public unsafe static void FftFwd(double[] x, int order, out double[] re, out double[] im)
{
IppStatus st;
int sz = 1 << order;
if (sz > 1 << 23 || sz < 4)
{
throw new Exception("Invalid FftFwd order");
}
double[] rw = new double[sz];
double[] iw = new double[sz];
double[] frw = new double[sz];
double[] fiw = new double[sz];
Array.Copy(x, rw, Math.Min(x.Length, rw.Length));
int specSz = 0;
int specBufSz = 0;
int bufSz = 0;
st = Ipps.ippsFFTGetSize_C_64f(order, Ipps.IppFftFlag.IPP_FFT_DIV_FWD_BY_N, IppHintAlgorithm.ippAlgHintNone, ref specSz, ref specBufSz, ref bufSz);
if (st != IppStatus.ippStsNoErr)
{
throw new Exception(string.Format("FFTGetSize returned error {0}", st));
}
byte[] spec = new byte[specSz];
byte[] specBuf = new byte[specBufSz];
byte[] buf = new byte[bufSz];
IntPtr pspec = IntPtr.Zero;
fixed(byte *ps = &spec[0])
{
//Spec needs to be fixed as used between ipp calls
st = Ipps.ippsFFTInit_C_64f(ref pspec, order, Ipps.IppFftFlag.IPP_FFT_DIV_FWD_BY_N, IppHintAlgorithm.ippAlgHintNone, ps, specBuf);
if (st != IppStatus.ippStsNoErr)
{
throw new Exception(string.Format("FFTInit returned error {0}", st));
}
st = Ipps.ippsFFTFwd_CToC_64f(rw, iw, frw, fiw, pspec, buf);
if (st != IppStatus.ippStsNoErr)
{
throw new Exception(string.Format("FFTFwd returned error {0}", st));
}
re = frw;
im = fiw;
}
}
public unsafe static double[] SpectrumBlockAverage(double[] x, int order, double percOverlap, bool power, bool zeroMean, double windowCorrection)
{
IppStatus st;
int sz = 1 << order;
if (sz > 1 << 23 || sz < 4)
{
throw new Exception("Invalid SpectrumBlockAverage order");
}
if (percOverlap < 0 || percOverlap >= 100)
{
throw new Exception("Invalid SpectrumBlockAverage percOverlap");
}
if (x == null || x.Length < 5)
{
throw new Exception("Invalid SpectrumBlockAverage data length");
}
double[] rw = new double[sz];
double[] iw = new double[sz];
double[] frw = new double[sz];
double[] fiw = new double[sz];
double[] psp = new double[sz];
double[] sum = new double[sz];
double[] res = new double[sz / 2];
int specSz = 0;
int specBufSz = 0;
int bufSz = 0;
st = Ipps.ippsFFTGetSize_C_64f(order, Ipps.IppFftFlag.IPP_FFT_DIV_FWD_BY_N, IppHintAlgorithm.ippAlgHintNone, ref specSz, ref specBufSz, ref bufSz);
if (st != IppStatus.ippStsNoErr)
{
throw new Exception(string.Format("FFTGetSize returned error {0}", st));
}
byte[] spec = new byte[specSz];
byte[] specBuf = new byte[specBufSz];
byte[] buf = new byte[bufSz];
IntPtr pspec = IntPtr.Zero;
fixed(byte *ps = &spec[0])
{
//Spec needs to be fixed as used between ipp calls
st = Ipps.ippsFFTInit_C_64f(ref pspec, order, Ipps.IppFftFlag.IPP_FFT_DIV_FWD_BY_N, IppHintAlgorithm.ippAlgHintNone, ps, specBuf);
if (st != IppStatus.ippStsNoErr)
{
throw new Exception(string.Format("FFTInit returned error {0}", st));
}
int count = 0;
int step = (int)(0.01 * (100.0 - percOverlap) * sz);
double[] win = HanningWindow(sz);
for (int ix = 0; ix < x.Length - sz; ix += step, ++count)
{
//Prepare input block
st = Ipps.ippsZero_64f(iw, iw.Length);
if (st != IppStatus.ippStsNoErr)
{
throw new Exception(string.Format("Zero returned error {0}", st));
}
//Window block
Array.Copy(x, ix, rw, 0, sz);
if (zeroMean)
{
//Subtract mean from block
double m;
st = Ipps.ippsMean_64f(rw, rw.Length, out m);
if (st != IppStatus.ippStsNoErr)
{
throw new Exception(string.Format("Mean returned error {0}", st));
}
st = Ipps.ippsAddC_64f_I(-m, rw, rw.Length);
if (st != IppStatus.ippStsNoErr)
{
throw new Exception(string.Format("Mean returned error {0}", st));
}
}
st = Ipps.ippsMul_64f(rw, win, rw, sz);
if (st != IppStatus.ippStsNoErr)
{
throw new Exception(string.Format("Mul returned error {0}", st));
}
//Correct for window
st = Ipps.ippsMulC_64f_I(windowCorrection, rw, sz);
if (st != IppStatus.ippStsNoErr)
{
throw new Exception(string.Format("MulC returned error {0}", st));
}
//Calculate FFT
st = Ipps.ippsFFTFwd_CToC_64f(rw, iw, frw, fiw, pspec, buf);
if (st != IppStatus.ippStsNoErr)
{
throw new Exception(string.Format("FFTFwd returned error {0}", st));
}
if (power)
{
//Calc power spectrum
st = Ipps.ippsPowerSpectr_64f(frw, fiw, psp, sz);
if (st != IppStatus.ippStsNoErr)
{
throw new Exception(string.Format("PowerSpectr returned error {0}", st));
}
}
else
{
//Calculate magnitude
st = Ipps.ippsMagnitude_64f(frw, fiw, psp, psp.Length);
if (st != IppStatus.ippStsNoErr)
{
throw new Exception(string.Format("Mag returned error {0}", st));
}
}
//Add result
st = Ipps.ippsAdd_64f(psp, sum, sum, psp.Length);
if (st != IppStatus.ippStsNoErr)
{
throw new Exception(string.Format("Add returned error {0}", st));
}
}
if (count > 0)
{
//Scale average
st = Ipps.ippsMulC_64f_I(1.0 / count, sum, sum.Length);
if (st != IppStatus.ippStsNoErr)
{
throw new Exception(string.Format("MulC returned error {0}", st));
}
//Calc result discarding upper half samples
res[0] = sum[0];
for (int i = 1; i < sum.Length / 2; ++i)
{
res[i] = 2 * sum[i];
}
}
return(res);
}
}