Dolby Digital 5.1 / uncompressed 5.1 output as multichannel pcm 7.1

I have an old Panasonic plasma hooked up to an HDFury Arcana and Apple TV 4K. If I have the Apple TV’s audio setting set to output Dolby Digital 5.1, the Sonos app reports “Dolby Digital 5.1”. But if I have Change Format turned off and Immersive Audio turned on on the Apple TV, when I watch Dolby Digital Plus 5.1 content, the Sonos app reports “Multichannel PCM 5.1” and Dolby Atmos content via Dolby Digital Plus reports as “Dolby Atmos”.

FYI… the Apple TV 4K uses Dolby MAT which is a form of PCM audio. That’s why you will often see “Multichannel PCM” rather than “Dolby Digital Plus” reported in the Sonos app.

hello,

My set-up:

LG OLED 55GX + ATV 4K Gen2 + Arc plugged with eARC

TV settings: 

• Output: HDMI ARC
• output: audio: passtrhough
• eARC enabled

ATV settings:

• Audio output by default: Receiver speakers
• Audio format: Auto, Atmos available/ change format: no, Immersive Sound: Dolby Atmos Yes
• Audio mode: Auto

With Netflix app on ATV, I launched Jurassic World Camp Cretaceous, which is HD 5.A, the Sonos App says I have PCM 7.1 on my Arc.

The same when I play the Dolby Test Tone 5.1.2 from Plex.

I realise why I only get multichannel pcm or atmos from the ATV4K, going by both your comments, it does seem to be an LG issue then, thank you both.

I have contacted LG in the past but they always seem to think its a problem with only my tv and give the same old rubbish about try this and that. Be great if Sonos could contact them, perhaps then LG might act and release a fix.

Had the same issue, with the LG CX and specifically Amazon on the ATV4K. (Outputting to 7.1 when I want 5.1 and I got lip sync issues.) I also noticed that my Xbox Series X when set to output 5.1 uncompressed was outputting multichannel 7.1.

I changed the LG from Passthrough to Auto, and that has resolved my ATV issues. Getting 5.1 and Atmos. (But sadly can’t output the Xbox to 5.1 now.)

Yeah AUTO solves it for the most part, but those that use passthrough gives the results you mention.

It seems its an LG oled issue with LPCM passthrough, I wish Sonos could press LG to try and fix it. 

It’s like going through hoops when you contact LG yourself.

Hello,

I have changed my TV settings from Passthrough to AUto.

Now, when I play Dolby Atmos content, the Sonos App is displaying PCM Multicanal 5.A

Should I see something different?

My setup: 

1. Sony A80J 77” OLED (eARC with auto pass through enabled)
2. Sonos ARC + 2x Sonos ONE SL surrounds + Sub
3. Apple TV 4K 2021 32gb

7.1 Dolby Atmos audio out of Apple TV passed to the ARC via eARC on my tv is fine - shows as “Dolby Atmos” on the system status in Sonos app.

Issue occurs when playing 5.1 audio out of Apple TV - it shows up as •”Multichannel PCM 5.1” . The audio itself seems to play and no sync or stutter issues. The problem is the the center/voice channel is playing on one of the rear surround speaker. Seems like either Apple TV or Sonos cannot correctly distinguish between 7.1 and 5.1. 
 

For context - playing 5.1 or 7.1 Atmos audio through native apps on Sony or my Amazon Fire TV vibe gives no problems and just seems to do the right thing so is the problem in Apple TV or how Sony is passing through the sound? Please help - this is driving me nuts. 

did you ever figure this out? I’ve got a Sony a9g and an Apple TV 4K with a Sonos Arc and two One SL’s. I’m having big issues with hearing voices on some content and volume between Dolby digital plus content and LPCM content (like between commercials and ads on streaming apps). It requires me jumping for the remote to turn down the volume during commercials and turning it back up to hear people talk during shows. It’s really annoying!

I have a very similar setup with an Sony A80J, Arc and a Sub along with a Apple TV 4K not the newest model. I happen to jump back and forth when it comes to audio. I have retuned using Trueplay multiple times and no matter what the dialogue is just not good. It is infuriating knowing that sound effects will be extremely loud but then dialogue is too low and having to guess when a scene is going to be too loud. I pretty much have ran out of options on what to do at this point. Loudness is not on either. Speech Enhancement does not really work that well. So yeah another person with the same problem.

I noticed the same thing.  I also have Apple TV —→ LG CX——> Sonos Arc. Noticed when set to pass through was coming as 7.1 because it was so much quieter.  I leave the TV set to auto to make sure I get Atmos when available.  If I leave on Passthroigh I get 7.1 instead of 5.1 on HBO Max app and atmos doesn’t trigger properly.  

So after a year I finally got my sonos arc /Apple tv4k / lg cxoled tv to work properly. I reset my tv and Apple TV. I opened up Apple Music. Dolby Atmos worked no problem. Then I went to Netflix on my Apple TV. Dolby Atmos worked and also the 5.1 finally worked. Before this I always had issues with no sound or coming out as pcm7.1. So I checked my tv sound settings that are now reset to default factory. It has my hdmi set to bitstream. Digital sound out to Auto. EARC off. Now everything works fine. Crazy. I guess eARC and pass through of any combo failed. Hope this helps. 

You are getting Dolby Atmos audio from the Apple TV 4K with eARC turned off?

Yes. Earc off and set to auto not pass through. 

I didn’t know Dolby Atmos audio from the Apple TV 4K was possible without eARC. Are you sure you are getting real Dolby Atmos audio or is the TV just converting the audio to Atmos? Do you hear any height channel effects above you?

I can't say for certain. It does sound great so assume it is what is says. When I go to non-Atmos songs it shows as PCM on app. When I turn on earc, it sometimes works or goes to pcm 7.1. Also sounds good. The big issue is with Netflix on Apple TV. If I leave earc on, sometimes I have no sound at all. 
My understanding is you only need arc for Dolby atmos. Maybe for true Dolby atmos via a blue ray player you need earc. Not certain. 

ARC allows Dolby Digital Plus, which carries the ‘lossy” version of Dolby Atmos. eARC allows MAT/Dolby Atmos, which is the “non-lossy” version.

Worth reading up on the two versions of Dolby Atmos...my impression, from last year when I read up on it, it sounded more like “lossy” meant fewer speaker channels, not a lower quality of sound. And certainly in a Sonos system, you’re limited to how many channels can be listened to. 

At the end of the day, though, it’s still a sound bar. A rather good one, to be sure, but if you’re that concerned about disparate channels, you likely shouldn’t be considering a sound bar at all, but a fully featured amplifier with wired separate speakers. 

Hmm. Interesting. On my Lg tv smart apps using Netflix I get Dolby digital plus with 5.1 content and Dolby atmos with atmos content. That is with earc and pass through enabled. The issue to me seems to be Apple TV. Same settings with Apple TV and I get no sound with 5.1 content and atmos content will show as 7.1 multichannel pcm. Apple TV with earc off will give me 5.1 with 5.1 content and atmos with atmos content. Anyways, very happy with sound. Just had to find the right settings. 

Well first off streaming apps use the DD+ lossy version of atmos.

It’s all to do with the sound carried over HDMI, which it’s not when you stream from onboard TV apps. I find it strange you get no sound with 5.1 audio with passthrough and eARC enabled via apple tv device.

I have no issue with those settings, just that all DD 5.1 audio is output as multichannel 7.1.

Its all a bit of a minefield, there was a similar thread to this to do with audio and missing channels on the sonos arc, big problem is Sonos support absolutely sucks massively. They used to reply often but now they pick and choose who to reply to.

Thank you, this has solved my issue.