Dolby 5.1 content outputting as multichannel PCM 7.1 (since LPCM update)

  • 16 November 2020
  • 57 replies
  • 19182 views
L
Userlevel 5
Badge +11

Hi

Thought I would create this thread as a few have reported this issue in the lpcm update threads that are marked as solved so perhaps best to keep it separate.

Issue:

Before the LPCM update last week my sonos arc would receive atmos and Dolby digital 5.1 from the Apple tv 4k box, audio settings were set to the default AUTO-Atmos available.

My LG CX is capable of passing LPCM.

 

Now since the LPCM update with the above settings I still get atmos from apps such as netflix, apple tv + on the apple 4k box, but any content in dolby 5.1 is now outputting as multichannel PCM 7.1, 7.1 being the issue, it should be outputting as multichannel PCM 5.1

 

I have seen similar posts with this issue on the same device and other devices as well.

 

Thank you 

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57 replies

N
Userlevel 1
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@Ryan S are you guys looking into this issue? We’re glad the LPCM update is out but there are multiple reports of devices defaulting to sending 7.1 tracks to the Arc and the soundbar is unable to downmix it to 5.1. In most cases this causes missing dialogue or audio coming out from the wrong channels. On top of that the sound volume when using LPCM is really low compared to bitstream.

B
Userlevel 4
Badge +7

@ledzep1 .  It may be that there is no single set of settings for various sources that will always deliver the format you want to the Arc.  If there is, i suspect it doesn’t involve ‘bitstream’ for the TV audio output.

The Arc isn’t going to process the audio, it is going to play what you send it (or nothing), IMO.

You are a little confused here.

What you have written does apply to formats like DTS which the Arc cannot process.

PCM is different. Every Soundbar/AVR/TV in the world supports PCM. How many channels of PCM they support however does differ (Stereo 2.0/5.1/7.1). It is up to a soundbar like the Sonos Arc to tell a device like a nintendo switch or TV if it supports more than just plain vanilla Stereo PCM. The only reason any device will send a 7.1 signal is if the Sonos Arc is telling it that it can process it. Note that until Sonos did their multichannel PCM update the Nintendo Switch only ever sent regular PCM Stereo 2.0 to the Sonos Arc.

In this case Sonos need to either have the Sonos Arc not incorrectly tell other devices it can process 7.1 LPCM or downconvert it to 5.1. In any case it is completely different to formats like DTS which are proprietary and not supported at all.

1 x Arc, 1 x Beam Gen 2, 1 x Amp, 2 x Sonos In Ceiling Speakers, 2 x Sub, 9 x Sonos Ones, 5 x Symfonisk Lamp
S

@RayCizel 

I believe the fault lies not with Apple TV, but with the Sonos ARC+LG CX combination. The problem with this combo is that they advertise to the client (I have tried PS4 and NVidia Shield TV Pro) as being capable of 7.1 LPCM. However, if one actually sends 7.1 LPCM with passthrough to Sonos, the 2 rear channels will be silent.

On the PS4, this can easily be demonstrated by doing a 360-degree rotation with respect to a sound-emitting object, and the sound will be almost inaudible when the object is right behind you. On the PS4, one can explicitly select 5.1 instead of 7.1 so that the PS4 will only send 5.1 sound-mix to Sonos. The 360-degree test will now sound normal.

On the nVidia Shield TV however, there is no option to choose 5.1 -- this creates a problem in apps/games that output 7.1 channels.

This issue is now being tracked in the following thread:

https://en.community.sonos.com/home-theater-228993/ps4-pro-outputting-pcm-via-lg-cx-shows-multichannel-pcm-7-1-for-sonos-arc-but-rear-surrounds-have-no-audio-6850771

Note: this has nothing to do with Dolby-encoded signals (DD, DD+ or TrueHD, with or without embedded Atmos), which can be correctly decoded and played by Sonos. This also has nothing to do with HDMI 2.0/2.1 -- assuming that both the TV (LG CX) and Sonos ARC have already been properly connected with HDMI 2.1 eARC.

J

I get the 7.1 if it is set to passthrough.  It changes to 5.1 if I set the tv to auto.   This is on 2020 75 LG Nano 90 and I also just got a 55 LG OLED CX.  It was the same, so I just returned it and just now realized my Nano 90 is doing the same thing.

A

I also have the 7.1 issue. I just wanted to chime in and say that AUTO does not work to output Multichannel PCM in 5.1 on the LG CX for me. If I do AUTO, then it will only play PCM 2.0.  My settings are HDMI Input Audio Format set to Bitstream and Digital Sound Out set to Pass Through. On my PS5, I have the Audio Format set to Linear PCM. When I play games,  the About My System page in the Sonos app shows Multichannel PCM 7.1. 

L
Userlevel 5
Badge +11

Can anyone from Sonos please advise, this might be more of an LG CX and latest LG models issue, but your update caused it.

Thank you

 

B
Userlevel 4
Badge +7

Can anyone from Sonos please advise, this might be more of an LG CX and latest LG models issue, but your update caused it.

Thank you

 

Exactly. To be honest even if the LG OLED is passing through a 7.1 LPCM signal, the Sonos Arc should be able to downmix it to 5.1. There is no such thing as Dolby Multichannel PCM 5.1 as the Sonos reports with certain content either, so clearly the first version of LPCM support on the Sonos Arc is buggy.

1 x Arc, 1 x Beam Gen 2, 1 x Amp, 2 x Sonos In Ceiling Speakers, 2 x Sub, 9 x Sonos Ones, 5 x Symfonisk Lamp
N
Userlevel 1
Badge

@Ryan S are you guys looking into this issue? We’re glad the LPCM update is out but there are multiple reports of devices defaulting to sending 7.1 tracks to the Arc and the soundbar is unable to downmix it to 5.1. In most cases this causes missing dialogue or audio coming out from the wrong channels. On top of that the sound volume when using LPCM is really low compared to bitstream.

I could be wrong, but I think Sonos HT speakers just play what they are sent (or silence if sent something incompatible like DTS), and don’t attempt to do any downmixing or other audio processing.  

I thought the demand for multichannel LPCM came from the gamers.  I am puzzled as to why there was an expectation this would deal with the DTS issue on Blu-rays.

Is the volume low on LPCM for all scenarios?  I ask in genuine curiosity.

I get the low volume on PS5, Series X and Apple TV 4K. The latter is the most problematic one with the 7.1 issue  since there’s no way to force 5.1 through settings like the consoles can.

L
Userlevel 5
Badge +11

@Ryan S are you guys looking into this issue? We’re glad the LPCM update is out but there are multiple reports of devices defaulting to sending 7.1 tracks to the Arc and the soundbar is unable to downmix it to 5.1. In most cases this causes missing dialogue or audio coming out from the wrong channels. On top of that the sound volume when using LPCM is really low compared to bitstream.

I could be wrong, but I think Sonos HT speakers just play what they are sent (or silence if sent something incompatible like DTS), and don’t attempt to do any downmixing or other audio processing.  

I thought the demand for multichannel LPCM came from the gamers.  I am puzzled as to why there was an expectation this would deal with the DTS issue on Blu-rays.

Is the volume low on LPCM for all scenarios?  I ask in genuine curiosity.

Hi

Well for me I got stereo from DTS blurays before the update, TV set to bitstream/passthrough and bluray player set to bitstream.

Not quite sure why you think this LPCM update was just for the gamers, I’m much happier to get multichannel pcm than stereo 2.0, just be nice if it was outputting correctly and not in 7.1.

Also all my content on my apple tv 4k box in dolby 5.1 is output as multichannel pcm 7.1.

So i’m not sure where you are coming from.

L
Userlevel 5
Badge +11

So what happens if you set your TV to DD5.1?

I have not looked to try, I know there is an auto setting but then that stops me getting full fat atmos from my oppo203.

Where I am coming from is that if you want a Sonos HT speaker to play DD5.1 you have to send it DD5.1.  Although id you want Atmos on the Arc it needs to be DD+

I’m not worried about DD 5.1 I just would like it to output correctly so multichannel pcm 5.1 not 7.1.

Yes streaming atmos is atmos DD+ but from my 203 I get Atmos (True HD)

Corry P
Userlevel 7
Badge +18

 Hi Everyone,

Well, this is embarrassing!

After some investigation, I’ve found that downmixing of 7.1 channel LPCM to 5.1 channel LPCM was indeed implemented on the Arc as a feature last year, but our literature wasn’t properly updated to reflect the change.

To be clear, the Arc does downmix 7.1 LPCM to 5.1, has done for some time, and we are working on updating our documentation to reflect the fact. Beam (Gen 2) has always supported LPCM and has always downmixed.

Thank you all for pointing this out to me so we can now make sure that this information becomes public. I’m sorry for the unnecessary confusion. I’ll post this in multiple threads.

This other issue with LG TVs is unrelated, but we’d very much like to get on top of it. We’ve requested the investigation of LPCM channels being played from the wrong speakers when an LG TV is involved, specifically when 7.1 channels are reported, and we will reach out to LG with details once we’ve gathered some solid evidence for them. Therefore, we’d very much appreciate it if anyone affected by this specific issue would visit this new thread I’ve made for gathering some details. Thank you.

 

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

So what happens if you set your TV to DD5.1?

I have not looked to try, I know there is an auto setting but then that stops me getting full fat atmos from my oppo203.

Also, have you considered powering off (not standby) the Apple TV4K and the LG TV for a few minutes and then first power-on the TV and set it’s HDMI-2 eARC port to ‘pass-through’ and then power on the Apple TV4K to see if that fixes the issue.

L
Userlevel 5
Badge +11

‘ I just would like it to output correctly’

By ‘it’ do you mean the Arc and by ‘output’ do you mean play?

 

Yes sorry, I want the ARC to play multichannel pcm 5.1, for me its “outputting multichannel pcm 7.1. 

Ken_Griffiths

Just to add, my LG HDMI eARC port is definitely set to pass-through - as you can perhaps just make out in the attached screenshot, hopefully?
 

I would try the ‘powering off’ suggestion,  I mentioned earlier as it might just resolve the handshake. Maybe power off the ARC completely too.

1 Attachment
L
Userlevel 5
Badge +11

Well take the Apple TV 4K for example on auto audio settings it sends atmos where available or LPCM, so any Dolby 5.1 content will play on the arc as multichannel channel pcm 5.1.

But for me it’s playing as multichannel pcm 7.1 

I don’t know what else to say really, it’s been said by others as well so I will leave it there and hope someone from Sonos will be able to tell me what the issue is.

 

@Ken_Griffiths thank you I did try power off, but no luck, it seems to be an issue with cx or later models of LG I think, anyone else with cx have same issue?

B
Userlevel 4
Badge +7

@billiejoe87 .  Thanks, that’s a very clear and enlightening explanation.  I wouldn’t say I was ‘confused’ on this point, rather ‘lacking in knowledge’.

Sorry, I wasn’t trying to sound rude. Just trying to explain that PCM is different from Dolby and DTS in that every system in the world supports it, as in it’s most basic form PCM is stereo. It’s just up to a device to negotiate how many channels it can support which seems to be where the problems with devices like the Nintendo Switch and Apple TV are having.

All in all somewhere along the line it is most likely that LG TV’s and the Sonos Arc are not handshaking correctly which is causing the issue.

1 x Arc, 1 x Beam Gen 2, 1 x Amp, 2 x Sonos In Ceiling Speakers, 2 x Sub, 9 x Sonos Ones, 5 x Symfonisk Lamp
J

There is no need to say sorry. I meant my previous post and wasn't in the least offended by your comments, which weren't rude at all.

In the last bit of my post I was trying to say that confusion implies a partial understanding,  which if anything was generous on your part!

B
Badge

No issues here LG B9 and sonos arc with Apple TV output 5.1content as multichannel PCM 5.1

L
Userlevel 5
Badge +11

Just to update happens on my xbox series x as well, which is set to uncompressed 5.1, and sonos arc outputs as 7.1

Perhaps its an lg cx issue, I know i’m not the only one with this issue, those that have the problem please state what tv you have.

L
Userlevel 5
Badge +11

I get the 7.1 if it is set to passthrough.  It changes to 5.1 if I set the tv to auto.   This is on 2020 75 LG Nano 90 and I also just got a 55 LG OLED CX.  It was the same, so I just returned it and just now realized my Nano 90 is doing the same thing.

Yeah seen a few mention AUTO works on lg cx, but for those that want to pass full fat atmos (true hd) from say a 4k bluray player, it needs to be set as passthrough.

Certainly a strange issue/bug.

L
Userlevel 5
Badge +11

I also have the 7.1 issue. I just wanted to chime in and say that AUTO does not work to output Multichannel PCM in 5.1 on the LG CX for me. If I do AUTO, then it will only play PCM 2.0.  My settings are HDMI Input Audio Format set to Bitstream and Digital Sound Out set to Pass Through. On my PS5, I have the Audio Format set to Linear PCM. When I play games,  the About My System page in the Sonos app shows Multichannel PCM 7.1. 

Good to know, hadn't tried Auto on the cx myself, just thought someone had mentioned that works, but perhaps not then.

 

B
Userlevel 2
Badge +1

Hi

Thought I would create this thread as a few have reported this issue in the lpcm update threads that are marked as solved so perhaps best to keep it separate.

Issue:

Before the LPCM update last week my sonos arc would receive atmos and Dolby digital 5.1 from the Apple tv 4k box, audio settings were set to the default AUTO-Atmos available.

My LG CX is capable of passing LPCM.

 

Now since the LPCM update with the above settings I still get atmos from apps such as netflix, apple tv + on the apple 4k box, but any content in dolby 5.1 is now outputting as multichannel PCM 7.1, 7.1 being the issue, it should be outputting as multichannel PCM 5.1

 

I have seen similar posts with this issue on the same device and other devices as well.

 

Thank you 


Hi

I have an LG OLED B7 and since the update I can now get my OPPO 203 to play pcm 5.1 when a DTS disc is in use which is great. the volume was a lot lower than when Atmos is playing. however it means I don’t need another Blu ray player.

K
Userlevel 2
Badge +4

I was really hoping that today’s speaker update was going to fix this.  Anyone able to see if this was addressed? The 5.1 content from Netflix through my ATV still shows Multichannel 7.1

R
Userlevel 4
Badge

Hi

Thought I would create this thread as a few have reported this issue in the lpcm update threads that are marked as solved so perhaps best to keep it separate.

Issue:

Before the LPCM update last week my sonos arc would receive atmos and Dolby digital 5.1 from the Apple tv 4k box, audio settings were set to the default AUTO-Atmos available.

My LG CX is capable of passing LPCM.

 

Now since the LPCM update with the above settings I still get atmos from apps such as netflix, apple tv + on the apple 4k box, but any content in dolby 5.1 is now outputting as multichannel PCM 7.1, 7.1 being the issue, it should be outputting as multichannel PCM 5.1

 

I have seen similar posts with this issue on the same device and other devices as well.

 

Thank you 


Hi

I have an LG OLED B7 and since the update I can now get my OPPO 203 to play pcm 5.1 when a DTS disc is in use which is great. the volume was a lot lower than when Atmos is playing. however it means I don’t need another Blu ray player.

I have the same issue with the Opposite 203 and my LG OLED C9. I now get 5.1 from DTS discs but the volume is so low it’s almost unwatchable. 

Really disappointing as I only bought the Arc as I knew it would eventually work with DTS content with the LPCM update but the quality of the audio this way is terrible.

J

@Ryan S are you guys looking into this issue? We’re glad the LPCM update is out but there are multiple reports of devices defaulting to sending 7.1 tracks to the Arc and the soundbar is unable to downmix it to 5.1. In most cases this causes missing dialogue or audio coming out from the wrong channels. On top of that the sound volume when using LPCM is really low compared to bitstream.

I could be wrong, but I think Sonos HT speakers just play what they are sent (or silence if sent something incompatible like DTS), and don’t attempt to do any downmixing or other audio processing.  

I thought the demand for multichannel LPCM came from the gamers.  I am puzzled as to why there was an expectation this would deal with the DTS issue on Blu-rays.

Is the volume low on LPCM for all scenarios?  I ask in genuine curiosity.

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