Pipewire Sound Server

I recently upgraded my PC and laptop to Linux Mint 22 (Wilma). It was somewhat harrowing experience -- the laptop (which is my canary in coal mine) updated fine, but the PC was bricked due to an issue with BIOS secure boot stuff. At power up there was a message involving some cryptic acronym I no longer remember. It had something to do with secure boot keys, and it prevented the PC from booting (even from a bootable USB drive). I spent an hour or two futzing with BIOS settings but eventually got secure boot and TPM turned off, which let the PC boot. I haven't had any problems since then.

One of the changes in Mint 22 is that the developers moved from ALSA to a newer sound (and video?) server called PipeWire. The changeover was initially invisible to me -- sound and video so far have worked flawlessly -- but necessitated changes to a couple of shell scripts I use. One of them is a convenience script that resets the speaker volume to my preferred level. It's handy when I have to crank volume up for some reason. The other is a script that launches Zoom. It turns up the volume before Zoom starts and then resets the volume when I exit from Zoom.

Fortunately, it wasn't hard to find the new commands (thank you Uncle Google). There's probably more than one way to control volume from the command line or a script, but I ended up using the WirePlumber library. I can't recall if it was installed automatically during the upgrade or if I had to add it. The key command is wpctl, which somewhat curiously does not seem to have a man page. Fortunately, wpctl --help will get you the information you need. My old scripts used 

pacmd set-sink-volume 0 27500
pacmd set-sink-volume 1 27500
sudo alsactl store

to reset the speaker volume. (I had to try both sink 0 and sink 1 because, for some reason, the speakers would sometimes be assigned to 0 and sometimes to 1 during boot.) With PipeWire I use

wpctl set-volume @DEFAULT_AUDIO_SINK@ 0.42

to do the same thing. 

There are a few improvements with the new approach. I apparently do not have to play "guess the sink" anymore. I do not need to escalate privileges (sudo) just to change the volume. Also, the volume setting is easier to interpret (0.42 is 42% of maximum -- I'm not sure how I settled on 27500 in the old approach, but it is not obvious to me that it equates to 42%).