No, the Apple TV doesn’t send HDMI ARC, only HDMI. It’s the TV set that figures out what it can send as the Audio Return Channel (ARC). 

Does this TV 100% def support Atmos passthrough ?
No big deal but don’t think it has screen off function.

Plently of hdmi splitters on Amazon - one I’m thinking about getting is Ezcootech SP12H2

Unfortunately no - Apple TV HDMI  is an output also Sonos HDMI is an output to the tv not an input. However it also receives audio back from the TV via the magic of arc.

I don’t how how but the optical adapter does turn it into an input though so it must be possible to make an adapter for HDMI  ??

The TV has eARC so I think it would be no issue on passthrough. Not sure about screen off but I thought all Samsung had it in this class.

I’ve tested Atmos from Apple TV through LG C8 and can confirm this seems to be working for me right now:

• ATV 4K > C8 HDMI-1 > C8 HDMI-ARC > Vizio SB3512-F6 (HDMI-ARC)

Vizio SB shows green indicator when Atmos working. Tried with Apple content and Disney+.

I figure if ATV 4k is outputing PCM to the TV then the TV probably just downmixes it to DD+ through the ARC-HDMI to the SB.  I’m not an expert at it but that typically is how all AV equipment works.  you want your output signal to be the best possible version and then the receiving equipment will take that signal and down mix it to what will work.  That is different than forcing a specific codec.  If you tell your source to output DTS and your input doesn’t support DTS, then you’ll get no sound.  Since PCM isn’t a codec, I just imagine the TV will take the info and use what it needs, ie you’ll get DD+ 5.1 or Atmos.  

Hi all,

Received my Arc today. I can confirm you can use the Sonos Arc with 4K Apple TV. The Arc is plugged into the eARC port on my 2019 LG OLED, I can successfully watch movies from iTunes with fully Dolby Atmos.

Disney plus however seems to be a problem on both the Apple TV and native app on the LG TV. I get audio, but not Dolby Atmos. Netflix works perfectly fine too with Atmos.

It was a given eARC would pass through.  The question at hand is will regular ARC pass through from ATV 4k. 

Not to everyone it wasn’t, I’ve read all the messages on this subject and it was rife with confusion across the board. 
 

My confirmation will satisfy the concerns of some, maybe not all. Helpful none the less. 

Many claimed that since the Arc was not Multi-Channel LPCM capable, the Apple TV 4k would downgrade to stereo, eARC or no eArc.  Turns out it wasn’t true in most cases.  

I’m in the same boat.

My TV has ARC (No eARC) but I only watch things on my Apple TV 4K.

Currently using the Beam, have preordered the Sonos Arc for Atmos, but now nervous this setup won’t work.

Let me know if someone tests this setup.

This depends on your TV if it can passthrough the Apple TV 4K Atmos signal to your ARC port. For me that’s a no (Samsung Q900R) - all I get is DD 5.1.

Do all eARC TVs pass it through?

Or is that also a TV by TV basis?

If it is, what spec item should I look for as I’m probably going to be on the market for a relatively inexpensive compatible 55”...

I have this problem. ATV → LG C9 → ARC

Atmos works perfectly, but DD5.1 now arrives at the ARC in a 2.0 format as the ARC cannot yet process LPCM beyond 2 channels.

I asked this question to LG and got the following answer:
 

I have a 2020 LG Nanocell TV. Does Sonos Arc accept LPCM? If not then AppleTV 4K will not play Dolby Atmos. I have been informed through other forums that the LG Apple TV app on 2020 TV’s will be updated to stream Atmos at some point this year.

It would be helpful if a Sonos employee could clear this up from their end for us.

I have,

ATV → LG CX → ARC

I am getting Atmos

I am getting DD 5.1

I have a 2017 LG C7 with an HDMI ARC connection.  I am also getting Atmos thorough Apple TV via Disney Plus, Netflix and Prime on listed Atomos content as well as DD 5.1 on non Atmos content. 

What TV Sounds settings do you have? I’ve got HDMI input set to PCM. If HDMI input set to Bitstream it will only play DD 5.1 not Atmos. 
 

HDMI Input is set to bitstream

Digital sound out is set to Passthrough

If that doesn’t do it I would double check the settings on the Apple TV

Thanks, I have those settings on my TV but I only get sound when the ATV is set to DD 5.1. If I set it to auto I get no sound at all. 
 

what are you ATV settings?

I assume you have eArc turned on.

And just for clarity, we are talking about an Apple TV 4k box and not the app on the TV.

Just copied all of the above and still no Atmos. 
 

yes AppleTV 4K

What content are you playing?

And are you seeing Atmos available in the audio format box?