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Single sideband.

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This commit is contained in:
Hexameron 2014-07-13 09:06:43 +01:00
parent 84d53dde4e
commit 30dab49869
7 changed files with 53 additions and 23 deletions
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2
include-gpl/dsp/fftfilt.h
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@ -48,7 +48,7 @@ public:
void create_filter(float f1, float f2);
void rtty_filter(float);
int run(const cmplx& in, cmplx **out);
int run(const cmplx& in, cmplx **out, bool usb);
};
#endif

39
plugins/channel/ssb/ssbdemod.cpp
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@ -36,15 +36,18 @@ SSBDemod::SSBDemod(AudioFifo* audioFifo, SampleSink* sampleSink) :
m_interpolator.create(16, m_sampleRate, 5000);
m_sampleDistanceRemain = (Real)m_sampleRate / 48000.0;
m_lowpass.create(21, 48000, 5000);
m_audioBuffer.resize(512);
m_audioBufferFill = 0;
m_undersampleCount = 0;
m_usb = true;
SSBFilter = new fftfilt(0.01, m_Bandwidth / 48000.0, ssbFftLen);
// if (!USBFilter) segfault;
}
SSBDemod::~SSBDemod()
{
if (SSBFilter) delete SSBFilter;
}
void SSBDemod::configure(MessageQueue* messageQueue, Real Bandwidth, Real volume)
@ -56,6 +59,8 @@ void SSBDemod::configure(MessageQueue* messageQueue, Real Bandwidth, Real volume
void SSBDemod::feed(SampleVector::const_iterator begin, SampleVector::const_iterator end, bool positiveOnly)
{
Complex ci;
cmplx *sideband;
int n_out;
bool consumed;
for(SampleVector::const_iterator it = begin; it < end; ++it) {
@ -63,10 +68,14 @@ void SSBDemod::feed(SampleVector::const_iterator begin, SampleVector::const_iter
c *= m_nco.nextIQ();
consumed = false;
// could squelch audio if RTL_SDR samplerate is not being fully decimated.
if(m_interpolator.interpolate(&m_sampleDistanceRemain, c, &consumed, &ci)) {
Real demod = ci.imag() + ci.real();
demod = 32768.0 * m_lowpass.filter(demod * 0.7);
n_out = SSBFilter->run(ci, &sideband, m_usb);
m_sampleDistanceRemain += (Real)m_sampleRate / 48000.0;
} else
n_out = 0;
for (int i = 0; i < n_out; i++) {
Real demod = (sideband[i].real() + sideband[i].imag()) * 0.7 * 32768.0;
// Downsample by 4x for audio display
if (!(m_undersampleCount++ & 3))
@ -80,7 +89,6 @@ void SSBDemod::feed(SampleVector::const_iterator begin, SampleVector::const_iter
uint res = m_audioFifo->write((const quint8*)&m_audioBuffer[0], m_audioBufferFill, 1);
m_audioBufferFill = 0;
}
m_sampleDistanceRemain += (Real)m_sampleRate / 48000.0;
}
}
if(m_audioFifo->write((const quint8*)&m_audioBuffer[0], m_audioBufferFill, 0) != m_audioBufferFill)
@ -102,6 +110,8 @@ void SSBDemod::stop()
bool SSBDemod::handleMessage(Message* cmd)
{
float band;
if(DSPSignalNotification::match(cmd)) {
DSPSignalNotification* signal = (DSPSignalNotification*)cmd;
qDebug("%d samples/sec, %lld Hz offset", signal->getSampleRate(), signal->getFrequencyOffset());
@ -113,9 +123,20 @@ bool SSBDemod::handleMessage(Message* cmd)
return true;
} else if(MsgConfigureSSBDemod::match(cmd)) {
MsgConfigureSSBDemod* cfg = (MsgConfigureSSBDemod*)cmd;
m_Bandwidth = cfg->getBandwidth();
m_interpolator.create(16, m_sampleRate, m_Bandwidth);
m_lowpass.create(21, 48000, cfg->getBandwidth());
band = cfg->getBandwidth();
if (band < 0) {
band = -band;
m_usb = false;
} else
m_usb = true;
if (band < 500.0f)
band = 500.0f;
m_Bandwidth = band;
m_interpolator.create(16, m_sampleRate, band * 2.0f);
SSBFilter->create_filter(0.3f / 48.0f, m_Bandwidth / 48000.0f);
m_volume = cfg->getVolume();
m_volume *= m_volume * 0.1;
cmd->completed();

7
plugins/channel/ssb/ssbdemod.h
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@ -22,10 +22,12 @@
#include "dsp/samplesink.h"
#include "dsp/nco.h"
#include "dsp/interpolator.h"
#include "dsp/lowpass.h"
#include "dsp/fftfilt.h"
#include "audio/audiofifo.h"
#include "util/message.h"
#define ssbFftLen 1024
class AudioFifo;
class SSBDemod : public SampleSink {
@ -75,11 +77,12 @@ private:
int m_undersampleCount;
int m_sampleRate;
int m_frequency;
bool m_usb;
NCO m_nco;
Interpolator m_interpolator;
Real m_sampleDistanceRemain;
Lowpass<Real> m_lowpass;
fftfilt* SSBFilter;
AudioVector m_audioBuffer;
uint m_audioBufferFill;

4
plugins/channel/ssb/ssbdemodgui.ui
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@ -42,10 +42,10 @@
<item row="0" column="1">
<widget class="QSlider" name="BW">
<property name="minimum">
<number>1</number>
<number>-8</number>
</property>
<property name="maximum">
<number>20</number>
<number>8</number>
</property>
<property name="pageStep">
<number>1</number>

4
plugins/channel/usb/usbdemod.cpp
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@ -68,7 +68,7 @@ void USBDemod::feed(SampleVector::const_iterator begin, SampleVector::const_iter
b += it->imag();
c = Complex(a / 65536.0, b / 65536.0);
n_out = USBFilter->run(c, &sideband);
n_out = USBFilter->run(c, &sideband, true);
for (int i = 0; i < n_out; i++) {
Real demod = (sideband[i].real() + sideband[i].imag()) * 0.7 * 32768.0;
@ -113,7 +113,7 @@ bool USBDemod::handleMessage(Message* cmd)
} else if(MsgConfigureUSBDemod::match(cmd)) {
MsgConfigureUSBDemod* cfg = (MsgConfigureUSBDemod*)cmd;
m_Bandwidth = cfg->getBandwidth();
USBFilter->create_filter(0.01, m_Bandwidth / 48000.0);
USBFilter->create_filter(0.3 / 48.0, m_Bandwidth / 48000.0);
m_volume = cfg->getVolume();
m_volume *= m_volume * 0.1;
cmd->completed();

1
plugins/channel/usb/usbdemod.h
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@ -22,7 +22,6 @@
#include "dsp/samplesink.h"
#include "dsp/nco.h"
#include "dsp/interpolator.h"
#include "dsp/lowpass.h"
#include "dsp/fftfilt.h"
#include "audio/audiofifo.h"
#include "util/message.h"

19
sdrbase/dsp/fftfilt.cxx
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@ -144,7 +144,7 @@ void fftfilt::create_filter(float f1, float f2)
}
// Filter with fast convolution (overlap-add algorithm).
int fftfilt::run(const cmplx & in, cmplx **out)
int fftfilt::run(const cmplx & in, cmplx **out, bool usb)
{
timedata[inptr++] = in;
@ -155,12 +155,19 @@ int fftfilt::run(const cmplx & in, cmplx **out)
memcpy(freqdata, timedata, flen * sizeof(cmplx));
fft->ComplexFFT(freqdata);
// Discard negative frequencies for ssb
for (int i = 0; i < flen2; i++) {
freqdata[i] *= filter[i];
freqdata[flen2 + i] = 0;
}
// Discard frequencies for ssb
if ( usb )
for (int i = 0; i < flen2; i++) {
freqdata[i] *= filter[i];
freqdata[flen2 + i] = 0;
}
else
for (int i = 0; i < flen2; i++) {
freqdata[i] = 0;
freqdata[flen2 + i] *= filter[flen2 + i];
}
// in-place FFT: freqdata overwritten with filtered timedata
fft->InverseComplexFFT(freqdata);
// overlap and add