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/***************************************************************************
LowPassFilter.h - transmission function of a low pass filter
-------------------
begin : Mar 15 2003
copyright : (C) 2003 by Thomas Eschenbacher
email : Thomas Eschenbacher <thomas.eschenbacher@gmx.de>
***************************************************************************/
/***************************************************************************
* *
* 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. *
* *
***************************************************************************/
#ifndef LOW_PASS_FILTER_H
#define LOW_PASS_FILTER_H
#include "config.h"
#include <QObject>
#include <QVariant>
#include "libkwave/SampleArray.h"
#include "libkwave/SampleSource.h"
#include "libkwave/TransmissionFunction.h"
namespace Kwave
{
class LowPassFilter: public Kwave::SampleSource,
public Kwave::TransmissionFunction
{
Q_OBJECT
public:
/** Constructor */
LowPassFilter();
/** Destructor */
~LowPassFilter() override;
/** @see TransmissionFunction::at() */
double at(double f) override;
/** does the calculation */
void goOn() override;
signals:
/** emits a block with the filtered data */
void output(Kwave::SampleArray data);
public slots:
/** receives input data */
void input(Kwave::SampleArray data);
/**
* Sets the cutoff frequency, normed to [0...2Pi]. The calculation is:
* fc = frequency [Hz] * 2 * Pi / f_sample [Hz].
* The default setting is 0.5.
*/
void setFrequency(const QVariant fc);
private:
/** reset/initialize the filter coefficients */
void initFilter();
/** calculate filter coefficients for a given frequency */
void normed_setfilter_shelvelowpass(double freq);
private:
/** buffer for input */
Kwave::SampleArray m_buffer;
/** cutoff frequency [0...PI] */
double m_f_cutoff;
/** structure with the filter coefficients */
struct {
double cx,cx1,cx2,cy1,cy2;
double x,x1,x2,y,y1,y2;
} m_filter;
};
}
#endif /* LOW_PASS_FILTER_H */
//***************************************************************************
//***************************************************************************
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