OK, thanks - I'm very keen to get this sorted out!

BTW, a key distinction that I'm making is between an AVR that does note extract audio and one that does. One that does not extract audio obviously does not require any keys of its own or to participate as a node in the authentication. (And, as such, can just physically repeat whatever bits show up to the downstream device.)

However, the AVRs we're talking about all do extract audio.

Thanks, again.