Apple TV > Mac Mini audio passthrough

The Mac Mini has an optical input and an optical output. I want to route the audio from my Apple TV through my Mac Mini and then back out to my receiver. This way both devices are connected without any need for switching cables.

I use the app LineIn at the moment. This works good for listening music via AirPlay, the audio from my Mac also get combined with the AirPlay music.

But when watching a movie on Netflix with the Apple TV the 5.1 (AC3 I think) signal gives problems. It keeps disconnecting randomly. In this case no sound is played with the Mac. The Mac must only pass the audio through.

I also used this terminal command: defaults write com.cod3r.a52codec attemptPassthrough 1

It would be nice to enable this audio passthrough without the use of an app, is there a way to do that? Are there other ways to passthrough the audio, other programs, tricks? The way I have it now is not stable enough.