matthiasm@0: /* -*- c-basic-offset: 4 indent-tabs-mode: nil -*-  vi:set ts=8 sts=4 sw=4: */
Chris@9: 
matthiasm@0: /*
Chris@9:     pYIN - A fundamental frequency estimator for monophonic audio
Chris@9:     Centre for Digital Music, Queen Mary, University of London.
Chris@9:     
Chris@9:     This program is free software; you can redistribute it and/or
Chris@9:     modify it under the terms of the GNU General Public License as
Chris@9:     published by the Free Software Foundation; either version 2 of the
Chris@9:     License, or (at your option) any later version.  See the file
Chris@9:     COPYING included with this distribution for more information.
matthiasm@0: */
matthiasm@0: 
matthiasm@0: #ifndef _MEAN_FILTER_H_
matthiasm@0: #define _MEAN_FILTER_H_
matthiasm@0: 
matthiasm@0: class MeanFilter
matthiasm@0: {
matthiasm@0: public:
matthiasm@0:     /**
matthiasm@0:      * Construct a non-causal mean filter with filter length flen,
matthiasm@0:      * that replaces each sample N with the mean of samples
matthiasm@0:      * [N-floor(F/2) .. N+floor(F/2)] where F is the filter length.
matthiasm@0:      * Only odd F are supported.
matthiasm@0:      */
matthiasm@0:     MeanFilter(int flen) : m_flen(flen) { }
matthiasm@0:     ~MeanFilter() { }
matthiasm@0: 
matthiasm@0:     /**
matthiasm@0:      * Filter the n samples in "in" and place the results in "out"
matthiasm@0:      */
matthiasm@0:     void filter(const double *in, double *out, const int n) {
matthiasm@0: 	filterSubsequence(in, out, n, n, 0);
matthiasm@0:     }
matthiasm@0: 
matthiasm@0:     /**
matthiasm@0:      * Filter the n samples starting at the given offset in the
matthiasm@0:      * m-element array "in" and place the results in the n-element
matthiasm@0:      * array "out"
matthiasm@0:      */
matthiasm@0:     void filterSubsequence(const double *in, double *out,
matthiasm@0: 			   const int m, const int n,
matthiasm@0: 			   const int offset) {
matthiasm@0: 	int half = m_flen/2;
matthiasm@0: 	for (int i = 0; i < n; ++i) {
matthiasm@0: 	    double v = 0;
matthiasm@0: 	    int n = 0;
matthiasm@0: 	    for (int j = -half; j <= half; ++j) {
matthiasm@0: 		int ix = i + j + offset;
matthiasm@0: 		if (ix >= 0 && ix < m) {
matthiasm@0: 		    v += in[ix];
matthiasm@0: 		    ++n;
matthiasm@0: 		}
matthiasm@0: 	    }
matthiasm@0: 	    out[i] = v / n;
matthiasm@0: 	}
matthiasm@0:     }
matthiasm@0: 
matthiasm@0: private:
matthiasm@0:     int m_flen;
matthiasm@0: };
matthiasm@0: 
matthiasm@0: #endif