Improved handling of audio subsystem delays

2021-01-06 12:13:14 +03:00
parent 2440d0aa3f
commit 0a3947ebf2
6 changed files with 104 additions and 71 deletions
@@ -0,0 +1,60 @@
+#include <complex>
+#include "fft.h"
+
+using namespace std;
+
+const long double PI = 3.1415926535897932384626433832795;
+
+int Rev(int i, int l)
+{
+	int res = 0;
+	int j;
+	for (j = 0; j < l; j++)
+	{
+		res <<= 1;
+		if (i & (1 << j)) res++;
+	}
+	return res;
+}
+
+void FFT(Complex *a, int n, bool inv)
+{
+	int i, j, k;
+	int logn = 0;
+	while ((1 << logn) < n) logn++;
+	for (i = 0; i < n; i++)
+	{
+		j = Rev(i, logn);
+		if (j > i)
+		{
+			Complex t = a[i];
+			a[i] = a[j];
+			a[j] = t;
+		}
+	}
+	Complex u, v;
+	for (i = 1; i <= logn; i++)
+	{
+		long double ang = 2 * PI / (1 << i);
+		if (inv) ang = -ang;
+		Complex w(cos(ang), sin(ang));
+		for (j = 0; j < n; j += (1 << i))
+		{
+			Complex wk(1, 0);
+			for (k = j; k < j + (1 << (i - 1)); k++)
+			{
+				u = a[k];
+				v = a[k + (1 << (i - 1))] * wk;
+				a[k] = u + v;
+				a[k + (1 << (i - 1))] = u - v;
+				wk *= w;
+			}
+			wk *= w;
+		}
+	}
+	if (inv)
+	{
+		for (i = 0; i < n; i++) a[i] /= n;
+	}
+}
+