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sdrangel/sdrbase/dsp/inthalfbandfiltereof.h

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///////////////////////////////////////////////////////////////////////////////////
// Copyright (C) 2018-2020 Edouard Griffiths, F4EXB <f4exb06@gmail.com> //
// Copyright (C) 2019 Davide Gerhard <rainbow@irh.it> //
// //
// Integer half-band FIR based interpolator and decimator //
// This is the even/odd double buffer variant. Really useful only when SIMD is //
// used //
// //
// 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 as 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 V3 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/>. //
///////////////////////////////////////////////////////////////////////////////////
#ifndef SDRBASE_DSP_INTHALFBANDFILTEREOF_H_
#define SDRBASE_DSP_INTHALFBANDFILTEREOF_H_
#include <stdint.h>
#include <cstdlib>
#include "dsp/dsptypes.h"
#include "dsp/hbfiltertraits.h"
template<uint32_t HBFilterOrder, bool IQOrder>
class IntHalfbandFilterEOF {
public:
IntHalfbandFilterEOF();
bool workDecimateCenter(float *x, float *y)
{
// insert sample into ring-buffer
storeSample(*x, *y);
switch(m_state)
{
case 0:
// advance write-pointer
advancePointer();
// next state
m_state = 1;
// tell caller we don't have a new sample
return false;
default:
// save result
doFIR(x, y);
// advance write-pointer
advancePointer();
// next state
m_state = 0;
// tell caller we have a new sample
return true;
}
}
void myDecimate(float x1, float y1, float *x2, float *y2)
{
storeSample(x1, y1);
advancePointer();
storeSample(*x2, *y2);
doFIR(x2, y2);
advancePointer();
}
/** Simple zero stuffing and filter */
void myInterpolateZeroStuffing(float *x1, float *y1, float *x2, float *y2)
{
storeSample(*x1, *y1);
doFIR(x1, y1);
advancePointer();
storeSample(0, 0);
doFIR(x2, y2);
advancePointer();
}
/** Optimized upsampler by 2 not calculating FIR with inserted null samples */
void myInterpolate(float *x1, float *y1, float *x2, float *y2)
{
// insert sample into ring double buffer
m_samples[m_ptr][0] = *x1;
m_samples[m_ptr][1] = *y1;
m_samples[m_ptr + HBFIRFilterTraits<HBFilterOrder>::hbOrder/2][0] = *x1;
m_samples[m_ptr + HBFIRFilterTraits<HBFilterOrder>::hbOrder/2][1] = *y1;
// advance pointer
if (m_ptr < (HBFIRFilterTraits<HBFilterOrder>::hbOrder/2) - 1) {
m_ptr++;
} else {
m_ptr = 0;
}
// first output sample calculated with the middle peak
*x1 = m_samples[m_ptr + (HBFIRFilterTraits<HBFilterOrder>::hbOrder/4) - 1][0];
*y1 = m_samples[m_ptr + (HBFIRFilterTraits<HBFilterOrder>::hbOrder/4) - 1][1];
// second sample calculated with the filter
doInterpolateFIR(x2, y2);
}
void myInterpolateInf(float *x1, float *y1, float *x2, float *y2, float *x3, float *y3, float *x4, float *y4)
{
myInterpolate(x1, y1, x2, y2);
myInterpolate(x3, y3, x4, y4);
// rotation
qint32 x;
x = *x1;
*x1 = *y1;
*y1 = -x;
*x2 = -*x2;
*y2 = -*y2;
x = *x3;
*x3 = -*y3;
*y3 = x;
}
void myInterpolateSup(float *x1, float *y1, float *x2, float *y2, float *x3, float *y3, float *x4, float *y4)
{
myInterpolate(x1, y1, x2, y2);
myInterpolate(x3, y3, x4, y4);
// rotation
qint32 x;
x = *x1;
*x1 = -*y1;
*y1 = x;
*x2 = -*x2;
*y2 = -*y2;
x = *x3;
*x3 = *y3;
*y3 = -x;
}
protected:
float m_even[2][HBFIRFilterTraits<HBFilterOrder>::hbOrder]; // double buffer technique
float m_odd[2][HBFIRFilterTraits<HBFilterOrder>::hbOrder]; // double buffer technique
float m_samples[HBFIRFilterTraits<HBFilterOrder>::hbOrder][2]; // double buffer technique
int m_ptr;
int m_size;
int m_state;
void storeSample(float x, float y)
{
if ((m_ptr % 2) == 0)
{
m_even[0][m_ptr/2] = IQOrder ? x : y;
m_even[1][m_ptr/2] = IQOrder ? y : x;
m_even[0][m_ptr/2 + m_size] = IQOrder ? x : y;
m_even[1][m_ptr/2 + m_size] = IQOrder ? y : x;
}
else
{
m_odd[0][m_ptr/2] = IQOrder ? x : y;
m_odd[1][m_ptr/2] = IQOrder ? y : x;
m_odd[0][m_ptr/2 + m_size] = IQOrder ? x : y;
m_odd[1][m_ptr/2 + m_size] = IQOrder ? y : x;
}
}
void advancePointer()
{
m_ptr = m_ptr + 1 < 2*m_size ? m_ptr + 1: 0;
}
void doFIR(float *x, float *y)
{
float iAcc = 0;
float qAcc = 0;
int a = m_ptr/2 + m_size; // tip pointer
int b = m_ptr/2 + 1; // tail pointer
for (int i = 0; i < HBFIRFilterTraits<HBFilterOrder>::hbOrder / 4; i++)
{
if ((m_ptr % 2) == 0)
{
iAcc += (m_even[0][a] + m_even[0][b]) * HBFIRFilterTraits<HBFilterOrder>::hbCoeffsF[i];
qAcc += (m_even[1][a] + m_even[1][b]) * HBFIRFilterTraits<HBFilterOrder>::hbCoeffsF[i];
}
else
{
iAcc += (m_odd[0][a] + m_odd[0][b]) * HBFIRFilterTraits<HBFilterOrder>::hbCoeffsF[i];
qAcc += (m_odd[1][a] + m_odd[1][b]) * HBFIRFilterTraits<HBFilterOrder>::hbCoeffsF[i];
}
a -= 1;
b += 1;
}
if ((m_ptr % 2) == 0)
{
iAcc += m_odd[0][m_ptr/2 + m_size/2] * 0.5f;
qAcc += m_odd[1][m_ptr/2 + m_size/2] * 0.5f;
}
else
{
iAcc += m_even[0][m_ptr/2 + m_size/2 + 1] * 0.5f;
qAcc += m_even[1][m_ptr/2 + m_size/2 + 1] * 0.5f;
}
*x = iAcc; // HB_SHIFT incorrect do not loose the gained bit
*y = qAcc;
}
void doInterpolateFIR(float *x, float *y)
{
qint32 iAcc = 0;
qint32 qAcc = 0;
qint16 a = m_ptr;
qint16 b = m_ptr + (HBFIRFilterTraits<HBFilterOrder>::hbOrder / 2) - 1;
// go through samples in buffer
for (int i = 0; i < HBFIRFilterTraits<HBFilterOrder>::hbOrder / 4; i++)
{
iAcc += (m_samples[a][0] + m_samples[b][0]) * HBFIRFilterTraits<HBFilterOrder>::hbCoeffsF[i];
qAcc += (m_samples[a][1] + m_samples[b][1]) * HBFIRFilterTraits<HBFilterOrder>::hbCoeffsF[i];
a++;
b--;
}
*x = iAcc * SDR_RX_SCALED;
*y = qAcc * SDR_RX_SCALED;
}
};
template<uint32_t HBFilterOrder, bool IQOrder>
IntHalfbandFilterEOF<HBFilterOrder, IQOrder>::IntHalfbandFilterEOF()
{
m_size = HBFIRFilterTraits<HBFilterOrder>::hbOrder/2;
for (int i = 0; i < 2*m_size; i++)
{
m_even[0][i] = 0.0f;
m_even[1][i] = 0.0f;
m_odd[0][i] = 0.0f;
m_odd[1][i] = 0.0f;
m_samples[i][0] = 0.0f;
m_samples[i][1] = 0.0f;
}
m_ptr = 0;
m_state = 0;
}
#endif /* SDRBASE_DSP_INTHALFBANDFILTEREOF_H_ */
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