Please describe the problem:
I'm unable to use my multimedia keys like volume up/down and mute. When typing
volume up, a little window appears on the screen but the volume doesn't change.

I had to install acme, and after a lot of search, it appears that the option
use_pcm in acme was solving my issues. It was working nicely.

Unfortunately, as acme is obsolete, I'm going back to
gnome-keybinding-properties and I'm unable to set an option similar to use_pcm,
so my multimedia keys are not working effectively. 


Steps to reproduce:
1. Have a sound card where master volume is PCM and not Master
2. Have a multimedia keyboard
3. What ever configuration options I try, the multimedia press triggers a new
little window but no volume change


Actual results:


Expected results:
I expect that volume changes when typing multimedia keys

Does this happen every time?
Yes

Other information: