Mint 15/Mate, Debian 9 + Mate: Volume wheel/buttons on keyboard are too insensitive, Keyboard shortcut daemon restart

This considers Linux Mint 15, Mate edition and Debian 9.4 + Mate

On a keyboard with volume wheel (Prodikeys, very handsome) I encountered a problem where every volume change was too much in either direction. One scroll up or down made a too big change in volume.

Better solution - adjust volume step

Open a terminal, run the following:
sudo apt-get install dconf-editor
dconf-editor

In the address bar, click on /org/ so you get to the bottom of the tree
Click on the search button (the magnifying glass)
Type 'volume-step' and press Enter
You should now be at /org/mate/settings-daemon/plugins/media-keys/volume-step
In the list, click on volume-step
Turn off Use default value
In the customized value, enter the desired step value - type 1 to get 1% change on volume control steps
Click on the confirmation button in the bottom right

Go to System -> Settings -> Hardware -> Keyboard shortcuts (or find Keyboard shortcuts)

Click on the Shortcut next to this item in the list:
Sound -> Volume down
Hold down the Window key and press arrow down key.

Do the same for this, but press the arrow up key instead:
Sound -> Volume up

Previous solution - workaround

This is the solution I found at first, which remaps the keyboard shortcuts for volume control to customized commands. The drawback of this method is that the graphical user interface does not get the changes and does not display them correctly.

System -> Settings -> Hardware -> Keyboard shortcuts (or find Keyboard shortcuts)

Then find this entries in the dialog:

Sound -> Volume 

And:

Sound -> Volume down

Click on the keyboard button in the right column - XF86AudioLowerVolume and XF86AudioRaiseVolume, when it says New shortcut, hit backspace to not assign any to it.

Then try the volume wheel (or buttons). They should not make a change in volume currently.

Continue the workaround by clicking on the Add button in the bottom of the dialog.

Make two new shortcuts:

Name: Volume Up
Command: 

/bin/bash -c "amixer set Master 5%+ && amixer set Speaker 5%+ && amixer set Headphone 5%+"

And:

Name: Volume Down
Command: 

/bin/bash -c "amixer set Master 5%- && amixer set Speaker 5%- && amixer set Headphone 5%-"

Click on the column for the keyboard for Volume Up and scroll up one step on the volume wheel (or hit the volume up keyboard button). Do the same for Volume Down - click to assign, scroll down (click down button).

Try the volume wheel / volume buttons now. If you need more or less change, edit the Volume Up and Volume Down shortcuts in the dialog by clicking on the shortcuts.

To debug you may also open a terminal and type alsamixer to see the volume levels.

Keyboard shortcut daemon restart

If you switch sound card and find that the keyboard somehow does not change the volume despite of what you have selected in the sound dialog, then restart the MATE settings daemon, this appears to be what is handling the keyboard shortcuts:

killall mate-settings-daemon

The daemon should restart automatically, check that it is there:

ps ax|grep mate-settings-daemon

If not, force it on - note that it should run as the regular user and not root:

mate-settings-daemon &