Hello,
just received the Arc and so far loving my first Sonos device 
I have an Apple TV 4K, LG OLED B9 (eARC support) and now the Sonos Arc.
When I play normal DD-Content on the ATV, the Arc only outputs Stereo. (The TV also says PCM)..
Is there anything I can do besides force the ATV to output DD? Because it would be not so nice to switch between the audio settings if I want to watch Atmos or DD-Content.
Thanks
Michael
Sounds like you’re running the latest LG firmware that introduced LPCM and this issue. The workaround is to go into the Apple TV settings and turn off Atmos when you want to watch DD 5.1 content. This will most likely go away once the Arc is updated to support multichannel LPCM.
I tried every TV setting I found, so far no luck.
Digital Sound default was Auto, and also tried Passthrough. The HDMI Input is set to Bitstream.
My guess is, that the Apple TV decodes DD and outputs multi-channel PCM
Received my Arc today and have just few minutes to do some test with my Apple TV
I although have Dolbiy Atmos (regarding to Sonos App) for Atmos contents, and PCM Stereo for non Atmos, when configuring the Apple TV with the auto / Atmos Settings,
And DD 5.1 when changing audio settings to DD5.1
My TV (Panasonic GZ1000) is ARC only, I’ll be forced to switch the audio parameters each time I want to watch Atmos / non Atmos content, frustrating...
and I still don’t understand what signal the Apple TV actually sends for Atmos Content. I thought the Dolby MAT signal was only metadatas, “real” sounds being transmitted in LPCM.
Still hope Apple enables (recode) DD+, the streaming services don’t offer higher audio anyway.
Yup agreed, I cannot believe that Sonos and apple didn't work this out, Sonos knew the output from ATV and some of there other set-top boxes why didn't they accept multiple inputs like most other atmos sounders. Its just very disappointing for everyone including those of us with a brand new EARC tv and those who dont. This really should not be this difficult, I know the DTS cost money for licensing but LPCM does not!
Good luck everyone hold tight and dont buy it or in my case sit and wait till its fixed!
Sorry sonos. But this is product is not something I would recommend anyone to buy.
I really regret going all in on this. Bought a new TV with Atmos and earc so it would be the be the perfect setup. And this is what I get.
Have 8 sonos product in my house. So this is very disappointing.
Apple TV outputs LPCM for uncompressed audio. I’m guessing that’s what it uses for DD+. Sonos has announced that the Arc will support LPCM in the future via software update. The Atmos is delivered via MAT container I believe which the Arc can decode.
You should get DD and DD+ via the tv internal apps though.
So first of all, I get Dolby Atmos on the Arc… but everything else from the Apple TV is Stereo.
Also a side info: When the TV is on passthrough in Sonos is shown “Dolby Atmos”. In “auto” it is “Dolby Atmos (DD+)”.. Which could indicate that the TV changes the audio-format.
To the best of my understanding, if the Apple TV 4K is outputting uncompressed LPCM audio, then it’s already decoded the Dolby Digital / Dolby Digital Plus bitstream from the source. The TV would then think it’s receiving regular old PCM audio and then try to pass that along to the Sonos Arc. The Arc, not seeing a MAT container or a Dolby Digital Plus bitstream and not currently being compatible with LPCM should do absolutely nothing (unless the Arc’s current behavior is to take a multichannel PCM stream and simply ignore all but the Left/Right stereo channels which could explain the behavior
@michary is seeing from his current setup).
I think with the HDMI-Arc the TV and Soundbar exchange which audio formats are supported. I would guess that the TV itself strips it to stereo.
Additional thought - Since every device in your chain is fully Atmos-compatible and uses eARC, maybe one or more of your HDMI cables is too old? During my research on this frustrating, but admittedly fascinating, topic, I learned that HDMI 2.1 / eARC basically adds Ethernet into the mix in order to provide the sort of massive bandwidth needed for all of this stuff.
I used the bundled HDMI cable from the Arc.. so this one should be save..
The Apple TV 4K only supports HDMI 2.0a.. seems like a long-shot but I can try it 
Oh sorry, I should have make it a little clearer..
I only use the Apple TV 4K:
I don’t exactly know how Dolby MAT works, but can’t the Apple TV always send LPCM, and add MAT for an ATMOS signal ?
And signal received by the ARC could be only PCM Stereo, plus MAT infos, resulting in “Dolby Atmos” indicated by the ARC ?
This would explain the PCM Stereo for a DD signal, and Atmos (but just stereo Atmos) for an Atmos signal.
I don’t exactly know how Dolby MAT works, but can’t the Apple TV always send LPCM, and add MAT for an ATMOS signal ?
And signal received by the ARC could be only PCM Stereo, plus MAT infos, resulting in “Dolby Atmos” indicated by the ARC ?
This would explain the PCM Stereo for a DD signal, and Atmos (but just stereo Atmos) for an Atmos signal.
I don’t think there is a thing like stereo Atmos. If the ATV received Atmos it will stream it in a MAT container which the Arc can decode. Everything else is streamed as LPMC. Depending on your TV it will either pass it through or change it into something else (PCM or DD). Anyway, this won’t be an issue when the Arc gets enabled for LPMC. Then the bitstream can get straight pass through via eARC and the Arc can play it.
I’m getting my C9 and my Arc delivered tomorrow so I’m guessing I’ll have all that fun over the weekend. Do you get DD when you’re using the internal apps ?
For privacy purposes the TV is not connected to the internet.. so I cannot test this.
I have the new LG 75NANO90UNA tv which has an EARC hdmi 2.0 I have that sending the signal to the Sonos Arc and I have the Apple TV connected to a regular hdmi 2.1 but it refuses to play a sound when it goes into a movie that has atmos. When I go to the menu for the movie the theme music plays and when I play a non atmos movie the sound goes through fine but the minute I play an atmos movie from atv it has no sound. I can play atmos from the Netflix app on the tv (Space Force) and it does show on the Sonos App that it is in Dolby Atmos. I am now at a complete loss as to what else to try as the entire reason I bought a brand new tv and the Sonos Arc was to be able to play my atmos movies I bought that are on my Apple TV. If anyone has any ideas I would love to hear them, I have tried every setting I can think of, and the tv has arc set to on and passthrough enabled also. The Apple TV is set to bitstream on the lg tv. The lg app for appletv+ doesn't play atmos but it is not supported as yet apparently but will be updated FYI but the LG Netflix app plays atmos perfectly.
ARGHHHHHH
Having read a lot it would appear that when the arc is in Dolby mode that it send out a mat signal and until Sonos update their software to include LPCM it won’t work
Let's hope that the Sonos staff is looking in this thread and see this huge issue. It should be an easy fix. Sonos Arc is not worth anything without this fix. It should have been working from day one.
Sonos can’t fix this. Apple should enable recode to Dolby Digital Plus as output or even better, bitstream the audio track.
Let's hope that the Sonos staff is looking in this thread and see this huge issue. It should be an easy fix. Sonos Arc is not worth anything without this fix. It should have been working from day one.
Sonos can’t fix this. Apple should enable recode to Dolby Digital Plus as output or even better, bitstream the audio track.
I was under the impression that Sonos needs to implement LPCM as a signal and it should all work. I basically don’t care who does it I just want it to work as DMD this should have been known before releasing this product and having people buying New TVs with EARC.
It is sonos that needs to fix this, not apple. Sonos could have implemented this before release. They could make this work in a few days IF they wanted to. It is free to use the codec. I have never bought sonos arc if I have known this. It's not very customer friendly to have this issue from day 1.
Apologies the topic starter was talking about EARC I confused this with another topic. But for the ARC TVs the fix is still on Apples side. EARC should indeed be fine with LPCM.
Still hope Apple enables (recode) DD+, the streaming services don’t offer higher audio anyway.
That sucks. I’m also stuck with my ATV and how Apple wants to do this. At least I get Atmos over DD+ via ARC to the Arc :)
+1
Arcana officially starts production! You can pre-order here: https://hdfury.com/product/4k-arcana-18gbps/
FYI: Arcana allows you to pass full Atmos to Sonos Arc while passthrough full video (up to 18gbps) to non-eARC TV.
I’m guessing it’s a TV setting since you’ve got full eARC support (and congrats! you’re one of the lucky few).
On your TV, go to Settings > Sound > Sound Out. There you should see settings for HDMI ARC. Make sure to set Digital Sound Out to Auto / Pass Through. If the Sonos Arc is connected to your TV via the HDMI ARC port, you should now be getting Dolby Digital / Dolby Digital Plus / Atmos sound.
You may also need to go into Settings > Video and Audio on the Apple TV to check that everything is correct there as well. Select Audio Format, then under Immersive Audio check that Dolby Atmos is On (you’ll probably only see this option once you’ve made the changes in your TV settings).
Good luck, and please report back how everything goes!
Apple TV outputs LPCM for uncompressed audio. I’m guessing that’s what it uses for DD+. Sonos has announced that the Arc will support LPCM in the future via software update. The Atmos is delivered via MAT container I believe which the Arc can decode.
You should get DD and DD+ via the tv internal apps though.
I think it’s a little more complicated than that (as if this needed to be more complicated, right?).
To the best of my understanding, if the Apple TV 4K is outputting uncompressed LPCM audio, then it’s already decoded the Dolby Digital / Dolby Digital Plus bitstream from the source. The TV would then think it’s receiving regular old PCM audio and then try to pass that along to the Sonos Arc. The Arc, not seeing a MAT container or a Dolby Digital Plus bitstream and not currently being compatible with LPCM should do absolutely nothing (unless the Arc’s current behavior is to take a multichannel PCM stream and simply ignore all but the Left/Right stereo channels which could explain the behavior
Since Dolby says “there is NO way of sending Dolby Atmos over PCM over HDMI, so you have to send Dolby Digital Plus or Dolby TrueHD to get the Dolby Atmos experience"(https://developer.dolby.com/blog/dolby-audio-over-hdmi-part-2-signaling-and-carriage/), then
I don’t have my Sonos Arc yet so I don’t have personal experience with this, but I still think my original advice is sound: make sure the television is set to correctly pass through audio on HDMI-ARC first, then make sure the Apple TV 4K is set to output Atmos. My assumption on that is that it’s basically working backwards through the Atmos chain: the Sonos Arc is connected to the TV and both recognize each other as Atmos-compatible devices (via some probably unhelpfully named and obscure setting buried in the TV’s menus). Then, once that connection is made, the Apple TV 4K can “see” that there’s an Atmos “receiver” at the end of the chain and gives the user the ability to select Atmos as the sound output (much in the same way it only presents the options for HDR or Dolby Vision if it detects that it’s connected to a compatible display).
(Sonos, if you’re reading all this, this is why it would have been REALLY helpful to simply put another damn HDMI pass-through connector on the stinking Arc….)
So first of all, I get Dolby Atmos on the Arc… but everything else from the Apple TV is Stereo.
Sorry, I’m not following. What are you getting Atmos on the Arc from? The Apple TV? The TV’s internal apps? And what do you mean by “everything else” from the Apple TV?
Oh sorry, I should have make it a little clearer..
I only use the Apple TV 4K:
Ah, now I understand. Thank you!
Unfortunately, though I understand what you mean, I still don’t understand what’s happening. ;-)
I get your comment now about the TV “stripping it to stereo” which I would agree with. If the Apple TV 4K is outputting Dolby Atmos, then obviously everything should be good. I ASSUME (there’s that word again) that if the ATV is playing a Dolby Digital 5.1 source then it SHOULD be sending the bitstream through the TV and on to the Sonos Arc…. but Apple TV’s use of Dolby MAT (Metadata-enhanced Audio Transmission) may complicate that.
Honestly, I’m not sure and have no way to currently test, so I may just be doing more harm than good here speculating. Here are a couple of interesting things I found trying to find an answer to this that may be helpful. If anyone can add more insight, please feel free:
https://discussions.apple.com/thread/250698778
https://www.dolby.com/us/en/technologies/dolby-atmos/dolby-atmos-for-the-home-theater.pdf
I’m getting my C9 and my Arc delivered tomorrow so I’m guessing I’ll have all that fun over the weekend. Do you get DD when you’re using the internal apps ?
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