Just to clarify, are you saying that when you use Apple Airplay or a direct connection from the Mac book pro (MBP) you get DD 5.1 audio, but when using a cable connection-out from the MBP that goes through the TV to the Arc. you only get stereo? - if so, my thoughts initially, are perhaps your TV does not pass-through the DD codec and the handshake between devices therefore results in PCM stereo audio out only - perhaps try another audio source connected to your TV HDMI ports to confirm if it passes through the codec … and just to add that I’m sorry if I may have misunderstood your post as some things mentioned were not entirely clear to me, but I hope that the above information proves to be helpful.

Hi Ken, 

Thanks for your reply!
I can only get DD5.1 audio by air project, that not apple airplay but other windown app name "Xunlei", it`s the  same moive stream when I use directly connect from my HDMI to TV it will shows PCM stereo.

There are 3 HDMI interface for my TV and I tried but all same PCM stereo, and I also tried change the other HDMI cable 1.4, 2.1 but it`s same result.

I am not sure the issue from my TV codec or not, Sharp 2017 model it support DTS 2.0 and DD audio. I understand DTS 2.0 = stereo but change "RAW" that means all stream will forward to ARC but not perfor in TV itself.

But, it`s weird why air project way it can works DD5.1?

I’m sorry @James Ng, I don’t know the software you mention and I’m not quite sure I understand your setup, so can’t answer your questions, but maybe others here, reading your posts, will be able to assist.

My only initial thoughts were that your TV might not be allowing the DD5.1 audio to pass-through it’s ports and out to the Arc, but if that’s working with the ‘air project’ App then I don’t know the answer to your issue.

Hi @Ken_Griffiths 

No issue and thanks for your reply!  it will more easy to understanding for other.

Now we may eye on to hardware that why air project works DD5.1 but direct connect shows PCM stereo?

hi All,

Confirmed when connect from laptop to TV that sound card output stereo mode only, whatever you sets to "dobly speaker atoms" or "dobly headphone mode" enable or not, the laptop hardware litmit function when detect connected by HDMI it change the mode to stereo. that`s why Sonos app shows PCM and I can hear it`s absolutly different sound between DD5.1 and PCM.

whatever I use kinds of player like porplay or VLC etc, it will not works!  But if you use another connect method that laptop HDMI connect to ampluter, ampluter decode than connect to TV and speaker that plays DD5.1 or DTS 7.1 or Atoms perfectly but that`s not Sonos solution!

So, if you want to hear the DD or DTS from your laptop to TV, you can use air project to TV,  it use DLNA method it plays the DD5.1 or DTS5.1.

or,  refer solution like me,
laptop share movies to apple TV 4k, apple tv connect to TV,   it perfectly get the DD5.1 or DTS5.1 sounds.