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Hi all


I have a LG CX connected to a Sonos ARC via eARC and HDMI 2.1 cable. I use the internal PLEX webos app to play back a variety of ripped media.

Plex server is running latest verion on Windows 11. Ryzen 5950x, 32GB Ram and RTX3070 gfx card. Enough to handle just about anything.
Sonos ARC doesn't supports DTS after update (convertes to PCM I believe)
The LG CX doesn't support DTS at all but pretty sure was updated to support 8 channel PCM. It will support TRUE HD + ATMOS via HDMI from an external source (bluray player etc). Internal sources (apps) will not passthrough True HD.


The TV HDMI sound output is set to passthrough (webos settings).
Plex webos app on LG CX set to accept all sound formats except DCA/DTS.


When playing media back via the Plex app TRUE HD is converted to Dolby Digital+ by the Plex server (confirmed by looking at Sonos app and plex dashboard).

DTS (unsupported by TV) is converted is to AAC by the Plex server (confirmed by plex dashboard). However the Sonos app shows Dolby PCM.


So


If DTS is being converted by Plex server to AAC why is Sonons Arc showing PCM? Is the LG CX then converting the AAC to PCM? Or is the LG CX passing though AAC to the Sonons Arc which is then converting the AAC to PCM?


Why can't Plex just convert the DTS signal to PCM and save a lot of stuffing around? I couldn't see any options in the server settings for this. Surely that would be better than the lossy AAC format. Unless it's because the LG CX only supports LPCM externally and not from internal app (like True HD).


Yes I know I can get a Nvidia Shield blah blah but not interested.


Hope I haven't thoroughly confused everyone.


 

Sonos does support DTS.  This is a fairly recent change (a few months back), so perhaps you setup your system before the change.  I would recommend the first thing to try is set Plex to DTS and your LG TV to passthrough.  Actually...this likely won’t work as I just released your running a plex app directly on the TV rather than a separate streaming device connected to the TV via HDMI.  I will still try it though, just to eliminate the option.

Sonos also supports AAC as an audio format for streaming music/audio, but I don’t believe that’s the case for home theatre codec sources (via optical or HDMI-ARC/eARC).  The CEC communication between your TV and Arc is telling the TV that Arc can’t play AAC, so the TV is converting to PCM before sending to the TV.

There may be someone on here who’s familiar enough to answer your question about Plex settings (DTS->PCM), but you’re probably better off asking the question with Plex support.  I do use Plex, but most, maybe all, of the movies I have are in Dolby digital or stereo PCM, and there old movies where sound quality isn’t a concern….so I’ve spent little time optimizing the audio.  And I use a Shield.  

Sorry can’t be more helpful.

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