update qm-dsp library

libs/qm-dsp/base/SincWindow.h

@@ -0,0 +1,61 @@
+/* -*- c-basic-offset: 4 indent-tabs-mode: nil -*-  vi:set ts=8 sts=4 sw=4: */
+
+/*
+    QM DSP library
+    Centre for Digital Music, Queen Mary, University of London.
+ 
+    This program is free software; you can redistribute it and/or
+    modify it under the terms of the GNU General Public License as
+    published by the Free Software Foundation; either version 2 of the
+    License, or (at your option) any later version.  See the file
+    COPYING included with this distribution for more information.
+*/
+
+#ifndef SINC_WINDOW_H
+#define SINC_WINDOW_H
+
+#include <vector>
+
+/**
+ * A window containing values of the sinc function, i.e. sin(x)/x with
+ * sinc(0) == 1, with x == 0 at the centre.
+ */
+class SincWindow
+{
+public:
+    /**
+     * Construct a windower of the given length, containing the values
+     * of sinc(x) with x=0 in the middle, i.e. at sample (length-1)/2
+     * for odd or (length/2)+1 for even length, such that the distance
+     * from -pi to pi (the nearest zero crossings either side of the
+     * peak) is p samples.
+     */
+    SincWindow(int length, double p) : m_length(length), m_p(p) { init(); }
+
+    int getLength() const {
+	return m_length;
+    }
+
+    const double *getWindow() const { 
+	return m_window.data();
+    }
+
+    void cut(double *src) const { 
+	cut(src, src); 
+    }
+
+    void cut(const double *src, double *dst) const {
+	for (int i = 0; i < m_length; ++i) {
+	    dst[i] = src[i] * m_window[i];
+	}
+    }
+
+private:
+    int m_length;
+    double m_p;
+    std::vector<double> m_window;
+
+    void init();
+};
+
+#endif