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__FORCETOC__
QEMU's JACK backend provides the best audio quality out of all the available options (Scream, PulseAudio, etc.). One of the easiest ways to leverage the JACK support is by using PipeWire, which emulates JACK.
First, you must make sure your distro's QEMU is built with JACK support:
* On Debian, this is not the case until QEMU 6.1. This is currently only in unstable and bullseye-backports. You should enable backports if you are using bullseye and upgrade if you are using something older.
Normally, you can run applications with PipeWire's JACK support by running it with <code>pw-jack</code>, but this is not possible when using libvirt. Instead, you need PipeWire to provide drop-in JACK support. To do this:
* on Debian: run <code>sudo cp /usr/share/doc/pipewire/examples/ld.so.conf.d/pipewire-jack-*.conf /etc/ld.so.conf.d/; sudo ldconfig</code>
* on Arch: install the [https://aur.archlinux.org/packages/pipewire<code>qemu-audio-jack-dropin</ code> package, which contains the jack driver for qemu, and the <code>pipewire-jack-dropin] AUR </code> package.
Once this is done, you have two options. You could run your virtual machines under your user, or you could set it up so that the QEMU user has access to your PipeWire socket. The former is easier, while the latter is more secure.
Then, you can run <code>virsh edit win10</code>, and perform the following changes:
# If the <code><domain></code> line doesn't already contain <code>xmlns:qemu</code>, add <code><nowiki>xmlns:qemu='http://libvirt.org/schemas/domain/qemu/1.0'</nowiki></code>. The line should look like:#: <syntaxhighlight lang="xml"><domain type='kvm' xmlns:qemu='http://libvirt.org/schemas/domain/qemu/1.0'></syntaxhighlight># Add the following block to the If there is an existing <code><devicessound></code> section:#: <syntaxhighlight lang="xml"> <audio id="1" type="jack"> <input clientName="win10" connectPorts="input-name"/> <output clientName="win10" connectPorts="output-name"/> </audio></syntaxhighlight>#: <code>input-name</code> and <code>output-name</code> block, it should be replaced with a regular expression that matches the name of the JACK input and output ports. You can get the names by looking at your patchbay, or run <code>jack_lsp</code>removed.
# Finally, we need to set PipeWire's runtime directory and latency. These are configured by environment variables. To do this, the following block right before <code></domain></code>:
#: <syntaxhighlight lang="xml">
/run/user/1000/pipewire-0 rw,
</source>
Once you shutdown your VM and restart it, you should see an emulated HD audio device, and any sound should go into PipeWire. If you don't hear anything, check your patchbay connections.
$ chmod 700 /srv/win10
$ setfacl -m u:libvirt-qemu:rx /srv/win10
$ touch /srv/win10/pipewire-0
</syntaxhighlight>
<output clientName="win10" connectPorts="output-name"/>
</audio>
<sound model="ich9">
<alias name="sound0"/>
</sound>
</syntaxhighlight>
#: <code>input-name</code> and <code>output-name</code> should be replaced with a regular expression that matches the name of the JACK input and output ports. Essentially, these are the names of microphone and speaker devices that the VM would connect to. You can get the names by looking at your patchbay, or run <code>jack_lsp</code>.#: If there is an existing <code><sound></code> block, it should be removed.
# Finally, we need to set PipeWire's runtime directory and latency. These are configured by environment variables. To do this, the following block right before <code></domain></code>:
#: <syntaxhighlight lang="xml">
/srv/win10/pipewire-0 rw,
</source>
If you are using NixOS, you'll also need to add <code><qemu:env name="LD_LIBRARY_PATH" value="$LD_LIBRARY_PATH:/run/current-system/sw/lib/pipewire"/></code> to your <code><qemu:commandline></code> section.
Once you shutdown your VM and restart it, you should see an emulated HD audio device, and any sound should go into PipeWire. If you don't hear anything, check your patchbay connections.
