SwtichresX solves Mac HDMI problems
I use a mac mini as a music only server with HDMI output. It's used mostly headless... if the projector is on it does display video of the desktop but it's used only for music. Many music servers use something other than HDMI for output but I listen to multi channel high res files (typically from my Blu rays like Dark Side of the Moon immersion set for example.)
The problem is (or was) whenever the video portion of my system was powered off I would lose the HDMI output from the mac mini.
I tried a EDID spoofing device with no luck.
SwitchResX keeps the HDMI output alive. I thing shutting down the projector does stop playback but I can instantly restart it. I like it a LOT better than trying to find a HDMI handshake gizmo to keep in my playback chain.