Chris@47: /* -*- c-basic-offset: 4 indent-tabs-mode: nil -*-  vi:set ts=8 sts=4 sw=4: */
Chris@47: /*
Chris@47:     This file is Copyright (c) 2012 Chris Cannam
Chris@47:   
Chris@47:     Permission is hereby granted, free of charge, to any person
Chris@47:     obtaining a copy of this software and associated documentation
Chris@47:     files (the "Software"), to deal in the Software without
Chris@47:     restriction, including without limitation the rights to use, copy,
Chris@47:     modify, merge, publish, distribute, sublicense, and/or sell copies
Chris@47:     of the Software, and to permit persons to whom the Software is
Chris@47:     furnished to do so, subject to the following conditions:
Chris@47: 
Chris@47:     The above copyright notice and this permission notice shall be
Chris@47:     included in all copies or substantial portions of the Software.
Chris@47: 
Chris@47:     THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
Chris@47:     EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
Chris@47:     MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
Chris@47:     NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR
Chris@47:     ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF
Chris@47:     CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
Chris@47:     WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
Chris@47: */
Chris@47: 
Chris@73: #ifndef MEAN_FILTER_H
Chris@73: #define MEAN_FILTER_H
Chris@47: 
Chris@47: class MeanFilter
Chris@47: {
Chris@47: public:
Chris@47:     /**
Chris@47:      * Construct a non-causal mean filter with filter length flen,
Chris@47:      * that replaces each sample N with the mean of samples
Chris@47:      * [N-floor(F/2) .. N+floor(F/2)] where F is the filter length.
Chris@47:      * Only odd F are supported.
Chris@47:      */
Chris@47:     MeanFilter(int flen) : m_flen(flen) { }
Chris@47:     ~MeanFilter() { }
Chris@47: 
Chris@47:     /**
Chris@47:      * Filter the n samples in "in" and place the results in "out"
Chris@47:      */
Chris@47:     void filter(const double *in, double *out, const int n) {
Chris@47: 	filterSubsequence(in, out, n, n, 0);
Chris@47:     }
Chris@47: 
Chris@47:     /**
Chris@47:      * Filter the n samples starting at the given offset in the
Chris@48:      * m-element array "in" and place the results in the n-element
Chris@48:      * array "out"
Chris@47:      */
Chris@47:     void filterSubsequence(const double *in, double *out,
Chris@47: 			   const int m, const int n,
Chris@47: 			   const int offset) {
Chris@47: 	int half = m_flen/2;
Chris@47: 	for (int i = 0; i < n; ++i) {
Chris@47: 	    double v = 0;
Chris@47: 	    int n = 0;
Chris@47: 	    for (int j = -half; j <= half; ++j) {
Chris@47: 		int ix = i + j + offset;
Chris@47: 		if (ix >= 0 && ix < m) {
Chris@73:                     double value = in[ix];
Chris@73:                     if (value == value) { // i.e. not NaN
Chris@73:                         v += value;
Chris@73:                     }
Chris@73:                     ++n;
Chris@47: 		}
Chris@47: 	    }
Chris@73:             if (n > 0) {
Chris@73:                 out[i] = v / n;
Chris@73:             } else {
Chris@73:                 out[i] = 0.0;
Chris@73:             }
Chris@47: 	}
Chris@47:     }
Chris@47: 
Chris@47: private:
Chris@47:     int m_flen;
Chris@47: };
Chris@47: 
Chris@47: #endif