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Downsample filtering.

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This commit is contained in:
John Greb 2014-11-17 19:51:36 +00:00
parent ff312a52a3
commit dcc9f1917c
3 changed files with 56 additions and 35 deletions
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53
include-gpl/dsp/inthalfbandfilter.h
View File

@ -223,9 +223,23 @@ public:
} }
} }
void myDecimate(Sample* sample1, Sample* sample2)
{
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,
20,21,22,23,24,25,26,27,28,29,30,31,32,0,1,2} ;
m_samples[m_ptr][0] = sample1->real();
m_samples[m_ptr][1] = sample1->imag();
m_ptr = mod33[m_ptr + 2 - 1];
m_samples[m_ptr][0] = sample2->real();
m_samples[m_ptr][1] = sample2->imag();
doFIR(sample2);
m_ptr = mod33[m_ptr + 2 - 1];
}
protected: protected:
qint16 m_samples[HB_FILTERORDER + 1][2]; qint16 m_samples[HB_FILTERORDER + 1][2];
int m_ptr; qint16 m_ptr;
int m_state; int m_state;
void doFIR(Sample* sample) void doFIR(Sample* sample)
@ -267,15 +281,17 @@ protected:
0.317491986549921390015072120149852707982 * (1 << HB_SHIFT) 0.317491986549921390015072120149852707982 * (1 << HB_SHIFT)
}; };
#elif HB_FILTERORDER == 32 #elif HB_FILTERORDER == 32
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,
20,21,22,23,24,25,26,27,28,29,30,31,32,0,1,2} ;
static const qint32 COEFF[8] = { static const qint32 COEFF[8] = {
-0.015956912844043127236437484839370881673 * (1 << HB_SHIFT), (qint32)(-0.015956912844043127236437484839370881673 * (1 << HB_SHIFT)),
0.013023031678944928940522274274371739011 * (1 << HB_SHIFT), (qint32)( 0.013023031678944928940522274274371739011 * (1 << HB_SHIFT)),
-0.01866942273717486777684371190844103694 * (1 << HB_SHIFT), (qint32)(-0.01866942273717486777684371190844103694 * (1 << HB_SHIFT)),
0.026550887571157304190005987720724078827 * (1 << HB_SHIFT), (qint32)( 0.026550887571157304190005987720724078827 * (1 << HB_SHIFT)),
-0.038350314277854319344740474662103224546 * (1 << HB_SHIFT), (qint32)(-0.038350314277854319344740474662103224546 * (1 << HB_SHIFT)),
0.058429248652825838128421764849917963147 * (1 << HB_SHIFT), (qint32)( 0.058429248652825838128421764849917963147 * (1 << HB_SHIFT)),
-0.102889802028955756885153505209018476307 * (1 << HB_SHIFT), (qint32)(-0.102889802028955756885153505209018476307 * (1 << HB_SHIFT)),
0.317237706405931241260276465254719369113 * (1 << HB_SHIFT) (qint32)( 0.317237706405931241260276465254719369113 * (1 << HB_SHIFT))
}; };
#else #else
#error unsupported filter order #error unsupported filter order
@ -283,8 +299,8 @@ protected:
// init read-pointer // init read-pointer
int a = (m_ptr + 1) % (HB_FILTERORDER + 1); int a = mod33[m_ptr + 2 + 1]; // 0 + 1
int b = (m_ptr + (HB_FILTERORDER - 1)) % (HB_FILTERORDER + 1); int b = mod33[m_ptr + 2 - 2]; //-1 - 1
// go through samples in buffer // go through samples in buffer
qint32 iAcc = 0; qint32 iAcc = 0;
@ -297,17 +313,16 @@ protected:
qAcc += qTmp * COEFF[i]; qAcc += qTmp * COEFF[i];
// update read-pointer // update read-pointer
a = (a + 2) % (HB_FILTERORDER + 1); a = mod33[a + 2 + 2];
b = (b + (HB_FILTERORDER - 1)) % (HB_FILTERORDER + 1); b = mod33[b + 2 - 2];
} }
a = (a + HB_FILTERORDER) % (HB_FILTERORDER + 1); a = mod33[a + 2 - 1];
iAcc += m_samples[a][0] * (qint32)(0.5 * (1 << HB_SHIFT)); iAcc += ((qint32)m_samples[a][0] + 1) << (HB_SHIFT - 1);
qAcc += m_samples[a][1] * (qint32)(0.5 * (1 << HB_SHIFT)); qAcc += ((qint32)m_samples[a][1] + 1) << (HB_SHIFT - 1);
// done, save result sample->setReal(iAcc >> HB_SHIFT);
sample->setReal((iAcc + (qint32)(0.5 * (1 << HB_SHIFT))) >> HB_SHIFT); sample->setImag(qAcc >> HB_SHIFT);
sample->setImag((qAcc + (qint32)(0.5 * (1 << HB_SHIFT))) >> HB_SHIFT);
} }
}; };

34
plugins/samplesource/rtlsdr/rtlsdrthread.cpp
View File

@ -96,7 +96,7 @@ void RTLSDRThread::decimate4(SampleVector::iterator* it, const quint8* buf, qint
for (int pos = 0; pos < len - 7; pos += 8) { for (int pos = 0; pos < len - 7; pos += 8) {
xreal = buf[pos+0] - buf[pos+3] + buf[pos+7] - buf[pos+4]; xreal = buf[pos+0] - buf[pos+3] + buf[pos+7] - buf[pos+4];
yimag = buf[pos+1] - buf[pos+5] + buf[pos+2] - buf[pos+6]; yimag = buf[pos+1] - buf[pos+5] + buf[pos+2] - buf[pos+6];
Sample s( xreal << 4, yimag << 4 ); Sample s( xreal << 3, yimag << 3 );
**it = s; **it = s;
(*it)++; (*it)++;
} }
@ -122,25 +122,29 @@ void RTLSDRThread::decimate16(SampleVector::iterator* it, const quint8* buf, qin
{ {
// Offset tuning: 4x downsample and rotate, then // Offset tuning: 4x downsample and rotate, then
// downsample 4x more. [ rotate: 0, 1, -3, 2, -4, -5, 7, -6] // downsample 4x more. [ rotate: 0, 1, -3, 2, -4, -5, 7, -6]
qint16 xreal, yimag; qint16 xreal[4], yimag[4];
for (int step = 0; step < len - 31; step +=32) { bool b;
xreal = yimag = 0; for (int pos = 0; pos < len - 31; ) {
for (int pos = step; pos < step + 32; pos += 8) { for (int i = 0; i < 4; i++) {
xreal += buf[pos+0] - buf[pos+3] + buf[pos+7] - buf[pos+4]; xreal[i] = (buf[pos+0] - buf[pos+3] + buf[pos+7] - buf[pos+4]) << 4;
yimag += buf[pos+1] - buf[pos+5] + buf[pos+2] - buf[pos+6]; yimag[i] = (buf[pos+1] - buf[pos+5] + buf[pos+2] - buf[pos+6]) << 4;
pos += 8;
} }
Sample s( xreal << 3, yimag << 3 ); Sample s1( xreal[0], yimag[0] );
**it = s; Sample s2( xreal[1], yimag[1] );
Sample s3( xreal[2], yimag[2] );
Sample s4( xreal[3], yimag[3] );
m_decimator2.myDecimate(&s1, &s2);
m_decimator2.myDecimate(&s3, &s4);
m_decimator4.myDecimate(&s2, &s4);
**it = s4;
(*it)++; (*it)++;
} }
} }
/*
Decimate everything by 16x, except 288kHz
TODO : no offset tuning for direct sampling
*/
// Decimate everything by 16x, except 288kHz
void RTLSDRThread::callback(const quint8* buf, qint32 len) void RTLSDRThread::callback(const quint8* buf, qint32 len)
{ {
qint16 xreal, yimag, phase; qint16 xreal, yimag, phase;
@ -149,14 +153,12 @@ void RTLSDRThread::callback(const quint8* buf, qint32 len)
int mode = 0; int mode = 0;
if (m_samplerate < 800000) if (m_samplerate < 800000)
mode = 2; mode = 2;
// if (directsampling) mode++;
switch(mode) { switch(mode) {
case 0: case 0:
decimate16(&it, buf, len); decimate16(&it, buf, len);
break; break;
case 1: case 1:
// no_rotate16(&it, buf, len);
break; break;
case 2: case 2:
@ -164,7 +166,6 @@ void RTLSDRThread::callback(const quint8* buf, qint32 len)
break; break;
case 3: case 3:
// norotate4(&it, buf, len);
break; break;
default: default:
@ -183,3 +184,4 @@ void RTLSDRThread::callbackHelper(unsigned char* buf, uint32_t len, void* ctx)
RTLSDRThread* thread = (RTLSDRThread*)ctx; RTLSDRThread* thread = (RTLSDRThread*)ctx;
thread->callback(buf, len); thread->callback(buf, len);
} }

4
plugins/samplesource/rtlsdr/rtlsdrthread.h
View File

@ -23,6 +23,7 @@
#include <QWaitCondition> #include <QWaitCondition>
#include <rtl-sdr.h> #include <rtl-sdr.h>
#include "dsp/samplefifo.h" #include "dsp/samplefifo.h"
#include "dsp/inthalfbandfilter.h"
class RTLSDRThread : public QThread { class RTLSDRThread : public QThread {
Q_OBJECT Q_OBJECT
@ -46,6 +47,9 @@ private:
int m_samplerate; int m_samplerate;
IntHalfbandFilter m_decimator2;
IntHalfbandFilter m_decimator4;
void run(); void run();
void decimate2(SampleVector::iterator* it, const quint8* buf, qint32 len); void decimate2(SampleVector::iterator* it, const quint8* buf, qint32 len);
void decimate4(SampleVector::iterator* it, const quint8* buf, qint32 len); void decimate4(SampleVector::iterator* it, const quint8* buf, qint32 len);