Overlap-and-save filter class. More...

#include <OSFilter.hxx>

Public Member Functions
	OSFilter (float low_cutoff, float low_pass_edge, float high_pass_edge, float high_cutoff, unsigned int filter_length, float filter_gain, float sample_rate, unsigned int inout_buffer_length, unsigned int suggested_transform_length=0)
	constructor More...

unsigned int	apply (std::complex< float > inbuf, std::complex< float > outbuf, float outgain=1.0)
	run the filter on a complex input stream More...

unsigned int	apply (float inbuf, float outbuf, float outgain=1.0, int instride=1, int outstride=1)
	run the filter on a real input stream More...

void	dump (std::ostream &os)
	dump the filter FFT to the output stream More...

std::pair< double, double >	getFilterEdges ()

Protected Member Functions
int	guessN ()
	pick a likely N - FFT length. More...

void	setupFFT ()

Protected Attributes
double	low_edge
	parameters that we keep to support display masks on the spectrogram More...

double	high_edge

unsigned int	M
	the input buffer length; More...

unsigned int	Q
	the filter length More...

unsigned int	N
	the total length of the transform N > (M + Q-1) More...

unsigned int	tail_index
	the beginning of the end. More...

std::complex< float > *	fft_input
	a copy of the input stream. More...

std::complex< float > *	fft_output
	the transformed input stream + overlap More...

std::complex< float > *	ifft_output
	the output stream + overlap discard More...

std::complex< float > *	filter_fft
	FFT image of the input filter. More...

fftwf_plan	forward_plan

fftwf_plan	backward_plan
	plans for fftw transform ops More...

Detailed Description

Overlap-and-save filter class.

Definition at line 50 of file OSFilter.hxx.

Constructor & Destructor Documentation

◆ OSFilter()

SoDa::OSFilter::OSFilter	(	float	low_cutoff,
		float	low_pass_edge,
		float	high_pass_edge,
		float	high_cutoff,
		unsigned int	filter_length,
		float	filter_gain,
		float	sample_rate,
		unsigned int	inout_buffer_length,
		unsigned int	suggested_transform_length = `0`
	)

constructor

constructor Build the filter from a filter spec for a bandpass filter

Parameters

low_cutoff	frequency below which the response is (ideally) zero
low_pass_edge	low end of the bandpass range
high_pass_edge	high end of the bandpass range
high_cutoff	frequency above which the response is (ideally) zero
filter_length	minimum number of effective filter taps
filter_gain	desired gain in passband
sample_rate	in samples/sec to allow normalization of the frequency specs
inout_buffer_length	used to set aside storage for overlap and save buffer
suggested_transform_length	a hint for optimizing FFT operations

Definition at line 123 of file OSFilter.cxx.

References filter_fft, guessN(), high_edge, low_edge, M, N, Q, setupFFT(), and tail_index.

Referenced by ipow().

Member Function Documentation

◆ apply() [1/2]

unsigned int SoDa::OSFilter::apply	(	std::complex< float > *	inbuf,
		std::complex< float > *	outbuf,
		float	outgain = `1.0`
	)

run the filter on a complex input stream

Parameters

inbuf	the input buffer I/Q samples (complex)
outbuf	the output buffer I/Q samples (complex)
outgain	normalized output gain

Returns: the length of the input buffer

Definition at line 334 of file OSFilter.cxx.

References backward_plan, fft_input, fft_output, filter_fft, forward_plan, ifft_output, M, N, Q, and tail_index.

Referenced by SoDa::BaseBandRX::demodulate(), SoDa::BaseBandRX::demodulateAM(), SoDa::BaseBandRX::demodulateNBFM(), SoDa::BaseBandRX::demodulateWBFM(), main(), and SoDa::BaseBandTX::run().

◆ apply() [2/2]

unsigned int SoDa::OSFilter::apply	(	float *	inbuf,
		float *	outbuf,
		float	outgain = `1.0`,
		int	instride = `1`,
		int	outstride = `1`
	)

run the filter on a real input stream

Parameters

inbuf	the input buffer samples
outbuf	the output buffer samples (this can overlap the inbuf vector)
outgain	normalized output gain
instride	index increment for the input buffer
outstride	index increment for the output buffer

Returns: the length of the input buffer

Definition at line 298 of file OSFilter.cxx.

References backward_plan, fft_input, fft_output, filter_fft, forward_plan, ifft_output, M, N, Q, and tail_index.

◆ dump()

void SoDa::OSFilter::dump ( std::ostream & os )

dump the filter FFT to the output stream

Parameters

os	an output stream.

Definition at line 364 of file OSFilter.cxx.

References filter_fft, and N.

Referenced by buildFilterMap().

◆ getFilterEdges()

std::pair<double, double> SoDa::OSFilter::getFilterEdges ( )

inline

Definition at line 117 of file OSFilter.hxx.

References high_edge, and low_edge.

Referenced by SoDa::BaseBandRX::repAFFilterShape().

◆ guessN()

int SoDa::OSFilter::guessN ( )

protected

pick a likely N - FFT length.

Definition at line 248 of file OSFilter.cxx.

References ipow(), M, and Q.

Referenced by ipow(), and OSFilter().

◆ setupFFT()

void SoDa::OSFilter::setupFFT ( )

protected

Definition at line 275 of file OSFilter.cxx.

References backward_plan, fft_input, fft_output, forward_plan, ifft_output, N, and Q.

Referenced by ipow(), and OSFilter().

Member Data Documentation

◆ backward_plan

fftwf_plan SoDa::OSFilter::backward_plan

protected

plans for fftw transform ops

Definition at line 150 of file OSFilter.hxx.

Referenced by apply(), and setupFFT().

◆ fft_input

std::complex<float>* SoDa::OSFilter::fft_input

protected

a copy of the input stream.

Definition at line 141 of file OSFilter.hxx.

Referenced by apply(), and setupFFT().

◆ fft_output

std::complex<float>* SoDa::OSFilter::fft_output

protected

the transformed input stream + overlap

Definition at line 142 of file OSFilter.hxx.

Referenced by apply(), and setupFFT().

◆ filter_fft

std::complex<float>* SoDa::OSFilter::filter_fft

protected

FFT image of the input filter.

Definition at line 146 of file OSFilter.hxx.

Referenced by apply(), dump(), ipow(), and OSFilter().

◆ forward_plan

fftwf_plan SoDa::OSFilter::forward_plan

protected

Definition at line 150 of file OSFilter.hxx.

Referenced by apply(), and setupFFT().

◆ high_edge

double SoDa::OSFilter::high_edge

protected

Definition at line 123 of file OSFilter.hxx.

Referenced by getFilterEdges(), and OSFilter().

◆ ifft_output

std::complex<float>* SoDa::OSFilter::ifft_output

protected

the output stream + overlap discard

Definition at line 143 of file OSFilter.hxx.

Referenced by apply(), and setupFFT().

◆ low_edge

double SoDa::OSFilter::low_edge

protected

parameters that we keep to support display masks on the spectrogram

Definition at line 123 of file OSFilter.hxx.

Referenced by getFilterEdges(), and OSFilter().

◆ M

unsigned int SoDa::OSFilter::M

protected

the input buffer length;

Definition at line 133 of file OSFilter.hxx.

Referenced by apply(), guessN(), ipow(), and OSFilter().

◆ N

unsigned int SoDa::OSFilter::N

protected

the total length of the transform N > (M + Q-1)

Definition at line 135 of file OSFilter.hxx.

Referenced by apply(), dump(), ipow(), OSFilter(), and setupFFT().

◆ Q

unsigned int SoDa::OSFilter::Q

protected

the filter length

Definition at line 134 of file OSFilter.hxx.

Referenced by apply(), guessN(), ipow(), OSFilter(), and setupFFT().

◆ tail_index

unsigned int SoDa::OSFilter::tail_index

protected

the beginning of the end.

Definition at line 138 of file OSFilter.hxx.

Referenced by apply(), ipow(), and OSFilter().

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

src/OSFilter.hxx
src/OSFilter.cxx

Public Member Functions

Protected Member Functions

Protected Attributes

Detailed Description

Constructor & Destructor Documentation

◆ OSFilter()

Member Function Documentation

◆ apply() [1/2]

◆ apply() [2/2]

◆ dump()

◆ getFilterEdges()

◆ guessN()

◆ setupFFT()

Member Data Documentation

◆ backward_plan

◆ fft_input

◆ fft_output

◆ filter_fft

◆ forward_plan

◆ high_edge

◆ ifft_output

◆ low_edge

◆ M

◆ N

◆ Q

◆ tail_index