Clementine-audio-player-Mac.../src/analyzers/fht.h

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/* This file is part of Clementine.
Copyright 2004, Melchior FRANZ <mfranz@kde.org>
Copyright 2010, 2014, John Maguire <john.maguire@gmail.com>
Copyright 2014, Krzysztof Sobiecki <sobkas@gmail.com>
Clementine 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 3 of the License, or
(at your option) any later version.
Clementine 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 Clementine. If not, see <http://www.gnu.org/licenses/>.
*/
/* Original Author: Melchior FRANZ <mfranz@kde.org> 2004
*/
#ifndef ANALYZERS_FHT_H_
#define ANALYZERS_FHT_H_
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/**
* 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 exp2_;
int num_;
float* buf_;
float* tab_;
int* log_;
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/**
* 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();
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/**
* Recursive in-place Hartley transform. For internal use only!
*/
void _transform(float*, int, int);
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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()
*/
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explicit FHT(int);
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~FHT();
inline int sizeExp() const { return exp2_; }
inline int size() const { return num_; }
float* copy(float*, float*);
float* clear(float*);
void scale(float*, float);
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/**
* 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);
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/**
* 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);
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/**
* Semi-logarithmic audio spectrum.
*/
void semiLogSpectrum(float*);
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/**
* Fourier spectrum.
*/
void spectrum(float*);
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/**
* 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*);
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/**
* 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. This is the fastest transform.
* @see FHT::power()
*/
void power2(float*);
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/**
* Discrete Hartley transform of data sets with 8 values.
*/
void transform8(float*);
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void transform(float*);
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};
#endif // ANALYZERS_FHT_H_