diff MeanFilter.h @ 47:f72a470fe4b5

Pull out mean filter, test it

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/MeanFilter.h	Tue Sep 11 16:37:47 2012 +0100
@@ -0,0 +1,73 @@
+/* -*- c-basic-offset: 4 indent-tabs-mode: nil -*-  vi:set ts=8 sts=4 sw=4: */
+/*
+    This file is Copyright (c) 2012 Chris Cannam
+  
+    Permission is hereby granted, free of charge, to any person
+    obtaining a copy of this software and associated documentation
+    files (the "Software"), to deal in the Software without
+    restriction, including without limitation the rights to use, copy,
+    modify, merge, publish, distribute, sublicense, and/or sell copies
+    of the Software, and to permit persons to whom the Software is
+    furnished to do so, subject to the following conditions:
+
+    The above copyright notice and this permission notice shall be
+    included in all copies or substantial portions of the Software.
+
+    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+    EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+    MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+    NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR
+    ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF
+    CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+    WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+*/
+
+#ifndef _MEAN_FILTER_H_
+#define _MEAN_FILTER_H_
+
+class MeanFilter
+{
+public:
+    /**
+     * Construct a non-causal mean filter with filter length flen,
+     * that replaces each sample N with the mean of samples
+     * [N-floor(F/2) .. N+floor(F/2)] where F is the filter length.
+     * Only odd F are supported.
+     */
+    MeanFilter(int flen) : m_flen(flen) { }
+    ~MeanFilter() { }
+
+    /**
+     * Filter the n samples in "in" and place the results in "out"
+     */
+    void filter(const double *in, double *out, const int n) {
+	filterSubsequence(in, out, n, n, 0);
+    }
+
+    /**
+     * Filter the n samples starting at the given offset in the
+     * m-element array "in" and place the results in "out"
+     */
+    void filterSubsequence(const double *in, double *out,
+			   const int m, const int n,
+			   const int offset) {
+	int half = m_flen/2;
+	for (int i = 0; i < n; ++i) {
+	    double v = 0;
+	    int n = 0;
+	    for (int j = -half; j <= half; ++j) {
+		int ix = i + j + offset;
+		if (ix >= 0 && ix < m) {
+		    v += in[ix];
+		    ++n;
+		}
+	    }
+	    out[i] = v / n;
+	}
+    }
+
+private:
+    int m_flen;
+};
+
+#endif