Arc/Atmos - TV support for passthrough from Apple 4k?

Good analysis. I’ve been looking too with no luck finding yet. If you find such a solution please post so we can all benefit.

I will indeed, the moment I find such a device. I fear it may not be before I get my Arc, however, as the time to market versus the new pent up demand is a bit short. It’s almost tempting to hire my own engineering firm and make one myself, and then sell it. But I suspect they can do it faster in Asia than I can here in the US, since it might be an extension of devices already designed and manufactured. 

Hey @dcb17, I’ve got the same setup as @AirKilroy (LG C9 with eARC, Apple TV 4K and an ordered Arc)… your insight here was really helpful. To dig a bit deeper, though, when you say ‘you will be fine’, is that with regard to just Netflix apps etc., as I’m mad keen to understand further the concerns around Apple TV playing TrueHD 7.1 content from apps like Infuse out as LPCM… do you reckon the Arc will then not be able to process/downgrade to 5.1 or stereo?

Thanks for your help.

Every user with an eARC TV and an Apple TV 4K should be fine. So no worries @shnuggleberry.

HDMI eARC is able to transmit the “special” format that Apple uses for Atmos. It was widely reported in the past (when the new Apple TV 4K was released) that the Apple TV 4K (only the 4K model is able to play Atmos!) plays Dolby Atmos in a “special” format (DOLBY MAT = “Dolby Metadata-enhanced Audio Transmission”). It looks like the reason for that is, that they want to mix the System Sounds and Siri voice over into the sound mix. By doing that, they have to decode the DD+ w Atmos Singal and put it back together with the System Sounds as a “DOLBY MAT” signal witch is a LPCM signal with Atmos information packed in it. This DOLBY MAT signal cannot be transmitted over regular HMDI ARC but only over eARC.

When “reviewers” with older TVs are reporting, that they managed to get Atmos from Apple TV over a regular ARC (not eARC) connection out of their TV, the reason is probably their TV. Some TVs are apparently able to convert an DOLBY MAT w/Atmos signal into DD+ w/Atmos and send it via regular ARC to a soundbar. It looks like older LG TV (7,8 series) are able to do that with a regular ARC connection if they are updated to the latest firmware (support for that came later with a firmware update).

Will this also work for my LG E6 ?

There is an option in the settings to output Dolby Digital Plus.

Who knows, this TV doesn’t do eARC, so we have to wait for someone to actually try it, or for Sonos to tell us which TVs are compatible with Apple TV + Atmos over ARC. They must have some idea as one assumes they have tested it with a bunch of different devices.

Thanks for the support, @GenAckbar73. Again, I could very easily be wrong… but from what I’ve been reading, the ‘special format’ you mentioned will work just fine only when I’m streaming in Apple TV apps like Netflix, Apple TV+ etc., however… other 3rd party app are forceded to output audio as LPCM from Apple TV 4K, meaning it would be downsampled for Sonos Arc? Not because of eARC, but because of the codecs supported by Sonos Arc, if that makes sense?

Grrr, all so confusing! I use a beautiful app called Infuse to stream my Blu-Ray rips (incomparible, ease of use/presentaiton-wise to Plex and Plex-like apps, in my opinion), with Apple TV 4K and an LG C9 (I’m very, very lucky here, I know… so odd to be moaning) and soon a Sonos Arc - so with all such modern equipment it would be crazy if Atmos just didn’t work!

It may be overkill but I’m considering purchasing a relatively affordable  LG SM90 (SM9000) tv which has EARC to act as a ‘receiver’ between the Sonos ARC and my projector.

i would also need a HDMI splitter to feed both the TV and projector from an Apple TV / Blu-ray player.

The TV could sit behind the projector screen and could be used for occasional viewing when the screen is up. I also believe LG TVs have a ‘screen off’ setting.

In this way I could have lossy Atmos from the connected Apple TV and lossless Atmos from a connected Blu-ray player.

If and when a company develops a HDMI matrix with arc capabilities it would probably cost a few 100 anyway.
Why wait for this technology which would be fairly niche and may never happen.For a few 100 more you could have the solution now with the added benefit of a second screen.

Any thoughts ?

I’m considering the same thing but with a smaller Samsung 43" Class TU8000.

Anyway, what splitter have you found to support everything?

Trying to get an answer to this question via this discussion:  will I get Atmos to my Arc if I feed the Arc directly from Apple TV, bypassing my TV audio, where the ATV app supports Atmos?   I believe the answer is no, as a result of the limitations of the type of ATV output - is that correct?