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256 lines
8.1 KiB
C++
256 lines
8.1 KiB
C++
///////////////////////////////////////////////////////////////////////////////////
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// Copyright (C) 2018 F4EXB //
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// written by Edouard Griffiths //
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// //
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// Integer half-band FIR based interpolator and decimator //
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// This is the even/odd double buffer variant. Really useful only when SIMD is //
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// used //
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// //
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// This program is free software; you can redistribute it and/or modify //
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// it under the terms of the GNU General Public License as published by //
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// the Free Software Foundation as version 3 of the License, or //
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// (at your option) any later version. //
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// //
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// This program is distributed in the hope that it will be useful, //
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// but WITHOUT ANY WARRANTY; without even the implied warranty of //
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the //
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// GNU General Public License V3 for more details. //
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// //
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// You should have received a copy of the GNU General Public License //
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// along with this program. If not, see <http://www.gnu.org/licenses/>. //
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///////////////////////////////////////////////////////////////////////////////////
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#ifndef SDRBASE_DSP_INTHALFBANDFILTEREOF_H_
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#define SDRBASE_DSP_INTHALFBANDFILTEREOF_H_
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#include <stdint.h>
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#include <cstdlib>
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#include "dsp/dsptypes.h"
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#include "dsp/hbfiltertraits.h"
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#include "export.h"
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template<uint32_t HBFilterOrder>
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class IntHalfbandFilterEOF {
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public:
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IntHalfbandFilterEOF();
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bool workDecimateCenter(float *x, float *y)
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{
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// insert sample into ring-buffer
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storeSample(*x, *y);
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switch(m_state)
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{
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case 0:
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// advance write-pointer
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advancePointer();
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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(x, y);
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// advance write-pointer
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advancePointer();
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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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void myDecimate(float x1, float y1, float *x2, float *y2)
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{
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storeSample(x1, y1);
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advancePointer();
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storeSample(*x2, *y2);
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doFIR(x2, y2);
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advancePointer();
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}
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/** Simple zero stuffing and filter */
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void myInterpolateZeroStuffing(float *x1, float *y1, float *x2, float *y2)
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{
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storeSample(*x1, *y1);
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doFIR(x1, y1);
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advancePointer();
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storeSample(0, 0);
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doFIR(x2, y2);
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advancePointer();
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}
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/** Optimized upsampler by 2 not calculating FIR with inserted null samples */
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void myInterpolate(float *x1, float *y1, float *x2, float *y2)
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{
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// insert sample into ring double buffer
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m_samples[m_ptr][0] = *x1;
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m_samples[m_ptr][1] = *y1;
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m_samples[m_ptr + HBFIRFilterTraits<HBFilterOrder>::hbOrder/2][0] = *x1;
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m_samples[m_ptr + HBFIRFilterTraits<HBFilterOrder>::hbOrder/2][1] = *y1;
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// advance pointer
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if (m_ptr < (HBFIRFilterTraits<HBFilterOrder>::hbOrder/2) - 1) {
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m_ptr++;
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} else {
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m_ptr = 0;
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}
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// first output sample calculated with the middle peak
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*x1 = m_samples[m_ptr + (HBFIRFilterTraits<HBFilterOrder>::hbOrder/4) - 1][0];
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*y1 = m_samples[m_ptr + (HBFIRFilterTraits<HBFilterOrder>::hbOrder/4) - 1][1];
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// second sample calculated with the filter
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doInterpolateFIR(x2, y2);
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}
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void myInterpolateInf(float *x1, float *y1, float *x2, float *y2, float *x3, float *y3, float *x4, float *y4)
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{
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myInterpolate(x1, y1, x2, y2);
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myInterpolate(x3, y3, x4, y4);
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// rotation
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qint32 x;
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x = *x1;
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*x1 = *y1;
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*y1 = -x;
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*x2 = -*x2;
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*y2 = -*y2;
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x = *x3;
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*x3 = -*y3;
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*y3 = x;
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}
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void myInterpolateSup(float *x1, float *y1, float *x2, float *y2, float *x3, float *y3, float *x4, float *y4)
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{
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myInterpolate(x1, y1, x2, y2);
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myInterpolate(x3, y3, x4, y4);
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// rotation
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qint32 x;
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x = *x1;
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*x1 = -*y1;
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*y1 = x;
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*x2 = -*x2;
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*y2 = -*y2;
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x = *x3;
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*x3 = *y3;
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*y3 = -x;
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}
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protected:
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float m_even[2][HBFIRFilterTraits<HBFilterOrder>::hbOrder]; // double buffer technique
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float m_odd[2][HBFIRFilterTraits<HBFilterOrder>::hbOrder]; // double buffer technique
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float m_samples[HBFIRFilterTraits<HBFilterOrder>::hbOrder][2]; // double buffer technique
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int m_ptr;
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int m_size;
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int m_state;
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void storeSample(float x, float y)
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{
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if ((m_ptr % 2) == 0)
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{
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m_even[0][m_ptr/2] = x;
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m_even[1][m_ptr/2] = y;
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m_even[0][m_ptr/2 + m_size] = x;
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m_even[1][m_ptr/2 + m_size] = y;
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}
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else
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{
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m_odd[0][m_ptr/2] = x;
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m_odd[1][m_ptr/2] = y;
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m_odd[0][m_ptr/2 + m_size] = x;
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m_odd[1][m_ptr/2 + m_size] = y;
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}
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}
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void advancePointer()
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{
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m_ptr = m_ptr + 1 < 2*m_size ? m_ptr + 1: 0;
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}
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void doFIR(float *x, float *y)
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{
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float iAcc = 0;
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float qAcc = 0;
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int a = m_ptr/2 + m_size; // tip pointer
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int b = m_ptr/2 + 1; // tail pointer
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for (int i = 0; i < HBFIRFilterTraits<HBFilterOrder>::hbOrder / 4; i++)
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{
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if ((m_ptr % 2) == 0)
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{
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iAcc += (m_even[0][a] + m_even[0][b]) * HBFIRFilterTraits<HBFilterOrder>::hbCoeffsF[i];
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qAcc += (m_even[1][a] + m_even[1][b]) * HBFIRFilterTraits<HBFilterOrder>::hbCoeffsF[i];
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}
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else
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{
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iAcc += (m_odd[0][a] + m_odd[0][b]) * HBFIRFilterTraits<HBFilterOrder>::hbCoeffsF[i];
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qAcc += (m_odd[1][a] + m_odd[1][b]) * HBFIRFilterTraits<HBFilterOrder>::hbCoeffsF[i];
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}
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a -= 1;
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b += 1;
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}
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if ((m_ptr % 2) == 0)
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{
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iAcc += m_odd[0][m_ptr/2 + m_size/2] * 0.5f;
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qAcc += m_odd[1][m_ptr/2 + m_size/2] * 0.5f;
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}
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else
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{
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iAcc += m_even[0][m_ptr/2 + m_size/2 + 1] * 0.5f;
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qAcc += m_even[1][m_ptr/2 + m_size/2 + 1] * 0.5f;
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}
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*x = iAcc; // HB_SHIFT incorrect do not loose the gained bit
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*y = qAcc;
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}
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void doInterpolateFIR(float *x, float *y)
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{
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qint32 iAcc = 0;
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qint32 qAcc = 0;
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qint16 a = m_ptr;
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qint16 b = m_ptr + (HBFIRFilterTraits<HBFilterOrder>::hbOrder / 2) - 1;
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// go through samples in buffer
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for (int i = 0; i < HBFIRFilterTraits<HBFilterOrder>::hbOrder / 4; i++)
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{
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iAcc += (m_samples[a][0] + m_samples[b][0]) * HBFIRFilterTraits<HBFilterOrder>::hbCoeffsF[i];
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qAcc += (m_samples[a][1] + m_samples[b][1]) * HBFIRFilterTraits<HBFilterOrder>::hbCoeffsF[i];
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a++;
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b--;
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}
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*x = iAcc * SDR_RX_SCALED;
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*y = qAcc * SDR_RX_SCALED;
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}
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};
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template<uint32_t HBFilterOrder>
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IntHalfbandFilterEOF<HBFilterOrder>::IntHalfbandFilterEOF()
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{
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m_size = HBFIRFilterTraits<HBFilterOrder>::hbOrder/2;
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for (int i = 0; i < 2*m_size; i++)
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{
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m_even[0][i] = 0.0f;
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m_even[1][i] = 0.0f;
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m_odd[0][i] = 0.0f;
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m_odd[1][i] = 0.0f;
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m_samples[i][0] = 0.0f;
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m_samples[i][1] = 0.0f;
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}
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m_ptr = 0;
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m_state = 0;
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}
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#endif /* SDRBASE_DSP_INTHALFBANDFILTEREOF_H_ */
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