"Sound" settings regularly break down with removable USB audio interfaces/USB soundcards
I have found the "Sound" settings regularly break down with removable USB audio interfaces/USB soundcards. This is pretty annoying on a desktop already but can usually be dealt with there, but it's IMHO a significant usability problem on the PinePhone or Librem 5 when trying to use USB-C audio adapters or USB-C headphones (= mini USB soundcards).
I regularly see the following issues with USB-C interfaces plugged in or removed with both GNOME 3+gnome-control-center on Fedora/x64, and Phosh+gnome-control-center on the PinePhone/Mobian/ARM64:
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After plugging in an USB soundcard, sometimes "Sound" now shows the wrong "Output Device", and any program that runs and uses default audio output will output to a different one. The system-wide volume shortcut keys do not work when this is the case. (This is a huge problem on mobile, since the volume keys are way more central on a phone.) Using the sound "Test" will simply not output any audio in this broken state if attempted. Simply switching the output device in the control center's "Sound" tab to another and back again usually fixes it, but on a phone that requires screen unlock, bringing down notification bar, tap settings, tap sound, tap output device, ... you see where I'm going with this, it's a dealbreaker.
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"Sound" shows separate analog and digital for some devices, and with an USB soundcard attached, of these two entries one sometimes randomly is broken. Switching to it in the UI will simply do nothing (sound remains with the old device) and enter the broken state of
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including disconnecting the volume buttons from the audio device and turning them nonoperational. Wildly switching back and forth sometimes appears to fix this, but usually it doesn't and you just need to use the respective other analog or digital entry that happens to work. -
Clicking the "Output device" combo box in the "Sound" tab sometimes just freezes gnome control center as a whole. It needs to be killed and restarted to remain operational. I also saw this both on desktop and the phone, although way more often on the phone.
pavucontrol appears to suffer from none of these problems, and will in all of these cases as far as I tested always 1. show the correct output device that is actually active, 2. not hang listing all devices, 3. allow switching with no issues. So these appear to be gnome-control-center specific bugs. I am mostly reporting this due to the major impact on volume keys on a phone, otherwise these bugs are more annoying than anything. But all of a sudden dead volume keys on a smartphone is just a big usability issue when on the run.
I tested this with: 1. Steinberg UR22 usb audio interface via intermediate powered USB 2 hub on desktop, 2. Razor USB-C audio adapter directly in USB-C plug on my phone, both of which I believe to be wildly different soundcards that likely share little technology, and plugged in via quite different ways. So it doesn't seem likely to me to be a driver issue either.