Windowed Sinc Low Pass

SincTest.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class SincTrial : MonoBehaviour {
	public int Phase, Period = 100;

	public float Fc = 0.14f;
	public int M = 100;
	public float[] H, T;

	public void Start() {
		Visualizer.Rescale(0, 2048);
		Visualizer.Rescale(1, 200);
	}

	public void OnAudioFilterRead(float[] data, int channels) {
		H = new float[M + 1];
		for (int i = 0; i <= M; i++) {
			if (i - M / 2 == 0) H[i] = 2 * Mathf.PI * Fc;
			else H[i] = Mathf.Sin(2 * Mathf.PI * Fc * (i - M / 2)) / (i - M / 2);

			H[i] *= 0.42f + 0.8f * Mathf.Cos(4 * Mathf.PI * i / M) - 0.5f * Mathf.Cos(2 * Mathf.PI * i / M);
		}

		float sum = 0;
		for (int i = 0; i <= M; i++) {
			sum += H[i];
		}
		for (int i = 0; i <= M; i++) {
			H[i] /= sum;
			Visualizer.Push(1, H[i]);
		}

		var temp = new float[data.Length / channels];
		for (int i = 0; i < temp.Length; i++) {
			temp[i] = (Phase > (Period >> 1) ? 0.5f : 0);
			Phase = (Phase + 1) % Period;
		}

		for (int i = 0; i < M; i++) {
			data[i * channels] = temp[i];
		}

		for (int i = M; i < temp.Length; i++) {
			for (int j = 0; j <= M; j++) {
				data[i * channels] += temp[i - j] * H[j];
			}

			Visualizer.Push(0, data[i * channels]);
		}
	}
}