Dolby 5.1 content outputting as multichannel PCM 7.1 (since LPCM update)

  • 16 November 2020
  • 57 replies
  • 19182 views
L
Userlevel 5
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Hi

Thought I would create this thread as a few have reported this issue in the lpcm update threads that are marked as solved so perhaps best to keep it separate.

Issue:

Before the LPCM update last week my sonos arc would receive atmos and Dolby digital 5.1 from the Apple tv 4k box, audio settings were set to the default AUTO-Atmos available.

My LG CX is capable of passing LPCM.

 

Now since the LPCM update with the above settings I still get atmos from apps such as netflix, apple tv + on the apple 4k box, but any content in dolby 5.1 is now outputting as multichannel PCM 7.1, 7.1 being the issue, it should be outputting as multichannel PCM 5.1

 

I have seen similar posts with this issue on the same device and other devices as well.

 

Thank you 

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57 replies

Corry P
Userlevel 7
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 Hi Everyone,

Well, this is embarrassing!

After some investigation, I’ve found that downmixing of 7.1 channel LPCM to 5.1 channel LPCM was indeed implemented on the Arc as a feature last year, but our literature wasn’t properly updated to reflect the change.

To be clear, the Arc does downmix 7.1 LPCM to 5.1, has done for some time, and we are working on updating our documentation to reflect the fact. Beam (Gen 2) has always supported LPCM and has always downmixed.

Thank you all for pointing this out to me so we can now make sure that this information becomes public. I’m sorry for the unnecessary confusion. I’ll post this in multiple threads.

This other issue with LG TVs is unrelated, but we’d very much like to get on top of it. We’ve requested the investigation of LPCM channels being played from the wrong speakers when an LG TV is involved, specifically when 7.1 channels are reported, and we will reach out to LG with details once we’ve gathered some solid evidence for them. Therefore, we’d very much appreciate it if anyone affected by this specific issue would visit this new thread I’ve made for gathering some details. Thank you.

 

"Common sense is the collection of prejudices acquired by age eighteen." - Albert Einstein
S

@RayCizel 

I believe the fault lies not with Apple TV, but with the Sonos ARC+LG CX combination. The problem with this combo is that they advertise to the client (I have tried PS4 and NVidia Shield TV Pro) as being capable of 7.1 LPCM. However, if one actually sends 7.1 LPCM with passthrough to Sonos, the 2 rear channels will be silent.

On the PS4, this can easily be demonstrated by doing a 360-degree rotation with respect to a sound-emitting object, and the sound will be almost inaudible when the object is right behind you. On the PS4, one can explicitly select 5.1 instead of 7.1 so that the PS4 will only send 5.1 sound-mix to Sonos. The 360-degree test will now sound normal.

On the nVidia Shield TV however, there is no option to choose 5.1 -- this creates a problem in apps/games that output 7.1 channels.

This issue is now being tracked in the following thread:

https://en.community.sonos.com/home-theater-228993/ps4-pro-outputting-pcm-via-lg-cx-shows-multichannel-pcm-7-1-for-sonos-arc-but-rear-surrounds-have-no-audio-6850771

Note: this has nothing to do with Dolby-encoded signals (DD, DD+ or TrueHD, with or without embedded Atmos), which can be correctly decoded and played by Sonos. This also has nothing to do with HDMI 2.0/2.1 -- assuming that both the TV (LG CX) and Sonos ARC have already been properly connected with HDMI 2.1 eARC.

R
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@Naekyr 

Their is lots of technical jargon that can go along with it but to simplify it. 
 

If you’re playing something and it says MULTICHANNEL you’re not getting the TRUEST FORM of sound output. 
 

If it says LPCM 7.1 or 5.1 WITHOUT MULTICHANNEL attached to it then your getting the TRUEST FORM of sound possible. 
 

Not to say MULTICHANNEL doesn’t sound good, but audiophiles want PURE PASSTHROUGH SOUND without the MULTICHANNEL gimmick. 

N
Userlevel 5
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can someone explain why these are different and what the difference is?

 

  • Multichannel PCM 5.1
  • LPCM 5.1
  • Mutichannel 5.1

 

My brain wants to think those are all the same thing, but apparently its not - why??

SONOS ARC | SONOS Sub | SONOS Play 1 x 2 | LG C9 OLED | PS5 | RTX3090 Gaming PC | Sennheiser GSP600 Headset | Audio Pro T8L Desktop Monitors
R
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@ledzep1

 

I’ll explain.

 

If you have the LG CX set on earc and PASSTHROUGH 

 

When playing a physical 4K Disc in your Xbox (which supports Atmos and HDMI 2.1) and you’ve applied the latest update from Sonos to your Sonos Arc Soundbar / Sub etc 

 

And while playing a 4K disc within your Xbox does it show in your Sonos App under “About” that it is playing in “Atmos” if so great. Now pop in another NON Atmos 4K or Blu-ray into your Xbox - play it - Check in your Sonos App (while playing the NON Atmos movie) and check “About” does it show LPCM 7.1 / LPCM 5.1? If it does that means it is truly passing through. 

 

If it shows LPCM 7.1 MULTICHANNEL or 5.1 MULTICHANNEL that means it is not PASSING THROUGH correctly. 

 

MULTICHANNEL is the key word while Looking at your Sonos App while playing a NON ATMOS movie. If it says MULTICHANNEL then it is not working as it should be. 

 

IF IT DOESN”T SAY MULTICHANNEL that means it is pass through correctly and that the problem lies within the PHYSICAL APPLE 4K TV AND “THIN” APPLE TV APPS PROVIDED WITHIN THE CX AND Xbox and PS5 Apps.

L
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@ledzep1


What happens if you pop an actual 4K disc in?

 

Does it play Dolby Atmos correctly via Passthrough? Also any other disc that doesn’t have Atmos. Does it passthrough?

 

This is a test I can’t perform based on the limitations of my PS5 and lack of Dolby Atmos output. 
 

If it does both those tests correctly via PASSTHROUGH is enabled on your TV then it still points to the physical Apple 4K TV and thin downloadable Apple TV apps we’re all experiencing problems with.

 

If this test doesn’t work using physical media then it very well could be an issue between Sonos Arc and the CX.

 

Still doesn’t takeaway from the other points stated but I’d be interested to know the results of this.

 

Hi

I don’t really understand all your response, but on the Xbox I only play games and I have audio output set to uncompressed 5.1, playing games the Sonos app reports multichannel 7.1

I can play uhd discs fine on my Blu-ray player and get atmos.

It would be nice to get some response from Sonos, they seem very quite on here lately.

R
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@ledzep1


What happens if you pop an actual 4K disc in?

 

Does it play Dolby Atmos correctly via Passthrough? Also any other disc that doesn’t have Atmos. Does it passthrough?

 

This is a test I can’t perform based on the limitations of my PS5 and lack of Dolby Atmos output. 
 

If it does both those tests correctly via PASSTHROUGH is enabled on your TV then it still points to the physical Apple 4K TV and thin downloadable Apple TV apps we’re all experiencing problems with.

 

If this test doesn’t work using physical media then it very well could be an issue between Sonos Arc and the CX.

 

Still doesn’t takeaway from the other points stated but I’d be interested to know the results of this.

 

R
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@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. 

L
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@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 device devices TVs/cables/and other peripherals THAT HAVE HDMI 2.1 support that seems to lack it. 

 

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.

V

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. 

R
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@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. 

V

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

R
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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. 

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@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. 

L
Userlevel 5
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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.

R
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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

L
Userlevel 5
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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?

N
Userlevel 5
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Sonos released a new update today

 and someone test if it fixed this issue? 

SONOS ARC | SONOS Sub | SONOS Play 1 x 2 | LG C9 OLED | PS5 | RTX3090 Gaming PC | Sennheiser GSP600 Headset | Audio Pro T8L Desktop Monitors
R
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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.

R
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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. 

L
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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.

J

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).

J

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!

B
Userlevel 4
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@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.

1 x Arc, 1 x Beam Gen 2, 1 x Amp, 2 x Sonos In Ceiling Speakers, 2 x Sub, 9 x Sonos Ones, 5 x Symfonisk Lamp
J

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

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