MHAFilter Namespace Reference

Namespace for IIR and FIR filter classes. More...

Classes
class	complex_bandpass_t
	Complex bandpass filter. More...
class	gamma_flt_t
	Class for gammatone filter. More...
class	thirdoctave_analyzer_t
class	filter_t
	Generic IIR filter class. More...
class	diff_t
	Differentiator class (non-normalized) More...
class	o1_ar_filter_t
	First order attack-release lowpass filter. More...
class	o1flt_lowpass_t
	First order low pass filter. More...
class	o1flt_maxtrack_t
	First order maximum tracker. More...
class	o1flt_mintrack_t
	First order minimum tracker. More...
class	iir_filter_state_t
class	iir_filter_t
	IIR filter class wrapper for integration into parser structure. More...
class	adapt_filter_state_t
class	adapt_filter_param_t
class	adapt_filter_t
	Adaptive filter. More...
class	fftfilter_t
	FFT based FIR filter implementation. More...
class	fftfilterbank_t
	FFT based FIR filterbank implementation. More...
struct	transfer_function_t
	a structure containing a source channel number, a target channel number, and an impulse response. More...
struct	transfer_matrix_t
	A sparse matrix of transfer function partitionss. More...
class	partitioned_convolution_t
	A filter class for partitioned convolution. More...
class	smoothspec_t
	Smooth spectral gains, create a windowed impulse response. More...
class	resampling_filter_t
	Hann shaped low pass filter for resampling. More...
class	polyphase_resampling_t
	A class that performs polyphase resampling. More...
class	blockprocessing_polyphase_resampling_t
	A class that does polyphase resampling and takes into account block processing. More...
class	iir_ord1_real_t
	First order recursive filter. More...

Functions
template<typename T , typename std::enable_if< std::is_floating_point< T >::value, T >::type * = nullptr>
void	make_friendly_number (T &x)
void	o1_lp_coeffs (const mha_real_t tau, const mha_real_t fs, mha_real_t &c1, mha_real_t &c2)
	Set first order filter coefficients from time constant and sampling rate. More...
void	butter_stop_ord1 (double *A, double *B, double f1, double f2, double fs)
	Setup a first order butterworth band stop filter. More...
std::vector< float >	fir_lp (float f_pass_, float f_stop_, float fs_, unsigned order_)
	Setup a nth order fir low pass filter. More...
MHASignal::waveform_t *	spec2fir (const mha_spec_t *spec, const unsigned int fftlen, const MHAWindow::base_t &window, const bool minphase)
	Create a windowed impulse response/FIR filter coefficients from a spectrum. More...
unsigned	gcd (unsigned a, unsigned b)
	greatest common divisor More...
double	sinc (double x)
	sin(x)/x function, coping with x=0. More...
std::pair< unsigned, unsigned >	resampling_factors (float source_sampling_rate, float target_sampling_rate, float factor=1.0f)
	Computes rational resampling factor from two sampling rates. More...

Detailed Description

Namespace for IIR and FIR filter classes.

Function Documentation

make_friendly_number()

template<typename T , typename std::enable_if< std::is_floating_point< T >::value, T >::type * = nullptr>

void MHAFilter::make_friendly_number ( T &  x )

inline

o1_lp_coeffs()

void MHAFilter::o1_lp_coeffs	(	const mha_real_t	tau,
		const mha_real_t	fs,
		mha_real_t &	c1,
		mha_real_t &	c2
	)

Set first order filter coefficients from time constant and sampling rate.

Parameters

tau	Time constant
fs	Sampling rate

Return values

c1	Recursive filter coefficient
c2	Non-recursive filter coefficient

butter_stop_ord1()

void MHAFilter::butter_stop_ord1	(	double *	A,
		double *	B,
		double	f1,
		double	f2,
		double	fs
	)

Setup a first order butterworth band stop filter.

This function calculates the filter coefficients of a first order butterworth band stop filter.

Return values

A	recursive filter coefficients
B	non recursive filter coefficients

Parameters

f1	lower frequency
f2	upper frequency
fs	sample frequency

fir_lp()

std::vector< float > MHAFilter::fir_lp	(	float	f_pass_,
		float	f_stop_,
		float	fs_,
		unsigned	order_
	)

Setup a nth order fir low pass filter.

This function calculates the filter coefficients of a nth order fir low pass filter filter. Frequency arguments above the nyquist frequency are accepted but the spectral response is truncated at the nyquist frequency

Returns

vector containing filter coefficients

Precondition

f_pass_ must be smaller or equal to f_stop_.

Parameters

f_pass_	Upper passband frequency
f_stop-	Lower stopband frequency
fs_	sample frequency

spec2fir()

MHASignal::waveform_t * MHAFilter::spec2fir	(	const mha_spec_t *	spec,
		const unsigned int	fftlen,
		const MHAWindow::base_t &	window,
		const bool	minphase
	)

Create a windowed impulse response/FIR filter coefficients from a spectrum.

Parameters

spec	Input spectrum
fftlen	FFT length of spectrum
window	Window shape (with length, e.g. initialized with MHAWindow::hanning(54)).
minphase	Flag, true if original phase should be discarded and replaced by a minimal phase function.

gcd()

unsigned MHAFilter::gcd ( unsigned  a, unsigned  b  )

inline

greatest common divisor

sinc()

double MHAFilter::sinc

(

double

x

)

sin(x)/x function, coping with x=0.

This is the historical sinc function, not the normalized sinc function.

resampling_factors()

std::pair< unsigned, unsigned > MHAFilter::resampling_factors	(	float	source_sampling_rate,
		float	target_sampling_rate,
		float	factor = 1.0f
	)

Computes rational resampling factor from two sampling rates.

The function will fail if either sampling_rate * factor is not an integer

Parameters

source_sampling_rate	The original sampling rate
target_sampling_rate	The desired sampling rate
factor	A helper factor to use for non-integer sampling rates

Returns

a pair that contains first the upsampling factor and second the downsampling factor required for the specified resampling.

Exceptions

MHA_Error

if no rational resampling factor can be found.