Could you rewrite this to use our string builtin?

E.g. `string match -rv '=|:$|^\s-' | string replace -ra '\s' \t

Also this seems like prime use of a for-loop or even function:

for thing in encoder demuxer muxer filter
    printf '%s\n' $thing=(ffmpeg -loglevel quiet -{$thing}s | ...)
end

And instead of using cut based on whitespace, which has to use a different field just because this does a positional "ED" thing, use string trim to trim leading whitespace. That way it won't break if e.g. ffmpeg decides to actually display "ED" for some of these, or to start displaying it as ".D" (like the legend says!)

I.e. I'd roughly do this as

for thing in encoder demuxer muxer filter
    printf '%s\n' $thing=(ffmpeg -loglevel quiet -"$thing"s | 
                          string trim |
                          string match -rv '=|:\$|^\s-' | 
                          string replace -rf '\S+\s+(\S+)\s+(\S+)' '$1\t$2')
end