LG G3 (webOS 23) only outputs PCM 2.0 while LG G1 outputs Dolby Digital 5.1 for same AC3 content

[Imhotep 0]

Hi all,

I’ve run into a consistent audio passthrough issue between two LG OLED TVs using the same Emby Server setup, and it seems to be related to the new audio handling in webOS 23.

Setup

• Emby Server: 4.8.11.0 (running on NAS)

• Clients tested:

• LG OLED65G39LA (G3, webOS 23)

  LG OLED65C17LB (G1, webOS 6)

• Sound system: Sonos Arc Ultra (connected via HDMI eARC)

• Emby App: current LG webOS version from Content Store

• Network & content: same Emby Server, same user, same AC3 5.1 media file

 

Problem

• When playing an AC3 5.1 file through Emby on the G3, the Sonos reports PCM 2.0.

• The same file, via Emby on the G1, plays correctly as Dolby Digital 5.1.

• Both TVs are configured identically:

  HDMI eARC: On

  Digital Audio Output: Passthrough

 

No other apps (e.g. Netflix, Disney+) show this issue — they correctly pass Dolby Digital Plus / Atmos to Sonos on both TVs.

 

Testing / Observations

• The media file contains a valid AC3 5.1 track (verified in MediaInfo).

• In the Emby Dashboard → Activity, playback on the G3 shows Direct Play (Audio: AC3), yet the TV outputs PCM 2.0 over eARC.

• The same file on the G1 outputs Dolby Digital 5.1 as expected.

• If the server is forced to transcode to AC3, Sonos correctly shows DD 5.1 again.

 

Likely Cause

Starting with webOS 23, LG replaced the legacy AVPlay playback API with the new MediaKit framework.
This framework no longer allows direct AC3 bitstream passthrough unless the app explicitly uses the new Bitstream API.

Because the Emby webOS client currently targets the older playback method, AC3 audio is decoded to PCM internallyby the TV before being sent to eARC — hence the “PCM 2.0” output.

The older G1 (webOS 6) still uses the old AVPlay engine, which supports direct AC3 bitstream passthrough — that’s why it outputs proper Dolby Digital 5.1.

 

Suggested Fix / Workaround

• Add support in the webOS client for MediaKit’s Bitstream passthrough API on webOS 23+.

• Or provide a setting to force AC3 transcoding server-side for LG clients running webOS 23 until passthrough is reimplemented.

---

Summary

TV Model	webOS	Emby Client Behavior	Output
LG G1 (C1, 2021)	webOS 6	Uses legacy AVPlay passthrough	Dolby Digital 5.1
LG G3 (2023)	webOS 23	MediaKit decodes AC3 to PCM	PCM 2.0

Would be great if the Emby team could confirm whether Bitstream passthrough for webOS 23 is already planned or if there’s a workaround for the new LG audio pipeline.

Thanks a lot for your time

 

 

[Luke 41280]

 

Hi there, let's look at an example. Please attach the information requested in how to report a media playback issue. Thanks!

 

[Imhotep 0]

Are the files attached, or is anything else needed?

ffmpeg-transcode-de16642f-9688-4e6c-8459-d2123ecbabaa_1.txt

[SamES 1041]

5 hours ago, Imhotep said:

Starting with webOS 23, LG replaced the legacy AVPlay playback API with the new MediaKit framework.
This framework no longer allows direct AC3 bitstream passthrough unless the app explicitly uses the new Bitstream API.

Because the Emby webOS client currently targets the older playback method, AC3 audio is decoded to PCM internallyby the TV before being sent to eARC — hence the “PCM 2.0” output.

The older G1 (webOS 6) still uses the old AVPlay engine, which supports direct AC3 bitstream passthrough — that’s why it outputs proper Dolby Digital 5.1.

 

Do you have a reference for this information?

[Imhotep 0]

No, not at the moment. All I can say is that it works without any problems with an Emby AppTV, emby FireTV, or on the emby LG G1 with the emby app.

 

 

[SamES 1041]

Assuming that on both LG TV's it is DirectPlaying (check Stats for Nerds) then it sounds like a TV/Firmware issue and probably hard for us to work around.

You say there is new audio handling for LG, but I'm not sure what you are referring to

[Imhotep 0]

As mentioned in the first post, both LG TVs are configured identically  the only difference is the generation. It seems that the LG G3 uses MediaKit for audio, while the LG G1 does not. With other apps, such as Jellyfin, everything works fine on the G3 as well, so the issue must be related to this specific app.

TV Model	webOS	Emby Client Behavior	Output
LG G1 (C1, 2021)	webOS 6	Uses legacy AVPlay passthrough	Dolby Digital 5.1
LG G3 (2023)	webOS 23	MediaKit decodes AC3 to PCM	PCM 2.0

[Imhotep 0]

I deleted the app and reinstalled it, and the problem seems to have been fixed. It's still strange, though. Thank you very much for your support. 

[SamES 1041]

2 hours ago, Imhotep said:

I deleted the app and reinstalled it, and the problem seems to have been fixed. It's still strange, though. Thank you very much for your support. 

Great, thanks for the update.  That will be helpful if anyone else has the same problem.

Where is this table from? I'd like to research it further

2 hours ago, Imhotep said:

TV Model	webOS	Emby Client Behavior	Output
LG G1 (C1, 2021)	webOS 6	Uses legacy AVPlay passthrough	Dolby Digital 5.1
LG G3 (2023)	webOS 23	MediaKit decodes AC3 to PCM	PCM 2.0

 

[Imhotep 0]

I compiled the table because the information about WebOS was scattered on the Internet.

[SamES 1041]

4 minutes ago, Imhotep said:

I compiled the table because the information about WebOS was scattered on the Internet.

Ah, OK.  I don't think this information is correct.  There are slight differences year to year (for example, DTS, support, etc) but the fundamental playback methods have not changed. AVPlay and MediaKit aren't part of any webOS frameworks for media playback.

This is the best reference - just compare the different model years.

https://webostv.developer.lge.com/develop/specifications/video-audio-230

https://webostv.developer.lge.com/develop/specifications/web-api-and-web-engine

 

[NakedPirate 12]

BTW, LG and audio really makes me sick...maybe it's a common TV manufacturers problem, but I only have LG's:

While every 15$ media player or SBC on this planet does real multichannel passthrough since 25 years,
LG was only able to send compressed AC3 in 5.1 max to the amplifier on all models. Yeah, maybe ARC bandwidth...

Starting with EARC and more than enough bandwidth, all LG TV's now send stereo (2-channel PCM) to the AVR, as soon as there are other codecs used than AC3!
So you have to fall back to ARC manually with ALL other codecs, even AAC, so the TV can make its DolbyD 5.1 out of it. (like ARC used to do the last years before EARC) 

Then why do I need EARC?
As I said: Every media player or my raspberry can do real passthrough or send multichannel PCM, no matter what codec, no matter how many channels.
If no multi-channel PCM or passthrough, the TV could at least forward multi-channel DD, as it was in ARC mode, so that you do not have to move back to ARC all the time. LG is ridiculous.

Just my 2 cents. 



 

 
 

[Imhotep 0]

LG supports passthrough (also with ARC or EARC, can be set) and passes it through. However, if the audio output does not support the codec, PCM is output. Therefore, I cannot confirm your description.

[NakedPirate 12]

28 minutes ago, Imhotep said:

LG supports passthrough (also with ARC or EARC, can be set) and passes it through. However, if the audio output does not support the codec, PCM is output.

What is this "audio output" supposed to be? I have 4 LG's from 2020-2025 and not one passes something through.
Example: Let's take any 5.1 or 7.1 AAC file: My 2 older LGs with only ARC make DD5.1 out of it. My newer TV's with EARC only send 2.0 PCM.
Kodi on Raspberry, every media player, ever other device sends all channels and my receiver does the rest, no matter if original or decoded.

So the LG's can't either bitstream nor decode and send multichannel PCM except AC3 and with ACR only. That's a fact with all my devices and codecs/profiles.
And why the hell do they decode anything in AC3 with ACR but not with EARC?

What am I missing?

[Imhotep 0]

If you are connecting your TV's HDMI 2 (arc/earc) port to your soundbar, for example, then you need to configure the settings as follows:

 

All settings > Sound > Advanced settings > Digital output > Pass-through

The images are from a German WebOS, so it may be called something different in your language. 

Now the signal is transmitted directly from the source to the soundbar, where it is also decoded. If your input signal comes from HDMI 1, for example, you need to set it to bitstream in the settings, then it will work without any problems. 

When connected and set up in this way, the TV passes the incoming audio signal through to the receiver without processing it. If the receiver cannot handle the signal, e.g. DTS:X Pro, the signal is usually output via PCM Multichannel.

 

 

Edited October 30 by Imhotep

[Imhotep 0]

9 minutes ago, Imhotep said:

If you are connecting your TV's HDMI 2 (arc/earc) port to your soundbar, for example, then you need to configure the settings as follows:

 

All settings > Sound > Advanced settings > Digital output > Pass-through

The images are from a German WebOS, so it may be called something different in your language. 

Now the signal is transmitted directly from the source to the soundbar, where it is also decoded. If your input signal comes from HDMI 1, for example, you need to set it to bitstream in the settings, then it will work without any problems. 

When connected and set up in this way, the TV passes the incoming audio signal through to the receiver without processing it. If the receiver cannot handle the signal, e.g. DTS:X Pro, the signal is usually output via PCM Multichannel.

 

 

If you are using the LG Emby app, you just need to set it to pass-through, and the signal will be sent 1:1 to the receiver.
With Kodi, you just need to set the HDMI to bitstream and also set Kodi itself to pass-through. 

[NakedPirate 12]

Yeah, no..this doesn't work. Really.
Non bitstreamable formats won't be sent over HDMI and EARC on LG won't decode multichannel.
This really only works with AC3.
As soon as there is any other codec involved -> EARC setting enabled in LG forces 2 channel decode. (With ARC it works multichannel.)
My receiver can handle every format.
But I must change the LG's back from EARC to ARC as soon as I use anything else than AC3 or I'm screwed with Stereo.

Media Player, Kodi, etc..: Receiver shows and plays 5.1 "multi-in", works as intended.
Media per USB on Receiver: As intended.
ARC on LG: DD5.1 decoded, works as supposed to work. But even there no PCM passthrough.
EARC on LG: DD2.0, NOT working as it should be.

I criticized this since the beginning of EARC across the net and AFAICS I'm not alone. LG decodes every signal into 2 channel PCM.

And thanks very much for your help! I appreciate every input and will go over all settings again!

Edited October 30 by NakedPirate

[NakedPirate 12]

For those interested in the topic....

I tried it again with 2 TV's and it still doesn't work.
As soon as LG makes a PCM out of anything, the AVR switches to "limited mode" with only Stereo.

The Denon's don't accept LG's PCMs as a correct raw multichannel signal, even it receives all 6 channels.
As I said before, all other devices, mediaplayers I ever tried can send the same file as perfect PCM, so Denon says ok and lets you use all available upmixers, Auro or just the famous "multi CH in".

I never could figure out if the problem is with the PCM stream itself or the metadata of the PCM or it is just a EDID Handshake thingy.

Neither Denon nor LG support could rudimantarily help, even I tried a hundred times to get to Level3 and 4 support. Denon wasn't even able to read or interpret my logs from the AVR and LG has the dumbest support on this planet. But they know about the problem for years and confirmed it.

 

So I still don't know what affects Denon's behavior with LG PCMs over EARC, while it woks in really every other case.