private static Dataset ifft1d(final Dataset a, final int n, final int axis) {
Dataset result = null;
Dataset dest = null;
int[] shape;
PositionIterator pi;
int[] pos;
boolean[] hit;
switch (a.getDtype()) {
case Dataset.FLOAT32:
case Dataset.COMPLEX64:
FloatFFT_1D ffft = new FloatFFT_1D(n);
float[] fdata = null;
shape = a.getShape();
shape[axis] = n;
result = new ComplexFloatDataset(shape);
dest = new ComplexFloatDataset(new int[] {n});
fdata = (float[]) dest.getBuffer();
pi = a.getPositionIterator(axis);
pos = pi.getPos();
hit = pi.getOmit();
while (pi.hasNext()) {
Arrays.fill(fdata, 0.f);
a.copyItemsFromAxes(pos, hit, dest);
ffft.complexInverse(fdata, true);
result.setItemsOnAxes(pos, hit, fdata);
}
break;
case Dataset.FLOAT64:
case Dataset.COMPLEX128:
DoubleFFT_1D dfft = new DoubleFFT_1D(n);
double[] ddata = null;
shape = a.getShape();
shape[axis] = n;
result = new ComplexDoubleDataset(shape);
dest = new ComplexDoubleDataset(new int[] {n});
ddata = (double[]) dest.getBuffer();
pi = a.getPositionIterator(axis);
pos = pi.getPos();
hit = pi.getOmit();
while (pi.hasNext()) {
Arrays.fill(ddata, 0.);
a.copyItemsFromAxes(pos, hit, dest);
dfft.complexInverse(ddata, true);
result.setItemsOnAxes(pos, hit, ddata);
}
break;
default:
logger.warn("Non-float dataset not yet supported");
break;
}
return result;
}
public static void coupe100(AudioSignal input) {
int fs = input.samplingRate;
int N = input.getLength();
float[] Y = Arrays.copyOf(input.data, 2 * N);
FloatFFT_1D fft = new FloatFFT_1D(N);
fft.realForwardFull(Y);
int threshold = 100 * 2;
Arrays.fill(Y, 0, Math.round(threshold * (float) N / fs), 0);
Arrays.fill(Y, Math.round(2 * N - threshold * (float) N / fs), 2 * N - 1, 0);
fft.complexInverse(Y, true);
for (int i = 0; i < N; i++) {
input.data[i] = Y[2 * i];
}
}