If you are playing media from the TV / Plex itself, it cannot pass the DTS audio to any other device nor decode to play the DTS internally.
You can use Plex to transcode the audio to something it or others can play. This is what I am doing as I currently don’t have an AVR or Soundbar and use the built-in speakers.
If instead you have an external DVD / Apple TV or other player, you would go to an AVR or Soundbar first to play the DTS, and then to the CX / GX For the video.
Those format has nothing to do with playing the sound from the TV back to the Receiver.
If the TV support e-ARC and the Receiver support it too it should capable to play HD audio (Dolby True HD / DTS-MA …all at 7.1 speaker format) .
The reason or the problem is in the PLEX software on the TV, they did not add the option of HD audio.
I guess they do not find it worth to add the option since the streaming media they provide do not support that type of heavy audio data,
The user that wish to play the HD audio are those that use the PLEX for free playing movies that they downloaded (without paying for monthly DATA) .
If Plex company even build the option to play the HD Audio from the TV application, I personally pay for it .
What can I do, plex thinking cheep because many customers are cheep…
Now , for PLEX company, please open the option for lossless audio (HD audio ) in your TV software. even for buying it.
Firstly LG do not support DTS in 2019 and 2020 models, secondly there is no Plex app software on the TV. The TV is a WebOS device therefore all apps are remote. What is on the TV is a loader to activate the WebOS app
As for eARC, will it transfer DTS to a supporting Device via a Ethernet port. I can not find any supporting argument. What I have heard, that from a HDMI 2.1 cable and port a supporting Player like a Nvida Shield or Blu Ray Player, eARC will pass thru DTS-MA.
So I definitely don’t see where Plex have failed or been delinquent for that matter, where LG dropped DTS support due to Licensing or whatever. The LG HDMI module supports the pass thru but I would guess the LG firmware does not support the transfer from Ethernet or WiFi, which is the normal passage from a networked TV connection. A supporting network HDMI device connection is the answer not Plex bashing.
Read the following LG support article.
Really very usefull comment. So you think that maybe a tv like LG OLED65B9PLA that supports both DTS decoding and has an HDMI 2,1 port should be able to passthrough DTS-MA to a compliant receiver? If yes it would be awesome, is there anyone here who has such a tv model and can confirm it / try it? I have a Samsung ES8000 with DTS passthrough support and i use it perfect with Plex, with no HD audio though. I am looking for a replacement but i see that Samsung and LG has dropped DTS support from their new models, so i try to find an alternative. I guess most say that the alternative is Nvidia Shiled but i dont want to have another device just for the DTS HD sound. Any recommendations?
From what I see 2019 LG models do support DTS (I know for sure the 55" does). I also have a CX which indeed doesn’t support DTS as of Client version 5.1.3 (platform version 5.1.1)… I hope the plex team can fix this in the next update.
In the meantime, I’ve got an Amazon Fire TV whose plex client seems to support everything. And audio is sent to LG CX with audio passthrough (via HDMI) without any issue.
Amazon FireTV devices support passthrough for Dolby Digital (AC3) and Dolby Digital Plus (EAC3), including Dolby Digital Plus + Atmos.
All dts formats and TrueHD are converted either to DD or DD+. Depending on FireTV model and configuration, the conversion may occur on the FireTV device, not the Plex Server. If this is the case, then Plex Media Server will show Direct Play / Direct Stream, as there is no feedback from the client to the server when the audio is converted.
The Plex app on the TV will not pass lossless audio such as dts-HD & TrueHD via HDMI-eARC.
TV manufacturers and/or the HDMI controllers do not allow that to happen. It is a TV restriction, not Plex. It applies to all apps, not just Plex. It applies to all TVs (Samsung, Vizio, etc), not just LG.
Audio from external devices, such as a Blu-ray player, connected to the TV will be passed via HDMI-eARC.
With regard to Plex, if you want passthrough of dts-HD and TrueHD (including Atmos) audio formats, it means using a Nvidia Shield. The Shield is the only off the shelf box that supports passthrough for those audio formats. Other devices, such as the AppleTV 4K, convert TrueHD & dts-HD audio to PCM. As PCM is lossless, there is no drop in quality. However, any Atmos and dts:X information is lost in the process. FYI, if you do obtain a 2019 Shield, get the Pro model. The non-Pro (tube) model has problems with high bit rate 4K HDR movies and lossless audio.
A Windows PC using Plex Media Player will passthrough dts-HD and TrueHD audio (I don’t know if Atmos data is also passed). However, PMP does not support HDR video, which would be problematic for those watching 4K HDR movies/shows.
Ok, I am really confused if this is going to affect me, so bear with me. I am considering getting a LG CX to replace an aging Panasonic plasma. My current setup is Nvidia Shield TV 2017 connected to Panasonic Viera GT50 via HDMI, then I have a toslink optical cable out from the TV to my Sonos Playbar (old one that doesn’t have HDMI). My server doesn’t have to transcode DTS (or at least it says that it doesn’t). Would I be able to replace the TV in this case with the LG CX OLED and be good to go without transcoding? Thanks for any input.
Your Limitation will be Toslink optical cable, 5.1 channel and no 7.1.
After some research your Playbar does not support DTS and LG CX does not either. I believe the LG will pass through DTS via HDMI. Most titles with DTS have a second audio track of DD, check it out with VLC.
Thank you! This finally fixed the issue!
Works !
For me when I disable DTS of the plex application on LG the audio and the video transcode. I don t know why the video is transcoded also.
Do you have subtitles turned on? If so, turn them off.
With the Plex app on LG, if the audio is transcoding, enabling subtitles forces a video transcode. Also, enabling PGS or VOBSUB (image based) subtitles forces a video transcode whether or not the audio is transcoding.
Subs are off too. Still the same issue.
Does the Movie have 5.1 audio track
Sorry for not saying that before. Yes it is DTS-HD MA 5.1
Thanks for this tip. I can enjoy 4k hdr without transcoding again. Still very weird LG dropped dts support, and even pass through.
This worked! 
I’m in the same boat. I have a sony 900h that i might return to get the lg cx. The sony can pass dd and dts via the tv plex app to my receiver. No true hd or dtsma but i can live with that.
Since the lg cx does not support dts, assuming that is the only track on my mkv, by unchecking dts on the plex app the plex app with transcode the dts track to another surround sound format.
But what format? Is it still discreet surround sound? How can it transcode dts to dd? Aren’t they different formats? And where does this transcoding take place? On my nas? Does anyone notice a big loss in sound quality when this happens?
I also assume this transcoding will allow the audio to play on the tv speakers for rooms without an avr?
Thanks
I ran a quick check with my LG B7 OLED.
Setup:
LG B7 OLED ← HDMI-ARC → Denon AVR-X4300H
Uncheck dts in Plex app audio settings.
LG App v5.6.1
PMS 1.21.1.3876 on Synology DS918+
Played blu-ray rips with dts and TrueHD audio. Monitored playback via Tautulli app, Denon front display, and Denon app.
dts 5.1 & dts-HD MA 5.1 are transcoded to AAC 5.1 by the Plex Media Server.
The TV sends the audio to the Denon as Dolby Digital 5.1
dts-HD MA 7.1 is transcoded to AAC 5.1 by the Plex Media Server.
The TV sends the audio to the Denon as Dolby Digital 5.1
Note: The log files for both PMS and the LG app only mention transcoding dts to AAC. There is no mention of Dolby Digital 5.1. Guessing that the AAC 5.1 to Dolby Digital 5.1 conversion is performed by the TV and is not visible to Plex.
TrueHD 7.1 is transcoded to Dolby Digital Plus 7.1 by the Plex Media Server.
The TV sends the audio to the Denon as Dolby Digital Plus 5.1. Unknown what happens to the two channels (dropped, muxed into surround channels, etc).
