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

Corry P
Userlevel 7
Badge +18

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.

 

 

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

62 replies

Corry P
Userlevel 7
Badge +18

Hi @Mutiny 

When switching to PCM on console the app shows Multichannel 7.1. Sound feels flat, volume is low and it feels like i am losing surround too, not sure how to describe it.

This is probably expected - as I mentioned earlier, I have a Samsung BluRay/Amplifier, and if I play 7.1 sources I need to crank up the volume, often to twice that I’d use on another source. It should sound more tonally balanced once you turn up the volume. If it’s not to your liking, all I can suggest is to not use the PCM setting.

Compromising to Dolby or DTS on console gives me the best result though, sound difference is quite amazing. Not sure of how much of a “compromise” it is from a technical standpoint, but it is what it is.

Apart from the difference in dynamic range - which you’ve already noticed and can be a hindrance when not in a cinema - you’re unlikely to be able to tell the difference in quality. Dolby and DTS are lossy formats, so some information is thrown away during the encoding process, but the codecs are engineered so that the lost information is restricted to being related to sounds that you are unable to hear anyway. You are unlikely to be able to tell any qualitative difference unless in a direct, switching-back-and-forth-between-streams comparison. It’s important to note that if the original source doesn’t have an LPCM stream, meaning the LPCM stream is the result of the decoding of a compressed stream, then there is no difference in quality - only in where the decoding is done.

 

With that out of the way, it does seem that quite a few people are misunderstanding what it is we’re looking into here. If your Sonos app is reporting 7.1 LPCM when a different source audio is selected, that’s because your LG TV is choosing to decompress the compressed stream into LPCM, rather than allowing the audio device to do it. It’s a bit strange, to be sure, but there is nothing we can do about it - only LG can address this behaviour. Nor is there anything to be investigated about it - we are aware and we understand the technicalities of it, if not the why.

It seems that no-one actually has mis-mapped channels to report, which is fantastic. As this thread is now more off-topic than on-topic, I’m going to close it soon. If anyone does have mis-mapped channels to report after this thread has closed, please DM me.

"Common sense is the collection of prejudices acquired by age eighteen." - Albert Einstein
Corry P
Userlevel 7
Badge +18

Hi @slongChez 

 

We don’t “drop” any channels - we downmix them so the channels that don’t have physical speakers to go to end up coming from equivalent speakers (so a side channel would play through the front and back speakers of that side, resulting in still appearing to come from the side). But yes, the end result may well be indistinguishable.

 

This is not the case for me. The side channel audio only comes out from the rear speakers.

Apologies - this was pure supposition on my part, and it turns out I was incorrect. Unfortunately, there isn’t any internal documentation for me to consult yet .

The rear surrounds (LRS, RRS) are mixed together with the surrounds channels (LS, RS) and the result is played solely from the satellite pair, rather than the surrounds channels (LS, RS) being mixed to both front (LF, RF) and the satellites, as I suggested. What you experienced is the expected behaviour.

Apologies again for any confusion. 

"Common sense is the collection of prejudices acquired by age eighteen." - Albert Einstein
Corry P
Userlevel 7
Badge +18

Hi All,

We feel it’s worth pointing out that, from a technical standpoint, there’s nothing wrong with LG sending a 6 channel stream via an 8 channel mapping - nothing is lost, and all channels appear to be playing from the correct speakers. We don’t view this as a fault that needs to be fixed, just a more unusual choice made by LG in this case.

When Sonos is given the opportunity to do the decoding, however, we will apply a gain boost to increase the volume, which is why DTS or DD will sound louder than LPCM. LG’s converting to LPCM may well be an attempt on their side to homogenise the volumes across various sources and compression types.

In the end, it’s really up to you, the end users, and what you prefer to listen to.

It does seem strange to me that the Passthrough setting on the TV does not seem to actually passthrough - this still might be something you’ll find worth reporting to them.

I hope this clears things up.

"Common sense is the collection of prejudices acquired by age eighteen." - Albert Einstein
S
Userlevel 3
Badge +2

It does seem strange to me that the Passthrough setting on the TV does not seem to actually passthrough - this still might be something you’ll find worth reporting to them.

It would be useful if Sonos could also report this to LG as I expect there would be a much higher chance of them actually looking into it and ultimately it would be to your benefit to have this resolved assuming LG TVs default to this behaviour with their new models going forward - less questions and support calls etc.

G
Userlevel 7

Hi @efrem81 & @JefDc 

Please describe the way in which your 7.1 playback results in mis-mapped channels. Thanks.

 

Hi

Is there any particular content/ test pattern we could use to test this issue, as I presume its not easy to hear if there is an issue? 

I have an LG CX and all content over HDMI, be it oppo203, apple tv 4k, all the DD 5.1 audio is ouput as multichannel pcm 7.1, but as you say LG seems to up convert it.

 

If the Oppo can play an MKV file, try this DTS-HD Master Audio 7.1 Sound Check:

https://thedigitaltheater.com/tools/

 

You should be able to AirPlay this 7.1 AAC MP4 file from an iOS device to your Apple TV 4K:

https://www2.iis.fraunhofer.de/AAC/7.1auditionOutLeader_v2_rtb.mp4

"Receive with simplicity everything that happens to you." - Rashi
E
Userlevel 1

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

G

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!

 

S
Userlevel 3
Badge +2


It’s definitely 6 CH, just checked;

 

GENERAL

HDMI3, HPD: HIGH, 5V : HIGH, R×Sense : HIGH 3840×2160P @ 23.97Hz RGB 8BIT NODATA PCM 6Ch 48000HZ

HDMI Mode : HDMI, HDR Type : SDR

 

 

E
Userlevel 1

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

 

Seriously? I have my CX and ATV4K 2nd Gen and of course still have the 7.1 issue on it. If you had the previous version and were getting 7.1, did you happen to notice an audio difference at all now that the new model shows proper 5.1?

I don’t have the misaligned audio issues with my full setup at all.

no, I didn't notice any audio difference, simply now the writing on the Sonos app is the right one. 
I had the previous Apple TV (2021) and I too was affected by the 7.1 bug instead of 5.1 read on the app, all resolved with Apple TV(2022)

S
Userlevel 3
Badge +2

I can confirm, went from 2021 to 2022 model and 5.1 shows correctly. However that now means I get the problem of sound dropouts on MPCM 5.1 signals reported elsewhere in this forum 

Corry P
Userlevel 7
Badge +18

Hi @ledzep1 

Is there any particular content/ test pattern we could use to test this issue, as I presume its not easy to hear if there is an issue? 

I have an LG CX and all content over HDMI, be it oppo203, apple tv 4k, all the DD 5.1 audio is ouput as multichannel pcm 7.1, but as you say LG seems to up convert it.

That is a good question which I personally can’t really help you with, other than to presume if you were watching an action/sci-fi/superhero movie it would, at some point, be obvious that something was off. Certainly dialogue should be the easiest to spot if not coming mainly from front and centre. If you can find/play a 7.1 test video on a platform/device capable of outputting 7.1 then that would obviously be ideal. If anyone knows of any such tool, please share details here. I have heard that some streaming services have these, but I’m not sure of the details (how many channels and what configuration).

As a few LG CX owners have already reported back stating that they experience no such issues, I’m starting to conclude that it was mis-reported in the first place, or resolved back in July ‘21 when we incorporated 7.1 downmixing to 5.1 into our software

Incidentally, there’s no real harm in the TV converting to LPCM - LPCM is how all digital, audio-capable devices handle audio internally after decompression. Also, the TV only does this when it knows the connected audio device can handle it. Unfortunately, there is often a volume difference, with LPCM being quieter - this is due to the Arc/Beam no longer having an opportunity to boost the gain post-decompression (there is no decompression with LCPM). Personally, I don’t have a Sonos Home Theatre device and I have to adjust the volume on my Samsung BluRay/amplifier with pretty much every program, movie or YouTube video I ever watch, with movies in 7.1 having to be turned up the most (and a lot). It’s just a fact of modern life.

For what it’s worth, I can’t believe there isn’t a setting on LG TVs to prevent them from outputting 7.1 LPCM - my guess would be to not use “Bitstream” as the output format, but my TV is Samsung too, so I can’t test it. Annoyingly, there’s also no way for me to know what codec is actually being played through my audio device - no helpful app!

"Common sense is the collection of prejudices acquired by age eighteen." - Albert Einstein
Corry P
Userlevel 7
Badge +18

Hi @ste_ms 

Whether channels are being mapped to the wrong speakers or not is almost irrelevant.

Not to this thread, which is expressly for the investigation of exactly that, and presumably not to anyone who has to tolerate it. I appreciate that you’re trying to solve a problem that you have, but this thread might not be where to do it.

It’s possible that the end result is the same (e.g. the TV is adding 2 empty channels which Sonos then drops)

 

We don’t “drop” any channels - we downmix them so the channels that don’t have physical speakers to go to end up coming from equivalent speakers (so a side channel would play through the front and back speakers of that side, resulting in still appearing to come from the side). But yes, the end result may well be indistinguishable.

I would assume it would be trivially easy to check some diagnostics and confirm what is happening? Maybe the Sonos end is somehow advertising itself as wanting a 7.1 signal, maybe it is too ambiguous and the TV assumes it’s 7.1 capable? Maybe the app is buggy and reporting 7.1 when in fact 5.1 is being played? Who knows, not the users on this forum certainly.

Yes - it is easy. In all cases, diagnostics report that the incoming stream from the TV is 7.1 McLPCM. We have no reason whatsoever to change the format, nor do we. We don’t even include the software libraries required to do so. The app reports 7.1 because that is what is being fed to the Arc or Beam, from the TV. Given that this issue only appears when certain LG TVs are involved, it’s also easy to say that the LG TV is doing it, and that it is doing it because it has been programmed to decide that 7.1 LPCM, regardless of the incoming format/codec, shall be sent to an audio device when that device is capable of receiving it. The Beam and Arc are capable; there’s no false advertising and the TV does not assume anything - it is told by the audio device over HDMI-CEC all the formats that will be accepted. However, they never state a preference, as you seem to suggest.

As I mentioned, I can’t believe there’s not a setting on the TV to control this behaviour - if there isn’t, I urge you to express your displeasure to LG. Technically, the “Passthrough” setting on the TV should make it feed the input stream directly to the audio device without alteration, though various reports from users on the forum (getting Atmos to play) have made me think at least some TV engineers might have a different definition.

Thanks to @GuitarSuperstar for providing those links! There’s a star in their name for a reason! 

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

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.

S
Userlevel 3
Badge +2

Not to this thread, which is expressly for the investigation of exactly that, and presumably not to anyone who has to tolerate it. I appreciate that you’re trying to solve a problem that you have, but this thread might not be where to do it.

I’ve read all of the many threads on this issue both here and elsewhere and have never seen a report of channels being swapped, only of rear channels missing which presumably was fixed as part of the 7.1 implementation last year. That may partly explain the lack of responses here as people are no longer seeing an issue and so not coming back to the forums.

Yes - it is easy. In all cases, diagnostics report that the incoming stream from the TV is 7.1 McLPCM. We have no reason whatsoever to change the format, nor do we. We don’t even include the software libraries required to do so. The app reports 7.1 because that is what is being fed to the Arc or Beam, from the TV.

I think this is the first time I have seen a response from Sonos that this has in fact been checked and found not to be an issue with Sonos and definitely on LG so that’s useful.

As I mentioned, I can’t believe there’s not a setting on the TV to control this behaviour - if there isn’t, I urge you to express your displeasure to LG

Using passthrough is what causes this issue, the alternative is to use Auto but that has other undesirable effects like converting some input signals to improve compatibility and preventing ‘full’ Atmos from being sent.

However, I’m fairly certain now that with Sonos confirmed to handle 7.1 inputs correctly and to not be incorrectly requesting a 7.1 signal that this is not an issue that impacts the sound and so not something to be concerned with so thanks for that.

 

S

LPCM 7.1 and 5.1 with ATV4K and LG TV Mis-directed channels Issue - Revisited

Old thread, but I just recently added rear surrounds (Ikea Bookshelfs) to my LG C1/Sonos Arc SL/ATV4K (2021) set up, and have since had multiple occasions where the sound from the ATV4K 5.1 source (being Prime, Netflix, and AppleTV+) is coming out the wrong channel - the main dialogue comes from the one or the other rear surround instead of the Arc SL). It is intermittent, but does keep happening.  The channel mis-assignment can be “fixed” in the moment by power-cycling (unplugging) the LG TV.  The ATV4K source also consistently shows as “multichannel 7.1” in the Sonos app, when it is of course a 5.1 PCM feed from the ATV.  I have the audio settings for the LG C1 set to “bitstream”, “enable eArc”, and “passthrough” and ATV4K set to “Atmos/Auto”. When the source is from apps on the TV itself, “multichannel 5.1” displays correctly in the Sonos app, and there is no channel mis-assignment.

I know that this is an LG/Apple issue, and not a Sonos issue, but I am raising it here now because @corryp sought evidence of this “wrong channel” behaviour, and it did not appear anyone reading the forum at that time was experiencing it. I took a diagnostic when it happened today (main dialogue from right rear speaker) – watching Netflix via the ATV4k – number 538943573. No need to post “so what is your question?” - i don’t have one - this is fyi for Sonos.

L
Userlevel 5
Badge +11


It’s definitely 6 CH, just checked;

 

GENERAL

HDMI3, HPD: HIGH, 5V : HIGH, R×Sense : HIGH 3840×2160P @ 23.97Hz RGB 8BIT NODATA PCM 6Ch 48000HZ

HDMI Mode : HDMI, HDR Type : SDR

 

 

Than you both very much! This has plagued me for so long now that I’m willing to spend the money and just buy a new Apple TV…

 

Hi

May are ask what your issue was?

I have multichannel pcm 7.1 via my 2021 Apple TV as well, but never found it to be an issue, I do get multichannel pcm 5.1 via my PS5, so it seems to be device dependent.

Do you just want a new 2022 Apple TV so it displays 5.1 correctly or is there an actual sound issue?

 

I thought this one got put to bed a while ago and there was any sound issues as such.

L
Userlevel 5
Badge +11

Hi @efrem81 & @JefDc 

Please describe the way in which your 7.1 playback results in mis-mapped channels. Thanks.

 

Hi

Is there any particular content/ test pattern we could use to test this issue, as I presume its not easy to hear if there is an issue? 

I have an LG CX and all content over HDMI, be it oppo203, apple tv 4k, all the DD 5.1 audio is ouput as multichannel pcm 7.1, but as you say LG seems to up convert it.

 

If the Oppo can play an MKV file, try this DTS-HD Master Audio 7.1 Sound Check:

https://thedigitaltheater.com/tools/

 

You should be able to AirPlay this 7.1 AAC MP4 file from an iOS device to your Apple TV 4K:

https://www2.iis.fraunhofer.de/AAC/7.1auditionOutLeader_v2_rtb.mp4

 

I tried this, although I don’t have rear surrounds, just the ARC and sub. the audio file played and I could hear the test voice speak all the channels and they all seemed to play correctly on the ARC.

 

Corry P
Userlevel 7
Badge +18

Hi @ajdz859 

I created this topic over a year ago to determine once and for all whether anyone was experiencing channel mis-mapping or not, as there had been some inconclusive chat at the time. No-one reported having the issue at the time, and as with all discussions here on the community forum, it was in reference to the mainline software version only. It seems there was no such issue, so there was nothing to resolve.

However, your mention of Beta was a red flag - not only is all discussion of Beta banned from this forum, it being a direct contravention of the agreement you made when signing up to the Beta programme, but you are using software that essentially wasn’t asked about - Beta software is expected to be different. So, while your subject may seem on-topic for this thread, the fact that you are using Beta software makes you off-topic for this entire site, which overrules you being on-topic for this thread.

I do realise I came in rather heavy-handed in replying to you, but I stand by my wanting to immediately emphasise that discussion of Beta is not permitted here. So, apologies for any offense taken at my tone, but I was trying to protect you from being censored and possibly barred from the site - depending on what you said next.

I hope this clears it up.

"Common sense is the collection of prejudices acquired by age eighteen." - Albert Einstein
E
Userlevel 1

I also just checked and it says pcm 6Ch 48000Hz
 

Apple TV 2022 and LG C1 

passthrough enabled

B


It’s definitely 6 CH, just checked;

 

GENERAL

HDMI3, HPD: HIGH, 5V : HIGH, R×Sense : HIGH 3840×2160P @ 23.97Hz RGB 8BIT NODATA PCM 6Ch 48000HZ

HDMI Mode : HDMI, HDR Type : SDR

 

 

Than you both very much! This has plagued me for so long now that I’m willing to spend the money and just buy a new Apple TV…

S
Userlevel 1
Badge +1

 

We don’t “drop” any channels - we downmix them so the channels that don’t have physical speakers to go to end up coming from equivalent speakers (so a side channel would play through the front and back speakers of that side, resulting in still appearing to come from the side). But yes, the end result may well be indistinguishable.

 

This is not the case for me. The side channel audio only comes out from the rear speakers.

S
Userlevel 3
Badge +2


It’s definitely 6 CH, just checked;

 

GENERAL

HDMI3, HPD: HIGH, 5V : HIGH, R×Sense : HIGH 3840×2160P @ 23.97Hz RGB 8BIT NODATA PCM 6Ch 48000HZ

HDMI Mode : HDMI, HDR Type : SDR

 

 

Than you both very much! This has plagued me for so long now that I’m willing to spend the money and just buy a new Apple TV…

Just beware of the sound drops with 5.1 signals if you have a beam

B


It’s definitely 6 CH, just checked;

 

GENERAL

HDMI3, HPD: HIGH, 5V : HIGH, R×Sense : HIGH 3840×2160P @ 23.97Hz RGB 8BIT NODATA PCM 6Ch 48000HZ

HDMI Mode : HDMI, HDR Type : SDR

 

 

Than you both very much! This has plagued me for so long now that I’m willing to spend the money and just buy a new Apple TV…

Just beware of the sound drops with 5.1 signals if you have a beam

Thanks for the heads up, we have a Sonos Arc 5.1 Setup, I hope everything will be fine!

R
Badge

Mine does this as well. Multichannel PCM 7.1. Happens on my PS4 Pro when watching Blu-Ray's and my Nintendo Switch.

 

I notice the center channel sounds left oriented and the right side sounds very hollow. 

 

LG C1 55" Passthrough, eArc enabled. 

Devices connected: Sonos Arc, Nvidia Shield Pro, Nintendo Switch, PS4 Pro. 

Sonos Arc, Sub, two One's. 

Diagnostic: 368466851

Corry P
Userlevel 7
Badge +18

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.

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

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