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Diffstat (limited to 'src/app/fht.h')
| -rw-r--r-- | src/app/fht.h | 126 |
1 files changed, 126 insertions, 0 deletions
diff --git a/src/app/fht.h b/src/app/fht.h new file mode 100644 index 0000000..3dc5387 --- /dev/null +++ b/src/app/fht.h @@ -0,0 +1,126 @@ +// FHT - Fast Hartley Transform Class +// +// Copyright (C) 2004 Melchior FRANZ - [email protected] +// +// This program is free software; you can redistribute it and/or +// modify it under the terms of the GNU General Public License as +// published by the Free Software Foundation; either version 2 of the +// License, or (at your option) any later version. +// +// This program is distributed in the hope that it will be useful, but +// WITHOUT ANY WARRANTY; without even the implied warranty of +// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU +// General Public License for more details. +// +// You should have received a copy of the GNU General Public License +// along with this program; if not, write to the Free Software +// Foundation, 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA +// +// $Id: fht.h,v 1.3 2004/06/05 20:20:36 mfranz Exp $ + +#ifndef FHT_H +#define FHT_H + +/** + * Implementation of the Hartley Transform after Bracewell's discrete + * algorithm. The algorithm is subject to US patent No. 4,646,256 (1987) + * but was put into public domain by the Board of Trustees of Stanford + * University in 1994 and is now freely available[1]. + * + * [1] Computer in Physics, Vol. 9, No. 4, Jul/Aug 1995 pp 373-379 + */ +class FHT +{ + int m_exp2; + int m_num; + float *m_buf; + float *m_tab; + int *m_log; + + /** + * Create a table of CAS (cosine and sine) values. + * Has only to be done in the constructor and saves from + * calculating the same values over and over while transforming. + */ + void makeCasTable(); + + /** + * Recursive in-place Hartley transform. For internal use only! + */ + void _transform(float *, int, int); + + public: + /** + * Prepare transform for data sets with @f$2^n@f$ numbers, whereby @f$n@f$ + * should be at least 3. Values of more than 3 need a trigonometry table. + * @see makeCasTable() + */ + FHT(int); + + ~FHT(); + inline int sizeExp() const { return m_exp2; } + inline int size() const { return m_num; } + float *copy(float *, float *); + float *clear(float *); + void scale(float *, float); + + /** + * Exponentially Weighted Moving Average (EWMA) filter. + * @param d is the filtered data. + * @param s is fresh input. + * @param w is the weighting factor. + */ + void ewma(float *d, float *s, float w); + + /** + * Test routine to create wobbling sine or rectangle wave. + * @param d destination vector. + * @param rect rectangle if true, sine otherwise. + */ + void pattern(float *d, bool rect); + + /** + * Logarithmic audio spectrum. Maps semi-logarithmic spectrum + * to logarithmic frequency scale, interpolates missing values. + * A logarithmic index map is calculated at the first run only. + * @param p is the input array. + * @param out is the spectrum. + */ + void logSpectrum(float *out, float *p); + + /** + * Semi-logarithmic audio spectrum. + */ + void semiLogSpectrum(float *); + + /** + * Fourier spectrum. + */ + void spectrum(float *); + + /** + * Calculates a mathematically correct FFT power spectrum. + * If further scaling is applied later, use power2 instead + * and factor the 0.5 in the final scaling factor. + * @see FHT::power2() + */ + void power(float *); + + /** + * Calculates an FFT power spectrum with doubled values as a + * result. The values need to be multiplied by 0.5 to be exact. + * Note that you only get @f$2^{n-1}@f$ power values for a data set + * of @f$2^n@f$ input values. + * @see FHT::power() + */ + void power2(float *); + + /** + * Discrete Hartley transform of data sets with 8 values. + */ + void transform8(float *); + + void transform(float *); +}; + +#endif |