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https://github.com/f4exb/sdrangel.git
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Downsample filtering.
This commit is contained in:
John Greb
parent
ff312a52a3
commit
dcc9f1917c
@ -223,9 +223,23 @@ public:
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}
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}
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void myDecimate(Sample* sample1, Sample* sample2)
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{
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static const qint16 mod33[38] = { 31,32,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,
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20,21,22,23,24,25,26,27,28,29,30,31,32,0,1,2} ;
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m_samples[m_ptr][0] = sample1->real();
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m_samples[m_ptr][1] = sample1->imag();
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m_ptr = mod33[m_ptr + 2 - 1];
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m_samples[m_ptr][0] = sample2->real();
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m_samples[m_ptr][1] = sample2->imag();
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doFIR(sample2);
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m_ptr = mod33[m_ptr + 2 - 1];
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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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qint16 m_ptr;
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int m_state;
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void doFIR(Sample* sample)
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@ -267,15 +281,17 @@ protected:
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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 qint16 mod33[38] = { 31,32,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,
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20,21,22,23,24,25,26,27,28,29,30,31,32,0,1,2} ;
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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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(qint32)(-0.015956912844043127236437484839370881673 * (1 << HB_SHIFT)),
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(qint32)( 0.013023031678944928940522274274371739011 * (1 << HB_SHIFT)),
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(qint32)(-0.01866942273717486777684371190844103694 * (1 << HB_SHIFT)),
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(qint32)( 0.026550887571157304190005987720724078827 * (1 << HB_SHIFT)),
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(qint32)(-0.038350314277854319344740474662103224546 * (1 << HB_SHIFT)),
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(qint32)( 0.058429248652825838128421764849917963147 * (1 << HB_SHIFT)),
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(qint32)(-0.102889802028955756885153505209018476307 * (1 << HB_SHIFT)),
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(qint32)( 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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@ -283,8 +299,8 @@ protected:
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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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int a = mod33[m_ptr + 2 + 1]; // 0 + 1
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int b = mod33[m_ptr + 2 - 2]; //-1 - 1
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// go through samples in buffer
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qint32 iAcc = 0;
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@ -297,17 +313,16 @@ protected:
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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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a = mod33[a + 2 + 2];
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b = mod33[b + 2 - 2];
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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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a = mod33[a + 2 - 1];
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iAcc += ((qint32)m_samples[a][0] + 1) << (HB_SHIFT - 1);
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qAcc += ((qint32)m_samples[a][1] + 1) << (HB_SHIFT - 1);
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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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sample->setReal(iAcc >> HB_SHIFT);
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sample->setImag(qAcc >> HB_SHIFT);
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}
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};
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@ -96,7 +96,7 @@ void RTLSDRThread::decimate4(SampleVector::iterator* it, const quint8* buf, qint
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for (int pos = 0; pos < len - 7; pos += 8) {
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xreal = buf[pos+0] - buf[pos+3] + buf[pos+7] - buf[pos+4];
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yimag = buf[pos+1] - buf[pos+5] + buf[pos+2] - buf[pos+6];
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Sample s( xreal << 4, yimag << 4 );
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Sample s( xreal << 3, yimag << 3 );
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**it = s;
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(*it)++;
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}
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@ -122,25 +122,29 @@ void RTLSDRThread::decimate16(SampleVector::iterator* it, const quint8* buf, qin
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{
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// Offset tuning: 4x downsample and rotate, then
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// downsample 4x more. [ rotate: 0, 1, -3, 2, -4, -5, 7, -6]
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qint16 xreal, yimag;
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for (int step = 0; step < len - 31; step +=32) {
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xreal = yimag = 0;
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for (int pos = step; pos < step + 32; pos += 8) {
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xreal += buf[pos+0] - buf[pos+3] + buf[pos+7] - buf[pos+4];
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yimag += buf[pos+1] - buf[pos+5] + buf[pos+2] - buf[pos+6];
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qint16 xreal[4], yimag[4];
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bool b;
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for (int pos = 0; pos < len - 31; ) {
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for (int i = 0; i < 4; i++) {
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xreal[i] = (buf[pos+0] - buf[pos+3] + buf[pos+7] - buf[pos+4]) << 4;
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yimag[i] = (buf[pos+1] - buf[pos+5] + buf[pos+2] - buf[pos+6]) << 4;
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pos += 8;
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}
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Sample s( xreal << 3, yimag << 3 );
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**it = s;
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Sample s1( xreal[0], yimag[0] );
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Sample s2( xreal[1], yimag[1] );
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Sample s3( xreal[2], yimag[2] );
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Sample s4( xreal[3], yimag[3] );
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m_decimator2.myDecimate(&s1, &s2);
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m_decimator2.myDecimate(&s3, &s4);
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m_decimator4.myDecimate(&s2, &s4);
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**it = s4;
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(*it)++;
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}
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}
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/*
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Decimate everything by 16x, except 288kHz
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TODO : no offset tuning for direct sampling
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*/
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// Decimate everything by 16x, except 288kHz
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void RTLSDRThread::callback(const quint8* buf, qint32 len)
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{
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qint16 xreal, yimag, phase;
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@ -149,14 +153,12 @@ void RTLSDRThread::callback(const quint8* buf, qint32 len)
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int mode = 0;
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if (m_samplerate < 800000)
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mode = 2;
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// if (directsampling) mode++;
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switch(mode) {
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case 0:
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decimate16(&it, buf, len);
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break;
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case 1:
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// no_rotate16(&it, buf, len);
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break;
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case 2:
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@ -164,7 +166,6 @@ void RTLSDRThread::callback(const quint8* buf, qint32 len)
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break;
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case 3:
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// norotate4(&it, buf, len);
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break;
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default:
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@ -183,3 +184,4 @@ void RTLSDRThread::callbackHelper(unsigned char* buf, uint32_t len, void* ctx)
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RTLSDRThread* thread = (RTLSDRThread*)ctx;
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thread->callback(buf, len);
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}
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@ -23,6 +23,7 @@
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#include <QWaitCondition>
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#include <rtl-sdr.h>
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#include "dsp/samplefifo.h"
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#include "dsp/inthalfbandfilter.h"
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class RTLSDRThread : public QThread {
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Q_OBJECT
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@ -46,6 +47,9 @@ private:
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int m_samplerate;
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IntHalfbandFilter m_decimator2;
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IntHalfbandFilter m_decimator4;
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void run();
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void decimate2(SampleVector::iterator* it, const quint8* buf, qint32 len);
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void decimate4(SampleVector::iterator* it, const quint8* buf, qint32 len);
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