I want to output video from my rMBP to my Apple TV but send the audio to AirPort Express connected to my sound system.
I have tried every way imaginable to accomplish this, and nothing seems to work. All links in the chain have updated software & firmware. Hardware is the following; rMBP Late 2012, Current Gen ATV, Current Gen APE. All running on rock solid WiFi.
If I start by sending video, it quits when I select the APE audio source, if I start by sending audio, it stops sending when I enable mirroring on the Mac.
I have tried under
System Preferences on the Mac to have the system audio routed to the AirPort Express, but no luck. I have tried routing the audio to the APE from the ATV's prefs, also a no go.
Strangely this works like a champ from an iOS device, not from my Mac. I can send the video from the Mac to the ATV and send the audio to APE via Airfoil, but there is a noticeable lip sync issue, so that is not an option.
I read a Lex Friedman article on MacWorld touting the ability to do this.