Modules
A conversion that leaves the video alone.
What a browser decodes, as it reported on connecting: a map with :hevc,
:av1, :vp9 (and whatever else you carry, such as :uhd for 4K). The
page can learn these with MediaSource.isTypeSupported /
canPlayType and send them as connect params
The ffmpeg command line for a conversion: pure, so what is run can be read and tested without running it.
Language codes as files carry them (eng, fre, jpn) — names and two-letter codes.
HLS master playlists: for a multi-audio conversion, for ffmpeg's own multi-audio TS output made fit for a player, and subtitle renditions added to either.
What is inside a file, by ffprobe: its streams' kinds, codecs and languages.
The registry of running conversions and the supervisor of their workers. Put it in your application's tree