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filter.cpp
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filter.cpp
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/* miniSynth - A Simple Software Synthesizer
Copyright (C) 2015 Ville Räisänen <vsr at vsr.name>
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 3 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, see <http://www.gnu.org/licenses/>.
*/
#include "filter.h"
#include <QDebug>
Filter::Filter(unsigned int _samplingRate, FilterParameters &filt) {
Filter(filt.type, filt.window_type, filt.size, _samplingRate, filt.freq1, filt.freq2);
}
Filter::Filter(unsigned int _type, unsigned int _window_type, unsigned int _size,
unsigned int _samplingRate, qreal _freq1, qreal _freq2) {
type = _type;
window_type = _window_type;
size = _size;
samplingRate = _samplingRate;
freq1 = _freq1;
freq2 = _freq2;
// Compute normalized frequencies:
qreal f1n = freq1 / samplingRate,
f2n = freq2 / samplingRate;
IR = new qreal[size];
for (unsigned int ind = 0; ind < size; ind++) {
IR[ind] = 0;
}
// 10 => sizemod = 1
// => ind_n = 0, 1, 2, .., 8
// ind_n = 0 => n = 0 - (10 - 1 - 1)/2 = -4
// ind_n = 8 => n = 8 - (10 - 1 - 1)/2 = 4
// 11 => sizemod = 0
// => ind_n = 0, 1, 2, ..., 10
// ind_n = 0 => n = 0 - (11 - 1)/2 = -5
// ind_n = 10 => n = 10 - (11 - 1)/2 = 5
// 2 => sizemod = 1;
// => ind_n = 0
// ind_n = 0 => n = 0 - (2 - 1 - 1)/2 = 0
if (type == FILTER_OFF) {
qDebug() << "FIROFF" << size;
IR[0] = 1;
return;
}
Q_ASSERT(size >= 2);
int sizemod = 1 - size % 2;
for (unsigned int ind_n = 0; ind_n < size - sizemod; ind_n++) {
int n = ind_n - (size-sizemod-1)/2;
qreal v = 0;
switch (type) {
case FILTER_LOWPASS:
if (n== 0) {
v = 2*f1n;
} else {
v = 2*f1n*qSin(n*2*M_PI*f1n) / (n*2*M_PI*f1n);
}
break;
case FILTER_HIGHPASS:
if (n== 0) {
v = 1 - 2*f1n;
} else {
v = -2*f1n*qSin(n*2*M_PI*f1n) / (n*2*M_PI*f1n);
}
break;
case FILTER_BANDPASS:
if (n== 0) {
v = 2*(f2n - f1n);
} else {
v = 2*f2n*qSin(n*2*M_PI*f2n) / (n*2*M_PI*f2n)
- 2*f1n*qSin(n*2*M_PI*f1n) / (n*2*M_PI*f1n);
}
break;
case FILTER_BANDSTOP:
if (n== 0) {
v = 1 - 2*(f2n - f1n);
} else {
v = 2*f1n*qSin(n*2*M_PI*f1n) / (n*2*M_PI*f1n)
- 2*f2n*qSin(n*2*M_PI*f2n) / (n*2*M_PI*f2n);
}
break;
}
switch (window_type) {
case WINDOW_HANNING:
v *= 0.5*(1 + qCos(2*M_PI*n/(size - sizemod)));
break;
case WINDOW_HAMMING:
v *= 0.54 + 0.46*qCos(2*M_PI*n/(size - sizemod));
break;
case WINDOW_BLACKMAN:
v *= 0.42 + 0.5 * qCos(2*M_PI*n/(size - sizemod - 1))
+ 0.08 * qCos(4*M_PI*n/(size - sizemod - 1));
break;
}
IR[ind_n] = v;
}
}
Filter::~Filter() {
delete [] IR;
}