Created attachment 122181 [details] Debian package info I often play audio from my phone through Bluetooth on my computer's speakers--and that works fantastically. There's only one wrinkle: When a system notification sound is played, there is a hard-to-describe transient after playback of the notification sound finishes. At best, there's a noticeable click. At worst, the A2DP stream plays at the wrong (and often very loud) volume for a fraction of a second. This happens also for the "plop" feedback sounds played by the Gnome 3 volume adjustment helper.
It sounds like an issue with the "deferred volume" feature. The term refers to the need to delay hardware volume changes when synchronizing with software volume changes. It's impossible to reliably make hardware and software volume changes simultaneously, and on your hardware the default parameters don't seem to work that well. The parameters can be tuned in /etc/pulse/daemon.conf, see "man pulse-daemon.conf" for more details. A simpler workaround is to disable the "flat volumes" feature (many distributions disable it by default). You can do that by putting "flat-volumes = no" to /etc/pulse/daemon.conf.
Thanks for the pointer. I can confirm that switching to flat volumes actually does successfully work around the issue for me. Nonetheless, I would like to suggest one of the following as a more permanent remedy: first, rather than trying to exactly time to instantaneous volume adjustments, it might just be easier to try and do a linear blend on both the sink and the stream volumes to get them to their desired states. I am aware that that will result in a bunch of more software complexity, but I do feel that the experience of loud volume transients is sufficiently janky that this may be merited. On the other hand, if that is not feasible, at least in the short term, it might be worthwhile to disable flat volumes by default. I know I will certainly lobby Debian to disable them.
Never mind: Plenty of people seem to hate flat volumes already. https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=674935 https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=697119 (and further bugs merged into that)
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