FeatureSpectralCentroid

computes the spectral centroid from the (squared) magnitude spectrum
> called by ::ComputeFeature
>
> @param X: spectrogram (dimension FFTLength X Observations)
> @param f_s: sample rate of audio data 
>
> @retval v spectral centroid (in Hz)
 ======================================================================

0001 %computes the spectral centroid from the (squared) magnitude spectrum
0002 %> called by ::ComputeFeature
0003 %>
0004 %> @param X: spectrogram (dimension FFTLength X Observations)
0005 %> @param f_s: sample rate of audio data
0006 %>
0007 %> @retval v spectral centroid (in Hz)
0008 % ======================================================================
0009 function [vsc] = FeatureSpectralCentroid (X, f_s)
0010 
0011     vsc = ((0:size(X, 1)-1)*X) ./ sum(X, 1);
0012     
0013     % avoid NaN for silence frames
0014     vsc (sum(X, 1) == 0) = 0;
0015         
0016     % convert from index to Hz
0017     vsc = vsc / (size(X, 1)-1) * f_s / 2;
0018 end