314 lines
8.5 KiB
C++
314 lines
8.5 KiB
C++
#ifndef INCLUDE_INTHALFBANDFILTER_H
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#define INCLUDE_INTHALFBANDFILTER_H
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#include <QtGlobal>
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#include "dsp/dsptypes.h"
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#include "util/export.h"
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// uses Q1.14 format internally, input and output are S16
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/*
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* supported filter orders: 64, 48, 32
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*/
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#define HB_FILTERORDER 32
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#define HB_SHIFT 14
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class SDRANGELOVE_API IntHalfbandFilter {
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public:
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IntHalfbandFilter();
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// downsample by 2, return center part of original spectrum
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bool workDecimateCenter(Sample* sample)
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{
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// insert sample into ring-buffer
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m_samples[m_ptr][0] = sample->real();
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m_samples[m_ptr][1] = sample->imag();
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switch(m_state) {
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case 0:
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// advance write-pointer
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m_ptr = (m_ptr + HB_FILTERORDER) % (HB_FILTERORDER + 1);
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// next state
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m_state = 1;
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// tell caller we don't have a new sample
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return false;
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default:
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// save result
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doFIR(sample);
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// advance write-pointer
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m_ptr = (m_ptr + HB_FILTERORDER) % (HB_FILTERORDER + 1);
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// next state
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m_state = 0;
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// tell caller we have a new sample
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return true;
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}
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}
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// downsample by 2, return edges of spectrum rotated into center
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bool workDecimateFullRotate(Sample* sample)
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{
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switch(m_state) {
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case 0:
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// insert sample into ring-buffer
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m_samples[m_ptr][0] = sample->real();
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m_samples[m_ptr][1] = sample->imag();
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// advance write-pointer
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m_ptr = (m_ptr + HB_FILTERORDER) % (HB_FILTERORDER + 1);
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// next state
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m_state = 1;
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// tell caller we don't have a new sample
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return false;
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default:
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// insert sample into ring-buffer
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m_samples[m_ptr][0] = -sample->real();
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m_samples[m_ptr][1] = sample->imag();
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// save result
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doFIR(sample);
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// advance write-pointer
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m_ptr = (m_ptr + HB_FILTERORDER) % (HB_FILTERORDER + 1);
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// next state
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m_state = 0;
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// tell caller we have a new sample
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return true;
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}
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}
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// downsample by 2, return lower half of original spectrum
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bool workDecimateLowerHalf(Sample* sample)
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{
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switch(m_state) {
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case 0:
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// insert sample into ring-buffer
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m_samples[m_ptr][0] = -sample->imag();
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m_samples[m_ptr][1] = sample->real();
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// advance write-pointer
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m_ptr = (m_ptr + HB_FILTERORDER) % (HB_FILTERORDER + 1);
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// next state
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m_state = 1;
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// tell caller we don't have a new sample
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return false;
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case 1:
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// insert sample into ring-buffer
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m_samples[m_ptr][0] = -sample->real();
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m_samples[m_ptr][1] = -sample->imag();
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// save result
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doFIR(sample);
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// advance write-pointer
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m_ptr = (m_ptr + HB_FILTERORDER) % (HB_FILTERORDER + 1);
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// next state
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m_state = 2;
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// tell caller we have a new sample
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return true;
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case 2:
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// insert sample into ring-buffer
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m_samples[m_ptr][0] = sample->imag();
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m_samples[m_ptr][1] = -sample->real();
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// advance write-pointer
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m_ptr = (m_ptr + HB_FILTERORDER) % (HB_FILTERORDER + 1);
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// next state
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m_state = 3;
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// tell caller we don't have a new sample
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return false;
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default:
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// insert sample into ring-buffer
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m_samples[m_ptr][0] = sample->real();
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m_samples[m_ptr][1] = sample->imag();
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// save result
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doFIR(sample);
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// advance write-pointer
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m_ptr = (m_ptr + HB_FILTERORDER) % (HB_FILTERORDER + 1);
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// next state
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m_state = 0;
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// tell caller we have a new sample
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return true;
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}
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}
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// downsample by 2, return upper half of original spectrum
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bool workDecimateUpperHalf(Sample* sample)
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{
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switch(m_state) {
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case 0:
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// insert sample into ring-buffer
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m_samples[m_ptr][0] = sample->imag();
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m_samples[m_ptr][1] = -sample->real();
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// advance write-pointer
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m_ptr = (m_ptr + HB_FILTERORDER) % (HB_FILTERORDER + 1);
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// next state
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m_state = 1;
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// tell caller we don't have a new sample
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return false;
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case 1:
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// insert sample into ring-buffer
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m_samples[m_ptr][0] = -sample->real();
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m_samples[m_ptr][1] = -sample->imag();
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// save result
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doFIR(sample);
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// advance write-pointer
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m_ptr = (m_ptr + HB_FILTERORDER) % (HB_FILTERORDER + 1);
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// next state
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m_state = 2;
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// tell caller we have a new sample
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return true;
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case 2:
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// insert sample into ring-buffer
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m_samples[m_ptr][0] = -sample->imag();
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m_samples[m_ptr][1] = sample->real();
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// advance write-pointer
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m_ptr = (m_ptr + HB_FILTERORDER) % (HB_FILTERORDER + 1);
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// next state
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m_state = 3;
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// tell caller we don't have a new sample
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return false;
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default:
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// insert sample into ring-buffer
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m_samples[m_ptr][0] = sample->real();
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m_samples[m_ptr][1] = sample->imag();
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// save result
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doFIR(sample);
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// advance write-pointer
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m_ptr = (m_ptr + HB_FILTERORDER) % (HB_FILTERORDER + 1);
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// next state
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m_state = 0;
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// tell caller we have a new sample
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return true;
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}
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}
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protected:
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qint16 m_samples[HB_FILTERORDER + 1][2];
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int m_ptr;
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int m_state;
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void doFIR(Sample* sample)
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{
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// coefficents
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#if HB_FILTERORDER == 64
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static const qint32 COEFF[16] = {
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-0.001114417441601693505720538368564120901 * (1 << HB_SHIFT),
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0.001268007827185253051302527005361753254 * (1 << HB_SHIFT),
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-0.001959831378850490895410230152151598304 * (1 << HB_SHIFT),
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0.002878308307661380308073439948657323839 * (1 << HB_SHIFT),
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-0.004071361818258721100571850826099762344 * (1 << HB_SHIFT),
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0.005597288494657440618973431867289036745 * (1 << HB_SHIFT),
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-0.007532345003308904551886371336877346039 * (1 << HB_SHIFT),
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0.009980346844667375288961963519795972388 * (1 << HB_SHIFT),
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-0.013092614174300500062830820979797863401 * (1 << HB_SHIFT),
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0.01710934914871829748417297878404497169 * (1 << HB_SHIFT),
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-0.022443558692997273018576720460259821266 * (1 << HB_SHIFT),
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0.029875811511593811098386197500076377764 * (1 << HB_SHIFT),
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-0.041086352085710403647667021687084343284 * (1 << HB_SHIFT),
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0.060465467462665789533104998554335907102 * (1 << HB_SHIFT),
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-0.104159517495977321788203084906854201108 * (1 << HB_SHIFT),
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0.317657589850154464805598308885237202048 * (1 << HB_SHIFT),
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};
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#elif HB_FILTERORDER == 48
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static const qint32 COEFF[12] = {
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-0.004102576237611492253332112767338912818 * (1 << HB_SHIFT),
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0.003950551047979387886410762575906119309 * (1 << HB_SHIFT),
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-0.005807875789391703583164350277456833282 * (1 << HB_SHIFT),
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0.00823497890520805998770814682075069868 * (1 << HB_SHIFT),
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-0.011372226513199541059195851744334504474 * (1 << HB_SHIFT),
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0.015471557140973646315984524335362948477 * (1 << HB_SHIFT),
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-0.020944996398689276484450516591095947661 * (1 << HB_SHIFT),
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0.028568078132034283034279553703527199104 * (1 << HB_SHIFT),
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-0.040015143905614086738964374490024056286 * (1 << HB_SHIFT),
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0.059669519431831075095828964549582451582 * (1 << HB_SHIFT),
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-0.103669138691865420076609893840213771909 * (1 << HB_SHIFT),
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0.317491986549921390015072120149852707982 * (1 << HB_SHIFT)
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};
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#elif HB_FILTERORDER == 32
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static const qint32 COEFF[8] = {
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-0.015956912844043127236437484839370881673 * (1 << HB_SHIFT),
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0.013023031678944928940522274274371739011 * (1 << HB_SHIFT),
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-0.01866942273717486777684371190844103694 * (1 << HB_SHIFT),
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0.026550887571157304190005987720724078827 * (1 << HB_SHIFT),
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-0.038350314277854319344740474662103224546 * (1 << HB_SHIFT),
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0.058429248652825838128421764849917963147 * (1 << HB_SHIFT),
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-0.102889802028955756885153505209018476307 * (1 << HB_SHIFT),
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0.317237706405931241260276465254719369113 * (1 << HB_SHIFT)
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};
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#else
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#error unsupported filter order
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#endif
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// init read-pointer
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int a = (m_ptr + 1) % (HB_FILTERORDER + 1);
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int b = (m_ptr + (HB_FILTERORDER - 1)) % (HB_FILTERORDER + 1);
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// go through samples in buffer
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qint32 iAcc = 0;
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qint32 qAcc = 0;
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for(int i = 0; i < HB_FILTERORDER / 4; i++) {
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// do multiply-accumulate
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qint32 iTmp = m_samples[a][0] + m_samples[b][0];
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qint32 qTmp = m_samples[a][1] + m_samples[b][1];
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iAcc += iTmp * COEFF[i];
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qAcc += qTmp * COEFF[i];
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// update read-pointer
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a = (a + 2) % (HB_FILTERORDER + 1);
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b = (b + (HB_FILTERORDER - 1)) % (HB_FILTERORDER + 1);
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}
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a = (a + HB_FILTERORDER) % (HB_FILTERORDER + 1);
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iAcc += m_samples[a][0] * (qint32)(0.5 * (1 << HB_SHIFT));
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qAcc += m_samples[a][1] * (qint32)(0.5 * (1 << HB_SHIFT));
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// done, save result
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sample->setReal((iAcc + (qint32)(0.5 * (1 << HB_SHIFT))) >> HB_SHIFT);
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sample->setImag((qAcc + (qint32)(0.5 * (1 << HB_SHIFT))) >> HB_SHIFT);
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}
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};
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#endif // INCLUDE_INTHALFBANDFILTER_H
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