The calculus time of an analysis varies depending on the analysis parameters.
The window size determines how much time takes to the FFT Buffer to get full and generate a complete spectrum
Filling Time Buffer = (Window Size/SR) * signal duration
Filling Time Buffer = (1/FR) * signal duration
This is proportional to the period of the frequency resolution, so to speak.
The higher the frequency resolution of the analysis, the longer the filling time buffer is.
Let's take a 10 sec. signal for instance, with a 1024 FFT Size and 44100 SR. We get :
FTB= (1024/44100) * 10 = 0,23 s
FTB = 1/(44100/1024) * 10 = (1/43) * 10 = 0,23
With a 4096 FFT Size and 44100 SR. We get :
FTB= (4096/44100) *10 = 0,93
FTB = (1/(44100/1024)) * 10= 1/43 = 0,93
We have seen that the size of the FFT – number of bins per window – could be increased proportionnally.
The buffering time increases linearly with the oversampling rate. If the oversampling rate is multplied by 4, the buffering time will be also multiplied by 4.
The window step increases the number of times a window is calculated.
The overlap factor increases the precision of the calcucus, and increases the calculus time proportionnally.