stk::DelayL Class Reference

STK linear interpolating delay line class. More...

#include <DelayL.h>

Inheritance diagram for stk::DelayL:

Public Member Functions
	DelayL (StkFloat delay=0.0, unsigned long maxDelay=4095)
	Default constructor creates a delay-line with maximum length of 4095 samples and zero delay.
	~DelayL ()
	Class destructor.
unsigned long	getMaximumDelay (void)
	Get the maximum delay-line length.
void	setMaximumDelay (unsigned long delay)
	Set the maximum delay-line length.
void	setDelay (StkFloat delay)
	Set the delay-line length.
StkFloat	getDelay (void) const
	Return the current delay-line length.
StkFloat	tapOut (unsigned long tapDelay)
	Return the value at tapDelay samples from the delay-line input.
void	tapIn (StkFloat value, unsigned long tapDelay)
	Set the value at tapDelay samples from the delay-line input.
StkFloat	lastOut (void) const
	Return the last computed output value.
StkFloat	nextOut (void)
	Return the value which will be output by the next call to tick().
StkFloat	tick (StkFloat input)
	Input one sample to the filter and return one output.
StkFrames &	tick (StkFrames &frames, unsigned int channel=0)
	Take a channel of the StkFrames object as inputs to the filter and replace with corresponding outputs.
StkFrames &	tick (StkFrames &iFrames, StkFrames &oFrames, unsigned int iChannel=0, unsigned int oChannel=0)
	Take a channel of the iFrames object as inputs to the filter and write outputs to the oFrames object.
Public Member Functions inherited from stk::Filter
	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 linear interpolating delay line class.

This class implements a fractional-length digital delay-line using first-order linear interpolation. If the delay and maximum length are not specified during instantiation, a fixed maximum length of 4095 and a delay of zero is set.

Linear interpolation is an efficient technique for achieving fractional delay lengths, though it does introduce high-frequency signal attenuation to varying degrees depending on the fractional delay setting. The use of higher order Lagrange interpolators can typically improve (minimize) this attenuation characteristic.

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

Constructor & Destructor Documentation

DelayL()

stk::DelayL::DelayL	(	StkFloat	delay = 0.0,
		unsigned long	maxDelay = 4095
	)

Default constructor creates a delay-line with maximum length of 4095 samples and zero delay.

An StkError will be thrown if the delay parameter is less than zero, the maximum delay parameter is less than one, or the delay parameter is greater than the maxDelay value.

Member Function Documentation

setMaximumDelay()

void stk::DelayL::setMaximumDelay

(

unsigned long

delay

)

Set the maximum delay-line length.

This method should generally only be used during initial setup of the delay line. If it is used between calls to the tick() function, without a call to clear(), a signal discontinuity will likely occur. If the current maximum length is greater than the new length, no memory allocation change is made.

setDelay()

void stk::DelayL::setDelay ( StkFloat  delay )

inline

Set the delay-line length.

The valid range for delay is from 0 to the maximum delay-line length.

{
  if ( delay + 1 > inputs_.size() ) { // The value is too big.
    oStream_ << "DelayL::setDelay: argument (" << delay << ") greater than  maximum!";
    handleError( StkError::WARNING ); return;
  }
 
  if (delay < 0 ) {
    oStream_ << "DelayL::setDelay: argument (" << delay << ") less than zero!";
    handleError( StkError::WARNING ); return;
  }
 
  StkFloat outPointer = inPoint_ - delay;  // read chases write
  delay_ = delay;
 
  while ( outPointer < 0 )
    outPointer += inputs_.size(); // modulo maximum length
 
  outPoint_ = (long) outPointer;   // integer part
 
  alpha_ = outPointer - outPoint_; // fractional part
  omAlpha_ = (StkFloat) 1.0 - alpha_;
 
  if ( outPoint_ == inputs_.size() ) outPoint_ = 0;
  doNextOut_ = true;
}

tapOut()

StkFloat stk::DelayL::tapOut

(

unsigned long

tapDelay

)

Return the value at tapDelay samples from the delay-line input.

The tap point is determined modulo the delay-line length and is relative to the last input value (i.e., a tapDelay of zero returns the last input value).

nextOut()

StkFloat stk::DelayL::nextOut ( void  )

inline

Return the value which will be output by the next call to tick().

This method is valid only for delay settings greater than zero!

{
  if ( doNextOut_ ) {
    // First 1/2 of interpolation
    nextOutput_ = inputs_[outPoint_] * omAlpha_;
    // Second 1/2 of interpolation
    if (outPoint_+1 < inputs_.size())
      nextOutput_ += inputs_[outPoint_+1] * alpha_;
    else
      nextOutput_ += inputs_[0] * alpha_;
    doNextOut_ = false;
  }
 
  return nextOutput_;
}

tick() [1/2]

StkFrames & stk::DelayL::tick ( StkFrames &  frames, unsigned int  channel = 0  )

inlinevirtual

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.

Implements stk::Filter.

{
#if defined(_STK_DEBUG_)
  if ( channel >= frames.channels() ) {
    oStream_ << "DelayL::tick(): channel and StkFrames arguments are incompatible!";
    handleError( StkError::FUNCTION_ARGUMENT );
  }
#endif
 
  StkFloat *samples = &frames[channel];
  unsigned int hop = frames.channels();
  for ( unsigned int i=0; i<frames.frames(); i++, samples += hop ) {
    inputs_[inPoint_++] = *samples * gain_;
    if ( inPoint_ == inputs_.size() ) inPoint_ = 0;
    *samples = nextOut();
    doNextOut_ = true;
    if ( ++outPoint_ == inputs_.size() ) outPoint_ = 0;
  }
 
  lastFrame_[0] = *(samples-hop);
  return frames;
}

tick() [2/2]

StkFrames & stk::DelayL::tick ( StkFrames &  iFrames, StkFrames &  oFrames, unsigned int  iChannel = 0, unsigned int  oChannel = 0  )

inline

Take a channel of the iFrames object as inputs to the filter and write outputs to the oFrames object.

The iFrames object reference is returned. Each channel argument must be less than the number of channels in the corresponding 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.

{
#if defined(_STK_DEBUG_)
  if ( iChannel >= iFrames.channels() || oChannel >= oFrames.channels() ) {
    oStream_ << "DelayL::tick(): channel and StkFrames arguments are incompatible!";
    handleError( StkError::FUNCTION_ARGUMENT );
  }
#endif
 
  StkFloat *iSamples = &iFrames[iChannel];
  StkFloat *oSamples = &oFrames[oChannel];
  unsigned int iHop = iFrames.channels(), oHop = oFrames.channels();
  for ( unsigned int i=0; i<iFrames.frames(); i++, iSamples += iHop, oSamples += oHop ) {
    inputs_[inPoint_++] = *iSamples * gain_;
    if ( inPoint_ == inputs_.size() ) inPoint_ = 0;
    *oSamples = nextOut();
    doNextOut_ = true;
    if ( ++outPoint_ == inputs_.size() ) outPoint_ = 0;
  }
 
  lastFrame_[0] = *(oSamples-oHop);
  return iFrames;
}

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

• DelayL.h