No audio with new setup using eARC (Nvidia Shield Pro)

Plex Players Streaming Devices
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Server Version#: 1.24.5.5173
Player Version#: 8.25.1.28703

I just got a new TV and soundbar, and am trying to get everything hooked up properly with eARC for audio. The hardware involved is:

  • Nvidia Shield Pro
  • TLC S546 TV
  • LG SN4A soundbar

The TV and soundbar are both supposed to support Dolby Atmos, which is why I am attempting to use eARC here. I have a movie with 3 audio stream options (TrueHD 7.1 Atmos, DTS-HD MA 7.1, and DD 5.1). The chain is like so:

Nvidia Shield --(HDMI 2.0 cable)–> into regular HDMI port on TV
out of eARC HDMI port on TV --(HDMI 2.1 eARC cable)–> into eARC HDMI input on soundbar

With this setup, I get no audio from Plex video content from any of those audio streams. I also did not get audio from an EAC3 audio stream from a different video file. Some things to note:

  • I AM getting audio from other apps on the Shield, like YouTube, Twitch, etc

  • These results are with the Plex app set to audio passthrough via HDMI

  • eARC mode is enabled in the TV settings

  • Dolby Atmos is enabled in the TV settings

  • Digital Audio Out is set to “Auto” in the TV settings

  • A “Dolby Atmos” icon appears on the TV UI when playing my Plex content this way, despite no audio

  • Attempt #2: If I set “audio passthrough” on the Plex app to disabled (with the above settings), then I get audio but the content is transcoded (the reason given is TrueHD not supported)

  • Attempt #3: If I keep “audio passthrough” on the Plex app to HDMI, and force my TV’s Digital Audio Out to “PCM”, I get audio and the Plex content is not transcoded. But doesn’t this defeat the purpose of Dolby Atmos? A “Dolby Atmos” icon appears on the TV UI when playing my Plex content this way, despite the PCM mode only passing stereo audio

  • Attempt #4: If I keep “audio passthrough” on the Plex app to HDMI, and force my TV’s Digital Audio Out to “Passthrough”, I get no audio and the Plex content is not transcoded. A “Dolby Atmos” icon appears on the TV UI when playing my Plex content this way, despite no audio

I am very new to this sort of thing so let me know if I can provide more info.

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Connect the Shield to an HDMI input on the soundbar. rtings.com reviewed the TCL S546 and had problems with audio passthrough. Connecting the Shield directly to the soundbar takes the TV out of the equation.

Verify the model number and capabilities of the soundbar. The LG website identifies the SN4A as a 2.1 soundbar and does not mention TrueHD or Atmos support (link).

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You appear to be correct, I was misinformed about the SN4A. It looks like it supports DTS Digital Surround and Dolby Digital, and NOT Dolby Atmos/TrueHD. With that being said, shouldn’t the third audio stream (DD 5.1) work in this setup? Unless this is a fault of the audio passthrough on the TV.

I was able to hook up the Shield’s HDMI directly into the soundbar, then from soundbar to the TV, but the video was limited to 1080p so I won’t be going that route. This leads me to believe that DTS Digital Surround/Dolby Digital won’t be possible in this setup because of the faulty audio passthrough on the TV.

On a side note, all audio options work if I connect the TV to the soundbar via optical cable, but I assume this does the same thing as forcing PCM over HDMI. If this setup with the optical cable achieves the maximum quality possible with the current hardware, I will likely choose this.

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Not sure it matters if you send the soundbar DD/DTS or just PCM.

The soundbar is 2.1, so the audio will have to be downmixed by the Shield, the TV, or the soundbar.

PCM is lossless, so if the conversion is of good quality, it won’t matter which device converts/downmixes the audio.

You might try setting the Shield Plex app passthrough = optical, even if using HDMI for all connections. This will bring up another setting to pick codecs. Enable both Dolby Digital and dts.

This tells the Shield Plex app to only passthrough Dolby Digital and dts audio (what an optical connection supports). Other formats will be converted by the Shield or transcoded by the Plex server.

One other thing to try is to go into the Shield (not Plex) audio settings. Instead of Auto, choose to manually select the supported codecs. Then, disable the unsupported audio formats.

No idea how the TV audio settings will affect things. I could not find a manual online that discusses the settings. Also, based on the rtings.com review, it seems the TCL has issues passing some audio formats.

You’ve some experimentation to perform to figure out what works. Hopefully you can find a configuration that passes both Dolby Digital and dts audio.

When testing with dts, use dts, not dts-HD. The TV might handle them differently. The rtings.com article mentioned issues with dts:X passthrough, and dts:X is based on dts-HD.

If you’ve MKV files with dts-HD audio, you can run them through MakeMKV. It will extract the dts core and add it as a separate audio track. All other tracks (video/audio/subtitle/etc) are copied unmodified to the new file.

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Setting the Shield Plex app passthrough to optical, but this caused everything to be transcoded. What I ended up doing was leaving the passthrough to HDMI, and just hook up the optical output on the TV to the soundbar. Thanks for all the help and info!

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