Please read if you have encountered issues with 7.1 LPCM playback on Sonos via an LG TV

I’m not sure if this is the same thing. I have a Beam Gen 2 and a Sub Mini running off a ATV 4k 3rd Gen and an LG C2. Sometimes the Beam will play surround channels only with no centre (vocals). I usually need to reboot everything to get it working again. This isn’t just with 7.1 audio though. 

Hi @MJW75 

It’s a different issue, but not one that you should have to put up with.

The next time this happens, please submit a support diagnostic while it is happening and before trying to fix it. Once complete, record the number given then do what you need to do to resolve the issue. Then, when convenient, I recommend you get in touch with our technical support team who have tools at their disposal that will allow them to give you advice specific to your Sonos system and what it reports - give them the diagnostic number and they will be able to see what was happening at the time.

I hope this helps.

LG C2 2022

Netflix via Apple TV 4K (first gen)

Sex Education: S2E7

Apple TV into HDMI 1, HDMI 2 eARC out into Beam Gen2

Diagnostic: 2018107307

issue: front and rear channels swapped in playback

Hi @JakeG 

Thanks for that report - I have passed the details to a colleague.

Hi @JakeG 

There seems to be a discrepancy between the format reported and the format actually being delivered.

We can see that it is because of this that the channels are getting downmixed to the incorrect outputs. That's why FC (Front Centre) and LFE (Sub/Low Frequency Effect) get rendered to RRC (Rear Right Channel) and RLC (Rear Left Channel) (which we downmix to LS/RS) resulting in the dialogue coming from the surrounds.

So if the Apple TV sends 7.1 MPCM, and the TV isn't passing it through correctly (some kind of mapping bug), it comes out of the LG signalled as 7.1 but it's only 6 channels instead of 8, and in the wrong order.

We believe using the following settings will fix things for you, as they have worked in our own (limited) testing:

I hope this helps.

Speaking to the original question, I do have problems with mismapped channels. I think I’ve narrowed the issue down to the Apple TV 4K 2021. It’s the only source device experiencing the issue. The issue is that each front channel seems to come out of all front speakers at the same time, and each rear channel seems to come out of both rear speakers at the same time. I’ve also submitted this issue to Apple, FB13404270, in case any Apple devs are lurking. Since this only seems to happen with Apple TV, I don't think it’s a problem with Sonos, but I’m posting here just in case.

My setup:

Apple TV 4k 2021 → HDMI → LG CX 55” → HDMI eARC → Sonos Beam Gen 2 + 2x One SL as 5.0 surround

Configuration:

Apple TV:
Audio Output: Receiver Speakers
Audio Format: Auto, Atmos Available (Change Format: Off)
Audio Mode: Auto

LG CX:
Sound Out: HDMI ARC
HDMI Input Audio Format: Bitstream
Digital Sound Out: Pass Through
eARC: on

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Your LG TV model number: LG CX 55”

Your media source device name and model number or TV app that the issue was noticed on, and the name of the movie/show that was affected: Apple TV 4K 2021, Netflix Test Patterns: https://www.netflix.com/watch/80164785 (see here to show it in the Apple TV Netflix app: https://www.tomsguide.com/how-to/how-to-use-the-netflix-test-screens)

Models of any other HDMI devices connected to the TV (if applicable): Nintendo Switch, PS5, which are off during testing but independently map channels correctly

The confirmation number of a Sonos system diagnostic submitted while the affected media was playing and 7.1 LPCM was reported in the Sonos app.: 2109599949

This is a Sonos community board. I’d be terribly surprised if any developers, including Sonos developers, are ‘lurking’. 

I am happy, however, as an owner of several Apple TVs myself, that you’ve reported the issue to Apple,

Corry P works for Sonos and specifically solicited this feedback from the community in the original post.

Hi @exchgr 

Thanks! I don’t know if yours is quite the situation my colleague was looking for when he asked me to open this thread, but I will pass your report over to him nonetheless - it’s fairly close!

I started having problems with sound playing from the wrong channel sometime over the summer.  Have LG G2 (latest firmware), Apple TV(latest os), xbox - and sonos arc, sonsos one and sub.  It seems to happen quite often after using the apple tv youtube app - not sure if that means anything - or maybe it is just noticed more due to watching lots of youtube, heh (doesn’t happen in youtube, but seems to trigger it in other apps like plex, netflix, etc).’

Anyway, I tried the fix listed here - setting the digital audio from ‘auto’ to ‘pass through’ and that seems to have fixed the problem, so thanks!