Hi @Mutiny 

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.

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.

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.

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.

Hi @slongChez 

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. 

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

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

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

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

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 

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)

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!

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.

Hi @ledzep1 

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!

No worries just wanted to make sure that you got some responses to this - hopefully some of the affected users from the other threads will pitch in here as it would be a shame to let this fizzle out, thanks.

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

Apple TV 2022 and LG C1 

passthrough enabled

Solved with money spent!

So this issue has been annoying me for months since I added the Beam 2 to my system which includes a subwoofer and Play One rear speakers. My TV is an 75” LG 75QNED85AQA and an Apple TV Model A2169, e.g. 2nd generation.

As with many others, Dolby Atmos worked well when included in the media with all the proper check boxes. But reverting to non-Atmos media the Sonos app said Multichannel 7.1 PCM and many sounds, including speech, were muted. My solution was to go back to the Apple settings and change the sound output from “Atmos available” to “Dolby 5.1” which would then work fine but removed Atmos until I again changed the setting. As you can guess, going back and forth with the setting was annoying and sometimes forgotten, but at least it provided satisfactory results when done.

I read in this forum (Sorry to whomever’s idea this was originally but I don’t know the proper attribution.) that the issue was the Apple TV Gen 2 lacking HDMI 2.1 capability, something included in the Gen 3. It seemed to make sense to me.

First I made sure to acquire newer updated and certified HDMI 2.1 cables. Adding them to the Apple TV Gen 2 changed nothing. Then I bought an Apple TV Gen 3. VOILA! Now the Apple TV Gen 3 stays in the “Atmos available” mode and the app tells me (and my ears agree) when the media has 2 channels (Stereo PCM), 5 channels (Multichannel 5.1 PCM) or Atmos (Dolby Atmos).

With both the ATV Gen 2 and Gen 3 I played quite a bit with the settings. Whether I put the LG TV setting on “pass-through” audio or “auto” the results did not change for any media I played.

Essentially, the fix in my case was to get the newer Apple TV module. (And also being sure my HDMI cables were up to snuff.)

There does seem to be one bonus: The faster chip in the new ATV improves switching services with differing resolutions. It also seems to produce a better, brighter, clearer image on both lower and high resolution videos. I have no numbers for this but the first time I turned on the TV with everything hooked up, a little “Wow!” was set off in the back of my head. (You know, where the brain interprets the signal from the eyes.)

So I agree with those saying the problem is in the Apple TV and that Apple “fixed” it by offering (at a price) a newer model. Not only did that work for me, it seems pretty typical of how Apple does things. They make great stuff but you gotta pay for it. (Oh, Sonos does that too!)

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!

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.

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.

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.

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.

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.

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 

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.

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