//====================================================================================== /// <summary> /// Compute a 1D fast Fourier transform of a dataset of complex numbers (as pairs of float's). /// </summary> /// <param name="data"></param> /// <param name="direction"></param> public static void FFT(float[] data, FourierDirection direction) { int length = data.Length; Debug.Assert(data != null); Debug.Assert(data.Length >= length * 2); Debug.Assert(Fourier.IsPowerOf2(length) == true); Fourier.SyncLookupTableLength(length); int ln = Fourier.Log2(length); // reorder array Fourier.ReorderArray(data); // successive doubling int N = 1; int signIndex = (direction == FourierDirection.Forward) ? 0 : 1; for (int level = 1; level <= ln; level++) { int M = N; N <<= 1; float[] uRLookup = _uRLookupF[level, signIndex]; float[] uILookup = _uILookupF[level, signIndex]; for (int j = 0; j < M; j++) { float uR = uRLookup[j]; float uI = uILookup[j]; for (int evenT = j; evenT < length; evenT += N) { int even = evenT << 1; int odd = (evenT + M) << 1; float r = data[odd]; float i = data[odd + 1]; float odduR = r * uR - i * uI; float odduI = r * uI + i * uR; r = data[even]; i = data[even + 1]; data[even] = r + odduR; data[even + 1] = i + odduI; data[odd] = r - odduR; data[odd + 1] = i - odduI; } } } }
/// <summary> /// Compute a 1D fast Fourier transform of a dataset of complex numbers. /// </summary> /// <param name="data"></param> /// <param name="direction"></param> public static void FFT(Complex[] data, FourierDirection direction) { int length = data.Length; if (data == null) { throw new ArgumentNullException("data"); } if (data.Length < length) { throw new ArgumentOutOfRangeException("length", length, "must be at least as large as 'data.Length' parameter"); } if (Fourier.IsPowerOf2(length) == false) { throw new ArgumentOutOfRangeException("length", length, "must be a power of 2"); } Fourier.SyncLookupTableLength(length); int ln = Fourier.Log2(length); // reorder array Fourier.ReorderArray(data); // successive doubling int N = 1; int signIndex = (direction == FourierDirection.Forward) ? 0 : 1; for (int level = 1; level <= ln; level++) { int M = N; N <<= 1; double [] uRLookup = _uRLookup[level, signIndex]; double [] uILookup = _uILookup[level, signIndex]; for (int j = 0; j < M; j++) { double uR = uRLookup[j]; double uI = uILookup[j]; for (int even = j; even < length; even += N) { int odd = even + M; double r = data[odd].Re; double i = data[odd].Im; double odduR = r * uR - i * uI; double odduI = r * uI + i * uR; r = data[even].Re; i = data[even].Im; data[even].Re = r + odduR; data[even].Im = i + odduI; data[odd].Re = r - odduR; data[odd].Im = i - odduI; } } } }