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Multichannel PCM on Arc



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5 months later and a $800 soundbar / $2k TV with a Switch outputs stereo. It’s embarrassing. 


Its embarrassing that Nintendo are too cheap to pay for a Dolby license, for sure.

My "at least for now" was more directed at the fact that hardware wise, the Beam does have the capability to potentially support DD+ and Atmos over DD+. Multichannel uncompressed is indeed not possible over ARC.

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The Arc should be down-mixing 7.1 to 5.1 for non-Atmos streams that are actually sending 7.1 channels, and should be following the Atmos instructions for where Atmos streams.
I’m guessing that most things will have nothing on those side center channels though, so I’d think it should be fine.

 

It’s not - I’ve done some testing and the Arc is currently not downmixing

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… It doesn’t look like this is even a technical issue, as the device supports Dolby MAT, which is multichannel PCM and additional dolby metadata on top. I mean, I’m not sure how it’s even possible to not support multichannel PCM in this case? I’m starting to hope that this is just a press error, considering how fatal an omission the lack of multichannel pcm would be for a device of this type that does not have DTS support.

Originally Dolby MAT was used for transporting TrueHD. When atmos was released, they allowed MAT to unpack both DD+ and TrueHD to multichannel PCM. So its possible sonos are supporting TrueHD MAT but not PCM MAT. God knows why not. 

Understood, thanks. Still is the difference between getting and not getting one when one has an earc equipped system with anything more than Netflix.

Thanks to everyone for the feedback so far. Support for multi-channel LPCM is in active development. We'll be testing over the next few months to be part of a future software update. We will update the community once it's available.

A few months?

 

I just got an LG BX and have my Arc plugged into the eARC port - yet when I play any Dolby Atmos content via my Apple TV 4K I get no sound (tried heaps of combinations of settings to no avail).

 

From what I understand this is due to the arcs lack of LPCM support. So my Arc will be a very large brick until this update is released in a few months?

You could perhaps ‘switch’ audio codec in the Apple TV settings to Dolby Digital 5.1. I believe that should keep things going with surround sound until the multichannel LPCM update arrives. 

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Thank you Nicholas for the response. 

Based on your response, I am understanding that Dolby Multi-channel PCM 5.1 is a better signal than Dolby Digital 5.1. 

Final clarification, with eARC set to Auto on the Samsung Q70T TV, Netflix/Amazon Prime/Disney+ apps that have content listed as 5.1 ( on Sonos Beam shows as Dolby Digital 5.1 ), now on Sonos ARC it shows Dolby Multi-channel PCM 5.1, so this is the best format outputting? 

It’s difficult to say if it’s the best output formatting or not in your case because the source may just be transcoding a lower fidelity encoding into this higher one. In that case, you’re not really getting a different experience. In general though, the higher bitrate encodings are going to be your best bet so I would stick with Dolby Multi-channel PCM 5.1.

The Arc should be down-mixing 7.1 to 5.1 for non-Atmos streams that are actually sending 7.1 channels, and should be following the Atmos instructions for where Atmos streams.
I’m guessing that most things will have nothing on those side center channels though, so I’d think it should be fine.

Thanks for sharing all of your feedback everyone. We will be adding Multi-Channel LPCM support to Arc as part of a future software update. We don’t have exact timing to share at this point and will update this thread when we do.

Legend! Look forward to when the update arrives

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Amazing! Thanks for the update!

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You’re welcome. I’m also renaming the thread slightly.

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Is LPCM = Dolby Multi-Channel PCM?


No. Dolby has nothing to do with PCM.

Dolby Multi-Channel PCM is the label used for a Dolby MAT container signal that contains PCM and metadata vs. a Dolby MAT container that contains TrueHD.


This is what I see on my Sonos app when I play a DD 5.1 content.. 

 

pretty confusing not knowing if my Sonos Arc is producing the right sound or it has a bug interpreting the Source audio Content as it doesn’t match what it says on the source title vs on Sonos system info

 

 

The Arc is likely not confusing the input. It’s more likely that the source content is DD 5.1 but the source device is deciding to decode it and wrap it in a MAT container before passing it onto the next link in the HDMI chain for consistency reasons.

 

: If you see my testing results on Sonos Beam, Beam is receiving Dolby Digital 5.1 content from the TV ( Netflix App on Samsung Q70T  → TV HDMI eARC → Sonos Beam’s ARC HDMI connection - Sonos Beam ) with the same settings. The only difference here is the Sonos Arc ( Netflix App on Samsung Q70T  → TV HDMI eARC → Sonos Arc eARC HDMI connection - Sonos Arc ) which is receiving Dolby Multi-Channel PCM 5.1

Right, each device has different audio format capabilities in part due to the bandwidth available over ARC vs. eARC. These capabilities are communicated to the TV in a couple of ways.

MAT is only available over eARC so only the Arc advertises this to the source. It is ultimately up to the source device what format it transmits. In your case it decided to prefer MAT over DD since it is available on Arc.

 

Can’t agree more with your explanation. Thank you!

So in an ideal cases what is the best format that the TV should be transmit to Sonos Arc over eARC for a DD 5.1 content? I some how feel that the DD 5.1 that is outputting from Xbox / Apple TV 4K ( using pass-through )  and transmitting to Sonos Arc sounds better than Dolby Multi-Channel PCM 5.1 via native app on the TV. 

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Add another voice to the “please add support for LPCM 5.1” chorus. As a Nintendo Switch owner it’d be really cool to have full surround support.

Blame Nintendo for using a format that cannot be passed over optical, or ARC. They don’t care if you want to take the audio from your TV (that gets it via HDMI) and do something else with it. They don’t want to pay the royalties to Dolby, that’s all.

eARC is the only transport that can handle LPCM 5.1 from a TV to an audio device.


why pay royalties to anyone. LPCM is superior and free.

The playstation 5 and new Xbox are using new 3d Audio codecs that blow Atmos away - I’ve tried the PS5 version and it makes Atmos look like a toy. Whats the point paying a license for that lol

Thanks for sharing all of your feedback everyone. We will be adding Multi-Channel LPCM support to Arc as part of a future software update. We don’t have exact timing to share at this point and will update this thread when we do.

Hooray! Let's hope its sooner than later! Thanks for the update, might just buy an arc after all....

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Is LPCM = Dolby Multi-Channel PCM?


No. Dolby has nothing to do with PCM.

Dolby Multi-Channel PCM is the label used for a Dolby MAT container signal that contains PCM and metadata vs. a Dolby MAT container that contains TrueHD.


This is what I see on my Sonos app when I play a DD 5.1 content.. 

 

pretty confusing not knowing if my Sonos Arc is producing the right sound or it has a bug interpreting the Source audio Content as it doesn’t match what it says on the source title vs on Sonos system info

 

 

The Arc is likely not confusing the input. It’s more likely that the source content is DD 5.1 but the source device is deciding to decode it and wrap it in a MAT container before passing it onto the next link in the HDMI chain for consistency reasons.

 

: If you see my testing results on Sonos Beam, Beam is receiving Dolby Digital 5.1 content from the TV ( Netflix App on Samsung Q70T  → TV HDMI eARC → Sonos Beam’s ARC HDMI connection - Sonos Beam ) with the same settings. The only difference here is the Sonos Arc ( Netflix App on Samsung Q70T  → TV HDMI eARC → Sonos Arc eARC HDMI connection - Sonos Arc ) which is receiving Dolby Multi-Channel PCM 5.1

Right, each device has different audio format capabilities in part due to the bandwidth available over ARC vs. eARC. These capabilities are communicated to the TV in a couple of ways.

MAT is only available over eARC so only the Arc advertises this to the source. It is ultimately up to the source device what format it transmits. In your case it decided to prefer MAT over DD since it is available on Arc.

 

Can’t agree more with your explanation. Thank you!

So in an ideal cases what is the best format that the TV should be transmit to Sonos Arc over eARC for a DD 5.1 content? I some how feel that the DD 5.1 that is outputting from Xbox / Apple TV 4K ( using pass-through )  and transmitting to Sonos Arc sounds better than Dolby Multi-Channel PCM 5.1 via native app on the TV. 

I would leave your settings as they are if you are getting the higher bandwidth formats (MAT or TrueHD). I can’t explain why DD would sound better with the same content unfortunately.

Userlevel 7
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Yep I’m another voicing my annoyance that LPCM has been left out. It’s free and is used across all gaming consoles as default. There is no logic behind why it’s not supported by the Sonos ARC especially with eARC


Oh I agree. I can think of no technical or legal reason that the Arc cannot support multi-channel LPCM, so maybe it will, given more engineering time. At least it is possible with eARC now.

On my C9 (stupid firmware update got me) on my Apple TV, i went to to settings > audio (I think it’s audio) and flip the audio from Auto to 5.1 it’s a temp work around to get audio out of the ARC. Otherwise, it comes through all kinds of messed up and you can’t hear anything.

With that said, i’m just as mad as everyone else and hope they get this LCPM update out ASAP.  Kinda disheartening to buy into a product thinking you’ll get Atmos sound only to have to revert back to 5.1.. Especially after spending over 1k on getting the whole setup.

 

I know they’re trying to fix the issue with an update but I would of rather them push the release back a bit and shipped with the firmware update… I feel like I’m beta testing a half baked product and it leaves a bad taste in my mouth. 

lol if anyone over in Sonos land is looking at this I will happily volunteer to use a beta firmware to fix this cause well, what do I have to lose at this point?

On my C9 (stupid firmware update got me) on my Apple TV, i went to to settings > audio (I think it’s audio) and flip the audio from Auto to 5.1 it’s a temp work around to get audio out of the ARC. Otherwise, it comes through all kinds of messed up and you can’t hear anything.

With that said, i’m just as mad as everyone else and hope they get this LCPM update out ASAP.  Kinda disheartening to buy into a product thinking you’ll get Atmos sound only to have to revert back to 5.1.. Especially after spending over 1k on getting the whole setup.

I have the same setup and Atmos works fine. The problem occurs when you have the Apple TV set to “Auto, Atmos” and play 5.1 content. The firmware update enabled LPCM for the LG C9. Apple TV set to “Auto, Atmos” will then deliver sound as LPCM as it now recognizes the C9’s support for it and considers it the next best thing to Atmos, i.e. rates it above DD5.1. 

The workaround, like you mention, is to set the Apple TV to “Dolby Digital 5.1” for 5.1 content. You will then need to switch back to “Auto, Atmos” for Atmos content.

For WebOS built-in apps there are no problems. Plays Atmos (when available) and Dolby Digital Plus for 5.1 content.

 

I’ll reiterate. The device is the Sonos Arc. Not the Sonos ARC. ARC stands for Audio Return Channel. 

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Disappointed still no LPCM support with 12.1

Standard HDMI-ARC doesn't have the bandwidth to transport multichannel PCM, so the Beam is limited by its hardware.

Userlevel 5
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Are you really not supporting multichannel PCM on the newly announced Arc?

Why? It’s not a licensing issue this time.

It seems like there is always something missing with your home theater products.

No multi channel PCM means no 5.1 for Nintendo Switch. Arghhh agree always something missing. 


ooh that's a good point I forgot about the switch. Yeah there is no way to get 5.1 sound from the switch on the Playbar, and no 5.1 for the Arc either 

Hi folks. Thanks for reaching out and sharing your thoughts here. I understand where you all coming from and as Ryan’s response we will be adding Multi-Channel LPCM support to Arc as part of a future software update. We don’t have the exact timing to share at this point and will keep you all posted when we do. All threads are being addressed and checked here so creating a new thread is not necessary as this has been forwarded and being worked on. Ryan’s response has just been marked as the best answer for you to easily see and know that we addressed it. 

Appreciate your patience and understanding. We and the community are always here to help.

The problem is with this is that it's pretty much the same response you gave 4 months ago…

From your customers perspective you've done nothing over the last 4 months. Saying it's "going to be added" doesn't exactly instill confidence when we are already 4 months down the road and you have nothing to say or show for it.

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The sonos app reporting 7.1 multichannel, I thought was a bug with Sonos ARC?

All my devices that that should be 5.1 say 7.1 on the sonos app.

 

My xbox series x,  if set to uncompressed 5.1 outputs as multichannel 7.1 according to sonos app.

My oppo 203 is exactly the same.

As is my apple tv 4k for any 5.1 content that it sends as LPCM outputs as 7.1

 

Is Sonos still working on a fix, thought I read something a while back that they were aware?

Not for me at least. When I make a change to 5.1 on a device like the PS5, it updates instantly in the Sonos app to LPCM 5.1 from 7.1. My Apple TV 4K works correctly, outputting 5.1 LCPM on 5.1 media without any settings adjustments (even though more and more DD 5.1 content is being upgraded to Atmos, I couldn’t even find a 5.1 movie last night) I use that surround speaker test app which is known as a baseline.  When the Sonos app says 7.1, the sound is messed up and has gaps where the 2 extra speakers should be. The bug for me is the PS4/5 thinking the setup is 7.1 without manual intervention. Are you sure this isn’t a TV pass through issue? Try that surround speaker test app in DD5.1 and see what the Sonos app shows. 

Weird, perhaps it is my LG CX, I know others reported the same that have the CX as well.

Where can I find the speaker test app please?

In the Apple TV App Store: “surround speaker check”. In the app try the 5.1 speaker check. 

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If you have a 2019 LG OLED (B9,C9,E9, W9) and use an Apple TV 4K then I strongly advise you to not update to the 04.80.03 update until Sonos update the Arc with LPCM 5.1 support. 

Because the TV after the 04.80.03 update supports LPCM 5.1 the Apple TV thinks (reads the TVs EDID) that it can now accept LPCM 5.1 so it sends LPCM 5.1 audio however because the Arc doesn't support it yet it then it only outputs 2 channels (Sonos app shows “Stereo 2.0” for all non Atmos content). Before the 04.80.03 update because TV didnt support LPCM 5.1 channels the Apple TV would just decode it to Dolby Digital 5.1 and everything worked well. 

I along with a lot of other users have update the TV and we are all having issues. The only way around it is now to change the setting on the Apple TV to “Change Format to Dolby Digital 5.1” however this turns off Dolby Atmos. 

This is only an issue with the Apple TV. I confirm everything is fine for the WebOS apps and other media devices. 

Really need LPCM support more than ever for the Arc now

I think this unveils another problem with the TV firmware.  The TV should only be reporting that it supports multichannel PCM if the soundbar reports that it supports multichannel PCM.

I assume that the Arc is reporting to the TV what formats it supports.  The TV really should be relaying that to your source device.

This causes a similar problem with DTS and Blu-ray players.  The Arc tells the TV that it doesn’t support  DTS, but the TV tells the Blu-ray player that it does support it.

Most players only have a bitstream or decode (or stereo) option.  Bitstream is required for TrueHD Atmos, but DTS doesn’t work when set to bitstream.  Once Sonos adds multichannel PCM, you can use bitstream for Atmos and decode for DTS.  For now, DTS requires going all of the way back to stereo, which is really unfortunate.

I am thinking of trying a HD Fury DR HDMI 4K to fake out the EDID going to the player, but this shouldn’t be needed if the TV was accurately relaying the soundbar’s capabilities.

Edit:  I should add that the reason for the HD Fury would be to tell the player that DTS isn’t supported.  Most players when set to bitstream will decode to PCM if the EDID indicates that the audio format is unsupported.

This could also be used to indicate that only 2 channel PCM is supported to fix the Apple TV problem, but that would only be temporary because we know that Sonos will support multichannel PCM eventually.

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Now the update is out for the Sonos Arc, I want to make sure I’m getting the best audio.

Playing Atmos content seems to work fantastic now. I am very happy with the sound from the Arc, Sub and 2 Ones.

When I play videos that have 5.1 audio, my Sonos app reports Multichannel PCM 7.1. Is this a problem as from what I understand my setup is not 7.1 (for reference, I am using an Apple TV 4K, LG GX, Sonos Arc, Sub and 2 Ones)?

Cheers.

I have the exact same setup and I am wondering the same. I use Infuse to play Blu-ray rips with DTS-HD streams. Infuse converts the audio to LPCM, but even a DTS-HD 5.1 stream is displayed as Linear PCM 7.1. I noticed the center channel (voice) is playing out of the rears when playing Ed Sheeran Jumping For Goalposts. Maybe something wrong with the channels?

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