Plex won't output surround sound signals

General Discussions
1

Plex web shows the audio for a file as 5.1. The file properties show it has six channels. When I play the file in VideoLANs VLC player, the sound is output properly to all speakers and the subwoofer.

But when I play the same video in Plex, only 3 channels are output. No sound comes from the rear speakers.

I see no settings that allow me to change any audio output for Plex.

2022-07-14 11_33_03-▶ Moon Knight - S1 · E1

2

I’m not an expert at the Plex Web App, but you can see from that image you posted, there is no choice for Audio Device, which jives with my understanding that the Web App is the wrong player to output your EAC3 track to an external DAC, AVR, or Soundbar via HDMI or Optical.

For digital audio output, I use Plex for Mac, and more and more often Plex HTPC.
Does that provide any insight?

3

I didn’t realize there ever was or could be an option for “audio device”. I’ll try HTPC, I didn’t even know it existed.

4

Great I love that HTPC. Here’s what I do.

  1. I run Plex for HTPC for all my surround sound content. That way I don’t have to fiddle once I get the audio output path sorted. I’m always sending encoded AC3, DTS, or PCM content to the DAC, which are its limitations.
  2. I run Plex for Mac for administration and watching anything else. It has audio device set to Auto Select Device so that it follows the System Default chosen in macOS Preferences.

Steps to getting Digital AC3 & DTS output from Plex HTPC to CalDigit TB3:

  1. With HTPC off, turn on the DAC. I see it’s name in macOS sound output choices.
  2. Set macOS system default sound the Mac’s internal speakers, not the DAC.
  3. Start HTPC. Navigate to Settings > Audio.
    – Exclusive Audio: yes
    – Audio Device: CalDigit Thunderbolt 3 Audio
    – Audio Device Kind: HDMI
    – Audio Channels: 5.1
    – Dolby Digital AC3: checked
    – DTS (DCA): checked
  4. Esc out to your home and play a film with AC3 sound.

Just remember only play PCM, AC3, DTS, or DTS HD-MA content with that setup because it sets the audio path to bypass the macOS internal mixer, to go directly to a DAC that can hang if sent unsupported codecs like TrueHD, FLAC, Opus, MP3.

Caveats -
In case you have optical like the CalDigit TB3, you can’t choose Optical S/PDIF as your
Audio Device Kind in HTPC, but rather have to use HDMI, a known bug.

5

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