public static float[] MakeLowPassKernel(double sampleRate, double passband, double stopband, double ripple, double attenuation)
{
double num = 2.0 * passband / sampleRate;
double num2 = 2.0 * stopband / sampleRate;
int num3 = (int)((double)FilterBuilder.EstimateOrder(num, num2, ripple, attenuation) * 1.4) | 1;
int num4 = Math.Max(1, num3 - 20);
int num5 = num4 + 40;
for (int i = num4; i < num5; i += 2)
{
int num6 = 50;
double num7 = 0.0;
for (int j = 0; j < 100; j++)
{
double normalizedCutoff = (num * (double)num6 + num2 * (double)(100 - num6)) / 100.0;
float[] array = FilterBuilder.MakeChebychevLowPass(i, normalizedCutoff, attenuation + num7);
double num8;
double num9;
FilterBuilder.GetFilterSpecs(array, num, num2, out num8, out num9);
if (num8 <= ripple && num9 >= attenuation)
{
return(array);
}
num6 += Math.Sign(ripple - num8);
num7 += (double)Math.Sign(attenuation - num9) * 0.15 - (double)Math.Sign(ripple - num8) * 2.5;
if (num7 < -20.0)
{
num7 = -20.0;
}
if (num7 > 20.0)
{
num7 = 20.0;
}
if (num6 < 0)
{
num6 = 0;
}
if (num6 > 100)
{
num6 = 100;
}
}
}
return(null);
}
