public WWComplex[] ConvolutionFft(WWComplex[] h, WWComplex[] x)
{
var r = new WWComplex[h.Length + x.Length - 1];
int fftSize = WWRadix2Fft.NextPowerOf2(r.Length);
var h2 = new WWComplex[fftSize];
Array.Copy(h, 0, h2, 0, h.Length);
var x2 = new WWComplex[fftSize];
Array.Copy(x, 0, x2, 0, x.Length);
var fft = new WWRadix2Fft(fftSize);
var H = fft.ForwardFft(h2);
var X = fft.ForwardFft(x2);
var Y = WWComplex.Mul(H, X);
var y = fft.InverseFft(Y);
Array.Copy(y, 0, r, 0, r.Length);
return(r);
}
private void FftStageN(int stageNr, WWComplex[] x, WWComplex[] y)
{
/*
* stage0: 2つの入力データにバタフライ演算 (length=8の時) 4回 (nRepeat=4, nSubRepeat=2)
* y[0] = x[0] + w_n^(0*4) * x[1]
* y[1] = x[0] + w_n^(1*4) * x[1]
*
* y[2] = x[2] + w_n^(0*4) * x[3]
* y[3] = x[2] + w_n^(1*4) * x[3]
*
* y[4] = x[4] + w_n^(0*4) * x[5]
* y[5] = x[4] + w_n^(1*4) * x[5]
*
* y[6] = x[6] + w_n^(0*4) * x[7]
* y[7] = x[6] + w_n^(1*4) * x[7]
*/
/*
* stage1: 4つの入力データにバタフライ演算 (length=8の時) 2回 (nRepeat=2, nSubRepeat=4)
* y[0] = x[0] + w_n^(0*2) * x[2]
* y[1] = x[1] + w_n^(1*2) * x[3]
* y[2] = x[0] + w_n^(2*2) * x[2]
* y[3] = x[1] + w_n^(3*2) * x[3]
*
* y[4] = x[4] + w_n^(0*2) * x[6]
* y[5] = x[5] + w_n^(1*2) * x[7]
* y[6] = x[4] + w_n^(2*2) * x[6]
* y[7] = x[5] + w_n^(3*2) * x[7]
*/
/*
* stage2: 8つの入力データにバタフライ演算 (length=8の時) 1回 (nRepeat=1, nSubRepeat=8)
* y[0] = x[0] + w_n^(0*1) * x[4]
* y[1] = x[1] + w_n^(1*1) * x[5]
* y[2] = x[2] + w_n^(2*1) * x[6]
* y[3] = x[3] + w_n^(3*1) * x[7]
* y[4] = x[0] + w_n^(4*1) * x[4]
* y[5] = x[1] + w_n^(5*1) * x[5]
* y[6] = x[2] + w_n^(6*1) * x[6]
* y[7] = x[3] + w_n^(7*1) * x[7]
*/
/*
* stageN:
*/
int nRepeat = Pow2(mNumStage - stageNr - 1);
int nSubRepeat = mNumPoints / nRepeat;
var t = new WWComplex();
for (int i = 0; i < nRepeat; ++i)
{
int offsBase = i * nSubRepeat;
bool allZero = true;
for (int j = 0; j < nSubRepeat / 2; ++j)
{
int offs = offsBase + (j % (nSubRepeat / 2));
if (Double.Epsilon < x[offs].Magnitude())
{
allZero = false;
break;
}
if (Double.Epsilon < x[offs + nSubRepeat / 2].Magnitude())
{
allZero = false;
break;
}
}
if (allZero)
{
for (int j = 0; j < nSubRepeat / 2; ++j)
{
y[j + offsBase].Set(0, 0);
}
}
else
{
for (int j = 0; j < nSubRepeat; ++j)
{
int offs = offsBase + (j % (nSubRepeat / 2));
y[j + offsBase].CopyFrom(x[offs]);
t.CopyFrom(mWn[j * nRepeat]);
t.Mul(x[offs + nSubRepeat / 2]);
y[j + offsBase].Add(t);
}
}
}
}
public override double[] FilterDo(double[] inPcm)
{
System.Diagnostics.Debug.Assert(inPcm.LongLength <= NumOfSamplesNeeded());
var fft = new WWRadix2Fft(FFT_LEN);
// Overlap and add continuous FFT
var inTime = new WWComplex[FFT_LEN];
for (int i = 0; i < inPcm.Length; ++i)
{
inTime[i].real = inPcm[i];
}
// FFTでinTimeをinFreqに変換
var inFreq = fft.ForwardFft(inTime);
inTime = null;
// FFT後、フィルターHの周波数ドメインデータを掛ける
var mulFreq = WWComplex.Mul(inFreq, mFilterFreq);
inFreq = null;
// inFreqをIFFTしてoutTimeに変換
var outTime = fft.InverseFft(mulFreq);
mulFreq = null;
double [] outReal;
if (mFirstFilterDo)
{
// 最初のFilterDo()のとき、フィルタの遅延サンプル数だけ先頭サンプルを削除する。
outReal = new double[NumOfSamplesNeeded() - FILTER_DELAY];
for (int i = 0; i < outReal.Length; ++i)
{
outReal[i] = outTime[i + FILTER_DELAY].real;
}
mFirstFilterDo = false;
}
else
{
outReal = new double[NumOfSamplesNeeded()];
for (int i = 0; i < outReal.Length; ++i)
{
outReal[i] = outTime[i].real;
}
}
// 前回のIFFT結果の最後のFILTER_LENGTH-1サンプルを先頭に加算する
if (null != mIfftAddBuffer)
{
for (int i = 0; i < mIfftAddBuffer.Length; ++i)
{
outReal[i] += mIfftAddBuffer[i];
}
}
// 今回のIFFT結果の最後のFILTER_LENGTH-1サンプルをmIfftAddBufferとして保存する
mIfftAddBuffer = new double[FILTER_LENP1];
for (int i = 0; i < mIfftAddBuffer.Length; ++i)
{
mIfftAddBuffer[i] = outTime[outTime.Length - mIfftAddBuffer.Length + i].real;
}
outTime = null;
return(outReal);
}
public static WWComplex Mul(WWComplex a, WWComplex b)
{
var r = new WWComplex(a);
r.Mul(b);
return r;
}
private void FftStageN(int stageNr, WWComplex[] x, WWComplex[] y)
{
/*
* stage0: 2つの入力データにバタフライ演算 (length=8の時) 4回 (nRepeat=4, nSubRepeat=2)
* y[0] = x[0] + w_n^(0*4) * x[1]
* y[1] = x[0] + w_n^(1*4) * x[1]
*
* y[2] = x[2] + w_n^(0*4) * x[3]
* y[3] = x[2] + w_n^(1*4) * x[3]
*
* y[4] = x[4] + w_n^(0*4) * x[5]
* y[5] = x[4] + w_n^(1*4) * x[5]
*
* y[6] = x[6] + w_n^(0*4) * x[7]
* y[7] = x[6] + w_n^(1*4) * x[7]
*/
/*
* stage1: 4つの入力データにバタフライ演算 (length=8の時) 2回 (nRepeat=2, nSubRepeat=4)
* y[0] = x[0] + w_n^(0*2) * x[2]
* y[1] = x[1] + w_n^(1*2) * x[3]
* y[2] = x[0] + w_n^(2*2) * x[2]
* y[3] = x[1] + w_n^(3*2) * x[3]
*
* y[4] = x[4] + w_n^(0*2) * x[6]
* y[5] = x[5] + w_n^(1*2) * x[7]
* y[6] = x[4] + w_n^(2*2) * x[6]
* y[7] = x[5] + w_n^(3*2) * x[7]
*/
/*
* stage2: 8つの入力データにバタフライ演算 (length=8の時) 1回 (nRepeat=1, nSubRepeat=8)
* y[0] = x[0] + w_n^(0*1) * x[4]
* y[1] = x[1] + w_n^(1*1) * x[5]
* y[2] = x[2] + w_n^(2*1) * x[6]
* y[3] = x[3] + w_n^(3*1) * x[7]
* y[4] = x[0] + w_n^(4*1) * x[4]
* y[5] = x[1] + w_n^(5*1) * x[5]
* y[6] = x[2] + w_n^(6*1) * x[6]
* y[7] = x[3] + w_n^(7*1) * x[7]
*/
/*
* stageN:
*/
int nRepeat = Pow2(mNumStage - stageNr - 1);
int nSubRepeat = mNumPoints / nRepeat;
var t = new WWComplex();
for (int i=0; i<nRepeat; ++i) {
int offsBase = i * nSubRepeat;
bool allZero = true;
for (int j=0; j < nSubRepeat/2; ++j) {
int offs = offsBase + (j % (nSubRepeat/2));
if (Double.Epsilon < x[offs].Magnitude()) {
allZero = false;
break;
}
if (Double.Epsilon < x[offs + nSubRepeat / 2].Magnitude()) {
allZero = false;
break;
}
}
if (allZero) {
for (int j=0; j < nSubRepeat / 2; ++j) {
y[j + offsBase].Set(0, 0);
}
} else {
for (int j=0; j < nSubRepeat; ++j) {
int offs = offsBase + (j % (nSubRepeat / 2));
y[j + offsBase].CopyFrom(x[offs]);
t.CopyFrom(mWn[j * nRepeat]);
t.Mul(x[offs + nSubRepeat / 2]);
y[j + offsBase].Add(t);
}
}
}
}