(In reply to comment #4)
> (In reply to comment #0)
> 
> > #2, without xorg.conf
> > The receiver sends its own EDID block, so I can extend via xrandr without
> > turning on the projector.
> > But the projector is turned off in most cases, so is there a way to disable
> > a display output but keep the HDMI audio output? (as a workaround for #1)
> 
> Nope, unfortunately not. It's by HDMI design, the audio signal is mixed into
> the vertical and horizontal blank periods of the video signal -> so if you
> don't have a video signal you don't have audio also.
> 
> As a workaround you could try to setup a second X server or framebuffer or
> something like that (kms console?) on the HDMI output to just get a video
> signal on it.

Okay, thanks for clearing that up.

Another workaround would be HDMI multichannel audio for radeon :)
Does AMD have any plans to implement that?