I want to turn OFF the 5.1 audio upmixer, a solution they provided doesn't work

In an initial bug report I created at Red Hat Bugzilla website two years ago where I was having 5.1 issues with Pipewire, I recently learned that Fedora is shipping a 5.1 audio upmixer and it’s turned ON by default but I don’t like it, therefore, they suggested to make a ~/.config/pipewire/pipewire-pulse.conf.d/10-no-upmix.conf file and put this in it:

stream.properties = {
channelmix.upmix = false
channelmix.upmix-method = none
channelmix.lfe-cutoff = 0.0
channelmix.fc-cutoff = 0.0
}

However, this is not working, the upmixer is still working when I connect my laptop to my AV receiver.

Any ideas?

Try this path, seams slightly different to RHEL:

cat client.conf
# Client config file for PipeWire version "0.3.63" #
#
# Copy and edit this file in /etc/pipewire for system-wide changes
# or in ~/.config/pipewire for local changes.
#
# It is also possible to place a file with an updated section in
# /etc/pipewire/client.conf.d/ for system-wide changes or in
# ~/.config/pipewire/client.conf.d/ for local changes.
#

I tried this one and it still upmixes the audio.

I renamed the file to client.conf does it matter the name of file?

If you make a

whereis pipewire
you get a:

pipewire: /usr/bin/pipewire /usr/share/pipewire /usr/share/man/man1/pipewire.1.gz

the second (marked) entry shows you where pipe-wire takes the global config from. Go to this location and
copy the file, where contains the properties you want to change.

Unfortunately there are more config files with this properties. The first I checked was client.conf. There are others like pipewire-pulse.conf

Copy this to the the desired location and change it (remove the #on the setting you want to use and change the value as needed) Just do not forget to restart pipewire and pipewire-pulse, to test it with:

systemctl --u restart pipewire-*

Keep the file name if you use the ../application/your-config.conf path.

While using ..application.d/name_the_additions_you_make.conf so you can see what you changed and added to the configuration. (The way you got told to do)

p.s.
What Fedora-Linux Version are you using?

Isn’t it better if I keep the original file there and edit it directly?

Fedora 36 Workstation.

As long you just have to configure for one user you might keep the overview. If there is more than one user you have on the same system you soon will loose the overview what you change for whom.

And also if you regularly make backups, you can better see the changes you made (if you use explaining filenames), and while using them on a other system you just copy the files back to the new system, changing one setting and not all of them.

In case of pipewire you find the global changes in /usr/share/pipewire. This files you should never change (explainings in the header of the files). When the system gets an update, you always need to check all the local files if you might overwrite a setting from a global (system wide config) file.
So checking just one sub directory for changes will make it easier than skim a whole of sub directories.

p.s.
In the end could you make the changes?

No, I still don’t have clear what to do, could you provide the final steps of what I should do?, this seem so complicated, there should be a switch to turn that thing on and off in sound settings.