Playing sound in Docker container on WSL in Windows 11 - windows

Question

Newer versions of Windows (build 21364 or later) enable GUI support in WSL2, including full audio support. This is pretty amazing.
Given that WSL2 now supports audio, how do we then get audio to work inside a Docker container running on Windows, using Docker's WSL2 engine?
On a Linux host, you can simply invoke a Docker image with e.g --device /dev/snd.
What is the equivalent command to run a sound-enabled Docker image from the Windows command line?

Answer 1

There is no /dev/snd or direct audio hardware emulation available in WSL, even in the new Windows 11 setup. Instead, the newest release of WSL achieves audio output by pointing PulseAudio clients to an external PulseAudio server via a socket in /mnt/wslg/. This server runs on yet another Linux distro calleed WSLg that runs inside Windows for the sole purpose of plumbing audio and graphical data between your WSL distro and Windows.
It looks a bit like this:
Docker container <-> WSL <-> WSLg <-> Windows 11
The actual PulseAudio server is located in WSLg. The location of the socket is stored in the environment variable PULSE_SERVER:
# On WSL
echo $PULSE_SERVER
/mnt/wslg/PulseServer
So, aside from making sure your Dockerfile has a basic PulseAudio installation (RUN apt-get install -y pulseaudio or equivalent), all you need to do is invoke the image like:
In WSL:
docker run -t -i -e "PULSE_SERVER=${PULSE_SERVER}" -v /mnt/wslg/:/mnt/wslg/ image_name
Or from the Windows command line like:
wsl docker run -t -i -e "PULSE_SERVER=/mnt/wslg/PulseServer" -v /mnt/wslg/:/mnt/wslg/ image_name
Or
docker run -t -i -e "PULSE_SERVER=/mnt/wslg/PulseServer" -v \\wsl$\Ubuntu\mnt\wslg:/mnt/wslg/ image_name