Getting 5.1 Surround Sound Working over HDMI ARC

Install the AC3 encoder plugin

Bazzite is an immutable OS, so software installs go through rpm-ostree rather than a standard package manager. Run this, then reboot.

sudo rpm-ostree install alsa-plugins-a52

The reboot is required before the plugin is available to ALSA.

Find your HDMI audio device

List your playback hardware to find which card and device number corresponds to your TV.

aplay -l

Look for your TV in the output - it'll usually be labelled by manufacturer name. Note down the card number and device number.

# Example output - yours will differ
card 1: HDMI [HDA ATI HDMI], device 10: HDMI 4 [SAMSUNG]

In this example: card 1, device 10. Keep these handy for the next step.

Release the HDMI device in PulseAudio Volume Control

Install PulseAudio Volume Control (pavucontrol) from the Bazzite app store. Open it, go to the Configuration tab, and disable the HDMI output connected to your TV. This releases it so our custom setup can take control.

Create the ALSA config

This tells ALSA how to encode audio as AC3 and route it to your HDMI output.

nano ~/.asoundrc

Paste the following - replacing hw:HDMI,10 with your actual card and device numbers from Step 2.

# Raw AC3 encoder
pcm.a52_raw {
    type      a52
    rate      48000
    bitrate   640
    channels  6
    format    S16_LE
    slavepcm  "hw:HDMI,10"  # your card and device here
}

# Safe wrapper - handles format conversion for apps
pcm.a52_safe {
    type plug
    slave.pcm "a52_raw"
    hint {
        show on
        description "TV (AC3 Surround)"
    }
}

The bitrate of 640kbit is the maximum for HDMI ARC.

Test the encoder

Run the speaker test to confirm audio is reaching your surround system before going further.

speaker-test -D a52_safe -c 6 -r 48000

You should hear test tones from each channel. If this works, carry on. If not, go back and check your card and device numbers in Step 2.

Create the PipeWire sink

mkdir -p ~/.config/pipewire/pipewire.conf.d
nano ~/.config/pipewire/pipewire.conf.d/ac3-sink.conf

context.objects = [
  {
    factory = adapter
    args = {
      factory.name     = api.alsa.pcm.sink
      node.name        = TV_AC3
      node.description = "TV Surround 5.1"
      media.class      = Audio/Sink
      api.alsa.path    = a52_safe
      audio.channels   = 6
      audio.rate       = 48000
    }
  }
]

PipeWire will create the TV_AC3 sink automatically at startup from this config file.

Create a keepalive service (recommended)

Without this, your receiver may click or go silent during quiet moments because it thinks the audio stream has ended. This service plays inaudible silence into the sink to keep it active.

nano ~/.config/systemd/user/ac3-keepalive.service

[Unit]
Description=Keep AC3 Output Alive with Silence
After=pipewire.service

[Service]
Type=simple
ExecStart=/usr/bin/paplay --raw --format=s16le --rate=48000 \
  --channels=2 --device=TV_AC3 \
  --property=media.role=background \
  --latency-msec=2000 /dev/zero
Restart=always
RestartSec=5

[Install]
WantedBy=default.target

systemctl --user daemon-reload
systemctl --user enable --now ac3-keepalive.service

Restart PipeWire and verify

systemctl --user restart pipewire pipewire-pulse wireplumber

Then check the sink exists:

pactl list short sinks

You should see TV_AC3 in the list. Set it as your default output in your audio settings, or select it per-application in PulseAudio Volume Control under the Playback tab.

Reboot and confirm

Reboot and run pactl list short sinks again. TV_AC3 should still be there - PipeWire creates it automatically from the config file on every startup.