Plex HTPC on Linux - Failed to initialize audio driver 'pulse' (audio passthrough fails)

Plex Players Desktop Players
1

Server Version#: 1.27.2.5929
Player Version#:

Hi all,
I am running Plex HTPC on Ubuntu 22.04 and struggling to get passthrough audio to work with pulseaudio. I have been able to disable pulse and use alsa directly to passthrough everything (AC3, dts, truehd/Atmos, DTS-HD) to my AVS, but this is not ideal as it kills desktop audio until I restart pulseaudio. I am also able to use mpv with pulseaudio and successfully passthrough audio to my AVS. I am using the hdmi-stereo output and have use pavcontrol to ‘check’ all of the passthrough boxes.

Looking through Plex HTPC.log I am seeing this error:

Jul 23, 2022 16:46:22.246 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] ao/pulse: result: stereo
Jul 23, 2022 16:46:22.247 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] ao/pulse: Stream failed.
Jul 23, 2022 16:46:22.247 [0x7f9ffbfff700] ERROR - [MPVEngine/mpv] ao: Failed to initialize audio driver 'pulse'

Curiously, the video will also display the first frame, but will not play until I seek forward or backward, then the video will play with stereo 2.0 pcm sound (the selected audio track is 5.1 AC3). Here is more context from the log file:

Jul 23, 2022 16:46:22.243 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] ao: Trying audio driver 'pulse'
Jul 23, 2022 16:46:22.243 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] ao: Using preferred device 'alsa_output.pci-0000_00_1f.3.hdmi-stereo'
Jul 23, 2022 16:46:22.243 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] ao/pulse: requested format: 48000 Hz, stereo channels, spdif-ac3
Jul 23, 2022 16:46:22.243 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] ao/pulse: Library version: 13.99.0
Jul 23, 2022 16:46:22.243 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] ao/pulse: Proto: 33
Jul 23, 2022 16:46:22.243 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] ao/pulse: Server proto: 4294967295
Jul 23, 2022 16:46:22.245 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] ao/pulse: Channel layouts:
Jul 23, 2022 16:46:22.245 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] ao/pulse:  - #fl
Jul 23, 2022 16:46:22.245 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] ao/pulse:  - #fr
Jul 23, 2022 16:46:22.245 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] ao/pulse:  - #fc
Jul 23, 2022 16:46:22.245 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] ao/pulse:  - #lfe
Jul 23, 2022 16:46:22.245 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] ao/pulse:  - #bl
Jul 23, 2022 16:46:22.245 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] ao/pulse:  - #br
Jul 23, 2022 16:46:22.245 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] ao/pulse:  - #flc
Jul 23, 2022 16:46:22.245 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] ao/pulse:  - #frc
Jul 23, 2022 16:46:22.245 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] ao/pulse:  - #bc
Jul 23, 2022 16:46:22.245 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] ao/pulse:  - #sl
Jul 23, 2022 16:46:22.245 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] ao/pulse:  - #sr
Jul 23, 2022 16:46:22.245 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] ao/pulse:  - #tc
Jul 23, 2022 16:46:22.245 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] ao/pulse:  - #tfl
Jul 23, 2022 16:46:22.245 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] ao/pulse:  - #tfc
Jul 23, 2022 16:46:22.245 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] ao/pulse:  - #tfr
Jul 23, 2022 16:46:22.246 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] ao/pulse:  - #tbl
Jul 23, 2022 16:46:22.246 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] ao/pulse:  - #tbc
Jul 23, 2022 16:46:22.246 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] ao/pulse:  - #tbr
Jul 23, 2022 16:46:22.246 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] ao/pulse: result: stereo
Jul 23, 2022 16:46:22.247 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] ao/pulse: Stream failed.
Jul 23, 2022 16:46:22.247 [0x7f9ffbfff700] ERROR - [MPVEngine/mpv] ao: Failed to initialize audio driver 'pulse'
Jul 23, 2022 16:46:22.247 [0x7f9ffbfff700] ERROR - [MPVEngine/mpv] ao: This audio driver/device was forced with the --audio-device option.
Jul 23, 2022 16:46:22.247 [0x7f9ffbfff700] ERROR - [MPVEngine/mpv] ao: Try unsetting it.
Jul 23, 2022 16:46:22.247 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] cplayer: Falling back to PCM output.
Jul 23, 2022 16:46:22.247 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] ad: Codec list:
Jul 23, 2022 16:46:22.247 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] ad:     ac3 - ATSC A/52A (AC-3)
Jul 23, 2022 16:46:22.247 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] ad: Opening decoder ac3

After seeking forward or backward, the video plays with 2.0 pcm and the log shows:

Jul 23, 2022 16:46:25.185 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] af: [in] 48000Hz 5.1(side) 6ch floatp
Jul 23, 2022 16:46:25.185 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] af: [userspeed] 48000Hz 5.1(side) 6ch floatp
Jul 23, 2022 16:46:25.185 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] af: [convert] 48000Hz 5.1(side) 6ch floatp
Jul 23, 2022 16:46:25.185 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] ao: Trying audio driver 'pulse'
Jul 23, 2022 16:46:25.185 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] ao: Using preferred device 'alsa_output.pci-0000_00_1f.3.hdmi-stereo'
Jul 23, 2022 16:46:25.185 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] ao/pulse: requested format: 48000 Hz, 5.1 channels, floatp
Jul 23, 2022 16:46:25.185 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] ao/pulse: Library version: 13.99.0
Jul 23, 2022 16:46:25.185 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] ao/pulse: Proto: 33
Jul 23, 2022 16:46:25.185 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] ao/pulse: Server proto: 4294967295
Jul 23, 2022 16:46:25.186 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] ao/pulse: Channel layouts:
Jul 23, 2022 16:46:25.186 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] ao/pulse:  - #fl
Jul 23, 2022 16:46:25.186 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] ao/pulse:  - #fr
Jul 23, 2022 16:46:25.186 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] ao/pulse:  - #fc
Jul 23, 2022 16:46:25.187 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] ao/pulse:  - #lfe
Jul 23, 2022 16:46:25.187 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] ao/pulse:  - #bl
Jul 23, 2022 16:46:25.187 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] ao/pulse:  - #br
Jul 23, 2022 16:46:25.187 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] ao/pulse:  - #flc
Jul 23, 2022 16:46:25.187 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] ao/pulse:  - #frc
Jul 23, 2022 16:46:25.187 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] ao/pulse:  - #bc
Jul 23, 2022 16:46:25.187 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] ao/pulse:  - #sl
Jul 23, 2022 16:46:25.187 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] ao/pulse:  - #sr
Jul 23, 2022 16:46:25.187 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] ao/pulse:  - #tc
Jul 23, 2022 16:46:25.187 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] ao/pulse:  - #tfl
Jul 23, 2022 16:46:25.187 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] ao/pulse:  - #tfc
Jul 23, 2022 16:46:25.187 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] ao/pulse:  - #tfr
Jul 23, 2022 16:46:25.187 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] ao/pulse:  - #tbl
Jul 23, 2022 16:46:25.187 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] ao/pulse:  - #tbc
Jul 23, 2022 16:46:25.187 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] ao/pulse:  - #tbr
Jul 23, 2022 16:46:25.187 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] ao/pulse: result: 5.1
Jul 23, 2022 16:46:25.188 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] ao/pulse: device buffer: 4800 samples.
Jul 23, 2022 16:46:25.188 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] ao/pulse: using soft-buffer of 9600 samples.
Jul 23, 2022 16:46:25.188 [0x7f9ffbfff700] INFO - [MPVEngine/mpv] cplayer: AO: [pulse] 48000Hz 5.1 6ch float
Jul 23, 2022 16:46:25.188 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] cplayer: AO: Description: PulseAudio audio output
Jul 23, 2022 16:46:25.188 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] autoconvert: inserting resampler
Jul 23, 2022 16:46:25.188 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] swresample: format change, reinitializing resampler
Jul 23, 2022 16:46:25.189 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] swresample: 48000Hz 5.1(side) floatp -> 48000Hz 5.1 float
Jul 23, 2022 16:46:25.189 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] swresample: Remix: 5.1(side) -> 5.1
Jul 23, 2022 16:46:25.189 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] swresample: Fudge: sl-sr -> bl-br
Jul 23, 2022 16:46:25.189 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] af: [out] 48000Hz 5.1 6ch float
Jul 23, 2022 16:46:25.191 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] cplayer: audio ready
Jul 23, 2022 16:46:25.191 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] cplayer: starting audio playback
Jul 23, 2022 16:46:25.191 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] cplayer: playback restart complete @ 30.030000, audio=playing, video=playing
Jul 23, 2022 16:46:25.191 [0x7f9ffbfff700] DEBUG - [MPVEngine/mpv] ao/pulse: starting AO

Pulse driver is successfully initialized and receiving decoded 5.1 PCM, but is only outputting 2.0 PCM.

Not sure what to do here, I have also tried every audio device listed in Plex HTPC, but no luck with any of them for passthrough audio.

Thanks in advance for any help you may be able to provide!

2

You should run mpv with --msg-level=all=v to see what it is doing. HTPC uses MPV for playback so it’s capable of the same things as MPV.

Likely the problem in PA. PA has been an issue for years and I obliterated it from any HTPC computer I have had for the past half-decade because of its issues.

3

Thanks, I ran mpv with --msg-level=all=v, I couldn’t really find anything in the output that was different, other than it tried the pulse driver and it worked; whereas with Plex HTPC it fails. I like your suggestion though to remove pulse audio. What did you replace it with? Would you recommend pipewire?

4

PA runs on top of ALSA. I removed PA on my HTPC machine so I could use ALSA directly.

5

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