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/* -*- 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 file Copyright 2006 Chris Cannam.
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 _WINDOW_H_
#define _WINDOW_H_
#include <cmath>
#include <iostream>
#include <map>
#include <vector>
enum WindowType {
RectangularWindow,
BartlettWindow,
HammingWindow,
HanningWindow,
BlackmanWindow,
BlackmanHarrisWindow,
FirstWindow = RectangularWindow,
LastWindow = BlackmanHarrisWindow
};
/**
* Various shaped windows for sample frame conditioning, including
* cosine windows (Hann etc) and triangular and rectangular windows.
*/
template <typename T>
class Window
{
public:
/**
* Construct a windower of the given type and size.
*
* Note that the cosine windows are periodic by design, rather
* than symmetrical. (A window of size N is equivalent to a
* symmetrical window of size N+1 with the final element missing.)
*/
Window(WindowType type, int size) : m_type(type), m_size(size) { encache(); }
Window(const Window &w) : m_type(w.m_type), m_size(w.m_size) { encache(); }
Window &operator=(const Window &w) {
if (&w == this) return *this;
m_type = w.m_type;
m_size = w.m_size;
encache();
return *this;
}
virtual ~Window() { delete[] m_cache; }
void cut(T *src) const { cut(src, src); }
void cut(const T *src, T *dst) const {
for (int i = 0; i < m_size; ++i) dst[i] = src[i] * m_cache[i];
}
WindowType getType() const { return m_type; }
int getSize() const { return m_size; }
std::vector<T> getWindowData() const {
std::vector<T> d;
for (int i = 0; i < m_size; ++i) {
d.push_back(m_cache[i]);
}
return d;
}
protected:
WindowType m_type;
int m_size;
T *m_cache;
void encache();
};
template <typename T>
void Window<T>::encache()
{
int n = m_size;
T *mult = new T[n];
int i;
for (i = 0; i < n; ++i) mult[i] = 1.0;
switch (m_type) {
case RectangularWindow:
for (i = 0; i < n; ++i) {
mult[i] = mult[i] * 0.5;
}
break;
case BartlettWindow:
if (n == 2) {
mult[0] = mult[1] = 0; // "matlab compatible"
} else if (n == 3) {
mult[0] = 0;
mult[1] = mult[2] = 2./3.;
} else if (n > 3) {
for (i = 0; i < n/2; ++i) {
mult[i] = mult[i] * (i / T(n/2));
mult[i + n - n/2] = mult[i + n - n/2] * (1.0 - (i / T(n/2)));
}
}
break;
case HammingWindow:
if (n > 1) {
for (i = 0; i < n; ++i) {
mult[i] = mult[i] * (0.54 - 0.46 * cos(2 * M_PI * i / n));
}
}
break;
case HanningWindow:
if (n > 1) {
for (i = 0; i < n; ++i) {
mult[i] = mult[i] * (0.50 - 0.50 * cos(2 * M_PI * i / n));
}
}
break;
case BlackmanWindow:
if (n > 1) {
for (i = 0; i < n; ++i) {
mult[i] = mult[i] * (0.42 - 0.50 * cos(2 * M_PI * i / n)
+ 0.08 * cos(4 * M_PI * i / n));
}
}
break;
case BlackmanHarrisWindow:
if (n > 1) {
for (i = 0; i < n; ++i) {
mult[i] = mult[i] * (0.35875
- 0.48829 * cos(2 * M_PI * i / n)
+ 0.14128 * cos(4 * M_PI * i / n)
- 0.01168 * cos(6 * M_PI * i / n));
}
}
break;
}
m_cache = mult;
}
#endif
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