Multichannel PCM 5.1 dropping out since 14.10 update

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Hi @OmriP 

So you’re saying LG is aware and is actively working on fixing this?

So I was informed; it’s not something I found out for myself, so I don’t know if this came from LG or from their customers. 

Is there any way to get in touch with the team that works on this to send them videos, diagnostics etc?

Because every time I tried to contract them they responded once after several days then simply stopped answering, it seems impossible to contact them.

Sorry - I have no idea.

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Hi @throwawaybeam2 

I don’t disagree - the timing with the update is worthy of note and we did alter some Home Theatre functionality in said update (though I don’t know if any of it pertained to 5.1 PCM specifically and only - it seems unlikely). I’m certain, however, that a reset of the TV is the best way to get the troubleshooting process to move forward, at the very least, given what the engineer I spoke to told me about what was found in the diagnostics.

There is no way to roll-back the software (I don’t like to speak in absolutes because many things are technically possible, but to all intents and purposes it can’t be done).

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Earlier in this post I mentioned unplugging and restarting all devices fixed it but it comes back after a while. It seems some actions, either changing settings, unplugging cables, resetting devices fix it for a while but it comes back, even if no changes in setup are done. This is not such a weird scenario either... My PS5 can output Dolby 5.1 instead  (no dropouts) but prefering uncompressed audio from the source is completely normal if your device supports it?


@RANDUSR23296 , could you keep us updated here if you receive a reply to your support case? Many thanks.


I think the fact that the mods are not engaging with this thread anymore is telling. I think Sonos have reproduced the issue and so don’t need any more diagnostics or support calls coming in.

At this point they either don’t know how long a fix will take, or how it can be done and hence don’t want to set expectations, or they know it’s unfixable and are hoping this just dies away in time.


Yeah that’s what really pisses me off. What sets Sonos apart is suppose to be their customer service but they’ve turned a blind eye to this issue. I’m done with this product. I’m selling it and moving on to something that lets me play switch games in surround sound without dropouts every minute. Thanks Sonos.

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Hi @throwawaybeam2 

As I mentioned, the best way for troubleshooting to move forward is to reset the TV - if this does not resolve the problem, I recommend you get in touch with our technical support team who will create a case for you and be in a better position to assist you, moving forward. 

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I was looking for a potential Beam replacement and came across the new-ish Bose Soundbar 600. Checking for feedback, I saw that they had an issue with LG OLEDs where it did not produce any sound at all. However, unlike Sonos, Bose was quick to acknowledge the issue and eventually released a firmware update to fix it. You can do a search on the Bose subreddit if interested.

Bose’s was a major issue, sure, but Sonos should also show accountability. I sound like a broken record but if it works on the Arc, why is it busted on the Beam? Pretty sure this is a Sonos issue.

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Is it just me or has it gotten much worse in the past month?

I used to be able to make the problem go away by playing around with the settings a few minutes and it would work until a power cycle happened (for example an electric blackout).

But since the past few weeks even fiddling around for hours doesn’t fix it anymore. I know there were some software updates on the TV (dunno if on Sonos) and it seems they’ve made it much worse now, and I can no longer make the problem disappear…


LG C2 and having pcm 5.1 dropouts from PS5 in HDMI 3 and 4. Moved PS5 to HDMI 1 so far no dropouts. Having contacted LG support bout this issue and this forum, I have had LG response:

"I am just getting in contact as our Technical Team has responded on file and have advised that there are no differences in the HDMI ports and so there should not be any reason as to why HDMI 3 and HDMI 4 would be different to HDMI 1. They have advised that we can book this in for a repair as this could be an issue with the HDMI 3 and 4 ports themselves."

So am now booked in for HDMI repair. 

Waste of time IMHO, your TV behaves exactly the same as any other LG TV of its model.

It works “as intended”, the problem is that the “as intended” is faulty.

It almost seems to infer that the LG Technical Team are aware of a hardware issue with that TV model. I would have the repair and just see what happens after that.

It really doesn't, but agreed, if LG are willing to commit some visible effort into trying to isolate this fault then worth pursuing. If they have prepared a h/w HDMI fix for C2, don't fancy the chances of it being back ported to C1/CX.

Will give the LG repair team a chance. As it is strange that the 5.1pcm works fine on hdmi 1 for the last week where in hdmi 3 for the last 3 months I've had to resort to 7.1pcm as the pauses in 5.1pcm have been very annoying.  Had the same on hdmi 4 but only tested for a few hours but it was immediately stuttering.

Yeah, I wouldn’t read too much into it either. Probably just a standard response from local LG support. As you are under warranty, they are willing to take a look at your TV. They probably don’t even know that this an issue specific to the Sonos Beam Gen 2 only.

If it’s home service, then you’ve got nothing to lose. But if you have to send the TV to them, I personally wouldn’t bother as it’s a high risk (they could damage the TV), low reward play. In my country, repair is limited to basic diagnostics and part replacement. They don’t tinker. Last resort, they simply replace the TV. And I doubt a simple part/TV replacement would do anything.

Yeah home repair, wouldn't have bothered if it had to go.

I have an Apple TV-4HD with LG C9 TV and Arc, surrounds & sub and it’s set to default - to output 5.1 multichannel LPCM.

I played the movie ‘6 underground’ from Netflix for 30 minutes or so, just as a test …and that’s all working okay without any audio dropouts.


What settings do you have set on your c9 for audio?

These are my LG C9 TV Audio Settings…

  • Sound -> HDMI ARC (Digital Sound Out = Pass-Through / eARC = ‘ON’)
  • Sound -> Additional Settings (DTV Audio = Auto) / HDMI input format = Bitstream for all HDMI ports.
  • Connection -> HDMI Device Settings (Auto Device Detection = ‘ON’ / Simplink = ‘ON’ / Auto Power Sync = ‘ON’)

I am having this same issue and it has been going on for months. This is specifically woth my switch which can only do pcm 5.1.


To further reinforce some other people's notes - this problem only occurs on my switch which is on hdmi 4. Same issue with hdmi 3. But like other people said - hdmi 1 did NOT have this issue when I tried the switch on that. Hdmi 2 is the earc so can't use that one. 


What is going on here? I really want to use my surrounds but the constant sound cut off is driving me nuts. My hdmi 1 is for my ps5 and don't want to be limited to one hdmi. This did not always used to happen so it's very frustrating. 


LG C2, Beam Gen 2 and two play1s.

Getting same drop outs with PS5 set to amplifier and 5.1. App read smultichannel pcm 5.1.

No dropouts on any other format.

When setting PS5 to soundbar, App reads multichannel pcm 7.1, no dropouts. 

Should I just keep 7.1 Sounds OK to me?

Would be nice that after sending £1000,'s on a system it would work as intended.

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I can also confirm this issue; LG C2 and Beam Gen 2, both with the latest firmware updates.

I experience this with my Nintendo Switch set to surround (reads as PCM 5.1) as well as the PS5 manually set to PCM 5.1 (same as the previous poster).

It’s not a huge problem for me personally yet as I am currently essentially stuck to stereo anyway (although I guess the Beam at least makes proper use of the center channel when downmixing 5.1). But I was planning to buy some One SL speakers later this year and set them up as surrounds, so it would be sad if this issue couldn’t be fixed.

Asides from the posts here, a quick search brings up many Reddit threads describing this bug with the LG TV + Beam combination and given how popular these choices are with consumers I am very surprised that neither LG nor Sonos seems to be looking into it properly on a larger scale (or if they do, they aren’t communicating it).

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@RANDUSR23296 Damn. Sonos should at least send you an Era 300 for all your work lmao. But thanks to you and @OmriP for zeroing in on the HDMI1 thing. If this lasts for me, I could probably hold off on sidegrading now for a real upgrade later.

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Anybody seeing a change on 15.5?

Ok - looks like that cable appears to have worked after about 30 mins of testing. Will report back if anything comes back but thanks to everyone here for doing so much troubleshooting and coming up with a work around! 


The only thing that makes me wonder about this though is if this process of reversing what the source should normally be on the cable would have any side effects that may not be readily apparent yet. It seems odd that it only works when the source side is on the TV and therefore you will not get the Sonos splash screen on HDMI 2. If the sound in the end is not effected than I suppose this works fine but it's just pretty interesting that this backwards method is what is working and idk if the this would end up preventing some features that people have not noticed just yet. Hopefully Sonos or LG comes up with an official fix soon but in the meantime I at least was able to find a reasonably priced cable to use. 

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@RANDUSR23296 Damn. Sonos should at least send you an Era 300 for all your work lmao. But thanks to you and @OmriP for zeroing in on the HDMI1 thing. If this lasts for me, I could probably hold off on sidegrading now for a real upgrade later.

I’d settle for Sonos sending me a human readable log of what events my Beam 2 (in my house, on my network) is seeing on the HDMI eARC pins around the 59s window ;-) Realistically, having spent a while on Google, the HDMI spec (1.4 and above) is such a trade secret there’s at least one good reason why that will never happen.

@MJW75 really made a break-though spotting the blips on the 11111 menu. I’ve tried pulling the HDMI plug on a 6ch source on my A1 and it immediately drops to 0Ch, so there’s a difference in how that signal is reported between those chipsets. Maybe the/another bug causes this difference, maybe it’s a recent intentional change from LG to monitor this specific issue. Unfortunately I don’t have a downloaded copy of C1 v03.33.11 firmware to downgrade to find out.


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When I run the following commands on Raspbian on a Raspberry Pi3 with Beam2 on eARC:

sudo speaker-test -Dhdmi:vc4hdmi -c6
sudo speaker-test -Dhdmi:vc4hdmi -c8

the 11111 menu displays either 'PCM 6Ch 48000Hz' or 'PCM 8Ch 48000Hz' during streaming and Sonos app also shows the appropriate Multichannel LPCM mode. 

When speaker-test is killed, Beam2 goes silent, Sonos app format goes blank immediately, 'cat /proc/asound/card1/pcm0p/sub0/hw_params' shows the RPI’s sound card device is already closed, but:

  • HDMI1 (not bugged) - 11111 holds the same PCM mode until a different speaker-test format stream is started, up to several minutes later
  • HDMI3 (bugged) - 11111 holds the same PCM mode, but only until the 59th second after the previous dropout, then 11111 shows the format being pushed to PCM 2.0, where it then stays (again, until a new speaker-test format is streamed)

The above behaviour is the same for 6Ch and 8Ch, the only difference I observed being that if speaker-test is streaming 6Ch during the 59th second on HDMI3, the Beam2 audio (as we know) is interrupted for 1 second. There is a 59 second event for both 5.1 and 7.1, but it is only audible on 5.1.

Replacing the Beam2 with an eARC AVR - when speaker-test is killed on HDMI3 there is no drop down to PCM 2Ch at 59s, both formats remain until a new stream is started. This doesn't give any indication how Beam2 is involved, but only its presence is triggering the TV into doing something every 59s. I couldn't find any obvious HDMI events/errors (CEC, handshakes, etc) on the RPI at the 59s intervals.

A post I found recently observes the dropout period is not tied to the amount of content played (back when it was approximately 40s):


If I unplug the HDMI cable after killing speaker-test, 11111 shows HPD/5V/etc drop low, Video shows 0x0I@0.0Hz, but audio still holds the most recent PCM 6Ch/8Ch value. This is the same on HDMI1 and HDMI3, for the RPI and PS5 as sources. The TV is not reporting the audio format on the input wire. Rather, I guess it’s whatever the mode the next circuit in the audio path was most recently configured to based on the the last frame of audio received. PCM 2.0 is only displayed again when HDMI cable is reconnected. On HDMI3, streaming 5.1/7.1 then resumes the 59s timer.

Bruh Sonos should be paying you for doing their job.

On another note, the sound drops stopped on their own since I installed the last Sonos update and I don’t know if it’s because of the update or because of some unrelated voodoo. I’ve had this problem for weeks now and gave up on fiddling around because it seemed unlike last time this time nothing I did worked, but yesterday it just fixed on its own, and that was the first time I used the TV since the update.

At this point I’m too happy to power cycle the beam and see whether the drops return or not XD

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They may simply be a forum mod, but now that the issue has gotten big couldn’t they have at least escalated the issue to their heads or engineering contacts?


To be fair, @Corry P has already stated earlier in this thread that cases cannot be publicly commented on. It would be difficult to provide any general update here without breaking that rule.

That being said, I've received no update on my case since I raised it and I'm not desperate enough to run through the L1 script again on chat/phone in an attempt to get a status update.

I hope that someone is collating case numbers behind the scenes for prioritisation in their backlog, but I've no idea if it's possible for Sonos mods/support to link posts in this thread to individual case numbers, or whether they set aside time to do so.

I have tried the same HDMI cable as suggested here and I can confirm this solution works for me with the Beam and LG C1: no more dropouts with the Nintendo Switch and Xbox Series X. I have also upgraded my Apple TV from a Gen 2 to a Gen 3, which fixed the issue of LPCM 5.1 being send as 7.1 (and thus lowering perceived audio quality).

Quite a costly solution, but at least everything is working as it should. I want to thank all the wonderful people in this thread for finding a solution to a problem which had been driving me crazy for over a year.

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Hi @OmriP & @mjsound 

I personally really don’t know much about it - I just found the information and shared it with you.

A search will reveal that many people with these particular TVs and all kinds of (non-Sonos) audio equipment experience the same. Here are three examples:

The issues also coincided with an LG firmware update for these particular models, and LG are actively seeking videos and other evidence from their customers in an effort to troubleshoot.

None of these linked issues are even remotely similar. 

Lmao what a shitshow. Skimmed the links:

1st link - PCM 5.1 no sound but DD 5.1 has sound. Turning the TV off and on again fixes the issue

2nd link - BOTH PCM 5.1 and 7.1 does not work

3rd link - Multichannel issue with ATV4K. Sometimes sounds do not come out of correct channels

Most seem to be generic uncompressed audio (arc vs earc) issue. Could be hardware/software, or could just be misconfigurations. But definitely not the HIGHLY SPECIFIC issue we are experiencing here i.e. everything works with Beam Gen 2 except PCM 5.1 which has a dropout every minute. PCM 7.1 works. Sonos Arc works.

While the provided links do not include exhaustive testing and only discussed limited use cases, it is safe to say that “None of these linked issues are even remotely similar.” You can type anything on google and you’ll find confirmations for whatever it is you want to see. And that’s just what Sonos lazily did.

I think Sonos is just capitalizing on the recently discovered cable (and to a lesser extent, HDMI1) workaround. Sonos wants to get out of this mess while the users have quieted down, already content with the solution they mostly paid for.


Edit: Who knows? Maybe one day Sonos will sell an official fiber optic HDMI cable.

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Seems like someone from The Verge is covering the popping sound issue. Sent them a PM and tagging them in case they’re intested to look into this as well @tomwarren 

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Hi all,

I highly recommend that anyone looking for this issue to be resolved get in touch with our technical support team to have your case sorted out. While we of course forward any and all information from the community here, it will help us all if you ‘officially’ create a case with our support engineers.
Please don't expect an immediate resolution, but each case will add further information that could help us get a resolution in place.

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The issue had been gone for a while without me having to do anything, so I thought perhaps some update had fixed it. However today the TV received a software update and the issue returned immediately afterwards. I’m thinking software updates (as well as power outages) somehow “reset” the state of the tv, including reintroducing this bug.

Anyways, nothing I’ve tried so far worked.

It isn’t clear from your post, so I’m just checking - did you read the last page of posts where a ‘workaround’ was discovered? 

If you mean the workaround with the cable then I’ve read it, unfortunately I don’t have such cable and Amazon doesn’t seem to have it available (or they’re not sending it here).

It may be possible to use a slither of insulation tape to cover pins 10 and/or 12 (TMDS clock) similar to others managing to block pin 13:

Looks quite fiddly, but if the TMDS clock is blocked then the TV shouldn't respond to any video signal, which reduces the number of pins needing covering. It may actually be easier though to cover all the TMDS pins (1-12) as the extra width will be less fiddly.

I have a short HDMI extender (can't remember it it came with the Beam or not), which should save the TV/Beam sockets from ingesting insulation tape should it come loose, so may try this a bit later.

Not sure of the warranty situation of doing this sort of thing either...



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Keep this menu displayed when playing 5.1 audio and when an audio drop comes, ‘6CH’ drops to ‘2CH’ momentarily before coming back (I managed to get this on video). Hit the up button on the remote every minute to stop the menu timing out while you do this.

Good spot, this is new behaviour.  I’ve recently seen the TV flick between 6ch and 2ch on this menu when I’ve confused it by making too many changes, but it’s the first time I’ve noticed the TV show any reaction at the time of a drop out. In my case it has just flicked between 6ch → 4ch → 6ch during the drop. It didn’t do this when I started looking at this months ago (when I’m certain HDMI 1 was also buggy). Perhaps this indicates LG is looking into this bug after all (or that I just have a bad memory...)

So it is not the sound bar. It is either the source (although no issue on my other TVs) or the TV. I’m guessing TV as why would it work on HDMI 1 if it was the source?.

There’s no issue on my alternative eARC devices either (Marantz in my case or Sonos ARC according to this thread), so that logic doesn’t quite stack up. Whilst the Beam 2 may not turn out to be buggy it isn’t blameless in this issue.

Same issue here. I have the latest Apple TV 4K (3rd Gen), LG C2 and Sonos Beam Gen 2 (all on the I also tried an earlier Apple TV 4K box (2nd Gen) and this bizarrely sends 5.1 audio as 7.1 - so I couldn’t use it to test with.

This is confirmed by a few posts on this thread - could be a h/w revision change between gen 1&2 and 3, or just that some manufacturers have no interest I back porting s/w fixes. I’m guessing Beam 3 won’t trigger this issue, will be interesting to see how C3 behaves (if not solved one way or the other by then).

Contributing factors to the bug seem to be:

  • Beam 2 reboots
  • CX-C2 (and G family) TVs
  • HDMI 3 (and 4?)
  • TV cache of HDMI devices (disconnecting the Beam 2 and reconnecting doesn’t clear the bug but fiddling with some of the TV audio/CEC settings can do)
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Extremely disappointing answer for all the people that has been extensively troubleshooting and reproducing the issue and giving mountains of data and details in this thread...