Interpolator Class Reference

#include <interpolator.h>

Public Member Functions
	Interpolator ()
	~Interpolator ()
void	create (int phaseSteps, double sampleRate, double cutoff, double nbTapsPerPhase=4.5)
void	free ()
bool	decimate (Real *distance, const Complex &next, Complex *result)
bool	interpolate (Real *distance, const Complex &next, Complex *result)
bool	resample (Real *distance, const Complex &next, bool *consumed, Complex *result)

Private Member Functions
void	createTaps (int nTaps, double sampleRate, double cutoff, std::vector< Real > *taps)
void	advanceFilter (const Complex &next)
void	advanceFilter ()
void	doInterpolate (int phase, Complex *result)

Static Private Member Functions
static void	createPolyphaseLowPass (std::vector< Real > &taps, int phaseSteps, double gain, double sampleRateHz, double cutoffFreqHz, double transitionWidthHz, double oobAttenuationdB)
static void	createPolyphaseLowPass (std::vector< Real > &taps, int phaseSteps, double gain, double sampleRateHz, double cutoffFreqHz, double nbTapsPerPhase)

Private Attributes
float *	m_taps
float *	m_alignedTaps
float *	m_taps2
float *	m_alignedTaps2
std::vector< Complex >	m_samples
int	m_ptr
int	m_phaseSteps
int	m_nTaps

Detailed Description

Definition at line 28 of file interpolator.h.

Constructor & Destructor Documentation

Interpolator()

Interpolator::Interpolator

(

)

Definition at line 70 of file interpolator.cpp.

                           :
    m_taps(0),
    m_alignedTaps(0),
    m_taps2(0),
    m_alignedTaps2(0),
    m_ptr(0),
    m_phaseSteps(1),
    m_nTaps(1)
{
}

~Interpolator()

Interpolator::~Interpolator

(

)

Definition at line 81 of file interpolator.cpp.

References free().

{
    free();
}

Here is the call graph for this function:

Member Function Documentation

advanceFilter() [1/2]

void Interpolator::advanceFilter ( const Complex &  next )

inlineprivate

Definition at line 121 of file interpolator.h.

    {
        m_ptr--;

        if (m_ptr < 0) {
            m_ptr = m_nTaps - 1;
        }

        m_samples[m_ptr] = next;
    }

advanceFilter() [2/2]

void Interpolator::advanceFilter ( )

inlineprivate

Definition at line 132 of file interpolator.h.

    {
        m_ptr--;

        if (m_ptr < 0) {
            m_ptr = m_nTaps - 1;
        }

        m_samples[m_ptr].real(0.0);
        m_samples[m_ptr].imag(0.0);
    }

create()

void Interpolator::create	(	int	phaseSteps,
		double	sampleRate,
		double	cutoff,
		double	nbTapsPerPhase = 4.5
	)

Definition at line 86 of file interpolator.cpp.

References createPolyphaseLowPass(), free(), i, m_alignedTaps, m_alignedTaps2, m_nTaps, m_phaseSteps, m_ptr, m_samples, m_taps, and m_taps2.

Referenced by WFMDemod::applyAudioSampleRate(), AMDemod::applyAudioSampleRate(), NFMDemod::applyAudioSampleRate(), BFMDemod::applyAudioSampleRate(), WFMMod::applyAudioSampleRate(), AMMod::applyAudioSampleRate(), NFMMod::applyAudioSampleRate(), SSBDemod::applyAudioSampleRate(), SSBMod::applyAudioSampleRate(), ChannelAnalyzer::applyChannelSettings(), WFMDemod::applyChannelSettings(), AMDemod::applyChannelSettings(), UDPSink::applyChannelSettings(), UDPSource::applyChannelSettings(), NFMDemod::applyChannelSettings(), DSDDemod::applyChannelSettings(), BFMDemod::applyChannelSettings(), WFMMod::applyChannelSettings(), AMMod::applyChannelSettings(), NFMMod::applyChannelSettings(), SSBDemod::applyChannelSettings(), FreeDVMod::applyChannelSettings(), SSBMod::applyChannelSettings(), FreeDVDemod::applyChannelSettings(), ATVMod::applyChannelSettings(), AMMod::applyFeedbackAudioSampleRate(), NFMMod::applyFeedbackAudioSampleRate(), SSBMod::applyFeedbackAudioSampleRate(), FreeDVMod::applyFreeDVMode(), FreeDVDemod::applyFreeDVMode(), ChannelAnalyzer::applySettings(), WFMDemod::applySettings(), AMDemod::applySettings(), UDPSink::applySettings(), UDPSource::applySettings(), NFMDemod::applySettings(), DSDDemod::applySettings(), BFMDemod::applySettings(), WFMMod::applySettings(), AMMod::applySettings(), NFMMod::applySettings(), SSBDemod::applySettings(), SSBMod::applySettings(), ATVDemod::applySettings(), ATVMod::applySettings(), LoRaDemod::handleMessage(), LoRaDemod::LoRaDemod(), FreqTracker::setInterpolator(), and UDPSink::UDPSink().

{
    free();

    std::vector<Real> taps;

    createPolyphaseLowPass(
        taps,
        phaseSteps, // number of polyphases
        1.0, // gain
        phaseSteps * sampleRate, // sampling frequency
        cutoff, // hz beginning of transition band
        nbTapsPerPhase);

    // init state
    m_ptr = 0;
    m_nTaps = taps.size() / phaseSteps;
    m_phaseSteps = phaseSteps;
    m_samples.resize(m_nTaps + 2);

    for (int i = 0; i < m_nTaps + 2; i++) {
        m_samples[i] = 0;
    }

    // reorder into polyphase
    std::vector<Real> polyphase(taps.size());

    for (int phase = 0; phase < phaseSteps; phase++)
    {
        for (int i = 0; i < m_nTaps; i++) {
            polyphase[phase * m_nTaps + i] = taps[i * phaseSteps + phase];
        }
    }

    // normalize phase filters
    for (int phase = 0; phase < phaseSteps; phase++)
    {
        Real sum = 0;

        for (int i = phase * m_nTaps; i < phase * m_nTaps + m_nTaps; i++) {
            sum += polyphase[i];
        }

        for (int i = phase * m_nTaps; i < phase * m_nTaps + m_nTaps; i++) {
            polyphase[i] /= sum;
        }
    }

    // move taps around to match sse storage requirements
    m_taps = new float[2 * taps.size() + 8];

    for (uint i = 0; i < 2 * taps.size() + 8; ++i) {
        m_taps[i] = 0;
    }

    m_alignedTaps = (float*)((((quint64)m_taps) + 15) & ~15);

    for (uint i = 0; i < taps.size(); ++i)
    {
        m_alignedTaps[2 * i + 0] = polyphase[i];
        m_alignedTaps[2 * i + 1] = polyphase[i];
    }

    m_taps2 = new float[2 * taps.size() + 8];

    for (uint i = 0; i < 2 * taps.size() + 8; ++i) {
        m_taps2[i] = 0;
    }

    m_alignedTaps2 = (float*)((((quint64)m_taps2) + 15) & ~15);

    for (uint i = 1; i < taps.size(); ++i)
    {
        m_alignedTaps2[2 * (i - 1) + 0] = polyphase[i];
        m_alignedTaps2[2 * (i - 1) + 1] = polyphase[i];
    }
}

Here is the call graph for this function:

Here is the caller graph for this function:

createPolyphaseLowPass() [1/2]

void Interpolator::createPolyphaseLowPass ( std::vector< Real > &  taps, int  phaseSteps, double  gain, double  sampleRateHz, double  cutoffFreqHz, double  transitionWidthHz, double  oobAttenuationdB  )

staticprivate

Definition at line 7 of file interpolator.cpp.

Referenced by create().

{
    double nbTapsPerPhase = (oobAttenuationdB * sampleRateHz) / (22.0 * transitionWidthHz * phaseSteps);
    return createPolyphaseLowPass(taps, phaseSteps, gain, sampleRateHz, cutoffFreqHz, nbTapsPerPhase);
}

Here is the caller graph for this function:

createPolyphaseLowPass() [2/2]

void Interpolator::createPolyphaseLowPass ( std::vector< Real > &  taps, int  phaseSteps, double  gain, double  sampleRateHz, double  cutoffFreqHz, double  nbTapsPerPhase  )

staticprivate

Definition at line 21 of file interpolator.cpp.

References cos(), i, M_PI, leansdr::max(), and sin().

{
    int ntaps = (int)(nbTapsPerPhase * phaseSteps);
    qDebug("Interpolator::createPolyphaseLowPass: ntaps: %d", ntaps);

    if ((ntaps % 2) != 0) {
        ntaps++;
    }

    ntaps *= phaseSteps;

    taps.resize(ntaps);
    std::vector<float> window(ntaps);

    for (int n = 0; n < ntaps; n++) {
        window[n] = 0.54 - 0.46 * cos ((2 * M_PI * n) / (ntaps - 1));
    }

    int M = (ntaps - 1) / 2;
    double fwT0 = 2 * M_PI * cutoffFreqHz / sampleRateHz;

    for (int n = -M; n <= M; n++)
    {
        if (n == 0) {
            taps[n + M] = fwT0 / M_PI * window[n + M];
        } else {
            taps[n + M] =  sin (n * fwT0) / (n * M_PI) * window[n + M];
        }
    }

    double max = taps[0 + M];

    for (int n = 1; n <= M; n++) {
        max += 2.0 * taps[n + M];
    }

    gain /= max;

    for (int i = 0; i < ntaps; i++) {
        taps[i] *= gain;
    }
}

Here is the call graph for this function:

createTaps()

void Interpolator::createTaps ( int  nTaps, double  sampleRate, double  cutoff, std::vector< Real > *  taps  )

private

decimate()

bool Interpolator::decimate ( Real *  distance, const Complex &  next, Complex *  result  )

inline

Definition at line 38 of file interpolator.h.

References floor().

Referenced by LoRaDemod::feed(), WFMDemod::feed(), AMDemod::feed(), DSDDemod::feed(), UDPSink::feed(), SSBDemod::feed(), NFMDemod::feed(), FreqTracker::feed(), BFMDemod::feed(), FreeDVDemod::feed(), ChannelAnalyzer::feed(), ATVDemod::feed(), UDPSource::pull(), AMMod::pull(), NFMMod::pull(), SSBMod::pull(), FreeDVMod::pull(), ATVMod::pull(), AMMod::pushFeedback(), NFMMod::pushFeedback(), and SSBMod::pushFeedback().

    {
        advanceFilter(next);
        *distance -= 1.0;

        if (*distance >= 1.0) {
            return false;
        }

        doInterpolate((int) floor(*distance * (Real)m_phaseSteps), result);

        return true;
    }

Here is the call graph for this function:

Here is the caller graph for this function:

doInterpolate()

void Interpolator::doInterpolate ( int  phase, Complex *  result  )

inlineprivate

Definition at line 144 of file interpolator.h.

References i.

    {
        if (phase < 0) {
            phase = 0;
        }
#if USE_SSE2
        // beware of the ringbuffer
        if(m_ptr == 0) {
            // only one straight block
            const float* src = (const float*)&m_samples[0];
            const __m128* filter = (const __m128*)&m_alignedTaps[phase * m_nTaps * 2];
            __m128 sum = _mm_setzero_ps();
            int todo = m_nTaps / 2;

            for(int i = 0; i < todo; i++) {
                sum = _mm_add_ps(sum, _mm_mul_ps(_mm_loadu_ps(src), *filter));
                src += 4;
                filter += 1;
            }

            // add upper half to lower half and store
            _mm_storel_pi((__m64*)result, _mm_add_ps(sum, _mm_shuffle_ps(sum, _mm_setzero_ps(), _MM_SHUFFLE(1, 0, 3, 2))));
        } else {
            // two blocks
            const float* src = (const float*)&m_samples[m_ptr];
            const __m128* filter = (const __m128*)&m_alignedTaps[phase * m_nTaps * 2];
            __m128 sum = _mm_setzero_ps();

            // first block
            int block = m_nTaps - m_ptr;
            int todo = block / 2;
            if(block & 1)
                todo++;
            for(int i = 0; i < todo; i++) {
                sum = _mm_add_ps(sum, _mm_mul_ps(_mm_loadu_ps(src), *filter));
                src += 4;
                filter += 1;
            }
            if(block & 1) {
                // one sample beyond the end -> switch coefficient table
                filter = (const __m128*)&m_alignedTaps2[phase * m_nTaps * 2 + todo * 4 - 4];
            }
            // second block
            src = (const float*)&m_samples[0];
            block = m_ptr;
            todo = block / 2;
            for(int i = 0; i < todo; i++) {
                sum = _mm_add_ps(sum, _mm_mul_ps(_mm_loadu_ps(src), *filter));
                src += 4;
                filter += 1;
            }
            if(block & 1) {
                // one sample remaining
                sum = _mm_add_ps(sum, _mm_mul_ps(_mm_loadl_pi(_mm_setzero_ps(), (const __m64*)src), filter[0]));
            }

            // add upper half to lower half and store
            _mm_storel_pi((__m64*)result, _mm_add_ps(sum, _mm_shuffle_ps(sum, _mm_setzero_ps(), _MM_SHUFFLE(1, 0, 3, 2))));
        }
#else
        int sample = m_ptr;
        const Real* coeff = &m_alignedTaps[phase * m_nTaps * 2];
        Real rAcc = 0;
        Real iAcc = 0;

        for (int i = 0; i < m_nTaps; i++) {
            rAcc += *coeff * m_samples[sample].real();
            iAcc += *coeff * m_samples[sample].imag();
            sample = (sample + 1) % m_nTaps;
            coeff += 2;
        }

        *result = Complex(rAcc, iAcc);
#endif

    }

free()

void Interpolator::free

(

)

Definition at line 164 of file interpolator.cpp.

References m_alignedTaps, m_alignedTaps2, m_taps, and m_taps2.

Referenced by create(), and ~Interpolator().

{
    if (m_taps != NULL)
    {
        delete[] m_taps;
        m_taps = NULL;
        m_alignedTaps = NULL;
        delete[] m_taps2;
        m_taps2 = NULL;
        m_alignedTaps2 = NULL;
    }
}

Here is the caller graph for this function:

interpolate()

bool Interpolator::interpolate ( Real *  distance, const Complex &  next, Complex *  result  )

inline

Definition at line 53 of file interpolator.h.

References floor().

Referenced by AMDemod::feed(), SSBDemod::feed(), NFMDemod::feed(), FreqTracker::feed(), FreeDVDemod::feed(), UDPSource::pull(), AMMod::pull(), WFMMod::pull(), NFMMod::pull(), SSBMod::pull(), FreeDVMod::pull(), ATVMod::pull(), AMMod::pushFeedback(), NFMMod::pushFeedback(), and SSBMod::pushFeedback().

    {
        bool consumed = false;

        if (*distance >= 1.0)
        {
            advanceFilter(next);
            *distance -= 1.0;
            consumed = true;
        }

        doInterpolate((int)floor(*distance * (Real)m_phaseSteps), result);

        return consumed;
    }

Here is the call graph for this function:

Here is the caller graph for this function:

resample()

bool Interpolator::resample ( Real *  distance, const Complex &  next, bool *  consumed, Complex *  result  )

inline

Definition at line 71 of file interpolator.h.

References floor().

    {
        while (*distance >= 1.0)
        {
            if (!(*consumed))
            {
                advanceFilter(next);
                *distance -= 1.0;
                *consumed = true;
            }
            else
            {
                return false;
            }
        }

        doInterpolate((int)floor(*distance * (Real)m_phaseSteps), result);

        return true;
    }

Here is the call graph for this function:

Member Data Documentation

m_alignedTaps

float* Interpolator::m_alignedTaps

private

Definition at line 94 of file interpolator.h.

Referenced by create(), and free().

m_alignedTaps2

float* Interpolator::m_alignedTaps2

private

Definition at line 96 of file interpolator.h.

Referenced by create(), and free().

m_nTaps

int Interpolator::m_nTaps

private

Definition at line 100 of file interpolator.h.

Referenced by create().

m_phaseSteps

int Interpolator::m_phaseSteps

private

Definition at line 99 of file interpolator.h.

Referenced by create().

m_ptr

int Interpolator::m_ptr

private

Definition at line 98 of file interpolator.h.

Referenced by create().

m_samples

std::vector<Complex> Interpolator::m_samples

private

Definition at line 97 of file interpolator.h.

Referenced by create().

m_taps

float* Interpolator::m_taps

private

Definition at line 93 of file interpolator.h.

Referenced by create(), and free().

m_taps2

float* Interpolator::m_taps2

private

Definition at line 95 of file interpolator.h.

Referenced by create(), and free().

---

The documentation for this class was generated from the following files:

• sdrbase/dsp/interpolator.h
• sdrbase/dsp/interpolator.cpp