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 have no issues with my Arc either, but that’s also not connected to an LG TV, I have a Sony TV. I could hook up my Apple TV to the Arcana/Beam, maybe I can reproduce the issue with that but I don’t think so. Unfortunately I don’t have a PS5, if anyone knows where I can get one, let me know . 

It seems they fix one thing and break another, I'm looking to replace the Playbar and it's not an ARC straight fight which is unfortunate due to having the Sub etc already.

@throwawaybeam2 

Yesterday I had finally some time to troubleshoot this. I ended up unplugging the LG to perform a full restart, the PS5 and the Beam2. After that I have been playing with the PS5 for more than one hour with PCM 5.1 as audio output  and I haven’t had a single dropout. Worth trying...

I’m seeing the same issue (Panasonic DP-UB450EB (LPCM) -> LG C1 (eARC) -> Beam2+Symfonisk) when transcoding 5.1 DTS discs in the player. No drops for 7.1 encoded discs. Repeatable switching between 5.1 and 7.1 LPCM on a games console. Occasionally 5.1 LPCM just doesn’t work at all. I tried swapping the Beam for an Amp as per Jay's thread, but of course the Amp is only ARC and therefore no multichannel LPCM to test with.

Frustrating that because LG are being stingy with their codecs (I get it), working around just hits a bug instead. Remains to be proven if this is in LG (v03.33.11) or Sonos (v14.14) or just user error on my part. It’s a narrow use case but it does mean some of my discs will currently only playback (without drops) in down mixed stereo.

Trying to run through this test case though made me think of a couple of gripes where Hifi meets Home Theatre in the same room: 

• It would be nice to see eARC codecs, some kind of centre speaker configuration and non-Sonance Trueplay on the Amp, which sounded great with standalone speaker frequency range and the wider sound stage.
• A line in on the soundbars/rears would be convenient for giving legacy components an input into the Sonos ecosystem. Seems odd, expensive and cluttered to need Amp/Speakers or headless port in the same room as a Beam/rears. I understand both the Amp’s and 5’s line in becomes non-operational when configured as rears.  

Ah, I see. I didn’t realise multichannel LPCM required eARC.

I’m a little confused as to how the fault could be with the TV though if it’s set to just passthrough the bitstream?

That hadn’t occurred to me either until I tried it, or that the Amp was just ARC. 

Presumably the TV shreds the HDMI data stream from the console/bluray and only copies the audio stream to the eARC HDMI port. There’s enough software there for a memory leak or an exception to disrupt the process inside the TV, we know the Beam 2 is reporting the stream drying up. From reading other threads and forums it seems LG have had a difficult time stabilising multichannel LPCM, especially on the 9/X models. Having said that, it doesn’t rule out the Beam provoking the TV into quitting sending data. Would be interesting to know if the diagnostics had shown any kind of handshake during the recovery of the audio drop outs.

My 5.1 dropouts seem to have gone, none for at least 12 hours of music/films/games. Sadly I cannot attribute a single setting to the behaviour change. I decided to test removing the (wireless) surrounds  which did not fix the dropouts, so I added them back to the Beam 2. Then

• Toggled “Sound Mode Share” out of curiosity (as it was mentioned in another thread) - didn’t notice any obvious change
• Changed “passthrough” to “auto” - this changed the Beam input type from “Multichannel PCM 5.1” to “Dolby Multichannel PCM 5.1” (whatever that’s meant to be - I’m guessing MAT?). This format however had no dropouts for 10 minutes or so, so I flipped back to “passthrough”, but I don’t remember if the dropouts returned at this point :(

my colleague spotted some issues happening on the CEC network and suggests you factory reset your TV

• Before factory resetting the TV as my next step (it’s not my main TV so not very inconvenient) I thought I’d try manually switching the devices on from standby instead of using CEC.

Then I noticed the dropouts had gone on “Multichannel PCM 5.1”. I then toggled CEC control on the source devices and the drop outs haven’t come back even when using CEC to standby/powerup .

I’ll try to isolate the steps above if the dropouts return, but I can see why the problem is not wide spread, seems to be a temporary state involving the C1/Beam2, possibly cleared by either the auto/passthrough setting or CEC order.

I can confirm that I am having the same issues on my LG C1 Oled with beam gen 2. The only audio file that I have cut outs with is PCM multichannel 5.1, when playing blu rays on my Sony X700 blu ray player. All other formats work fine, including Atmos. Neither Sonos support or LG support have been able to help. Really frustrating as obviously a lot of blu rays have 5.1 tracks on them and I would rather not have to watch them with standard stereo pcm which sounds as bad as the TV speakers. (Hyperbole). 

PCM Multichannel began cutting out again, now on Sonos v14.16 still LG v03.33.11. I tried toggling all the settings I tried previously (I didn’t see “Dolby Multichannel PCM 5.1” this time, only stereo) and disabling CEC on the sources but the drop outs persisted.

I then factory reset the C1, but that did not clear the issue either, so I then generated diagnostic #997513791. 

If you have tried the various things mentioned in this thread and it’s repeatable, then it is suggested earlier by Staff, to get in touch with the Sonos technical support team directly, so they can perhaps look into the matter. I would perhaps give them a call and see if that leads to the issue being resolved with your TV/Devices.

Support have raised a case. I also decided to time the audio drops, I thought they were random but today I measured them as a regular 39.8 seconds apart.

The dropout duration is almost exactly 1 second, which leaves 38.8 seconds of sound (crudely measured by recording onto my computer). If my assumptions (LPCM signal is 24-bit/channel, a full channel is wasted on LFE) and calculations are correct then probably still co-incidence that this is close to the region of 32MB of data:

2^25 Bytes / 6 channels / 3 bytes / 48KHz = 38.836 seconds

Same problem here since Sonos v14 update with LG C1. Really frustrating :(

In my case, I have 1 second cutoff every exactly 59 seconds.

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.

Coincidentally I did follow up on progress on the support chat a few days ago. We went through the same L1 questions and was asked to submit a diagnostic. When I pointed out the diagnostic ID already tagged to the issue I was told to then use the phone support for further updates/escalation, which I may try if I can find enough time/patience.

I did try transcodong LPCM and DTS to Dolby but there was too much lag introduced which I wasn't inclined to investigate.

My dropout frequency has also change now to every 59.8 seconds, but the drop remains approximately 1 second. The only relevant thing that I’m aware has changed (other than the dog destroying the TV remote) is Sonos firmware, now on 14.18 (without the grey dots in the app).

I'm also having this issue when watching blu ray amd uhd discs on my ps5 that's linked to a lg c1.

All of my setting are 110% correct as I've spent hours going through them one at a time to see if they was causing the issue.

Please let us know of you get an update/solution!

Same issue here with a LG C1 and Sonos Beam (gen 2).

I get dropouts on Multichannel PCM 5.1 from my Shield Pro.

It start after the Sonos update 14.18.

It seem that restart the Sonos Beam (unplug power) temporarily fix the issue but dropouts are back few time after. 

Have you provided hard data to Sonos via a diagnostic, and called them to discuss it? Unless you notify them in a call, they don’t automatically look at each diagnostic….

Yes, there is at least one user from this post that has done that (see some messages above). Still waiting for a solution/fix.

Sure, but there’s no guaranty that the cause of your issue is exactly the same as the previous poster, even if the expression of the issue is the same. 

@Airgetlam I will contact the support this week. We will see ! 

Even if it turns out to be the same cause, giving Sonos programmers more hard data to analyze is only a win. And if it turns out to be a different issue causing what may be similar problems, then they can identify that, and help resolve it. 

Okay, so I fix it by myself. It wasn’t a Sonos issue but an LG issue. I saw that a lot of people with that issue own an LG TV. So I look for more information on that. I found an issue on Reddit link to 5.1.

What I did on my LG C1

• Remove my Sonos Beam from the external output as a sound bar
• Reconfigure Sonos Beam as a sound bar (Sonos is not directly proposed by LG you have to enter the brand in the search bar)
• Uncheck one of the conditions of use to reboot of my LG. 

Since I don’t have issues anymore and that without reset!

WebOS version: 03.33.11

Sonos version: 14.18