“Help! No Volume Mute under Plasma 5!”

One of the subjects I blog about, is a computer I named ‘Plato’, which is running Debian / Stretch (Debian 9), and the desktop manager of which is Plasma 5, which is the successor to KDE 4.x .

One of the features which KDE 4 definitely had, was an icon in the notification-tray, from which we could control our volume levels easily, as well as to mute the sound temporarily, eventually to be unmuted again, at which point the earlier, unmuted settings should be remembered. At first glance it would seem that Plasma 5 has done away with this capability. Trying to solve this can cause people to spend hours searching the Internet, changing their Plasma 5 preferences, and maybe even forgetting their Plasma 5 preferences, because they disabled all their System Sounds from there.

Recently, I was on a fact-finding mission about this, and am willing to share my solutions.

Under Plasma 5, we really only need to have 2 packages installed, in order to control our volume-levels, etc., assuming that we have gotten our hardware recognized first. Those packages would be:

  1. ‘plasma-pa’
  2. ‘pavucontrol’

The first of these packages integrates with Plasma, and is also responsible for the icon in the notification tray. The second package gives us more control, over our sound-levels specifically, since Plasma 5 uses the Pulse Audio sound-server by default.

If we can see the icon in the notification tray, then a detail which we may overlook after we left-click on that icon, is a tiny little loudspeaker-symbol, on the left end of one of the volume sliders:


Left-clicking on this little symbol will cause the volume-bar to the right of it to become slightly pale, which will mean, that the device in question has been muted. I’m saying that ‘we’ could overlook that we even have this feature, because earlier, ‘I’ did not know that I have this feature.

But, this is only what the ‘plasma-pa’ package can show us. The ‘pavucontrol’ package gives us the ability to fine-tune our sound-levels as shown below:


Now, there’s an aspect to how this setup now works, which is slightly more complicated than how KDE 4 used to handle it. The Pulse Audio server attempts to adjust playback as well as recording levels, on a per-application basis. Thus, the view above is almost empty, because there were no applications playing back any sounds, at the moment I recorded this screen-shot.

A frustrating fact which can exist with this, is that some applications will only play a sound for 2 seconds, during which an additional volume-bar appears in the GUI, and after which that volume-bar disappears again, even if we did not have enough time to adjust one volume level. This happens to result from the design-decision, that volume-control should exist at the per-application level. Hence, even if we use media-control keys on our keyboard, those keys will only affect the one main application which happens to be playing, at any given moment. They won’t affect System Sounds.

But this description might sound like I have to say, ‘There is no problem,’ when in fact, under Debian / Stretch, There Is a problem. That problem, as I see it, lies in the fact that by default, the one volume-bar which the GUI has shown above, for all System Sounds, may not even work.

(Updated 04/26/2018 … )

(As of 04/23/2018 : )

Now, a solution which other sources on the Internet have suggested was, that instead of installing ‘pavucontrol’, which is a GTK-3 -based application, we should just install the Qt-based application. What the Qt-version of ‘pavucontrol’ will allow us to do, is to mute the System Sounds, but to have the volume-bar not go all the way to the left, to show us zero volume. The way the GTK-3 GUI works, the volume bar will show zero volume, as long as the channel in question is muted. If we unmute that, the volume bar remembers its non-zero volume-level.

The Qt-version of this application still won’t allow us to adjust the System Sound Level, besides muting it, if we were unable to do so before. And the reason for this is probably – according to my guess – the possibility that the user may have given the Pulse Audio server, the VLC back-end. The VLC back-end is nice, in that it will allow Pulse Audio to send stream to our devices, but just has as a fault, that to try to adjust the System Sound Levels to anything but 100% or muted, won’t work.

The way I solved this issue on ‘Plato’, is by installing the following two packages as well:

  1. ‘gstreamer1.0-alsa’
  2. ‘phonon4qt5-backend-gstreamer’

What this does is allow the GStreamer back-end to appear as available, for users to choose if they wish, in addition to the VLC back-end:


The GStreamer back-end, finally allows us to adjust the System Sound Level to something distinct, and unto itself…

(Update 04/26/2018 : )

One side-effect which I had noticed, immediately after I had made this modification to my Pulse Audio server, was that the Message-Box did no longer play any sound, when alerting me to KOrganizer / Calendar Scheduled Events.

But the real reason why this was once happening, was the fact that I, myself had Disabled All Notification Sounds, in the System Settings page responsible (“Plasma Workspace”), because of an earlier quest to quiet them. After having made my configuration change, I re-enabled most of the Notification Sounds, except one:


I had somehow felt that to re-enable “Information Message” would also cause the Calendar Notifications to play their beep again.

But the way ‘KOrgac’ works, is that if an event notification has been set to play an alarm, the alarm that the application will choose by default, is the beeper that old computer have on their internal circuit-board. And, because many Linux installs do not even have access to this beeper, it’s necessary to enable an alternative notification sound.

Hence, I had forgotten to re-enable “Beep – Sound Bell” as a system sound, and the reason fw Calendar Notifications were not playing – for a while – was this simple omission in my settings. :-)



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