r8b::CDSPFIRFilterCache Class Reference

FIR filter cache class. More...

#include <CDSPFIRFilter.h>

Inheritance diagram for r8b::CDSPFIRFilterCache:

Static Public Member Functions
static CDSPFIRFilter &	getLPFilter (const double ReqNormFreq, const double ReqTransBand, const double ReqAtten, const EDSPFilterPhaseResponse ReqPhase, const double ReqGain, const double *const AttenCorrs=NULL)
static int	getObjCount ()

Friends
class	CDSPFIRFilter

Detailed Description

FIR filter cache class.

Class that implements cache for calculated FIR filters. The required FIR filter should be obtained via the getLPFilter() static function.

Member Function Documentation

getLPFilter()

static CDSPFIRFilter & r8b::CDSPFIRFilterCache::getLPFilter ( const double  ReqNormFreq, const double  ReqTransBand, const double  ReqAtten, const EDSPFilterPhaseResponse  ReqPhase, const double  ReqGain, const double *const  AttenCorrs = NULL  )

static

Function calculates or returns reference to a previously calculated (cached) low-pass FIR filter. Note that the real transition band and attenuation achieved by the filter varies with the magnitude of the required attenuation, and are never 100% exact.

Parameters

ReqNormFreq	Required normalized frequency, in the range 0 to 1, inclusive. This is the point after which the stop-band spans.
ReqTransBand	Required transition band, in percent of the 0 to ReqNormFreq spectral bandwidth, in the range CDSPFIRFilter::getLPMinTransBand() to CDSPFIRFilter::getLPMaxTransBand(), inclusive. The transition band specifies the part of the spectrum between the -3 dB and ReqNormFreq points. The real resulting -3 dB point varies in the range from -3.00 to -3.05 dB, but is generally very close to -3 dB.
ReqAtten	Required stop-band attenuation in decibel, in the range CDSPFIRFilter::getLPMinAtten() to CDSPFIRFilter::getLPMaxAtten(), inclusive. Note that the actual stop-band attenuation of the resulting filter may be 0.40-4.46 dB higher.
ReqPhase	Required filter's phase response.
ReqGain	Required overall filter's gain (1.0 for unity gain).
AttenCorrs	Attentuation correction table, to pass to the filter generation function. For internal use.

See also

EDSPFilterPhaseResponse

Returns

A reference to a new or a previously calculated low-pass FIR filter object with the required characteristics. A reference count is incremented in the returned filter object which should be released after use via the CDSPFIRFilter::unref() function.

getObjCount()

static int r8b::CDSPFIRFilterCache::getObjCount ( )

static

Returns

The number of filters present in the cache now. This value can be monitored for debugging "forgotten" filters.