96 lines
2.6 KiB
C
96 lines
2.6 KiB
C
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#ifndef MENGA_INTERPOLATION
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#define MENGA_INTERPOLATION
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#include "mengumath.h"
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#include "fastmath.h"
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#include <cmath>
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#include <cstdint>
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// Helper functions for various interpolation and windowing methods
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namespace Mengu {
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namespace dsp{
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// The hann function
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inline float hann(float a0, float x) {
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return a0 - (1.0 - a0) * std::cos(MATH_TAU * x);
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// equals
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// a - (1-a) (c2 -s2)
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// a (1 - c2 + s2) - (c2 - s2)
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// a (2s2) - 2s2 - 1
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// (a - 1) 2 s2
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}
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// root of the hann function designed to be used once each before and after processing
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inline float hann_root(float a0, float x) {
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return std::sqrt(2.0 *(a0 - 1)) * std::sin(MATH_PI * x);
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}
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// the hann function, centered around 0
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// inline float hann_centered(float a0, float x) {
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// return hann(a0, (x + 0.5f));
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// }
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// windows are 1 at 1, 0 at 0
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inline float hann_window(float x) {
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return hann(0.5, 0.5f * x);
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}
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inline float hamming_window(float x) {
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return hann((float)25 / 46, 0.5f * x);
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}
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// windows are 1 at 1, 0 at 0
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inline float hann_window_root(float x) {
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return std::sin(0.5 * MATH_PI * x);
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}
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// does windowing to both ends of a sequence, in place
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template<class T>
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inline void window_ends(T* a, uint32_t a_size, uint32_t window_size, float window_f (float)) {
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window_size = MIN(a_size / 2, window_size);
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for (uint32_t i = 0; i < window_size; i++) {
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const float w = window_f((float) i / window_size);
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a[i] *= w;
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a[a_size - 1 - i] *= w;
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}
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}
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// added the tail and head of an array after applying a window function to bothe sides
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template<class T>
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inline void overlap_add(const T *prev, const T *next, T *output, uint32_t size, float window_f (float)) {
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for (uint32_t i = 0; i < size; i++) {
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const float w = window_f((float) i / size);
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output[i] = w * next[i] + (1- w) * prev[i];
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}
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}
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// overlap and extend after applying a window function first
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// overlap_size may be larger than new_data.size(), in which case only new_data.size() is added. the offset is the same
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template<class T, class NewT>
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inline void mix_and_extend(T &array, const NewT &new_data, const uint32_t &overlap_size, float window_f (float)) {
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uint32_t i = 0;
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for(; i < MIN(overlap_size, new_data.size()); i++) {
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float w = (float) i / overlap_size;
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float w1 = window_f(w);
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float w2 = window_f(1.0-w);
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w2 = 1.0f - w1;
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uint32_t ind = array.size() - overlap_size + i;
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array[ind] = array[ind] * w2 + new_data[i] * w1;
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}
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for (; i < new_data.size(); i++) {
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array.push_back(new_data[i]);
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}
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}
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}
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}
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#endif
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