Hello,
I'm sorry for the trouble i caused, it was my fault as i was using custom remote.conf which i was using on my Ubuntu O.S  

Here is the needed keys for the USB volume controls
KBD.Volume+    000000000000002B
KBD.Volume-     000000000000002D
KBD.Mute          0000001B5B32307E
XKeySym.Volume+    KP_Add
XKeySym.Volume+    plus
XKeySym.Volume+    XF86AudioRaiseVolume
XKeySym.Volume-     KP_Subtract
XKeySym.Volume-     minus
XKeySym.Volume-     XF86AudioLowerVolume
XKeySym.Mute          XF86AudioMute
I figured it out while testing MLD v5.4.
lirc is not required and i don't have it installed.
Sorry again.
Edit: I unpacked vdr_2.2.0.213.8-214_amd64 today and it doesn't contain the XKeySym!
Which means that MLD 5.3 lacks the USB volume controls, If so then it wasn't my fault  
