/// <summary>Calculates IIR</summary>
/// <param name="sample">sample rate</param>
/// <param name="b">biquad pointer</param>
public void BiQuad(ref Int16 sample, biquad *b)
{
// compute result
double result = b->a0 * sample + b->a1 * b->x1 + b->a2 * b->x2 - b->a3 * b->y1 - b->a4 * b->y2;
// shift x1 to x2, sample to x1
b->x2 = b->x1;
b->x1 = sample;
// shift y1 to y2, result to y1
b->y2 = b->y1;
b->y1 = result;
sample = (Int16)result;
}
/// <summary>Release heap memory</summary>
/// <param name="pmem">memory address</param>
private void Free(biquad *b)
{
HeapFree(GetProcessHeap(), 0, b);
}
public void FreeMem(biquad *b)
{
Free(b);
}
private static extern bool HeapFree(IntPtr hHeap, uint dwFlags, biquad *lpMem);