I have recently begun having a very annoying issue with audio playback in Firefox 87 (Ubuntu 18.04 with Unity Desktop; application-based volumes are a thing there too), possibly due to a Firefox update (which I didn't notice, but I'm fairly sure the version number is higher). I had assumed that it was due to a number of other listed issues (such as Inconsistent Sound Volume Ubuntu 20.04 or Firefox keeps resetting Pulse volume to 0), all of which I have tried.
However, I just noticed that the issue is only with Youtube videos (so far). In fact, the regular volume is being kept just fine (the example was a HTML5 music player) as shown in the first Firefox entry. The second one appears only while Youtube is being played, and apparently deletes itself or disappears and resets the volume to a bit less than 50% every time I pause or stop a video. This is playing merry hell with my audio preferences since I'm alternately deafened or unable to hear what I'm trying to watch.
Does anyone have any ideas? I've even looked for "volume" in about:config and those seem normal...
(Also, is this spawning a bunch of configs in my audio settings app for all the new Firefox profiles? I'd hate to be accidentally filling up my precious SSD space with one-off never-to-be-used again audio profiles)
EDIT: Here's the output of the command in the comments:
total 152
drwx------ 2 dracos dracos 4096 Apr 30 2019 .
drwx------ 71 dracos dracos 20480 Apr 23 22:07 ..
-rw------- 1 dracos dracos 256 Sep 18 2017 cookie
-rw-r--r-- 1 dracos dracos 40960 Apr 25 17:21 eb0493ce214748b3add5028fdff3fa37-card-database.tdb
-rw-r--r-- 1 dracos dracos 39 Apr 26 01:35 eb0493ce214748b3add5028fdff3fa37-default-sink
-rw-r--r-- 1 dracos dracos 49 Apr 26 01:35 eb0493ce214748b3add5028fdff3fa37-default-source
-rw-r--r-- 1 dracos dracos 12288 Apr 26 10:55 eb0493ce214748b3add5028fdff3fa37-device-volumes.tdb
-rw-r--r-- 1 dracos dracos 12288 Apr 26 12:15 eb0493ce214748b3add5028fdff3fa37-stream-volumes.tdb
ls -al $HOME/.config/pulse
please add this to your question. Maybe helpful bbs.archlinux.org/viewtopic.php?id=196044pacmd
then give in the clillist-modules
Is the part <module-stream-restore> loaded?