The volume control is currently linear rather than log. All volume controls on audio hardware (and nearly all software) are logarithmic, which makes the position of the control match the perceived loudness. Currently the linear control in VLC MP makes most of the perceived volume change in the first few percent of the slider's range.
The VLC MP volume control should be changed to match the standard practice. The volume display should be changed at the same time so that what is now "100%" becomes "0 dB", 200% becomes "+3 dB" and mute becomes something like "-120 db" or "-[infinity symbol] dB" (if vsf=volume scaling factor, e.g.: vsf=1 = 100%, then dB=10*log(vsf); if vsf=0 then display "-[infinity symbol] dB" / check for vsf > 0 before attempting to take the log, obviously.)
This should only take changing a line or two of code.
(I'd like to see similar changes to some of the other slider controls such as effects and playback speed, but for this post I'll stick to the single easiest and most essential improvement that this great program could use.)