Re: "I kind of had the impression that the producers / consumers should not be involved in command protocol details, but would be passed populated data structures representing their options."
If the '--' token is to be treated as a realm-separator, letting everything to the right of it be inner parameters to an inner realm, wouldn't it be impossible to parse and interpret it (in the generic case) in amcp-code since it by definition is not amcp?

But that doesn't really matter right now. I only had reservations about introducing the new '--' token in amcp, but you've convinced me that a realm-separator like that is useful. And if we only implement it in the ffmpeg-producer for now that's just fine since it's the only producer taking advantage of it. It can easily be made generic later on.