normalize audio in mp4s

[Emanuel Berg <moasenwood@zoho.eu>]

how can I normalize the audio in mp4 video files? both WRT not
having to lower the volume when there's a firefight and raise it
when they start talking again, _and_ WRT playing several files, e.g.
music videos, and having them have basically the same volume?

if need be, I can set volume modifications to each file, manually if
I knew how to do it. this wouldn't work for firefight/talk
movies tho.

or can it be done automatically, on the fly?

I use mpv.

TIA

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