Fix crackling sound in Libvirt VM with PulseAudio

So I run a Fedora virtual machine on a Libvirt host running in my garage.

I use SPICE and virt-viewer from my laptop in the office to connect to the VM.

Despite the cabled gigabit link, SPICE performances are not optimal.

While I can live with poor full screen video performances in SPICE, I can’t stand crackling audio.

The crackling audio was particularly bad when scrolling in a webpage in a browser or any kind of zooming on pictures.

Receiving end / PulseAudio Server / Audio output / The Laptop

Install the paprefs package.

Start paprefs.

Navigate to the “Network Server” tab".

Tick “Enable network access to local sound devices”. I ticked the authentication box as I have strict firewall rules between the source and destination.

At the command line kill PulseAudio with pulseaudio -k.

If PulseAudio doesn’t restart automatically (it should) you can run pulseaudio --start.

Open the TCP/4713 port used for receiving the audio.

firewall-cmd --add-port=4713/tcp --permanent
firewall-cmd --reload

Sending end / Client / Audio input / the VM

Edit /etc/pulse/default.pa.

At the end of the file add the following line:

load-module module-tunnel-sink-new server=laptop.example.org sink_name=Remote channels=2 rate=44100

Replace laptop.example.org by the hostname of IP of your server.

Restart PulseAudio with pulseaudio -k.

If PulseAudio doesn’t restart automatically (it should) you can run pulseaudio --start.

Start PulseAudio volume control with pavucontrol.

Start your music player.

You should be able to send your audio through the tunnel:

You can also control the volume of the output:

I now enjoy a crackle free audio experience.

The beauty and other advantage of the setup is that I can close the remote viewer and music will keep playing on my laptop.