LG OLED 65C9PTA TrueHD 7.1 transcodes

Plex Players Smart TVs
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Server Version#: 1.16.3.1402
Player Version#: Plex for LG 4.1.1,
WebOS: 4.6.0

TV: LG OLED 65C9PTA
Soundbar: LG SL9YG + rear Kit (4.1.2 + rear kit) ATMOS,DTS:X

Problem desctiption: When trying to play TrueHD 7.1 audio the plex app transcodes instead of direct stream. The same is not a problem while playing using XPLAY.

Plex Media Server: running on QNAP 453A

Player Settings:
I have enabled AC3, EAC3 and DTS on the audio settings of the player Audio settings

Video Settings:
Direct play and Direct Stream enabled
Local/Remote Quality set to Original
Max H.264 level set to: None

TV Settings:
sourbar connected through ARC
eARC: turned on.
Digital sound out: Pass through

How do I direct Play TrueHD 7.1 content on this setup. I am able to get Atmos on Netfilx with no issues.

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The ability to stream Netflix Atmos audio does not mean you can pass TrueHD 7.1 + Atmos audio over the same HDMI connection.

Netflix, Amazon Video, Apple Video, & other such streaming services do not stream TrueHD 7.1 + Atmos audio. The Atmos version they use is EAC3 + Atmos, colloquially referred to as “Streaming Atmos” or “Lossy Atmos.” This lets them stream using much less bandwidth and also pass Atmos audio over HDMI-ARC connections.

Edit: It seems LG does not support passing TrueHD audio over eARC from TV apps, only from devices connected to other HDMI ports on the TV.

https://lgcommunity.us.com/discussion/4633/c9-earc-not-passing-truehd-atmos-through-to-receiver

Does the soundbar support eARC?

The manual for your soundbar mentions HDMI ARC, but not HDMI eARC capability.

If the soundbar does not support eARC, then you cannot pass TrueHD 7.1 audio to it from the TV. Both devices must support eARC. Otherwise the connection will fall back to ARC, which does not support TrueHD audio.

Without eARC, the only way you can direct play TrueHD 7.1 + Atmos audio is to connect an external box, such as a Nvidia Shield, to the HDMI input port on the soundbar.

1 Like
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Hi Ford,
Thanks for the reply. I have a follow-up question:

  1. if I invest in a Nvidia shield, will I be able to play plex HDR content with the shield connected to the soundbar HDMI input?

with regards,
Ranjith

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Yes.

You may also want to look at the AppleTV 4K. It receives much positive comment on the forum. Note that due to Apple limitations, TrueHD audio is sent to the audio gear as multi-channel PCM. This is not an issue for straight up TrueHD audio, as PCM is also lossless. However, it means that Atmos information is lost, so no TrueHD + Atmos playback. EAC3 + Atmos is supported by Apple, as they use it for their streaming video service.

Regarding the Shield:

The Shield supports HDR10 video. It does not support Dolby Vision, HLG, or other HDR formats. Playing a DV, etc video will result in PMS transcoding the video.

The Shield will passthrough audio formats supported by the soundbar. Any unsupported audio format will be transcoded by PMS, or possibly decoded on the Shield, to a supported format.

There are certain unsupported audio formats that I’ve run across. This is not an official list, just things I’ve noticed: a) FLAC 96kbps/24bit plays as noise (48/16 is OK); b) dts-HRA audio (different from dts-HD) either plays as noise or is silent (I don’t remember which); c) AAC 7.1 plays correctly, but is identified as AAC 5.1 and the video breaks up when jumping forward/back (Plex bug, they’re working on it).

None of my movies/shows have those audio formats, so not a concern to me. However, it does affect some people.

My setup: Shield <–> Denon 4300 <–> LG B7 OLED

The Denon supports almost every audio format I’ve found on DVDs & Blu-rays. This includes AC3, EAC3, EAC3 + Atmos, TrueHD, TrueHD + Atmos, dts, dts-HD MA, dts:X, AAC, FLAC.

The Shield bitstreams (passthrough) all those formats to the Denon (FLAC is passed as PCM, since it cannot be bitstreamed over HDMI).

The Shield also direct plays PGS, VOBSUB, & SRT subtitles. The Plex SmartTV app (i.e. LG app), can only direct play SRT subtitles. Invoking PGS or VOBSUB subtitles forces a video transcode. I do not know how the AppleTV 4K handles subtitles.

Note: With the Shield, if audio is transcoding and you enable subtitles, video will also transcode. This happens with any Android TV client and is done to keep audio, video, & subtitles in sync.

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Thanks for the detailed explanation. Based on my understanding. I need to spend extra$ on Shield or ATV.
observations:

  1. Plex on LG TV for C9 plays DTS-MA and DD+ 5.1 without issues
    1.1 TV natively supports Dolby Vision and Atmos, Netflix passes lossy atmos to the soudbar
  2. Only TrueHD 7.1 is trans coded.
  3. LG SL9Y does not support eARC. (I want to future proof my purchase)

I will return my soundbar and get a NV shield as ATV does what the LG C9 TV does. (please correct me if I am wrong)
I will wait for the dust to settle on eARC and pick-up a Samsung Q90R or a Sony HT-ST5000 since both released a firmware update for eARC recently. (Plan to pickup the PS5 for Xbox 2 when they launch)
Would anyone know if LG OLED C9 + Samsung HW-Q90R combination to work?

Is this a good idea?

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It looks like a good combination. The soundbar supports the right codecs and 7.1.4 Atmos. The Sony looks like a nice soundbar as well, and supports 7.1.2 Atmos.

You could connect the Shield directly to the soundbar, avoiding any possible issues with passing audio through the TV.

If/when eARC issues shake out you can look at using the Plex app on the TV in place of the Shield if desired.

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I now purchased the Samsung HW-Q90R with a Nvidia shield directly connected to the soundbar. Happy so far. It plays anything that is thrown at it.

with regards,
Ranjith

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So the new Shield TV will be the only solution for truehd atmos if you have an LG TV then, no updates on that front? Was hoping to keep my setup simple without involving yet another device and remote.

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I am also interested here. I wanted to update my LG TV to the 2019 models which support eARC. My soundbar already supports eARC, so theoretically, I should be able to get Atmos to work. However, seems like it can passthrough lossless Atmos for devices connected to the TV, but not for apps directly on the TV?

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Hi guys! Would anyone share their picture settings whenever using plex? I’m on a 77C9 here.

I tried whatever I could find on Rtings, but the result for me is way too washed out. (As a matter of fact I’m surprised they suggest to start from the Expert dark mode?)

Overall I really feel I’m not “getting” how the settings on this TV work. I feel like the brightness is often too low, and I’m really struggling with the “pc mode” settings whenever I use my computer for gaming.

I haven’t tried playing with the HDR yet… not sure what to expect there.

A little help would go a long way!

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Avoid HD-MA 7.1 unless you use DLNA or you connected via HDMI. For your audio if your TV and receiver support eARC.

I have no issue with any 5.1 channel audio

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My current setup is Shield connected to LG OLED E9 --》 earc audio output to Marantz SR7013 which works fine for bitstreaming all the used codecs. But was disappointed I actually needed a shield instead of the native app. This is off course an issue with the LG software but are there any indications that LG is going to fix this in the 2020 update concerning EARC?

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