LG OLED C9 -> Sonos Arc -> Apple TV Sound Problem

bmarkjones

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I searched the C9 forum before posting this but could not find a reference to this problem. I have the setup shown in the title and the Apple TV is the latest version. When the Apple TV is set to Dolby Atmos, it plays Dolby Atmos content perfectly. However, on that same Apple TV setting, Dolby Digital 5.1 content comes to the Sonos Arc as Stereo 2.0. On the C9, sound is set to Passthrough and eArc.

However, when go to Audio Format on the Apple TV and turn on Change Format and set it to Dolby Digital 5.1, sound comes to the Arc as Dolby Digital 5.1. Obviously I shouldn't have to switch a setting on the Apple TV to go from DD5.1 to Dolby Atmos. It should switch automatically depending on the sound format coming in.

I got to Apple third-level support, and they feel the problem is LG's, with the Passthrough setting not working correctly. They said it's a known problem that LG is aware of.

Does anyone have any experience with this issue?

Thanks,
Mark
 
Have you tried turning earc off and just running arc? As you will only be streaming DD+ with atmos, only arc will be required

I get issues playing lossless audio via earc from the C9 to my soundbar which requires me to plug in/out the hdmi on my shield.
 
I haven't tried that because according to Sonos, the best Atmos sound will be through eArc:

From Sonos:
Most Dolby Atmos audio can be played through HDMI-ARC using the Dolby Digital Plus codec. HDMI-eARC is required to play lossless Dolby Atmos audio using the Dolby TrueHD codec.

I'll try it though. Thanks.

Mark
 
It depends on what you're playing, I'm not overly familiar with Apple TV but if you're using the likes of Netflix, Disney plus then it's lossy atmos so the sound you will receive will be the same whether using earc or arc.

Earc is only required for lossless audio like TrueHD with atmos, DTS-HD/X
 
Okay, I disabled eArc on the C9 then played Hamilton from Disney+ and it's coming into the Sonos Arc as Dolby Atmos. Now when I play DD 5.1 content from the Apple TV, it shows Dolby Atmos (DD+) coming into the Sonos Arc. I haven't listened carefully, so I don't know if that's as good as or superior to DD 5.1

I wish it would just truly Passthrough whatever it's receiving and do no conversion at all, as passthrough implies.

Thoughts or possible solutions welcome. Thanks!
 
I've had to do a bit of homework on this one as I do remember reading something about Apple TV doing something different with audio, someone step in and correct me if I'm wrong!

In your apple TV settings, you should have audio output set to auto. Now I believe that the apple TV will decode the stream to PCM to the TV and then to the arc via the arc channel. In this instance, you would need to have earc enabled to passthrough multichannel PCM. Also ensure that your C9 has the latest firmware update so that it can passthrough multichannel PCM too.

The thread below will explain a bit more about how Apple TV handles audio:

 
It's a little different now on the latest version of the Apple TV (that forum link was from 2018). Here are the current instructions from Apple:

Check if Dolby Atmos is set up
On your Apple TV 4K, go to Settings > Video and Audio and select Audio Format. Under Immersive Audio, check that Dolby Atmos is on. If you don't see Immersive Audio and Dolby Atmos as an option, you might need to change how your home entertainment system is set up.
 
I've just had a search on the sonos forum, looks like the issue is that Arc does not support multichannel PCM at present but will be added in a future firmware update. From what I can read, you will need to switch around the audio settings on your apple TV when listening to atmos or DD 5.1 as you will only get PCM 2.0 when listening to 5.1 when the Apple TV is set to atmos.

Basically, have the Apple TV set to auto, atmos when you want to listen to atmos content but change the audio settings to Dolby Digital 5.1 when you want to listen to regular 5.1 content.

I'd have a read up on the Arc threads on here or have a look at the sonos boards to see what, I've just read. There is meant to be a firmware update due soon, although sonos have been saying this for a couple of months. It doesn't help that Apple insist on decoding the stream to output in PCM. Your choices for now are tweak the apple TV settings depending on the content you're listening to, wait for the firmware update or invest in a new media player!
 
You're right - that's exactly what I've been experiencing and the workaround I've had to make. Thanks so much for researching the in more depth. I certainly appreciate it. Hopefully Sonos will fix this soon.

Thanks again,
Mark
 
Hi guys. I just found this page as I received my Sonos Arc today. I have set it up this afternoon with my LG CX and Apple TV 4K. I am playing atmos movies fine but if I play any iTunes movie which has a menu screen the sound keeps cutting out! It then works fine on the actual movie. Has anyone here experienced that too? Thanks.
 
Don’t worry about my question guys. Problem has resolved itself this morning. Must have been an iTunes issue. 😀👍🏻
 
Hi

i have the exact same system. And problem.

Any updates on this issue?

(I now have a more strange problem: after testing all settings back and forth I am not able anymore to get atoms from my Apple TV to the arc anymore. If I set Atmos on in ATV I only get stereo 2.0 on the sonos arc and the dialog is silent ).

I’m very disappointed about this and are considering returning the entity system. My old LG sound bar played atmos and Dolby 5.1 from ATV flawless.

Thanks
Clarence
 
I have the C9 and considering the Sonos Arc. I do not have and do not even plan to have Apple TV device. Will I be affected by the issues in this thread?
 
I have the C9 and considering the Sonos Arc. I do not have and do not even plan to have Apple TV device. Will I be affected by the issues in this thread?
Hi,
I have C9 + Sonos Arc and apps inside the C9 supports both Dolby Vision and Dolby Atmos. I have used Netflix, Apple TV+ and Disney+ with success. So you will not be affected by the Apple TV problem we describe in this thread.
/Clarence
 
Hi

i have the exact same system. And problem.

Any updates on this issue?

(I now have a more strange problem: after testing all settings back and forth I am not able anymore to get atoms from my Apple TV to the arc anymore. If I set Atmos on in ATV I only get stereo 2.0 on the sonos arc and the dialog is silent ).

I’m very disappointed about this and are considering returning the entity system. My old LG sound bar played atmos and Dolby 5.1 from ATV flawless.

Thanks
Clarence

Have you figured out a solution to this issue? I just started getting it. I have a Vizio Elevate soundbar that was working fine at first, but now when I listen to non Atmos content on my Apple TV 4K the dialog is basically silent. I’ve tried numerous fixes including making sure all software up to date, doing multiple factory resets, etc. It seems to only be affecting content purchased on iTunes, but any purchased Atmos titles play fine.
 
Have you figured out a solution to this issue? I just started getting it. I have a Vizio Elevate soundbar that was working fine at first, but now when I listen to non Atmos content on my Apple TV 4K the dialog is basically silent. I’ve tried numerous fixes including making sure all software up to date, doing multiple factory resets, etc. It seems to only be affecting content purchased on iTunes, but any purchased Atmos titles play fine.
Hi, since my post, I have updated the software/firmware on Apple TV + LG Oled + Sonos Arc. After this it seems to work. The dialogue is possible to hear.
 

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