leansdr::cnr_fft< T > Struct Template Reference

#include <sdr.h>

Inheritance diagram for leansdr::cnr_fft< T >:

Collaboration diagram for leansdr::cnr_fft< T >:

Public Member Functions
	cnr_fft (scheduler *sch, pipebuf< complex< T >> &_in, pipebuf< float > &_out, float _bandwidth, int nfft=4096)
void	run ()
Public Member Functions inherited from leansdr::runnable
	runnable (scheduler *_sch, const char *name)
Public Member Functions inherited from leansdr::runnable_common
	runnable_common (const char *_name)
virtual	~runnable_common ()
virtual void	shutdown ()

Public Attributes
float	bandwidth
float *	freq_tap
float	tap_multiplier
int	decimation
float	kavg
Public Attributes inherited from leansdr::runnable_common
const char *	name

Private Member Functions
void	do_cnr ()
float	avgslots (int i0, int i1)

Private Attributes
pipereader< complex< T > >	in
pipewriter< float >	out
cfft_engine< T >	fft
T *	avgpower
int	phase

Additional Inherited Members
Protected Attributes inherited from leansdr::runnable
scheduler *	sch

Detailed Description

template<typename T>
struct leansdr::cnr_fft< T >

Definition at line 1708 of file sdr.h.

Constructor & Destructor Documentation

cnr_fft()

template<typename T>

leansdr::cnr_fft< T >::cnr_fft ( scheduler *  sch, pipebuf< complex< T >> &  _in, pipebuf< float > &  _out, float  _bandwidth, int  nfft = 4096  )

inline

Definition at line 1710 of file sdr.h.

                                               : runnable(sch, "cnr_fft"),
                                                 bandwidth(_bandwidth),
                                                 freq_tap(NULL),
                                                 tap_multiplier(1),
                                                 decimation(1048576),
                                                 kavg(0.1),
                                                 in(_in),
                                                 out(_out),
                                                 fft(nfft),
                                                 avgpower(NULL),
                                                 phase(0)
    {
        if (bandwidth > 0.25)
            fail("CNR estimator requires Fsampling > 4x Fsignal");
    }

Member Function Documentation

avgslots()

template<typename T>

float leansdr::cnr_fft< T >::avgslots ( int  i0, int  i1  )

inlineprivate

Definition at line 1794 of file sdr.h.

    { // i0 <= i1
        T s = 0;

        for (int i = i0; i <= i1; ++i)
            s += avgpower[i & (fft.n - 1)];

        return s / (i1 - i0 + 1);
    }

do_cnr()

template<typename T>

void leansdr::cnr_fft< T >::do_cnr ( )

inlineprivate

Definition at line 1751 of file sdr.h.

    {
        float center_freq = freq_tap ? *freq_tap * tap_multiplier : 0;
        int icf = floor(center_freq * fft.n + 0.5);
        complex<T> *data = new complex<T>[fft.n];
        memcpy(data, in.rd(), fft.n * sizeof(data[0]));
        fft.inplace(data, true);
        T *power = new T[fft.n];

        for (int i = 0; i < fft.n; ++i)
            power[i] = data[i].re * data[i].re + data[i].im * data[i].im;

        if (!avgpower)
        {
            // Initialize with first spectrum
            avgpower = new T[fft.n];
            memcpy(avgpower, power, fft.n * sizeof(avgpower[0]));
        }

        // Accumulate and low-pass filter
        for (int i = 0; i < fft.n; ++i)
            avgpower[i] = avgpower[i] * (1 - kavg) + power[i] * kavg;

        int bwslots = (bandwidth / 4) * fft.n;

        if (!bwslots)
        {
            delete[] power;
            delete[] data;
            return;
        }

        // Measure carrier+noise in center band
        float c2plusn2 = avgslots(icf - bwslots, icf + bwslots);
        // Measure noise left and right of roll-off zones
        float n2 = (avgslots(icf - bwslots * 4, icf - bwslots * 3) + avgslots(icf + bwslots * 3, icf + bwslots * 4)) / 2;
        float c2 = c2plusn2 - n2;
        float cnr = (c2 > 0 && n2 > 0) ? 10 * logf(c2 / n2) / logf(10) : -50;
        out.write(cnr);
        delete[] power;
        delete[] data;
    }

run()

template<typename T>

void leansdr::cnr_fft< T >::run ( )

inlinevirtual

Reimplemented from leansdr::runnable_common.

Definition at line 1734 of file sdr.h.

    {
        while (in.readable() >= fft.n && out.writable() >= 1)
        {
            phase += fft.n;

            if (phase >= decimation)
            {
                phase -= decimation;
                do_cnr();
            }

            in.read(fft.n);
        }
    }

Member Data Documentation

avgpower

template<typename T>

T* leansdr::cnr_fft< T >::avgpower

private

Definition at line 1807 of file sdr.h.

bandwidth

template<typename T>

float leansdr::cnr_fft< T >::bandwidth

Definition at line 1729 of file sdr.h.

decimation

template<typename T>

int leansdr::cnr_fft< T >::decimation

Definition at line 1731 of file sdr.h.

Referenced by DATVDemod::InitDATVFramework().

fft

template<typename T>

cfft_engine<T> leansdr::cnr_fft< T >::fft

private

Definition at line 1806 of file sdr.h.

freq_tap

template<typename T>

float* leansdr::cnr_fft< T >::freq_tap

Definition at line 1730 of file sdr.h.

in

template<typename T>

pipereader<complex<T> > leansdr::cnr_fft< T >::in

private

Definition at line 1804 of file sdr.h.

kavg

template<typename T>

float leansdr::cnr_fft< T >::kavg

Definition at line 1732 of file sdr.h.

out

template<typename T>

pipewriter<float> leansdr::cnr_fft< T >::out

private

Definition at line 1805 of file sdr.h.

phase

template<typename T>

int leansdr::cnr_fft< T >::phase

private

Definition at line 1808 of file sdr.h.

tap_multiplier

template<typename T>

float leansdr::cnr_fft< T >::tap_multiplier

Definition at line 1730 of file sdr.h.

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The documentation for this struct was generated from the following file:

• plugins/channelrx/demoddatv/leansdr/sdr.h