ledzep1,
I see this in the ‘About my Sonos System’ for the Arc when playing an ATV Netflix DD5.1 source, but it’s an LG C9 TV and an Apple 4HD (not 4K) (just set to ‘Auto’ audio out). So not sure if that is what you’re looking to see as your output/input? I’d expect the ATV 4K to output the same audio, but note I am running the latest ‘public beta’ of Apple’s tvOS software.

 

Tried your suggestion still same, in fact I can get multichannel pcm 5.1 if I change my LG cx audio output to AUTO instead of passthrough, but that’s not ideal because I need passthrough for full fat atmos.

So I think the issue is the cx perhaps , but not sure.

ledzep1,

The A/V source from ATV4 that I was playing to get that audio output shown was a TV series called ‘The Fall’ S01E01, if that also assists?

@ledzep1 .  It may be that there is no single set of settings for various sources that will always deliver the format you want to the Arc.  If there is, i suspect it doesn’t involve ‘bitstream’ for the TV audio output.

The Arc isn’t going to process the audio, it is going to play what you send it (or nothing), IMO.

Just to add, my LG HDMI eARC port is definitely set to pass-through - as you can perhaps just make out in the attached screenshot, hopefully?
 

I would try the ‘powering off’ suggestion,  I mentioned earlier as it might just resolve the handshake. Maybe power off the ARC completely too.

Well take the Apple TV 4K for example on auto audio settings it sends atmos where available or LPCM, so any Dolby 5.1 content will play on the arc as multichannel channel pcm 5.1.

But for me it’s playing as multichannel pcm 7.1 

I don’t know what else to say really, it’s been said by others as well so I will leave it there and hope someone from Sonos will be able to tell me what the issue is.

@Ken_Griffiths thank you I did try power off, but no luck, it seems to be an issue with cx or later models of LG I think, anyone else with cx have same issue?

I am having the same issue with LG Nano91.  Switching the TV to Auto does send the Arc 5.1, Passthrough sends 7.1

You are a little confused here.

What you have written does apply to formats like DTS which the Arc cannot process.

PCM is different. Every Soundbar/AVR/TV in the world supports PCM. How many channels of PCM they support however does differ (Stereo 2.0/5.1/7.1). It is up to a soundbar like the Sonos Arc to tell a device like a nintendo switch or TV if it supports more than just plain vanilla Stereo PCM. The only reason any device will send a 7.1 signal is if the Sonos Arc is telling it that it can process it. Note that until Sonos did their multichannel PCM update the Nintendo Switch only ever sent regular PCM Stereo 2.0 to the Sonos Arc.

In this case Sonos need to either have the Sonos Arc not incorrectly tell other devices it can process 7.1 LPCM or downconvert it to 5.1. In any case it is completely different to formats like DTS which are proprietary and not supported at all.

@billiejoe87 .  Thanks, that’s a very clear and enlightening explanation.  I wouldn’t say I was ‘confused’ on this point, rather ‘lacking in knowledge’.

Sorry, I wasn’t trying to sound rude. Just trying to explain that PCM is different from Dolby and DTS in that every system in the world supports it, as in it’s most basic form PCM is stereo. It’s just up to a device to negotiate how many channels it can support which seems to be where the problems with devices like the Nintendo Switch and Apple TV are having.

All in all somewhere along the line it is most likely that LG TV’s and the Sonos Arc are not handshaking correctly which is causing the issue.

There is no need to say sorry. I meant my previous post and wasn't in the least offended by your comments, which weren't rude at all.

In the last bit of my post I was trying to say that confusion implies a partial understanding,  which if anything was generous on your part!

I think I owe an apology to @ledzep1 , too.  I clearly did not appreciate the difference in nature of PCM and the degree of user control over its form (or relative lack of control).

No you don’t. You were trying to help. 

I just hope Sonos can look into this, as a few of us have noticed this now.

Yea I’ve tried all the above, very frustrating considering the amounts of money we’ve all spent for this setup to finally get “the update” that was supposed to correct all this. 
 

This isn’t IT but that’s what I do for a living so troubleshooting is in my wheelhouse but we’re talking about 3 different devices trying to make this happen. 
 

1. Sonos Arc
2. Apple 4K TV 
3. LG CX 

Personally I think Sonos will have to be number one at solving this as Apple and LG probably could care less given other equipment beyond Sonos (maybe working fine) Sonos please get this solved as this is a major issue and what was to be a game changer has been a total bust. 
 

Also interesting enough I actually traded in my Bose 700 series Soundbar and Sub (for this) - (which didn’t support Atmos BUT it too had the same idiotic sound malfunctions (judder sound/ make out every other word) going from ANY (movie) which did have Atmos as an option (even though the Bose 700 didn’t support it. To remedy it I had to play a Dolby Vision or 4K HDR movie which didn’t have an Atmos track on it in order to reset the sound back to “normal”

SAY ALL THAT TO SAY THIS it was happening on Bose as well. Which to me points to Apple TV and or the CX.

Or worse, both. 
 

Another idea is Apple 4K TV doesn’t support HDMI 2.1 - which could be the culprit all along trying to feed all these other components including cables with this newer technology. 

Found this: 

https://www.google.com/amp/s/www.trustedreviews.com/news/new-apple-tv-box-3944661/amp

Biggest thing is this in this article: 

What does the new Apple TV 2021 look like?

One thing that has been consistent about the new Apple TV box is that its the physical design will remain the same.

That’s not to say it couldn’t use an update. The current box has a single HDMI 2.0 output and a move to HDMI 2.1 would enable eARC for Atmos audio.

So the bottleneck very well could be the current Apple 4K TV itself.

Sonos released a new update today

 and someone test if it fixed this issue? 

app or system update?

*Just checked for updates and no updates available , I’m on 12.2.1, Im guessing you only just updated this or do you have newer version?

I’m telling you guys, to me (and this is now my own personal theory) is that the Apple TV 4K is the reason none of this works like it should. Based on these facts. 
 

1. using local Apple TV native App on the LG CX doesn’t have sound or judder switching in between different audio formats - although the audio is not the same or yield as good of audio as what can be provided via an actual physical Apple 4K TV device 
2. Physical Apple 4K TV only has HDMI 2.0 - speaking in technical terms like as if in I.T. You can can have a GIGABIT router but if you feed a 10/100 switch whatever devices are plugged into the 10/100 switch will only get 10/100 AND NOT GIGABIT speed (bottleneck) 
3. This was happening on the Bose 700 series (which it didn’t have Atmos BUT DID HAVE HDMI 2.1) 

I’m chalking it up to ATV4K at this point. If I’m wrong I’m wrong it just makes logical sense and eliminates all other possibilities as every device (TV/cables/Sonos Arc) provides HDMI 2.1

It happens on my Oppo 203 and Xbox series x as well, which the latter is hdmi 2.1.

@ledzep1

I have a PS5 (which it too has HDMI 2.1) as it doesn’t offer DV nor Atmos. 

Key thing I’ve noticed with the Apple TV app on the PS5 (like the Native app on the CX) is there is no way to go into the Native Apple TV app and adjust any sound settings within the “thin client” which is provided on the CX/PS5 thin client apps - can’t speak for Xbox. 
 

Thin client ATV apps are a great option but aren’t relatively based or designed as a replacement of a Physical Device such as a player (Apple 4K TV) which was designed to output specified settings and overall architectural design. 
 

kind of like playing Madden Mobile vs Madden on a Xbox or PS - just isn’t the same thing/experience. Might have the same name but isn’t the same thing. 

And in no way is this meant to sound argumentative. 

Think of it this was as well. 
 

If the CX / Sonos Arc / and the current physical Apple 4K TV all have HDMI 2.1 and your HDMI cables were older and outdated and don’t support HDMI 2.1 then the bottleneck would be your cables. 
 

I believe Sonos has actually held their end up by providing this update to support all these new features and that based on isolation it isolates to the ATV4K. 
 

I believe this not be a software issue but rather a hardware issue with the limitations being that of the HDMI infrastructure built within the current ATV. 
 

As of writing if you do your research no one is claiming they’ve gotten this setup to work with everything setup like the way we have it. In addition to the lack of HDMI 2.1 on ATV4K could also explain the handshake not happening properly switching between Atmos and other audio formats. 

I’ve been having the same problem recently with my AppleTV 4K. The file playing is a Dolby Digital Plus 5.1, but according to the Sonos app it’s playing as Multichannel PCM 7.1. 
Result is usually that I can’t hear any speech in movies, only the music…

If I play the same file directly from the TV, then it seems to work correctly… so not sure if it’s maybe an issue with the AppleTV…. I’ve tried Infuse, Plex, Netflix, they all suffer from the same problem.
 

using tvOS 14.2

Sonos Arc + Sub + 2x One’s with version 12.2.1 

AppleTV → HDMI → LG OLED65CX6LA → eARC → Sonos Arc

@Veldkornet

As I stated based upon my own personal belief is this entire problem lies within the Apple 4K TV and it’s lack of HDMI 2.1 support which rests on its own hardware deficiencies as it’s only capable of handling HDMI 2.0. 
 

I have heard the LG CX has a new update out (3.11.41) which hasn’t pushed out yet to my LG CX 65’ but am interested to see if it can offer anything. 
 

Hardware is Hardware so if my theory holds true no software/firmware will fix a hardware port designated and designed only for HDMI 2.0 (ATV4K) there is just no way around it as it’s embedded and fixed into the hardware itself which so far is the only culprit amongst all devices TVs/cables/and other peripherals THAT HAVE HDMI 2.1 support that seems to lack it. 

Hmm, my CX is still on 3.11.25, I’ll keep a look out for it though.

What a pain in the ***, the AppleTV was working so nicely until recently. 

You mean 3.11.30?

That was released to a lot yesterday, but it doesn't fix the issue. Also I think I replied to you when you mentioned its the fault of the apple tv 4k because a lack of hdmi 2.1 support, if that’s the case why does my series x (hdmi 2.1) exhibit the same issue

I have the series x set to uncompressed 5.1 and sonos app reports multichannel pcm 7.1.

I think the issue lies with the LG CX or the Sonos.

@ledzep1

I believe I responded to you as well. I have a PS5 (HDMI 2.1) but doesn’t have Dolby Vision nor Atmos (which is ridiculous and makes it irrelevant to your question) 

What I believe with respect to your Xbox is you downloaded the “THIN Apple TV app) on your Xbox. 
 

If you go within your Apple TV App on your Xbox and go under settings you’ll notice their is no “sound options” LIKE within an Actual Apple TV to make any sort of output adjustments in regards to sound (JUST LIKE THE BUILT IN THIN CLIENT ON THE LG CX) 

Because BOTH your Xbox and even the LG CX lacks this feature it rules out your HDMI 2.1 your Xbox is capable but handicapped by the THIN APP at this point JUST LIKE the LG CX (which in all honesty should be the FULL PROOF WAY of getting around this BUT because it’s a THIN WATERED DOWN VERSION of Apple TV you get handicapped by the Limitations of the App itself. 
 

I know it seems ridiculous but THATS EXACTLY WHAT IT IS.