Hello. Here is my set up:
1) Apple TV connected to Sony XBR-65X900F via HDMI - Audio output set to Dolby 5.1
2) Cable box connected to Sony via HDMI.
3) Sonos Beam connected via HDMI/Arc to Sony.
Here's the issue: I am getting great audio from Cable box and most things on Apple TV. Netflix outputs 5.1 through Beam (as per "About my Sonos")
iTunes movie rentals and certain TV shows output 5.1 and the audio is great.
Apps & SOME TV shows purchased on Apple TV do not output any sound to Beam.
It's very strange that 95 % of things I watch on the Cable box and Apple TV work and a few don't. Does anyone have any ideas?