Dolby TrueHD Support on LG WebOS Plex App? When?

Plex Players Smart TVs
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Server Version#: Version 1.41.3.9314
Player Version#: Plex for LG Client 5.90.1, Platform 9.2.2
WebOS Version#: webOS24 9.2.2-1805
TV: LG C4 2024

I am using the webOS version of Plex with audio output over HDMI eARC to an external receiver.

In the settings I don’t see any options to enable any HD audio codecs like the Plex HTPC edition.
Despite having no specific audio settings to enable DTS-MA, TrueHD, the webOS plex client does play DTS-MA, but not Dolby TrueHD.
The TV does list support for TrueHD 48kHz - which is what the content is,

Playing with PLEX HTPC direct to TV via HDMI input - Dolby TrueHD is passed over eARC to my receiver without issue, as with all other HD audio codecs.

Summary:
TV passes all HD audio codecs received from HDMI over eARC.
TV passes all but TrueHD codec from Plex webOS over eARC.

So far the webOS client is playing HDR10, and DV content without issue - just now need support for all the HD audio CODECS.

There is a BIG difference in audio quality and impact between TrueHD 7.1 vs. lossy EAC5.1

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It is a TV manufacturer, not Plex, restriction.

No TV (LG, Samsung, Sony, etc.) supports passing TrueHD audio from a TV based app over HDMI-eARC.

Not in list of audio codecs: https://www.lg.com/us/tvs/lg-oled77c4pua-oled-4k-tv

Audio Codec

AC4, AC3(Dolby Digital), EAC3, HE-AAC, AAC, MP2, MP3, PCM, WMA, apt-X (Refer to manual)

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If that was correct - it would be a great explanation.
My issue is getting audio codecs output bitstream unmolested over eARC
Basically eARC passthrough within webOS apps - PLEX client in this case.

As per my original post
Plex Client for webOS will pass DTS-HD MA over eARC bitstream passthrough to my receiver.
You will notice that this codec is not listed in your quoted specs of audio codecs.

In the PDF Manual - OLED C4 Manual the only audio specifications are under HDMI and where it gets muddy is “Supported HDMI Audio format (Depending upon model):
True HD (48 kHz),”

There is no clarification of which model supports what.

I can confirm that I have had no issue with any HD audio codec bitstream being passed over eARC from an HDMI connected device. I have passed 48kHz TrueHD from HDMI 1 to eARC on HDMI 2.

It’s the “smart tv” audio support that is unclear. I fail to understand why the webOS plex client can pass DTS-HD MA within webOS but not TrueHD?
DTS-HD MA is not listed as a supported audio codec according to LG’s web page specifications, and PLEX audio settings - yet it plays fine.

I fail to understand why supported audio codecs from webOS apps would be any different than HDMI - especially when you are just passing the data, not processing it.

It’s really a shame that audio support is often overlooked by manufacturers.
eARC is a great way to simplify connectivity and satisfy all but the most extreme of home theatre audio enthusiasts.

Why does the manual indicate HDMI DTS-HD supported to 192kHz, but Dolby TrueHD only to 48kHz, when Dolby TrueHD can support 192kHz and bit rates to 18Mbps?
Is licensing cost more expensive for 192kHz vs. 48kHz?

The C4 has full 48Gbps HDMI 2.1 support - why not use that pipe for lossless audio good?

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@markus101 We’d appreciate clarification.
Coming from an Android streaming box I’m really missing some ecperience with my 77G48LW

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Hi @Subversion365 …

FordGuy is correct, however it may need to be a little clearer for some…

There is no TV on the market today that supports passing HD audio codecs from the INTERNAL apps on the TV. This includes DTS-HD and TrueHD.

However…

Most TV’s do support passing HD audio codecs from EXERNALLY connected equipment, connected via HDMI, such as an Nvidia Shield, a PC, a Firestick etc.

So if you are using the Plex app (or any other app for that matter) directly on the TV, HD audio won’t work.

But if you are using the Plex app via an externally connected device, it’ll work just fine.

However some people have stated that they have been able to pass DTS-HD from an internal app, but if that is true, then that would be considered an anomaly.

Hope that helps…

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Well, thats the case for me too :wink:
So somehow the TV DOES support it, seems just needs to be figuered out^^

1 Like
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So ähnlich verhält es sich bei mir mit dem AV1-Codec. Mein Samsung QN90C (Tizen-OS 8.0) unterstützt angeblich kein AV1. Wenn ich jedoch “Force Direct Play” am TV aktiviere, wird es sauber (sogar 4K) über die TV-Plex-App abgespielt!

2 Likes
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The term “support” means that the technology has officially been certified as working by the manufacturer, so I would not agree with you on that one. It is absolutely not supported, and because of that, Plex will very likely not attempt to do any work with their software to fix something that is not supported by the manufacturer.

However if DTS-HD is working for you, then that is indeed an anomaly.

Unfortunately you are going to have to accept that unless the TV industry decides otherwise, TrueHD will simply never work via the internal apps.

You would be much better off saving up some money and getting a good player, such as the Nvidia Shield.

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Careful with claims you can’t back up.

Fact:
2024 LG C4 - Plex webOS client does pass DTS-HD MA bitstream over eARC to my receiver. It does NOT pass TrueHD.
I don’t think my experience is unique as Red-Naxela has attested to.

Shield?

I’m not going to purchase an external box like the shield pro that was released in 2019.
If they update the shield with new hardware, the latest codec support - then yes - that is an option.

I don’t understand why a bitstream can be sent passthrough over eARC from HDMI connected sources, but not from an internal WebOS source. It’s not as though it has to process the bitstream to convert to PCM.
I get the whole DoVi licensing thing - but audio?

Direct Play should be just that. eARC should just passthrough whatever bitstream is there for audio.

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I can back up this claim because it’s true.

As I stated earlier…

Now you are more than welcome to have a hunt online and see if you can prove me wrong by finding a manufacturers documentation in Jan 2025, but I think you would be hard pressed to do so.

Because the manufacturers don’t currently deem it a valuable feature, much like they still don’t supply TV’s with gigabit ethernet sockets… They are still choked at 100 Mbps.

It does indeed seem that a number of people experience this, but that doesn’t mean it is supported. It just means that for some reason and by sheer fluke, DTS-HD appears to work.

That’s fair enough… There have been rumors of new hardware, but nothing concrete.

However which ever way you swing it, you are still going to need some other external device in order to get TrueHD passthrough, and until you do that, you are not going to be able to experience full fat TrueHD Atmos, which I can tell you right now, is far punchier than EAC3 Atmos (aka DD+)

Trust me, I had an internal battle with myself for some time, arguing the pros and cons of getting the Shield, but eventually I relented and have never looked back… Although that was 3 years ago now.

The only technology that I am missing with the Shield (or at least that I am interested in) is the lack of HDR in the YouTube app, but other than that, the Shield rocks.

The AI upscaling alone is worth the price… The way it upscales 1080p content is amazing.

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DTS-HD MA passthrough with webOS Plex smart tv client is not a fluke.

Challenge Accepted…
Reference read:

webOS TV 24 Streaming Protocol and DRM

Specifically one of the most popular containers such as .mkv states:

Audio : Dolby Digital, Dolby Digital Plus, AAC, PCM, Opus, DTS), DTS-HD), DTS:X11), MPEG-1 LayerI, II, MPEG-1 Layer III (MP3)

Notice that there is no Dolby TrueHD in the list. Not sure why.

I do have problems with these specifications as it also claims video support bitrate stops at 60Mbps:

  • H.264 3840x2160@30P BP/MP/HP@L5.1 Maximum 50Mbps
  • HEVC 3840x2160@60P Main/Main10@L5.1 Maximum 60Mbps VP9 3840x2160@60P Maximum 50Mbps
  • AV1 3840x2160@60P Maximum 50Mbps

I have played higher bitrate content - max I have is 125 Mbps - 4K24p, H264, 8bpp, 4:2:0, bt709, and it plays with ZERO dropped frames. That’s wifi as wired I believe is limited to 100Mbps for unknown reason?

Direct Play HEVC 58.3Mbps HDR, DTS-HD MA 5.1

     Audio:
     Codec:dca
     Bitrate: 2.4Mbps
     Channels:5.1

     Decision:
     Reasons:
         User forced direct play in settings.

Receiver reports DTS-HD MA.

Direct Stream HEVC 55.6Mbps HDR, TrueHD
If I don’t force direct play with the client - then TrueHD content reports:

     Mode : Direct Stream, speed 8.3

     Audio:
     Codec: truehd->eac3
     Bitrate:4805->1032
     Channels 7.1 ->

     Decision:
     Reasons:
     Cannot direct play with protocol http: codec:truehd. Not found in profile
     Cannot direct stream with protocol: his, codec:truehd.  Not found in profile
     Direct play not available; Conversion OK.

It’s the channels blank that is a problem.

No idea why it just can’t passthrough the TrueHD content the same way it does DTS-MA.
I would totally understand if I was trying to configure it for multi-channel PCM ourput of TrueHD content.

Also - the documentation makes in clear:

  1. Dolby AC-4, MPEG-H 3D Audio, DTS, DTS-HD, and DTS:X are available in specific models only.

So I guess in my case the 2024 LG C4 model is one of those specific models.

I have a bunch of audio codec demo material
TrueHD 5.1, 7.1, Atmos 9.1.6, 7.1.4, 7.1.2, 5.1.4, 5.1.2, DTS-HD MA 5,1, 7.1, 11.1 Auro-3D from 2.0 to 13.1 in DTS, and LPCM.

webOS appears to max out at 8 channels with the LG C4.
This aligns with the supported audio properties reported by a windows PC.

Now - TrueHD atmos above 7.1 channels using side and back surrounds? Don’t care. I’m OK with just run of the mill 5.1 side surround HD codecs for my setup. I’m valuing bit rate over number of channels.

I don’t have an Atmos setup, nor a treated room that would get the most out of spacial audio.

Over the holidays, where I was staying they had a 2019 shield pro - purchased on my recommendation BTW. It’s OK. Great value for what they charge.
But it’s limited - especially with full HDMI 2.1 support and new video codecs - say H.266 VVC.
Regarding 1080p upscaling - I would hope that a 2024 LG TV would have a better upscaler than a device released 5 years earlier.

New Shield if released would be worthy of consideration.
The new google TV doesn’t support any HD audio.

I’ve been dabbling in home theatre this since XBMC on XBOX and yet I’ve yet to find a single device that just works with everything.

Admittedly I value sound over video, but I do appreciate what HDR and OLED brings in terms of visual impact.

1 Like
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Well, I have to concede this one to you… :rofl:

It does indeed seem that webOS legitimately supports DTS-HD “in specific models only”… and that would certainly explain why it works for you.

However you are still limited by max bitrate when using HEVC, and that could prove problematic.

Either way, you are still gonna have to wait for support for TrueHD, maybe even years.

As far as I’m concerned 150 to 200 pounds / dollars is not a huge amount of money to spend on a gadget that supports everything you might need with current technology… Yes, the Shield doesn’t support AV1 or VP9, but they are of no interest to me right now.

Ultimately we are all going to walk our preferred path, and that’s all that really matters :+1:

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I’ve thrown 125Mbps H.264 at webOS plex - no issues with video playback.
So I’m suspicious of the specifications stating bitrate limits.
Who knows - with updates to webOS - maybe TrueHD will be sent passthrough.
It may be a simple matter of changing an attribute in the profile stating the particular codec is supported. See - `deviceinfo’ method in the webOSTV.js library.

Perhaps I need to either upgrade my GPU to a NVIDIA 3050 and up on my existing HTPC for ~$200, or get a dedicated box that can do everything for ~$200. Plex on KODI works quite well. There are some suggestions on the KODI forum for hardware - Best Kodi Media Player Options 2025.

I did play with a minisforum minipc with Radeon 780M and it was butter - 4K120 HDR 10 bit. I could output 4:4:4 as well.
Then with the 780M/890M there is support for encode/decode any format that I’m currently interested in.
Bit more than $150-$200 though, admittedly much more flexible and powerful.

Another solution would be to find a tool to remux the TrueHD audio to DTS-HD MA.
Just plain 5.1, or 7.1. But I have not found such a tool.
I’m not interested in object based audio - Dolby Atmos or DTS:X

It’s a shame that PLEX for webOS 24 doesn’t passthrough TrueHD. In the C4 - I find the speed of PLEX perfectly adequate.
I’ll see what webOS 25 brings.

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@markus101 As of the latest premium LG-TVs per se support TrueHD via HDMI, for me Plex does NOT transcode and no sound is playing at all (without an error-message)

PLEASE! offer an option in the client, to disable TrueHD!

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I’d much appreciate some attention to this topic, even with a low amount of affected users

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I seem fortunate that my LG C2 plays TrueHD on the native Plex app if I force direct play. Many say it’s not possible but… it seems to be? Captured on Tautulli a while back:

IMG_2446
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That’s interesting…
What does your end device recognise the audio stream as?
I Investigated on the 2024 C4
TV is setup for eARC and AUTO for audio type output.
eARC into AV Receiver (No ATMOS - 5.1 setup)
WebOS PLEX is set to force direct play
WebOS TV Version WebOS24 / 9.2.2-1808

I started playing a 4K HDR (HEVC Main 10) with TRUEHD with the WebOS Plex client.
The Plex web app showing activity shows:

image
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So you would think all is good?
Not so.
The receiver connected over eARC displays DD+ only not TRUEHD.
In some TRUEHD content the receiver just displays stereo.
In the WebOS version of Plex - displaying the INFO overlay you can see the issue:

Decision:
Reasons:
Cannot direct play with protocol: https, codec:truehd. Not found in profile
Cannot direct stream with protocol: hls, codec:truehd. Not found in profile.

This aligns with the WebOS developer pages.

Now - this content has TRUEHD, AC3, DTSHD-MA

image
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Passes this audio DTSHD-MA confirmed at the receiver.

Investigated more…
In the TV settings - Digital Sound Output - Help:
Settings/Settings/Sound/Advanced Settings/Digital Sound Output.

In the Dolby TrueHD section it has in brackets (HDMI only)
For DTS-HD, and DTS:X there is no similar mention of (HDMI only)

See LG OLED EVO online manual under sound/digital sound output

image
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The caveat - Some models may not be supported. Which models?

I’d be fine with multichannel PCM if I knew the lossless codec was being converted into multi-channel PCM.

This aligns with my experience.
All the audio codecs - TrueHD, DTS-HD MA pass fine over eARC from HDMI sources, just not with any internal WebOS application.

I don’t know if it’s going to change.
It’s really strange as the audio stream is just passed bitstream, it’s not decoded by plex - so there shouldn’t be any licensing issues.

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@markus101 Thx for the new update. Could you please take a look here, so we can atleast get TrueHD to transcode, to e.g. eAC3 etc.

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PMS version?

1.41.7.9823 & 1.41.8.x should transcode TrueHD to EAC3 (as should 1.41.6 & earlier).

1.41.7 introduced a bug transcoding to Dolby formats that caused playback to fail.

This affected the Plex LG & Roku clients, as Plex Media Server normally transcodes TrueHD to EAC3 for them (other clients may also have been affected).

The problem was fixed in 1.41.7.9823: Plex Media Server - #677 by chris_decker08

You must also disable Force Direct Play if enabled in the Plex client app.

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Please at least read the first post ^^
The problem is, that the tv itself supports TrueHD over HDMI, but not via Plex. Therefore it does not get transcoded → Fix “Plex TrueHD->TV/HDMI eARC” if possible or alternatively transcode it