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stk::Filter Class Referenceabstract

STK abstract filter class. More...

`#include <Filter.h>`

Inheritance diagram for stk::Filter:

## Public Member Functions
| Filter (void)
| Class constructor.
unsigned int | channelsIn (void) const
| Return the number of input channels for the class.
unsigned int | channelsOut (void) const
| Return the number of output channels for the class.
virtual void | clear (void)
| Clears all internal states of the filter.
void | setGain (StkFloat gain)
| Set the filter gain.
StkFloat | getGain (void) const
| Return the current filter gain.
StkFloat | phaseDelay (StkFloat frequency)
| Return the filter phase delay at the specified frequency.
const StkFrames & | lastFrame (void) const
| Return an StkFrames reference to the last output sample frame.
virtual StkFrames & | tick (StkFrames &frames, unsigned int channel=0)=0
| Take a channel of the StkFrames object as inputs to the filter and replace with corresponding outputs.
Public Member Functions inherited from stk::Stk
void | ignoreSampleRateChange (bool ignore=true)
| A function to enable/disable the automatic updating of class data when the STK sample rate changes.

## Additional Inherited Members
Static Public Member Functions inherited from stk::Stk
static StkFloat | sampleRate (void)
| Static method that returns the current STK sample rate.
static void | setSampleRate (StkFloat rate)
| Static method that sets the STK sample rate.
static void | clear_alertList ()
| Static method that frees memory from alertList_.
static std::string | rawwavePath (void)
| Static method that returns the current rawwave path.
static void | setRawwavePath (std::string path)
| Static method that sets the STK rawwave path.
static void | swap16 (unsigned char *ptr)
| Static method that byte-swaps a 16-bit data type.
static void | swap32 (unsigned char *ptr)
| Static method that byte-swaps a 32-bit data type.
static void | swap64 (unsigned char *ptr)
| Static method that byte-swaps a 64-bit data type.
static void | sleep (unsigned long milliseconds)
| Static cross-platform method to sleep for a number of milliseconds.
static bool | inRange (StkFloat value, StkFloat min, StkFloat max)
| Static method to check whether a value is within a specified range.
static void | handleError (const char *message, StkError::Type type)
| Static function for error reporting and handling using c-strings.
static void | handleError (std::string message, StkError::Type type)
| Static function for error reporting and handling using c++ strings.
static void | showWarnings (bool status)
| Toggle display of WARNING and STATUS messages.
static void | printErrors (bool status)
| Toggle display of error messages before throwing exceptions.
Static Public Attributes inherited from stk::Stk
static const StkFormat | STK_SINT8
static const StkFormat | STK_SINT16
static const StkFormat | STK_SINT24
static const StkFormat | STK_SINT32
static const StkFormat | STK_FLOAT32
static const StkFormat | STK_FLOAT64
Protected Member Functions inherited from stk::Stk
| Stk (void)
| Default constructor.
virtual | ~Stk (void)
| Class destructor.
virtual void | sampleRateChanged (StkFloat newRate, StkFloat oldRate)
| This function should be implemented in subclasses that depend on the sample rate.
void | addSampleRateAlert (Stk *ptr)
| Add class pointer to list for sample rate change notification.
void | removeSampleRateAlert (Stk *ptr)
| Remove class pointer from list for sample rate change notification.
void | handleError (StkError::Type type) const
| Internal function for error reporting that assumes message in `oStream_` variable.

## Detailed Description

STK abstract filter class.

This class provides limited common functionality for STK digital filter subclasses. It is general enough to support both monophonic and polyphonic input/output classes.

by Perry R. Cook and Gary P. Scavone, 1995–2023.

## Member Function Documentation

## ◆ setGain()

void stk::Filter::setGain | ( | StkFloat | gain | ) |
| inline

Set the filter gain.

The gain is applied at the filter input and does not affect the coefficient values. The default gain value is 1.0.

42{ gain_ = gain; };

## ◆ phaseDelay()

StkFloat stk::Filter::phaseDelay | ( | StkFloat | frequency | ) |
| inline

Return the filter phase delay at the specified frequency.

Note that the phase delay calculation accounts for the filter gain. The frequency value should be greater than 0.0 and less than or equal to one-half the sample rate.

94{
95 if ( frequency <= 0.0 || frequency > 0.5 * Stk::sampleRate() ) {
96 oStream_ << "Filter::phaseDelay: argument (" << frequency << ") is out of range!";
97 handleError( StkError::WARNING ); return 0.0;
98 }
99
100 StkFloat omegaT = 2 * PI * frequency / Stk::sampleRate();
101 StkFloat real = 0.0, imag = 0.0;
102 for ( unsigned int i=0; i<b_.size(); i++ ) {
103 real += b_[i] * std::cos( i * omegaT );
104 imag -= b_[i] * std::sin( i * omegaT );
105 }
106 real *= gain_;
107 imag *= gain_;
108
109 StkFloat phase = atan2( imag, real );
110
111 real = 0.0, imag = 0.0;
112 for ( unsigned int i=0; i<a_.size(); i++ ) {
113 real += a_[i] * std::cos( i * omegaT );
114 imag -= a_[i] * std::sin( i * omegaT );
115 }
116
117 phase -= std::atan2( imag, real );
118 phase = std::fmod( -phase, 2 * PI );
119 return phase / omegaT;
120}
stk::Stk::handleError
static void handleError(const char *message, StkError::Type type)
Static function for error reporting and handling using c-strings.
stk::Stk::sampleRate
static StkFloat sampleRate(void)
Static method that returns the current STK sample rate.
Definition Stk.h:148

## ◆ tick()

virtual StkFrames & stk::Filter::tick | ( | StkFrames & | frames,
|  | unsigned int | channel = `0`
| ) |  |
| pure virtual

Take a channel of the StkFrames object as inputs to the filter and replace with corresponding outputs.

The StkFrames argument reference is returned. The `channel` argument must be less than the number of channels in the StkFrames argument (the first channel is specified by 0). However, range checking is only performed if STK_DEBUG is defined during compilation, in which case an out-of-range value will trigger an StkError exception.

Implemented in stk::BiQuad, stk::Delay, stk::DelayA, stk::DelayL, stk::Fir, stk::FormSwep, stk::Iir, stk::OnePole, stk::OneZero, stk::PoleZero, stk::TapDelay, stk::TwoPole, and stk::TwoZero.

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

- Filter.h

The Synthesis ToolKit in C++ (STK)
©1995--2023 Perry R. Cook and Gary P. Scavone. All Rights Reserved.