My understanding is you need to switch off Multichannel PCM and switch to Bitstream and Atmos TrueHD codec on your compatible source device - Ensure eARC is enabled on the connected TV that supports the pass-through of that Dolby ‘uncompressed’ codec and play it to either the Sonos Arc, or Beam gen2 (connected to the TV’s eARC port) and you will then see Dolby TrueHD (Atmos) displayed on the Sonos App ‘Now Playing’ screen for the Arc Room.

I don’t personally have an Atmos capable player, or Atmos movie disc for that matter, but I have a Dolby TrueHD player and Blu-Ray movie and if I switch that from LPCM to Bitstream and Dolby TrueHD, I have no issues here getting a Dolby TrueHD source to play on Sonos. See screenshot attached. I assume the same would work for DD TrueHD (Atmos) had I got the components to play that audio source.

I’m also quite fortunate (lucky) because my TV also passes through DTS 5.1 audio, (more luck than any judgement on my part) so I can leave the connected player set to Bitstream, rather than Multi-Channel LPCM. It’s a ‘slight’ pain otherwise having to switch these settings.

I only really need the Multichannel PCM codec if the disc has DTS-X/HQ audio only - but I have all but given up on Blu-Ray discs and switched to the streaming services now anyway. DD+ 5.1 (with/without Atmos), albeit compressed audio, is fine to my ears and just so much easier and convenient to stream from Netflix/Disney+ etc.

What exactly are you playing? From what device and app? What model TV do you have?

Hi @Revsl 

Welcome to the Sonos Community!

Sonos will downmix 7.1 to 5.1, so you will not be losing any audio channels - they’ll just be played out of different speakers than if you had a 7.1 system.

I hope this helps.