Headliner II

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

Forum|Forum|5 years ago
November 16, 2020
57 replies
20930 views

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

This topic has been closed for further comments. You can use the search bar to find a similar topic, or create a new one by clicking Create Topic at the top of the page.

Show previous replies

K

khaz22

Avid Contributor III

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

B

billiejoe87

Chromatic Producer I

@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.

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.

1 x Arc, 1 x Beam Gen 2, 1 x Amp, 2 x Sonos In Ceiling Speakers, 2 x Sub, 4 x Sonos Ones, 2 x Sonos Era 100, 5 x Symfonisk Lamp (Gen 2)

J

John B

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

B

billiejoe87

Chromatic Producer I

@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, 4 x Sonos Ones, 2 x Sonos Era 100, 5 x Symfonisk Lamp (Gen 2)

J

John B

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!

J

John B

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).

L

ledzep1Author

Headliner II

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.

R

RayCizel

Lyricist III

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.

Sonos Arc
Apple 4K TV
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.

R

RayCizel

Lyricist III

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: