private double Convolution()
{
double v = 0.0;
// FIRフィルター係数が左右対称なので参考文献[3]の方法で乗算回数を半分に削減できる。
int center = mCoeffs.Length / 2;
for (int i = 0; i < center; ++i)
{
v += mCoeffs[i] * (
mDelay.GetNthDelayedSampleValue(i) +
mDelay.GetNthDelayedSampleValue(mCoeffs.Length - i - 1));
}
v += mCoeffs[center] * mDelay.GetNthDelayedSampleValue(center);
return(v);
}
public double[] Filter(double[] inPcm)
{
var outPcm = new double[inPcm.Length];
if (mParity == WWMath.WWParity.Odd)
{
int lastOffs = mHalfCoeffs.Length * 2 - 2;
for (int pos = 0; pos < inPcm.Length; ++pos)
{
double x = inPcm[pos];
mDelay.Filter(x);
double y = 0;
for (int i = 0; i < mHalfCoeffs.Length - 1; ++i)
{
y += mHalfCoeffs[i] * (mDelay.GetNthDelayedSampleValue(i)
+ mDelay.GetNthDelayedSampleValue(lastOffs - i));
}
y += mHalfCoeffs[mHalfCoeffs.Length - 1] * mDelay.GetNthDelayedSampleValue(mHalfCoeffs.Length - 1);
outPcm[pos] = y;
}
}
else
{
int lastOffs = mHalfCoeffs.Length * 2 - 1;
for (int pos = 0; pos < inPcm.Length; ++pos)
{
double x = inPcm[pos];
mDelay.Filter(x);
double y = 0;
for (int i = 0; i < mHalfCoeffs.Length; ++i)
{
y += mHalfCoeffs[i] * (mDelay.GetNthDelayedSampleValue(i)
+ mDelay.GetNthDelayedSampleValue(lastOffs - i));
}
outPcm[pos] = y;
}
}
return(outPcm);
}