Airplay: Choose Sound Output?

[Rufuss Sewell]

Can someone explain in detail how to select the sound output when I'm watching a movie over Airplay?

I have a fancy speaker system hooked up to the thunderbolt port on my MBP. It's no problem to choose that system in System Preferences: Sound or by clicking on the speaker icon.

But when I Airplay (via iTunes) to my Apple TV which is plugged into a projector via HDMI, the sound comes from the tiny projector speaker no matter what I have selected in Sound Prefs.

If I do screen mirroring it works but the video is super choppy. From iTunes, it ignores my sound prefs.

 

[Rufuss Sewell]

I just got off chat with Apple support. He had me do an SMC and PRAM reset but neither worked. Also in Safe Mode there was still issues. He gave up. Not sure what to try next.