Hi Khaled,
The make-up gain is added to the gain computed by the compressor.
Let's call your signal x, and the (computed, in dB) gain to be applied to your signal G. If make-up gain is zero dB, then your output is:
in_gain = 10.^(G /20);
y = x .* lin_gain;
If you pecify a non-zero make-up gain, G_makeup, then your output will be:
G = G + G_makeup; % in dB
in_gain = 10.^(G /20);
y = x .* lin_gain;
