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


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Hi,

We want to gather some details from people experiencing issues with playback of 7.1 LPCM audio streams on a Sonos Arc or Beam (Generation 2), via an LG television set. Specifically, when channels are playing from the wrong speakers - for example, but not limited to, if you hear dialogue only coming from the rear speakers, consistently.

If you have experienced this channel mis-mapping, please provide, in this thread, the following details:

Your LG TV model number

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

Models of any other HDMI devices connected to the TV (if applicable)

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.

Thank you for your assistance.

 

 


73 replies

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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. 

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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

Userlevel 7
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Hi @JakeG 

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

Userlevel 7
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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.

Userlevel 1
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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

---

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,

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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.

Userlevel 7
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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!

 

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Just for information, I don't have problems of wrong audio channels, but with lg C1, arc, sub gen 3 and two one as surround the “source also consistently shows as “multichannel 7.1” problem is completely solved with Apple TV 4K 3rd generation (2022) in fact now always shows "multichannel 5.1" when the track is in that format

Confirming that upgrading from a 2nd gen to a 3rd gen Apple TV 4K fixed all my multichannel PCM 7.1 mapping issues. Now the Sonos app shows multichannel PCM 5.1 for 5.1 content, and everything is mapped correctly. So this issue definitely lies with the 2nd gen Apple TV 4K. Since the two generations run the same tvOS, I’m assuming this is a hardware issue in the 2nd gen.

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Hi @exchgr 

Thanks for the update - glad to hear you got things working properly.

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I’m having some serious channel mismapping issues with my setup. I’ve got an LG C2 and a Sonos Beam Gen2 with 2 Era’s as Surrounds using eARC (Bitstream, Pass through). I recently purchased an Apple TV 4K (Gen 2) where everything is converted to LPCM 7.1, even 5.1 signals.

Generally higher end Bluray Remuxes and Dolby Atmos stuff (over DD+) seems fine. However, I’ve watched an episode of Rick & Morty in Dolby Digital 5.1 which sounds very weird. Dialog coming from the the sides rather than front. If I set “Change Format” to “Dolby Digital 5.1” in the Apple TV settings, everything is fine. Unfortunately that severly degrades audio quality for other higher end sources.

Is there a fix in the works for the 2nd gen Apple TV or do i need to upgrade to a 3rd gen?

Diagnostics number: 1022034678

Userlevel 1
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I’m having some serious channel mismapping issues with my setup. I’ve got an LG C2 and a Sonos Beam Gen2 with 2 Era’s as Surrounds using eARC (Bitstream, Pass through). I recently purchased an Apple TV 4K (Gen 2) where everything is converted to LPCM 7.1, even 5.1 signals.

Generally higher end Bluray Remuxes and Dolby Atmos stuff (over DD+) seems fine. However, I’ve watched an episode of Rick & Morty in Dolby Digital 5.1 which sounds very weird. Dialog coming from the the sides rather than front. If I set “Change Format” to “Dolby Digital 5.1” in the Apple TV settings, everything is fine. Unfortunately that severly degrades audio quality for other higher end sources.

Is there a fix in the works for the 2nd gen Apple TV or do i need to upgrade to a 3rd gen?

Diagnostics number: 1022034678

I haven’t been able to get a response from Apple on this re: the Apple TV 4K gen 2, but I can confirm that the Apple TV 4K gen 3 fixes this particular issue. With Apple TV 4K gen 2, 5.1 surround sources were converted to Multichannel PCM 7.1 and the channels were incorrectly mapped, whereas with the Apple TV 4K gen 3, 5.1 surround sources are converted to Multichannel PCM 5.1, and everything is mapped correctly. I assume it’s a hardware issue that got fixed in the latest gen, but I can’t be sure.

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I`ve made some little different experiences with LPCM and my Sonos system.

 

I own a LG C2, Sonos Arc with 2 Era 300 and Sub & Apple TV 4K, newest Gen.

I use the system for atmos, and most of the time it works flawlessly.

 

But sometimes when I start a stream (e.g. Amazon Prime) all voices are missing and I can only hear the music and some effects. I have to restart the stream an everything works fine again.

 

And sometimes I only get stereo PCM although I know, that it should be Multichannel PCM 5.1.

A new start of the stream or sometimes closing und opening the app again helps.

 

So for me it could be a problem of mapping the LPCM the right way. But who is guilty in the row? (Apple/LG/Sonos)

 

Has anyone had similar experiences?

 

 

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Noone?

 

Yesterday in PrimeVideo again - 5.1 Multichanel was recognized as Stereo PCM = I cannot hear voices, only music.

 

Even restarting the app did not help. Only after playing a stream with real Stereo PCM the 5.1 Multichanel on Amazon was recognized correctly.

 

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I have same issue, LGCX, Beam 2, sub, 2x 1 sl’s. Blu ray 5.1 dts-hd discs play in multichannel 7.1pcm.

I can get the standard dts 5.1 surround via a work around (optical out on the ub820 conv to hdmi), but it means swapping out the hdmi leads at the back of the soundbar each time i want to watch a dts film.

My question is: 

Given the 7.1 to 5.1 down mix issue? Which is better, multichannel 7.1pcm or the just the standard dts 5.1 surround ?

Thanks M

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Hi @Professio7 

Thanks for the diagnostic - I will forward it on to my colleague.

It does seem to be a hardware issue, so I don't know if there will ever be a fix made available - it would be best to ask Apple.

 

Hi @hitmaker77 

Apologies - I have been off for a while.

The next time this happens, please submit a support diagnostic immediately afterwards and report the given number here when convenient. Thanks. Please note, however, that it is unlikely that we will be able to resolve this for you.

 

Hi ​​​@mac74 

Given the 7.1 to 5.1 down mix issue? Which is better, multichannel 7.1pcm or the just the standard dts 5.1 surround ?

Assuming the source media contains the DTS track, it’s better to just select that to be played to your Beam. It’s likely that the McLPCM track is being created from that anyway, so there shouldn’t be any quality difference.

 

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@Corry P 

It happened again.

Diagnostic number: 1039983902

 

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Hi @hitmaker77 

Thanks! - I’ll pass that along to my colleague.

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Hi @hitmaker77 

My colleague reported finding the same issue on occasion when testing with the latest revision of Apple TV hardware (Gen 3).

He mentioned that he found that the easiest way to force a renegotiation between the devices is to disable eARC in the TV’s settings, then re-enable - it should be easier than having to start different media.

I hope this helps.

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Thank you.

 

So is it a special Apple TV (handshake) problem with no chance of a solution from Sonos side?

 

It is not a very big problem because it does not happen very often.

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Hi @hitmaker77 

It seems that way, yes - if a renegotiation between devices helps, then something went wrong with the negotiation in the first place, presumably. I’ve only heard of such reports from LG owners, however, so it may not wholly be Apple’s issue to address. I really don’t know enough about it to say anything for sure here.

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