stk::BlitSquare Class Reference

STK band-limited square wave class. More...

#include <BlitSquare.h>

Inheritance diagram for stk::BlitSquare:

Public Member Functions
	BlitSquare (StkFloat frequency=220.0)
	Default constructor that initializes BLIT frequency to 220 Hz.
	~BlitSquare ()
	Class destructor.
void	reset ()
	Resets the oscillator state and phase to 0.
void	setPhase (StkFloat phase)
	Set the phase of the signal. More...
StkFloat	getPhase () const
	Get the current phase of the signal. More...
void	setFrequency (StkFloat frequency)
	Set the impulse train rate in terms of a frequency in Hz.
void	setHarmonics (unsigned int nHarmonics=0)
	Set the number of harmonics generated in the signal. More...
StkFloat	lastOut (void) const
	Return the last computed output value.
StkFloat	tick (void)
	Compute and return one output sample.
StkFrames &	tick (StkFrames &frames, unsigned int channel=0)
	Fill a channel of the StkFrames object with computed outputs. More...
unsigned int	channelsOut (void) const
	Return the number of output channels for the class.
const StkFrames &	lastFrame (void) const
	Return an StkFrames reference to the last output sample frame.
void	ignoreSampleRateChange (bool ignore=true)
	A function to enable/disable the automatic updating of class data when the STK sample rate changes. More...

Static Public Member Functions
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. More...
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
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
void	handleError (StkError::Type type) const
	Internal function for error reporting that assumes message in oStream_ variable.
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.

Detailed Description

STK band-limited square wave class.

This class generates a band-limited square wave signal. It is derived in part from the approach reported by Stilson and Smith in "Alias-Free Digital Synthesis of Classic Analog Waveforms", 1996. The algorithm implemented in this class uses a SincM function with an even M value to achieve a bipolar bandlimited impulse train. This signal is then integrated to achieve a square waveform. The integration process has an associated DC offset so a DC blocking filter is applied at the output.

The user can specify both the fundamental frequency of the waveform and the number of harmonics contained in the resulting signal.

If nHarmonics is 0, then the signal will contain all harmonics up to half the sample rate. Note, however, that this setting may produce aliasing in the signal when the frequency is changing (no automatic modification of the number of harmonics is performed by the setFrequency() function). Also note that the harmonics of a square wave fall at odd integer multiples of the fundamental, so aliasing will happen with a lower fundamental than with the other Blit waveforms. This class is not guaranteed to be well behaved in the presence of significant aliasing.

Based on initial code of Robin Davies, 2005. Modified algorithm code by Gary Scavone, 2005–2006.

Member Function Documentation

setPhase()

void stk::BlitSquare::setPhase ( StkFloat  phase )

inline

Set the phase of the signal.

Set the phase of the signal, in the range 0 to 1.

{ phase_ = STK_PI * phase; };

getPhase()

StkFloat stk::BlitSquare::getPhase ( ) const

inline

Get the current phase of the signal.

Get the phase of the signal, in the range [0 to 1.0).

{ return phase_ / STK_PI; };

setHarmonics()

void stk::BlitSquare::setHarmonics

(

unsigned int

nHarmonics = 0

)

Set the number of harmonics generated in the signal.

This function sets the number of harmonics contained in the resulting signal. It is equivalent to (2 * M) + 1 in the BLIT algorithm. The default value of 0 sets the algorithm for maximum harmonic content (harmonics up to half the sample rate). This parameter is not checked against the current sample rate and fundamental frequency. Thus, aliasing can result if one or more harmonics for a given fundamental frequency exceeds fs / 2. This behavior was chosen over the potentially more problematic solution of automatically modifying the M parameter, which can produce audible clicks in the signal.

tick()

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

inlinevirtual

Fill a channel of the StkFrames object with computed outputs.

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::Generator.

{
#if defined(_STK_DEBUG_)
  if ( channel >= frames.channels() ) {
    oStream_ << "BlitSquare::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 )
    *samples = BlitSquare::tick();
 
  return frames;
}

setSampleRate()

static void stk::Stk::setSampleRate ( StkFloat  rate )

staticinherited

Static method that sets the STK sample rate.

The sample rate set using this method is queried by all STK classes that depend on its value. It is initialized to the default SRATE set in Stk.h. Many STK classes use the sample rate during instantiation. Therefore, if you wish to use a rate that is different from the default rate, it is imperative that it be set BEFORE STK objects are instantiated. A few classes that make use of the global STK sample rate are automatically notified when the rate changes so that internal class data can be appropriately updated. However, this has not been fully implemented. Specifically, classes that appropriately update their own data when either a setFrequency() or noteOn() function is called do not currently receive the automatic notification of rate change. If the user wants a specific class instance to ignore such notifications, perhaps in a multi-rate context, the function Stk::ignoreSampleRateChange() should be called.

ignoreSampleRateChange()

void stk::Stk::ignoreSampleRateChange ( bool  ignore = true )

inlineinherited

A function to enable/disable the automatic updating of class data when the STK sample rate changes.

This function allows the user to enable or disable class data updates in response to global sample rate changes on a class by class basis.

{ ignoreSampleRateChange_ = ignore; };

Member Data Documentation

STK_SINT8

const StkFormat stk::Stk::STK_SINT8

staticinherited

-128 to +127

STK_SINT16

const StkFormat stk::Stk::STK_SINT16

staticinherited

-32768 to +32767

STK_SINT24

const StkFormat stk::Stk::STK_SINT24

staticinherited

Lower 3 bytes of 32-bit signed integer.

STK_SINT32

const StkFormat stk::Stk::STK_SINT32

staticinherited

-2147483648 to +2147483647.

STK_FLOAT32

const StkFormat stk::Stk::STK_FLOAT32

staticinherited

Normalized between plus/minus 1.0.

STK_FLOAT64

const StkFormat stk::Stk::STK_FLOAT64

staticinherited

Normalized between plus/minus 1.0.

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

• BlitSquare.h