The bolded part is incorrect.  The Arc isn’t going to downsample anything like that.  If it receives an atmos signal (either TrueHD or dolby digital +, it will play it. If there is downsampling going on, it would happen in Shield or your TV, and I don’t know if that’s the case.  Sounds like Shield can handle it fine, and your TV is suppose to handle it.

As for your question about the connection, eARC stands for Enhanced Audio Return Channel, meaning  audio is returning in the opposite direction from normal HDMI. So yes, your Shield sends data for HDMI to one of your TVs HDMI inputs, and audio is then sent by the TV over eARC to the Sonos Arc.

One word of advice, a lot of users are finding that their TV restricts some of the audio content, or adds processing delays to the audio before it gets to the Arc.  Many of us have gotten  HDFury’s Arcana as a means to extracting the audio from the source and sending it directly to the Arc, bypassing the TV for audio.

Thanks for the response. I did also look at the HDFury Arcana however would I be correct that the Arcana alone will not help without an Nvidia Shield? I.e. I could not use the Arcana on its own in between the TV and the Arc?

Apologies for all the queries. I’m new to this.

The LG CX series has audio pass-through on its HDMI ports so the Arcana will add nothing… if the sending device is sending the uncompressed Dolby TrueHD codec (with atmos metadata) it will pass-through the LG TV over eARC and the Sonos Arc will receive/play it… just ensure pass-through and eARC are switched on in ‘Settings/Sound’ on the TV. The rest is down to the sending devices audio-out settings

Nvidia Shield also has TrueHD ‘pass-through’ capability...and I don’t really know what that means in this context, for a media player like Shield.  For a TV, pass through just means than if TrueHD comes through on an HDMI input, then it can pass it through to whatever is connected on it’s eARC port, as Ken describled.  For the Shield though, it looks like it means you would need an app on the Shield that supports TrueHD.  Shield would not be able to play a file stored locally or on a connected drive directly.

https://www.nvidia.com/en-us/geforce/forums/shield-tv/9/420024/shield-2019-pro-truehd-atmos-audio-random-single/

So for example, I believe you could set your PC up as a Plex server, then use the Plex app to play your content stored in TrueHD.  Full disclosure, I have not done this myself and have not tested.  I do have a shield and do use Plex, but my Shield is my Plex server, thus not exactly doing a pass through situation.  And I don’t have any 4k/TRUE HD files to test this with if I did.  I did see you posted the same question on Nvidia forums, so hopefully you get a better answer there.

Thanks guys for the advice.

My understanding is that the Shield does more than just pass through the HD audio because it enables the Atmos metadata to be retained through to the Sonos Arc. With my current setup (Serviio on a Windows PC that hosts my movie files) when I stream from Serviio onto my LG TV using the built-in media server connectivity solution on the TV the TrueHD Atmos is played as regular DD 5.1 on the Arc and I do not get the Atmos logo in the Sonos app.

Perhaps it depends on the media server software. I will try using Plex on my PC instead of Serviio in case that makes a difference. No point splashing out on a Shield or Arcana unnecessarily.

Regarding the Arcana, some forum posts I have seen suggest that even when using an eArc port on an LG TV there can be stutter issues, so the Arcana can be used to bypass the TV altogether for the audio stream. 

‘My understanding is that the Shield does more than just pass through the HD audio because it enables the Atmos metadata to be retained through to the Sonos Arc.’

Your understanding is incorrect.  This really does not make sense.

Are you confident thet your PC is capable of outputting Atmos in the first place?

The Arcana makes the Arc think it is receiving an eARC signal from a TV.  This is useful to me as my TV doesn’t have eARC, but not for you because your TV does.  I have a Shield so as to stream through the Arcana rather than use internal apps, because my TV doesn’t handle Atmos.  Your TV does (I believe).

If the Arc receives Atmos metadata, it will play it.  The Shield can’t make the Arc retain anything.

This is most likely because your TV doesn’t support TrueHD  natively/directly, which is really not that surprising.  It probably supports passthrough of TrueHD, through the HDMI inputs, but it can’t do TrueHD through it own apps or by reading a file directly.

I don’t think you will get  a different result here, as you would still be using the native TV functionality, rathering than passing through content from HDMI input.  I don’t know that Shield is your only option, as I don’t know the alternatives, but it looks like it is one option as an HDMI input.  If Shield supports Serviio, then you probably don’t need to switch to Plex.

If your PC has HDMI output, maybe try a direct connection between the PC and TV to see if that gets you TrueHD.

Yep, since your TV is eARC, there is a chance you won’t need the Arcana.  I would focus on getting your content to the TV via an HDMI input first and then see where you are at before the Arcana.  However, it’s not a bad idea to get Arcana even if you don’t technically need it, just to get more of a true component system, without having to worry about your TVs audio processing capabilities.

Yes I think this is the crux of the problem. When I play a movie file with a HD Atmos track the TV shows a popup saying something like ‘this audio is not supported’ followed by another popup showing the HDR logo. But then it does still play the movie with 5.1 audio, however this is non-HD and non-Atmos. This is with the TV audio set to passthrough and the eArc option enabled, streaming from PC over wired ethernet to the TV then via eArc HDMI to the Sonos Arc. So the popup suggests that the HD Atmos data is reaching the TV but cannot be processed, instead becoming ‘regular’ 5.1 without TrueHD or Atmos.

When I stream Atmos content from the Netflix app on the TV I do get the Atmos logo in the Sonos app but this will be compressed DD+ Atmos, not TrueHD Atmos.

Possibly if I used an Nvidia Shield as a media server connected to the TV and then the TV connected via eArc to the Sonos Arc I may or may not still have the same issue because I would be using the Shield’s Plex app instead of the TV’s built in app, but the TV would still be in between the Shield and the Arc so might not be able to handle the TrueHD/Atmos, in which case I guess that is when an Arcana would be useful to bypass the TV completely.

I don’t have ‘Atmos’ metadata available on a blu-ray Movie here, but I can confirm the slightly older LG C9 TV will certainly pass-through the (uncompressed) Dolby TrueHD audio format as per screenshot attached and it plays on the Arc/Surrounds without any issues in my test. So presumably the later LG CX model will do that too. 
 

I also know the TV will both play and pass-through the (compressed) DD+ Atmos codec aswell - so this will certainly come down to the sending source/device and it delivering Dolby TrueHD Atmos audio .. I’m quite sure the TV will let through that format and the Arc will most definitely play it.

‘streaming from PC over wired ethernet to the TV ‘

Not HDMI?

I think there’s a good chance it work.  For whatever reason, it’s not uncommon for TVs to have different audio capabilities for streaming sources (through internal smart apps) and from HDMI input sources.  It makes sense in that 99% of streaming sources will not be TrueHD, but DD+ since that’s what streaming services use.  TrueHD is almost always going to be off discs in an external disc player.  There that are going to stream TrueHD like you, but even they are likely to directly connect their media player via HDMI, rather than stream through a local server.

A bit more forum surfing reveals this thread which does seem to confirm that the in-built LG TV apps will not process TrueHD and also suggests that a separate media player (such as a Shield) will work:

https://www.reddit.com/r/sonos/comments/h7iq8c/lg_c9cx_truehd_and_sonos_arc/

No because my PC is upstairs in the study and my TV is downstairs in the living room, so I’m using powerline adaptors and ethernet cables to stream from the PC to the TV. It works fine. WiFi also works but sometimes causes stutter due to the size of the movie file data stream, hence the wired alternative.

You also aren’t tied to down to a single TV, or even to TV in your home.  At least that’s the case with Plex. 

In the same shoes as the OP

LG CX and Sonos Arc 

When I try stream Dolby Atmos demo TrueHD 7.1 the Emby degrades it to AC3.

When directly connecting USB to TV it says audio not supported and then the video stutters and what not… 

But when I play witcher series on netflix i get dolby atmos and dolby vision, whole package.

I dont understand. Losing my head over this...

You need a nvidia shield as the lg cx does not play TrueHD 7.1.

Hi Bornstrong,

Streaming services (Netflix / Prime) use a lossy (dumbed down / lower bitrate) form of dolby Atmos, which is basically DDP or DD+ (dolby digital +) with Atmos metadata. TrueHD is essentially a lossless “format” and it cannot be streamed (currently) from say a PC, NAS or an external HDD or any “player” through WiFi or ethernet only through BluRay players connected directly to a compatible TV - anyone, please correct me if I’m wrong, but so far I couldn’t find any examples. The catch is that you need to pass TrueHD Atmos through a 2.0+ HDMI attached to an Nvidia Shield, which can “pass through” the lossless Atmos to the LG CX, which then (through the eARC) passes this through to Sonos ARC, which can play it.

Going through several forums, this is not always problem free and when you want to go “above and beyond” to have a lossless Dolby Vision  - profile 7 or 8 - as well then things get even more complicated (formats like MKV, mp4 starts to matter so as MEL /FEL coding etc.)

In a nutshell, you will need a Nvida Shield (2019 pro) to play TrueHD Atmos on your ARC.

How to set up: Sonos Arc→(through eARC) LG Cx → Nvidia Shield (through one of the 4K HDMIs, any of the remaining 3) running Plex or some other media server.

Does it have to be an nivdia shield or will a Roku Ultra 2020 or an Apple TV 4k do this as well? Thanks.

@rishey A Roku Ultra or Apple TV does not support Dolby TrueHD audio. 

I was under the impression that the MAT used by Apple’s own apps carried a TrueHD signal. Which may not be the case by other apps, such as Netflix, etc.

Here are the audio formats supported by the Apple TV 4K from Apple’s website:

HE-AAC (V1), AAC (up to 320 Kbps), protected AAC (from iTunes Store), MP3 (up to 320 Kbps), MP3 VBR, Apple Lossless, FLAC, AIFF, and WAV; AC-3 (Dolby Digital 5.1), E-AC-3 (Dolby Digital Plus 7.1 surround sound), and Dolby Atmos

Hi all,

For the benefit of people looking for a similar set up, i wanted to get this out there so it may help someone. My setup: LG 65GXPTA with Sonos Arc (eARC) + Sub3 + Ones (for rear surround) and NVidia Shield Pro (HDMI2) works for:-

1. Dolby Vision + Dolby Atmos + HDR from content on Netflix, Disney+, AppleTV +, Prime Video clients on NVidia Shield Pro
2. UltraHD 4K/HDR + Dolby Atmos TrueHD from Plex Client + Plex Media Server on DiskStation 920+ (DSM 7)

I am using Monoprice UltraHD + Monoprice Certified.

Patrick