feature_mfccs_init.m

function mfccParams = feature_mfccs_init(windowLength, fs)

% function mfccParams = feature_mfccs_init(windowLength, fs)
% 
% This function is used to initalize the mfcc quantities 
% used in the MFCC calculation
%
% ARGUMENTS:
% - windowLength: the length of the window analysis (in number of samples)
% - fs:         : the sampling frequency (in Hz)
%
% RETURNS:
% - mfccParams  : returns a structure with the mfcc params:
%
% (c) 2014 T. Giannakopoulos, A. Pikrakis

% number of cepstral coefficients:
mfccParams.cepstralCoefficients = 13;

% fft resolution:
mfccParams.fftSize = round(windowLength / 2);
% filter parameters:
mfccParams.lowestFrequency = 133.3333;
mfccParams.linearFilters = 13;
mfccParams.linearSpacing = 66.66666666;
mfccParams.logFilters = 27;
mfccParams.logSpacing = 1.0711703;
mfccParams.totalFilters = mfccParams.linearFilters + ...
    mfccParams.logFilters;
mfccParams.freqs = mfccParams.lowestFrequency + ...
    (0:mfccParams.linearFilters-1)*mfccParams.linearSpacing;
mfccParams.freqs(mfccParams.linearFilters+1:mfccParams.totalFilters+2) = ...
    mfccParams.freqs(mfccParams.linearFilters) * ...
    mfccParams.logSpacing.^(1:mfccParams.logFilters+2);
mfccParams.lower = mfccParams.freqs(1:mfccParams.totalFilters);
mfccParams.center = mfccParams.freqs(2:mfccParams.totalFilters+1);
mfccParams.upper = mfccParams.freqs(3:mfccParams.totalFilters+2);
mfccParams.mfccFilterWeights = zeros(mfccParams.totalFilters,mfccParams.fftSize);
mfccParams.triangleHeight = 2./(mfccParams.upper-mfccParams.lower);
mfccParams.fftFreqs = (0:mfccParams.fftSize-1)/mfccParams.fftSize*fs;

for chan=1:mfccParams.totalFilters % for each filter:
    % compute the respective filter weights:
	mfccParams.mfccFilterWeights(chan,:) = (mfccParams.fftFreqs > ...
        mfccParams.lower(chan) & mfccParams.fftFreqs <= mfccParams.center(chan)).* ...
        mfccParams.triangleHeight(chan).*...
        (mfccParams.fftFreqs-mfccParams.lower(chan))/...
        (mfccParams.center(chan)-mfccParams.lower(chan)) + ...
        (mfccParams.fftFreqs > mfccParams.center(chan) & ...
        mfccParams.fftFreqs < mfccParams.upper(chan)).* ...
          mfccParams.triangleHeight(chan).*...
          (mfccParams.upper(chan)-mfccParams.fftFreqs)/...
          (mfccParams.upper(chan)-mfccParams.center(chan));
end

% matrix used in the DCT calculation:
mfccParams.mfccDCTMatrix = 1/sqrt(mfccParams.totalFilters/2)*...
    cos((0:(mfccParams.cepstralCoefficients-1))' * ...
    (2*(0:(mfccParams.totalFilters-1))+1) * pi/2/mfccParams.totalFilters);
mfccParams.mfccDCTMatrix(1,:) = mfccParams.mfccDCTMatrix(1,:) * sqrt(2)/2;