stk::LentPitShift Class Reference

Pitch shifter effect class based on the Lent algorithm. More...

#include <LentPitShift.h>

Inheritance diagram for stk::LentPitShift:

Public Member Functions
	LentPitShift (StkFloat periodRatio=1.0, int tMax=RT_BUFFER_SIZE)
	Class constructor.
void	clear (void)
	Reset and clear all internal state.
void	setShift (StkFloat shift)
	Set the pitch shift factor (1.0 produces no shift).
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::Effect
	Effect (void)
	Class constructor.
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.
virtual void	clear ()=0
	Reset and clear all internal state.
virtual void	setEffectMix (StkFloat mix)
	Set the mixture of input and "effected" levels in the output (0.0 = input only, 1.0 = effect only).
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.

Protected Member Functions
void	process ()
	Apply the effect on the input samples and store it.
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.

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

Detailed Description

Pitch shifter effect class based on the Lent algorithm.

This class implements a pitch shifter using pitch tracking and sample windowing and shifting.

by Francois Germain, 2009.

Member Function Documentation

tick() [1/2]

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

inline

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.

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

tick() [2/2]

StkFrames & stk::LentPitShift::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_ << "LentPitShift::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 ) {
    *oSamples = tick( *iSamples );
  }
 
  return iFrames;
}

process()

void stk::LentPitShift::process ( )

inlineprotected

Apply the effect on the input samples and store it.

The samples stored in the input frame vector are processed and the delayed result are stored in the output frame vector.

{
  StkFloat x_t;    // input coefficient
  StkFloat x_t_T;  // previous input coefficient at T samples
  StkFloat coeff;  // new coefficient for the difference function
 
  unsigned long alternativePitch = tMax_;  // Global minimum storage
  lastPeriod_ = tMax_+1;         // Storage of the lowest local minimum under the threshold
 
  // Loop variables
  unsigned long delay_;
  unsigned int n;
 
  // Initialization of the dt coefficients.  Since the
  // frames are of tMax_ length, there is no overlapping
  // between the successive windows where pitch tracking
  // is performed.
  for ( delay_=1; delay_<=tMax_; delay_++ )
    dt[delay_] = 0.;
 
  // Calculation of the dt coefficients and update of the input delay line.
  for ( n=0; n<inputFrames.size(); n++ ) {
    x_t = inputLine_.tick( inputFrames[ n ] );
    for ( delay_=1; delay_<= tMax_; delay_++ ) {
      x_t_T = inputLine_.tapOut( delay_ );
      coeff = x_t - x_t_T;
      dt[delay_] += coeff * coeff;
    }
  }
 
  // Calculation of the pitch tracking function and test for the minima.
  for ( delay_=1; delay_<=tMax_; delay_++ ) {
    cumDt[delay_] = dt[delay_] + cumDt[delay_-1];
    dpt[delay_] = dt[delay_] * delay_ / cumDt[delay_];
 
    // Look for a minimum
    if ( delay_ > 1 && dpt[delay_-1]-dpt[delay_-2] < 0 && dpt[delay_]-dpt[delay_-1] > 0 ) {
      // Check if the minimum is under the threshold
      if ( dpt[delay_-1] < threshold_ ){
        lastPeriod_ = delay_-1;
        // If a minimum is found, we can stop the loop
        break;
      }
      else if ( dpt[alternativePitch] > dpt[delay_-1] )
        // Otherwise we store it if it is the current global minimum
        alternativePitch = delay_-1;
    }
  }
 
  // Test for the last period length.
  if ( dpt[delay_]-dpt[delay_-1] < 0 ) {
    if ( dpt[delay_] < threshold_ )
      lastPeriod_ = delay_;
    else if ( dpt[alternativePitch] > dpt[delay_] )
      alternativePitch = delay_;
  }
 
  if ( lastPeriod_ == tMax_+1 )
    // No period has been under the threshold so we used the global minimum
    lastPeriod_ = alternativePitch;
 
  // We put the new zero output coefficients in the output delay line and 
  // we get the previous calculated coefficients
  outputLine_.tick( zeroFrame, outputFrames );
 
  // Initialization of the Hamming window used in the algorithm
  for ( int n=-(int)lastPeriod_; n<(int)lastPeriod_; n++ )
    window[n+lastPeriod_] = (1 + cos(PI*n/lastPeriod_)) / 2    ;
 
  long M;  // Index of reading in the input delay line
  long N;  // Index of writing in the output delay line
  double sample;  // Temporary storage for the new coefficient
 
  // We loop for all the frames of length lastPeriod_ presents between inputPtr and tMax_
  for ( ; inputPtr<(int)(tMax_-lastPeriod_); inputPtr+=lastPeriod_ ) {
    // Test for the decision of compression/expansion
    while ( outputPtr < inputPtr ) {
      // Coefficients for the linear interpolation
      env[1] = fmod( outputPtr + tMax_, 1.0 );
      env[0] = 1.0 - env[1];
      M = tMax_ - inputPtr + lastPeriod_ - 1; // New reading pointer
      N = 2*tMax_ - (unsigned long)floor(outputPtr + tMax_) + lastPeriod_ - 1; // New writing pointer
      for ( unsigned int j=0; j<2*lastPeriod_; j++,M--,N-- ) {
        sample = inputLine_.tapOut(M) * window[j] / 2.;
        // Linear interpolation
        outputLine_.addTo(env[0] * sample, N);
        outputLine_.addTo(env[1] * sample, N-1);
      }
      outputPtr = outputPtr + lastPeriod_ * periodRatio_; // new output pointer
    }
  }
  // Shifting of the pointers waiting for the new frame of length tMax_.
  outputPtr -= tMax_;
  inputPtr  -= tMax_;
}

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

• LentPitShift.h