PS4 Pro outputting PCM via LG CX shows Multichannel PCM 7.1 for Sonos Arc, but rear surrounds have no audio



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I have a similar issue. I just changed from a beam to a beam gen2. I am using an Apple TV as source with an lg cx tv. When using the earc connection and digital out passthrough on the tv I get multichannel pcm 7.1 whenever I play any dolby 5.1 on the Apple TV. Changing the digital out to auto it changes the signal to Dolby Multichannel PCM 5.1. A similar thing happens on the ps4 using pcm. I feel like the lg cx is telling source devices to send multichannel pcm 7.1 instead of multichannel pcm 5.1.

Passthrough is exactly what it sounds like, the audio is “passed through” the TV exactly as it comes from the source.  So if the source is 7.1, you get 7.1.  

While that may be true LG is doing some processing even when set to passthrough. Both my Apple TV and PS5 send a 7.1 signal instead of 5.1 even when the audio source is 5.1. LG have been absolutely silent on the issue and I don’t see them ever fixing the problem. Once Sonos adds down mixing, in theory everything should be fixed but for now LG owners will have to continue to keep their audio out to ‘auto’ which unfortunately means losing surround sound for the Nintendo Switch and fully lossless audio. 

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Perhaps its not an issue as such, and just how the lg and sonos arc report everything in LPCM as 7.1.

I must admit when the sonos arc reports something as multichannel pcm 7.1 it sounds fine to me.

i don’t have any rears though, just the ARC and Sub here.

 

In any case It would be nice if someone from support could respond, as much as I love sonos, I think their communication could be a lot better.

 

So this down mixing feature/fix do you have any update sonos support?

I’m sure even the sonos ceo tweeted a long while ago that its in the works and in active testing. I can’t find the tweet now though. Please respond sonos, silence is not a good approach.

I recently bought a Beam 2 and have it hooked up to a new LG CX and an Apple TV. I am seeing the same behavior as others with Multichannel 7.1 being displayed in the Sonos app when watching non-Atmos content with eARC enabled and pass through on the ATV. 

However using the native Smart TV apps on the LG for Netflix, Prime and YouTube TV i get different results. With eARC enabled and output set to pass through everything works - I get DD 5.1 when watching Netflix/Prime/YouTube TV 5.1 content and Atmos when watching Atmos content. Everything actually sounds great.

On my Shield the only issue I get is with DTS content and since I know LG will not pass through DTS - Sonos outputs Multichannel PCM 7.1 through Kodi. This is less of a concern as i rarely use Kodi on this TV. Either way, this is somewhat expected given LG’s inability to pass DTS.

So at this point I guess my ATV is a doorstop until someone fixes this. Which is a shame as I love it. I can’t be bothered constantly switching between Auto/passthrough or toggling eARC on/off. I’ll use the native LG apps for now. This thread is more than a year old so I’m guessing that may never happen.

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LG G1

Apple tv 4k

Sonos Beam 2

 

also still waiting for downmixing 7.1 to 5.1 bug to be input to use pas trough on my tv….

 

one year…. Still nothing 

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LG G1

Apple tv 4k

Sonos Beam 2

 

also still waiting for downmixing 7.1 to 5.1 bug to be input to use pas trough on my tv….

 

one year…. Still nothing 

 

There was an update today, version 14.0, not had chance to check it out yet.

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LG G1

Apple tv 4k

Sonos Beam 2

 

also still waiting for downmixing 7.1 to 5.1 bug to be input to use pas trough on my tv….

 

one year…. Still nothing 

 

There was an update today, version 14.0, not had chance to check it out yet.

Yep
Tested yesterday and problem still here.

Add me to the list with this issue: LG CX, apple tv 4k 2021, sonos arc, sub, ones.

Still not understanding if lg or sonos issue, but who am I to figure this out. I just want a proper working setup...

I created an account on this forum exclusively to comment on this thread about how disappointed I am that this multichannel LPCM issue hasn’t been fixed. I get absolutely nothing (no sound) when using lpcm on any setting other than stereo on my CX. Some sources can change their output to something like dolby, but some can’t, and for those that can’t, you’re stuck with stereo...its not a small deal if you invested enough in the ecosystem to get a 5.1 system.

 

Whether sonos or lg, I just wish someone would fix this. 

Just thought I’d chime in how annoying it is. Also not sure whether it’s LG or apple that’s the problem but my main issue is the loss of volume when 5.1 is output to 7.1.  All channels output to the right speaker, but it’s like the gain is the. 50% of all other sound formats.  Stereo and Atmos come through fine.  Only 5.1 passes through as 7.1.  

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Seems like this is not just an LG issue, I have the following setup/problem:

HARDWARE

- Philips 55OLED856/12

- AppleTV 4K (2nd Gen)

- Sonos Arc, Sonos Sub, 2 Sonos One’s as Surrounds

CONNECTIONS

- Sonos Arc connected via HDMI-2 - eArc

- AppleTV Connected to HDMI-1 - Arc

TV Audio Settings

- Audio Output - HDMI Sound System

- eARC - Automatic

- Digital Out Format - Multichannel (bypass)

AppleTV Audio Settings

- Audio Output - Receiver Speakers

- Audio Format - Auto

- Audio Mode - Auto

 

When playing video from AppleTV that is in DolbyAtmos/DolbyVision all the sound is sent to the correct channels. When playing video that is not in DolbyAtmos (normally from Disney+, Netflix or Amazon Video) the audio is not being sent to the correct audio channels. It seems that the Voice Audio that would normally come from the centre channel is being sent to the rear surround channels.

 

I have tested and this appears to be only be happening when the video/audio is coming from the AppleTV. I have tested Netflix and Disney+ from the AppleTV - TV - Arc and the audio that is sent to the Arc is passed as Multichannel PCM 5.1. When this happens the audio for Voice that would normally be played via the centre channel is coming though the rear surrounds. However, if the audio passed from Netflix, Disney+ apps is DolbyAtmos the sound is coming correctly to the right channels.

I tested the Netflix, Disney+ etc apps that are natively installed on the TV and the Audio sent from the same shows is sent as Dolby Digital Plus 5.1, (not Multichannel PCM. 5.1) and this audio comes through to the channels correctly.

The problem seems to be with the encoding of the Audio when it is received from the TV eARC as Multichannel PCM 5.1, as the audio (voice) channel are mixed up and played through the rear surrounds.

I am not sure if this problem is with the TV or how the Arc is determining Multichannel PCM 5.1.

 

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Perhaps its not an issue as such, and just how the lg and sonos arc report everything in LPCM as 7.1.

I must admit when the sonos arc reports something as multichannel pcm 7.1 it sounds fine to me.

i don’t have any rears though, just the ARC and Sub here.

 

In any case It would be nice if someone from support could respond, as much as I love sonos, I think their communication could be a lot better.

 

So this down mixing feature/fix do you have any update sonos support?

I’m sure even the sonos ceo tweeted a long while ago that its in the works and in active testing. I can’t find the tweet now though. Please respond sonos, silence is not a good approach.

 

Hey look at this, 3 months ago, posts since and no response from sonos support on anything in this thread for ages.

I have resurrected a few threads on the subjects to keep the possible issue highlighted and to show how poor sonos support has been on giving updated feedback on any progress, they did say they were working/testing this a long while back.

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I’ve raised this again in another thread and had a response from Sonos that this is not a bug apparently

https://en.community.sonos.com/home-theater-228993/sonos-arc-and-7-1-downmix-to-5-1-6863804

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That is correct it is not a bug. What is is poor design choices and poor quality assurance during testing on Sonos part, knowingly and or unknowingly releasing a feature that would inherently lead to push back from users - whether they had anticipated this or not is irrelevant, the fact is it happened. 
 

The reason it's not a bug is because the feature claims to work with 5.1 lpcm and it does; the thing is Sonos never bother actually testing the feature using consumer products that users would have to use, they either used some in-house custom audio equipment or just did all work in virtual environments. If they had tested this feature using consumer audio visual equipment they would have seen that they had a big problem with the way lpcm is handled by audio equipment.

 

Sonos has designed its LPCM support using a fairy tale lalaland idea of how its speakers would interact with other audio visual equipment and this is the outcome. It's still not bug though. I don't know how LPCM support is advertised for the Arc’s product page I haven't checked the main Sonos site in a while but they should possibly just remove all mention of LPCM and stop selling the ARC to people who expect flawless LPCM playback; it's reasonable for users who spend lots of money to expect something to just work without excuses so if they can't deliver that then stop advertising it that's my opinion 

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I have resurrected a few threads on the subjects to keep the possible issue highlighted and to show how poor sonos support has been on giving updated feedback on any progress, they did say they were working/testing this a long while back.

I'm not sure intentionally cross posting on a forum is a very good idea.

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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.

 

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