signalsmith::envelopes::BoxStackFilter< Sample > Class Template Reference

#include <envelopes.h>

Detailed Description

template<typename Sample = double>
class signalsmith::envelopes::BoxStackFilter< Sample >

FIR filter made from a stack of BoxFilters.

This filter has a non-negative impulse (monotonic step response), making it useful for smoothing positive-only values. It provides an optimal set of box-lengths, chosen to minimise peaks in the stop-band:

Impulse responses for various stack sizes at length N=1000

Since the underlying box-averages must have integer width, the peaks are slightly higher for shorter lengths with higher numbers of layers:

Frequency responses for various stack sizes at length N=30

Static Methods
static std::vector< double >	optimalRatios (int layerCount)
	Returns an optimal set of length ratios (heuristic for larger depths) More...
static constexpr double	layersToBandwidth (int layers)
	Approximate (optimal) bandwidth for a given number of layers. More...
static constexpr double	layersToPeakDb (int layers)
	Approximate (optimal) peak in the stop-band. More...

Methods
	BoxStackFilter (int maxSize, int layers=4)
void	resize (int maxSize, int layerCount)
	Sets size using an optimal (heuristic at larger sizes) set of length ratios. More...
template<class List >
auto	resize (int maxSize, List ratios) -> decltype(void(std::begin(ratios)), void(std::end(ratios)))
	Sets the maximum (and current) impulse response length and explicit length ratios. More...
void	resize (int maxSize, std::initializer_list< double > ratios)
void	set (int size)
	Sets the impulse response length (does not reset if size ≤ maxSize) More...
void	reset (Sample fill=Sample())
	Resets the filter. More...
Sample	operator() (Sample v)

Method Details

layersToBandwidth()

template<typename Sample = double>

static constexpr double signalsmith::envelopes::BoxStackFilter< Sample >::layersToBandwidth ( int  layers )

inlinestaticconstexpr

Approximate (optimal) bandwidth for a given number of layers.

Approximate main lobe width (bandwidth)

layersToPeakDb()

template<typename Sample = double>

static constexpr double signalsmith::envelopes::BoxStackFilter< Sample >::layersToPeakDb ( int  layers )

inlinestaticconstexpr

Approximate (optimal) peak in the stop-band.

Heuristic stop-band peak

optimalRatios()

template<typename Sample = double>

static std::vector<double> signalsmith::envelopes::BoxStackFilter< Sample >::optimalRatios ( int  layerCount )

inlinestatic

Returns an optimal set of length ratios (heuristic for larger depths)

reset()

template<typename Sample = double>

void signalsmith::envelopes::BoxStackFilter< Sample >::reset ( Sample  fill = Sample() )

inline

Resets the filter.

resize() [1/2]

template<typename Sample = double>

void signalsmith::envelopes::BoxStackFilter< Sample >::resize ( int  maxSize, int  layerCount  )

inline

Sets size using an optimal (heuristic at larger sizes) set of length ratios.

resize() [2/2]

template<typename Sample = double>

template<class List >

auto signalsmith::envelopes::BoxStackFilter< Sample >::resize ( int  maxSize, List  ratios  ) -> decltype(void(std::begin(ratios)), void(std::end(ratios)))

inline

Sets the maximum (and current) impulse response length and explicit length ratios.

set()

template<typename Sample = double>

void signalsmith::envelopes::BoxStackFilter< Sample >::set ( int  size )

inline

Sets the impulse response length (does not reset if size ≤ maxSize)