FeatureTimeZeroCrossingRate

computes the zero crossing rate from a time domain signal
> called by ::ComputeFeature
>
> @param x: audio signal
> @param iBlockLength: block length in samples
> @param iHopLength: hop length in samples
> @param f_s: sample rate of audio data (unused)
>
> @retval vzc zero crossing rate
> @retval t time stamp
 ======================================================================

0001 %computes the zero crossing rate from a time domain signal
0002 %> called by ::ComputeFeature
0003 %>
0004 %> @param x: audio signal
0005 %> @param iBlockLength: block length in samples
0006 %> @param iHopLength: hop length in samples
0007 %> @param f_s: sample rate of audio data (unused)
0008 %>
0009 %> @retval vzc zero crossing rate
0010 %> @retval t time stamp
0011 % ======================================================================
0012 function [vzc, t] = FeatureTimeZeroCrossingRate(x, iBlockLength, iHopLength, f_s)
0013  
0014     % blocking
0015     [x_b, t] = ToolBlockAudio(x, iBlockLength, iHopLength, f_s);
0016     iNumOfBlocks = size(x_b, 1);
0017     
0018     % allocate memory
0019     vzc = zeros(1, iNumOfBlocks);
0020     
0021     for n = 1:iNumOfBlocks
0022         % compute the zero crossing rate
0023         vzc(n)  = 0.5 * mean(abs(diff(sign(x_b(n, :)))));
0024     end
0025 end