flix/flix/lpf.h

// Copyright (c) 2023 Oleg Kalachev <okalachev@gmail.com>
// Repository: https://github.com/okalachev/flix

// Low pass filter implementation

#pragma once

template <typename T> // Using template to make the filter usable for scalar and vector values
class LowPassFilter {
public:
	float alpha; // smoothing constant, 1 means filter disabled
	T output;

	LowPassFilter(float alpha): alpha(alpha) {};

	T update(const T input)
	{
		if (alpha == 1) { // filter disabled
			return input;
		}

		if (!initialized) {
			output = input;
			initialized = true;
		}
		return output = output * (1 - alpha) + input * alpha;
	}

	void setCutOffFrequency(float cutOffFreq, float dt)
	{
		alpha = 1 - exp(-2 * PI * cutOffFreq * dt);
	}

	void reset()
	{
		initialized = false;
	}

private:
	bool initialized = false;
};