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1 /* -*- c-basic-offset: 4 -*- vi:set ts=8 sts=4 sw=4: */
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2
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3 /*
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4 A waveform viewer and audio annotation editor.
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5 Chris Cannam, Queen Mary University of London, 2005
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6
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7 This is experimental software. Not for distribution.
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8 */
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9
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10 #ifndef _WINDOW_H_
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11 #define _WINDOW_H_
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12
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13 #include <cmath>
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14 #include <iostream>
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15 #include <map>
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16
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17 enum WindowType {
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18 RectangularWindow,
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19 BartlettWindow,
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20 HammingWindow,
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21 HanningWindow,
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22 BlackmanWindow,
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23 GaussianWindow,
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24 ParzenWindow
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25 };
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26
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27 template <typename T>
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28 class Window
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29 {
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30 public:
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31 /**
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32 * Construct a windower of the given type.
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33 */
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34 Window(WindowType type, size_t size) : m_type(type), m_size(size) { encache(); }
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35 Window(const Window &w) : m_type(w.m_type), m_size(w.m_size) { encache(); }
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36 Window &operator=(const Window &w) {
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37 if (&w == this) return;
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38 m_type = w.m_type;
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39 m_size = w.m_size;
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40 encache();
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41 return *this;
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42 }
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43 virtual ~Window() { delete m_cache; }
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44
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45 void cut(T *src) const { cut(src, src); }
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46 void cut(T *src, T *dst) const {
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47 for (size_t i = 0; i < m_size; ++i) dst[i] = src[i] * m_cache[i];
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48 }
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49
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50 WindowType getType() const { return m_type; }
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51 size_t getSize() const { return m_size; }
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52
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53 protected:
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54 WindowType m_type;
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55 size_t m_size;
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56 T *m_cache;
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57
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58 void encache();
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59 };
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60
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61 template <typename T>
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62 void Window<T>::encache()
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63 {
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64 size_t n = m_size;
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65 T *mult = new T[n];
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66 size_t i;
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67 for (i = 0; i < n; ++i) mult[i] = 1.0;
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68
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69 switch (m_type) {
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70
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71 case RectangularWindow:
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72 for (i = 0; i < n; ++i) {
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73 mult[i] = mult[i] * 0.5;
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74 }
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75 break;
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76
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77 case BartlettWindow:
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78 for (i = 0; i < n/2; ++i) {
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79 mult[i] = mult[i] * (i / T(n/2));
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80 mult[i + n/2] = mult[i + n/2] * (1.0 - (i / T(n/2)));
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81 }
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82 break;
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83
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84 case HammingWindow:
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85 for (i = 0; i < n; ++i) {
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86 mult[i] = mult[i] * (0.54 - 0.46 * cos(2 * M_PI * i / n));
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87 }
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88 break;
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89
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90 case HanningWindow:
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91 for (i = 0; i < n; ++i) {
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92 mult[i] = mult[i] * (0.50 - 0.50 * cos(2 * M_PI * i / n));
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93 }
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94 break;
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95
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96 case BlackmanWindow:
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97 for (i = 0; i < n; ++i) {
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98 mult[i] = mult[i] * (0.42 - 0.50 * cos(2 * M_PI * i / n)
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99 + 0.08 * cos(4 * M_PI * i / n));
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100 }
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101 break;
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102
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103 case GaussianWindow:
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104 for (i = 0; i < n; ++i) {
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105 mult[i] = mult[i] * exp((-1.0 / (n*n)) * ((T(2*i) - n) *
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106 (T(2*i) - n)));
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107 }
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108 break;
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109
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110 case ParzenWindow:
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111 for (i = 0; i < n; ++i) {
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112 mult[i] = mult[i] * (1.0 - fabs((T(2*i) - n) / T(n + 1)));
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113 }
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114 break;
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115 }
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116
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117 m_cache = mult;
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118 }
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119
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120 #endif
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