Hi Pede67.

Welcome to the Sonos community and thanks for bringing this to our attention. I understand that you are having trouble listening to your Apple TV 4K through Sonos on a Dolby Digital format. Let me help you out.

Thanks for the detailed description of what works and what does not as you have perfectly described the isolation process in which you have made it clear that the issue is when watching video from Apple TV 4K as all other videos within the TV work fine. I would suggest trying to check if the audio format of the Apple TV 4K is also set to Dolby digital as the issue only happens when the source is your Apple TV 4K. I would like to share with you a guide from Apple’s support website on how to check and change the Audio format of your Apple TV 4K. I would also like to suggest after doublechecking to make sure that the Apple TV 4K is running on the desired/preferred audio format, please submit a diagnostic so we can check the Sonos behavior while having the video source from Apple TV.

Please let us know how it goes. We are always here to help.

Thanks,

I use an Apple TV app called Surround Speaker Check. I had a rather odd setup with a Beam and a tv that wouldn’t do pass through so used an HDMI splitter meaning it was hard to work out what my correct settings would be. The app will allow you to prove that you’re getting 5.1 surround correctly with a test track that also visually shows on the screen which speaker should be working. This allows you to adjust the Apple TV audio settings and prove which one facilitates your Sonos getting the correct signal. It’s more logical than just looking in the About section of the Sonos app.

 It doesn’t ‘prove’ ATMOS at time of writing but that can be seen quickly and easily in the screen of your Sonos app and only applies to the Arc. 

What audio settings do you have set on TV and apple box?

I have an LG CX and I think they are the same feature wise, and I get atmos and 5.1 fine from netflix and any other app on apple 4k box.

On TV I have sound settings set to passthrough and eARC on

Apple box left at default sound settings which says automatic/atmos available.