mirror of
https://github.com/f4exb/sdrangel.git
synced 2024-08-19 20:46:33 -04:00
147 lines
5.3 KiB
C
147 lines
5.3 KiB
C
|
///////////////////////////////////////////////////////////////////////////////////
|
||
|
// Copyright (C) 2018 F4EXB //
|
||
|
// written by Edouard Griffiths //
|
||
|
// //
|
||
|
// Float half-band FIR based interpolator and decimator //
|
||
|
// This is the double buffer variant //
|
||
|
// //
|
||
|
// 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 //
|
||
|
// //
|
||
|
// 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 INCLUDE_INTHALFBANDFILTER_DBF_H
|
||
|
#define INCLUDE_INTHALFBANDFILTER_DBF_H
|
||
|
|
||
|
#include <stdint.h>
|
||
|
#include "dsp/dsptypes.h"
|
||
|
#include "dsp/hbfiltertraits.h"
|
||
|
#include "export.h"
|
||
|
|
||
|
template<typename AccuType, typename SampleType, uint32_t HBFilterOrder>
|
||
|
class SDRBASE_API IntHalfbandFilterDBF {
|
||
|
public:
|
||
|
IntHalfbandFilterDBF();
|
||
|
|
||
|
void myDecimate(AccuType x1, AccuType y1, AccuType *x2, AccuType *y2)
|
||
|
{
|
||
|
storeSample(x1, y1);
|
||
|
advancePointer();
|
||
|
|
||
|
storeSample(*x2, *y2);
|
||
|
doFIR(x2, y2);
|
||
|
advancePointer();
|
||
|
}
|
||
|
|
||
|
/** Optimized upsampler by 2 not calculating FIR with inserted null samples */
|
||
|
void myInterpolate(qint32 *x1, qint32 *y1, qint32 *x2, qint32 *y2)
|
||
|
{
|
||
|
// insert sample into ring double buffer
|
||
|
m_samplesDB[m_ptr][0] = *x1;
|
||
|
m_samplesDB[m_ptr][1] = *y1;
|
||
|
m_samplesDB[m_ptr + HBFIRFilterTraits<HBFilterOrder>::hbOrder/2][0] = *x1;
|
||
|
m_samplesDB[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_samplesDB[m_ptr + (HBFIRFilterTraits<HBFilterOrder>::hbOrder/4) - 1][0];
|
||
|
*y1 = m_samplesDB[m_ptr + (HBFIRFilterTraits<HBFilterOrder>::hbOrder/4) - 1][1];
|
||
|
|
||
|
// second sample calculated with the filter
|
||
|
doInterpolateFIR(x2, y2);
|
||
|
}
|
||
|
|
||
|
protected:
|
||
|
SampleType m_samplesDB[2*(HBFIRFilterTraits<HBFilterOrder>::hbOrder - 1)][2]; // double buffer technique
|
||
|
int m_ptr;
|
||
|
int m_size;
|
||
|
int m_state;
|
||
|
|
||
|
void storeSample(AccuType x, AccuType y)
|
||
|
{
|
||
|
m_samplesDB[m_ptr][0] = x;
|
||
|
m_samplesDB[m_ptr][1] = y;
|
||
|
m_samplesDB[m_ptr + m_size][0] = x;
|
||
|
m_samplesDB[m_ptr + m_size][1] = y;
|
||
|
}
|
||
|
|
||
|
void advancePointer()
|
||
|
{
|
||
|
m_ptr = m_ptr + 1 < m_size ? m_ptr + 1: 0;
|
||
|
}
|
||
|
|
||
|
void doFIR(AccuType *x, AccuType *y)
|
||
|
{
|
||
|
int a = m_ptr + m_size; // tip pointer
|
||
|
int b = m_ptr + 1; // tail pointer
|
||
|
AccuType iAcc = 0;
|
||
|
AccuType qAcc = 0;
|
||
|
|
||
|
for (int i = 0; i < HBFIRFilterTraits<HBFilterOrder>::hbOrder / 4; i++)
|
||
|
{
|
||
|
iAcc += (m_samplesDB[a][0] + m_samplesDB[b][0]) * HBFIRFilterTraits<HBFilterOrder>::hbCoeffsF[i];
|
||
|
qAcc += (m_samplesDB[a][1] + m_samplesDB[b][1]) * HBFIRFilterTraits<HBFilterOrder>::hbCoeffsF[i];
|
||
|
a -= 2;
|
||
|
b += 2;
|
||
|
}
|
||
|
|
||
|
iAcc += m_samplesDB[b-1][0] / 2.0;
|
||
|
qAcc += m_samplesDB[b-1][1] / 2.0;
|
||
|
|
||
|
*x = iAcc; // HB_SHIFT incorrect do not loose the gained bit
|
||
|
*y = qAcc;
|
||
|
}
|
||
|
|
||
|
void doInterpolateFIR(qint32 *x, qint32 *y)
|
||
|
{
|
||
|
qint16 a = m_ptr;
|
||
|
qint16 b = m_ptr + (HBFIRFilterTraits<HBFilterOrder>::hbOrder / 2) - 1;
|
||
|
|
||
|
// go through samples in buffer
|
||
|
AccuType iAcc = 0;
|
||
|
AccuType qAcc = 0;
|
||
|
|
||
|
for (int i = 0; i < HBFIRFilterTraits<HBFilterOrder>::hbOrder / 4; i++)
|
||
|
{
|
||
|
iAcc += (m_samplesDB[a][0] + m_samplesDB[b][0]) * HBFIRFilterTraits<HBFilterOrder>::hbCoeffsF[i];
|
||
|
qAcc += (m_samplesDB[a][1] + m_samplesDB[b][1]) * HBFIRFilterTraits<HBFilterOrder>::hbCoeffsF[i];
|
||
|
a++;
|
||
|
b--;
|
||
|
}
|
||
|
|
||
|
*x = iAcc * SDR_RX_SCALED;
|
||
|
*y = qAcc * SDR_RX_SCALED;
|
||
|
}
|
||
|
};
|
||
|
|
||
|
template<typename AccuType, typename SampleType, uint32_t HBFilterOrder>
|
||
|
IntHalfbandFilterDBF<AccuType, SampleType, HBFilterOrder>::IntHalfbandFilterDBF()
|
||
|
{
|
||
|
m_size = HBFIRFilterTraits<HBFilterOrder>::hbOrder - 1;
|
||
|
|
||
|
for (int i = 0; i < m_size; i++)
|
||
|
{
|
||
|
m_samplesDB[i][0] = 0;
|
||
|
m_samplesDB[i][1] = 0;
|
||
|
}
|
||
|
|
||
|
m_ptr = 0;
|
||
|
m_state = 0;
|
||
|
}
|
||
|
|
||
|
#endif // INCLUDE_INTHALFBANDFILTER_DBF_H
|