Mnemonic constant

Value

Meaning

SCALE_LINEAR

0

The returned volume is based upon a linear scale and can be in the range from 0.0 (silence) to 100.0 (max volume)

SCALE_LOG

1

The returned volume, expressed in dB, is based upon a logarithmic scale and can be in the range from -100  (silence) to 0 (max volume) 

The actual applied formula for converting a linear volume into a logarithmic volume is the following: 

VolumeInDB = 20 * log10 (VolumeLinear/100) 

The C syntax for converting a logarithmic volume into a linear volume is the following: 

float e = 2.7182818281f; 

float exp = (float)((fVolumeInDB + (20 * log(100))) / 20); 

fVolumeLinear = (float) pow (e, exp);