ComputePitch

computes the fundamental frequency of the (monophonic) audio
>
> supported pitch trackers are:
>  'SpectralAcf',
>  'SpectralHps',
>  'TimeAcf',
>  'TimeAmdf',
>  'TimeAuditory',
>  'TimeZeroCrossings',
>
> @param cPitchTrackName: feature to compute, e.g. 'SpectralHps'
> @param x: time domain sample data, dimension channels X samples
> @param f_s: sample rate of audio data
> @param afWindow: FFT window of length iBlockLength (default: hann), can be [] empty
> @param iBlockLength: internal block length (default: 4096 samples)
> @param iHopLength: internal hop length (default: 2048 samples)
>
> @retval f frequency
> @retval t time stamp for the frequency value
 ======================================================================

0001 %computes the fundamental frequency of the (monophonic) audio
0002 %>
0003 %> supported pitch trackers are:
0004 %>  'SpectralAcf',
0005 %>  'SpectralHps',
0006 %>  'TimeAcf',
0007 %>  'TimeAmdf',
0008 %>  'TimeAuditory',
0009 %>  'TimeZeroCrossings',
0010 %>
0011 %> @param cPitchTrackName: feature to compute, e.g. 'SpectralHps'
0012 %> @param x: time domain sample data, dimension channels X samples
0013 %> @param f_s: sample rate of audio data
0014 %> @param afWindow: FFT window of length iBlockLength (default: hann), can be [] empty
0015 %> @param iBlockLength: internal block length (default: 4096 samples)
0016 %> @param iHopLength: internal hop length (default: 2048 samples)
0017 %>
0018 %> @retval f frequency
0019 %> @retval t time stamp for the frequency value
0020 % ======================================================================
0021 function [f, t] = ComputePitch (cPitchTrackName, x, f_s, afWindow, iBlockLength, iHopLength)
0022 
0023     % set function handle
0024     hPitchFunc = str2func (['Pitch' cPitchTrackName]);
0025 
0026     % set default parameters if necessary
0027     if (nargin < 6)
0028         iHopLength = 2048;
0029     end
0030     if (nargin < 5)
0031         iBlockLength = 4096;
0032     end
0033   
0034     % pre-processing: down-mixing
0035     x = ToolDownmix(x);
0036 
0037     % pre-processing: normalization (not necessary for many features)
0038     if (length(x)> 1)
0039         x = x/max(abs(x));
0040     end
0041  
0042     x = [x; zeros(iBlockLength, 1)];
0043     
0044     if (IsSpectral_I(cPitchTrackName))
0045         if (nargin < 4 || isempty(afWindow))
0046             afWindow = hann(iBlockLength, 'periodic');
0047         end
0048         
0049         % check FFT window function
0050         if (length(afWindow) ~= iBlockLength)
0051             error('window length mismatch');
0052         end        
0053 
0054         % in the real world, we would do this block by block...
0055         [X, f, t] = ComputeSpectrogram(x, ...
0056                                     f_s, ...
0057                                     afWindow, ...
0058                                     iBlockLength, ...
0059                                     iHopLength);
0060         
0061         % compute frequency
0062         f = hPitchFunc(X, f_s);
0063     end %if (IsSpectral_I(cPitchTrackName))
0064     
0065     if (IsTemporal_I(cPitchTrackName))
0066         % compute frequency
0067         [f,t] = hPitchFunc( x, ...
0068                             iBlockLength, ...
0069                             iHopLength, ...
0070                             f_s);
0071     end %if (IsTemporal_I(cPitchTrackName))
0072 end
0073 
0074 function [bResult] = IsSpectral_I(cName)
0075     bResult = false;
0076     iIdx    = strfind(cName, 'Spectral');
0077     if (~isempty(iIdx))
0078         if (iIdx(1) == 1)
0079             bResult = true;
0080         end
0081     end
0082 end
0083 
0084 function [bResult] = IsTemporal_I(cName)
0085     bResult = false;
0086     iIdx    = strfind(cName, 'Time');
0087     if (~isempty(iIdx))
0088         if (iIdx(1) == 1)
0089             bResult = true;
0090         end
0091     end
0092 end