MBEAudioInterpolatorFilter Class Reference

#include <filtermbe.h>

Collaboration diagram for MBEAudioInterpolatorFilter:

Public Member Functions
	MBEAudioInterpolatorFilter ()
	~MBEAudioInterpolatorFilter ()
void	useHP (bool useHP)
bool	usesHP () const
float	run (const float &sample)
float	runHP (const float &sample)
float	runLP (const float &sample)

Private Attributes
IIRFilter< float, 2 >	m_filterLP
IIRFilter< float, 2 >	m_filterHP
bool	m_useHP

Static Private Attributes
static const float	m_lpa [3] = {1.0, 1.392667E+00, -5.474446E-01}
static const float	m_lpb [3] = {3.869430E-02, 7.738860E-02, 3.869430E-02}
static const float	m_hpa [3] = {1.000000e+00, 1.667871e+00, -7.156964e-01}
static const float	m_hpb [3] = {8.459039e-01, -1.691760e+00, 8.459039e-01}

Detailed Description

Uses the generic IIR filter internally

Low pass / High pass:

This is a 2 pole Chebyshev (recursive) filter using coefficients found in table 20-1 (low pass) or table 20-2 (high pass) of http://www.analog.com/media/en/technical-documentation/dsp-book/dsp_book_Ch20.pdf

For low pass fc = 0.075 For high oass fc = 0.01

Convention taken here exchanges A and B coefficients as shown in this image: https://cdn.mikroe.com/ebooks/img/8/2016/02/digital-filter-design-chapter-03-image-2-9.gif So A applies to Y and B to X

At the interpolated sampling frequency of 48 kHz the -3 dB corner is at 48 * .075 = 3.6 kHz which is perfect for voice The high pass has a 3 dB corner of 48 * 0.01 = 0.48 kHz

Low pass:

b0 = 3.869430E-02 (a0 = 1.0) b1 = 7.738860E-02 a1 = 1.392667E+00 b2 = 3.869430E-02 a2 = -5.474446E-01

High pass:

b0 = 9.567529E-01 (a0 = 1.0) b1 = -1.913506E+00 a1 = 1.911437E+00 b2 = 9.567529E-01 a2 = -9.155749E-01

given x[n] is the new input sample and y[n] the returned output sample:

y[n] = b0*x[n] + b1*x[n] + b2*x[n] + a1*y[n-1] + a2*y[n-2]

This one works directly with floats

Definition at line 64 of file filtermbe.h.

Constructor & Destructor Documentation

MBEAudioInterpolatorFilter()

MBEAudioInterpolatorFilter::MBEAudioInterpolatorFilter

(

)

Definition at line 27 of file filtermbe.cpp.

                                                       :
        m_filterLP(m_lpa, m_lpb),
        m_filterHP(m_hpa, m_hpb),
        m_useHP(false)
{
}

~MBEAudioInterpolatorFilter()

MBEAudioInterpolatorFilter::~MBEAudioInterpolatorFilter

(

)

Definition at line 34 of file filtermbe.cpp.

{}

Member Function Documentation

run()

float MBEAudioInterpolatorFilter::run

(

const float &

sample

)

Definition at line 37 of file filtermbe.cpp.

References m_filterHP, m_filterLP, m_useHP, and IIRFilter< Type, Order >::run().

{
    return m_useHP ? m_filterLP.run(m_filterHP.run(sample)) : m_filterLP.run(sample);
}

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runHP()

float MBEAudioInterpolatorFilter::runHP

(

const float &

sample

)

Definition at line 42 of file filtermbe.cpp.

References m_filterHP, and IIRFilter< Type, Order >::run().

Referenced by AMBEWorker::noUpsample(), and AMBEWorker::upsample().

{
    return m_filterHP.run(sample);
}

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runLP()

float MBEAudioInterpolatorFilter::runLP

(

const float &

sample

)

Definition at line 47 of file filtermbe.cpp.

References m_filterLP, and IIRFilter< Type, Order >::run().

Referenced by AMBEWorker::upsample().

{
    return m_filterLP.run(sample);
}

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useHP()

void MBEAudioInterpolatorFilter::useHP ( bool  useHP )

inline

Definition at line 70 of file filtermbe.h.

References useHP().

Referenced by AMBEWorker::handleInputMessages(), and useHP().

{ m_useHP = useHP; }

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usesHP()

bool MBEAudioInterpolatorFilter::usesHP ( ) const

inline

Definition at line 71 of file filtermbe.h.

Referenced by AMBEWorker::noUpsample(), and AMBEWorker::upsample().

{ return m_useHP; }

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Member Data Documentation

m_filterHP

IIRFilter<float, 2> MBEAudioInterpolatorFilter::m_filterHP

private

Definition at line 78 of file filtermbe.h.

Referenced by run(), and runHP().

m_filterLP

IIRFilter<float, 2> MBEAudioInterpolatorFilter::m_filterLP

private

Definition at line 77 of file filtermbe.h.

Referenced by run(), and runLP().

m_hpa

const float MBEAudioInterpolatorFilter::m_hpa = {1.000000e+00, 1.667871e+00, -7.156964e-01}

staticprivate

Definition at line 84 of file filtermbe.h.

m_hpb

const float MBEAudioInterpolatorFilter::m_hpb = {8.459039e-01, -1.691760e+00, 8.459039e-01}

staticprivate

Definition at line 85 of file filtermbe.h.

m_lpa

const float MBEAudioInterpolatorFilter::m_lpa = {1.0, 1.392667E+00, -5.474446E-01}

staticprivate

Definition at line 81 of file filtermbe.h.

m_lpb

const float MBEAudioInterpolatorFilter::m_lpb = {3.869430E-02, 7.738860E-02, 3.869430E-02}

staticprivate

Definition at line 82 of file filtermbe.h.

m_useHP

bool MBEAudioInterpolatorFilter::m_useHP

private

Definition at line 79 of file filtermbe.h.

Referenced by run().

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

• sdrbase/dsp/filtermbe.h
• sdrbase/dsp/filtermbe.cpp