private static float[] MakeChebychevWindow(int length, double attenuation)
{
double num = Math.Pow(10.0, attenuation / 20.0);
float[] array = new float[length];
float num2 = 0f;
double num3 = Math.Cosh(FilterBuilder.ACosh(num) / (double)(length - 1));
double num4 = (double)((length - 1) / 2);
if (length % 2 == 0)
{
num4 += 0.5;
}
for (int i = 0; i < length / 2 + 1; i++)
{
double num5 = (double)i - num4;
double num6 = 0.0;
for (int j = 1; (double)j <= num4; j++)
{
num6 += FilterBuilder.ChebychevPoly(length - 1, num3 * Math.Cos(3.1415926535897931 * (double)j / (double)length)) * Math.Cos(2.0 * num5 * 3.1415926535897931 * (double)j / (double)length);
}
array[i] = (float)(num + 2.0 * num6);
array[length - i - 1] = array[i];
if (array[i] > num2)
{
num2 = array[i];
}
}
float num7 = 1f / num2;
for (int k = 0; k < length; k++)
{
array[k] *= num7;
}
return(array);
}
