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stk::LentPitShift Class Reference

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

#include <LentPitShift.h>

Inheritance diagram for stk::LentPitShift:
stk::Effect stk::Stk

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.
 
StkFramestick (StkFrames &frames, unsigned int channel=0)
 Take a channel of the StkFrames object as inputs to the filter and replace with corresponding outputs. More...
 
StkFramestick (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. More...
 
- 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 StkFrameslastFrame (void) const
 Return an StkFrames reference to the last output sample frame.
 
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. More...
 

Protected Member Functions

void process ()
 Apply the effect on the input samples and store it. More...
 

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. More...
 
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

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.

224 {
225 #if defined(_STK_DEBUG_)
226  if ( channel >= frames.channels() ) {
227  oStream_ << "LentPitShift::tick(): channel and StkFrames arguments are incompatible!";
228  handleError( StkError::FUNCTION_ARGUMENT );
229  }
230 #endif
231 
232  StkFloat *samples = &frames[channel];
233  unsigned int hop = frames.channels();
234  for ( unsigned int i=0; i<frames.frames(); i++, samples += hop ) {
235  *samples = tick( *samples );
236  }
237 
238  return frames;
239 }
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.

242 {
243 #if defined(_STK_DEBUG_)
244  if ( iChannel >= iFrames.channels() || oChannel >= oFrames.channels() ) {
245  oStream_ << "LentPitShift::tick(): channel and StkFrames arguments are incompatible!";
246  handleError( StkError::FUNCTION_ARGUMENT );
247  }
248 #endif
249 
250  StkFloat *iSamples = &iFrames[iChannel];
251  StkFloat *oSamples = &oFrames[oChannel];
252  unsigned int iHop = iFrames.channels(), oHop = oFrames.channels();
253  for ( unsigned int i=0; i<iFrames.frames(); i++, iSamples += iHop, oSamples += oHop ) {
254  *oSamples = tick( *iSamples );
255  }
256 
257  return iFrames;
258 }
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.

110 {
111  StkFloat x_t; // input coefficient
112  StkFloat x_t_T; // previous input coefficient at T samples
113  StkFloat coeff; // new coefficient for the difference function
114 
115  unsigned long alternativePitch = tMax_; // Global minimum storage
116  lastPeriod_ = tMax_+1; // Storage of the lowest local minimum under the threshold
117 
118  // Loop variables
119  unsigned long delay_;
120  unsigned int n;
121 
122  // Initialization of the dt coefficients. Since the
123  // frames are of tMax_ length, there is no overlapping
124  // between the successive windows where pitch tracking
125  // is performed.
126  for ( delay_=1; delay_<=tMax_; delay_++ )
127  dt[delay_] = 0.;
128 
129  // Calculation of the dt coefficients and update of the input delay line.
130  for ( n=0; n<inputFrames.size(); n++ ) {
131  x_t = inputLine_.tick( inputFrames[ n ] );
132  for ( delay_=1; delay_<= tMax_; delay_++ ) {
133  x_t_T = inputLine_.tapOut( delay_ );
134  coeff = x_t - x_t_T;
135  dt[delay_] += coeff * coeff;
136  }
137  }
138 
139  // Calculation of the pitch tracking function and test for the minima.
140  for ( delay_=1; delay_<=tMax_; delay_++ ) {
141  cumDt[delay_] = dt[delay_] + cumDt[delay_-1];
142  dpt[delay_] = dt[delay_] * delay_ / cumDt[delay_];
143 
144  // Look for a minimum
145  if ( dpt[delay_-1]-dpt[delay_-2] < 0 && dpt[delay_]-dpt[delay_-1] > 0 ) {
146  // Check if the minimum is under the threshold
147  if ( dpt[delay_-1] < threshold_ ){
148  lastPeriod_ = delay_-1;
149  // If a minimum is found, we can stop the loop
150  break;
151  }
152  else if ( dpt[alternativePitch] > dpt[delay_-1] )
153  // Otherwise we store it if it is the current global minimum
154  alternativePitch = delay_-1;
155  }
156  }
157 
158  // Test for the last period length.
159  if ( dpt[delay_]-dpt[delay_-1] < 0 ) {
160  if ( dpt[delay_] < threshold_ )
161  lastPeriod_ = delay_;
162  else if ( dpt[alternativePitch] > dpt[delay_] )
163  alternativePitch = delay_;
164  }
165 
166  if ( lastPeriod_ == tMax_+1 )
167  // No period has been under the threshold so we used the global minimum
168  lastPeriod_ = alternativePitch;
169 
170  // We put the new zero output coefficients in the output delay line and
171  // we get the previous calculated coefficients
172  outputLine_.tick( zeroFrame, outputFrames );
173 
174  // Initialization of the Hamming window used in the algorithm
175  for ( int n=-(int)lastPeriod_; n<(int)lastPeriod_; n++ )
176  window[n+lastPeriod_] = (1 + cos(PI*n/lastPeriod_)) / 2 ;
177 
178  long M; // Index of reading in the input delay line
179  long N; // Index of writing in the output delay line
180  double sample; // Temporary storage for the new coefficient
181 
182  // We loop for all the frames of length lastPeriod_ presents between inputPtr and tMax_
183  for ( ; inputPtr<(int)(tMax_-lastPeriod_); inputPtr+=lastPeriod_ ) {
184  // Test for the decision of compression/expansion
185  while ( outputPtr < inputPtr ) {
186  // Coefficients for the linear interpolation
187  env[1] = fmod( outputPtr + tMax_, 1.0 );
188  env[0] = 1.0 - env[1];
189  M = tMax_ - inputPtr + lastPeriod_ - 1; // New reading pointer
190  N = 2*tMax_ - (unsigned long)floor(outputPtr + tMax_) + lastPeriod_ - 1; // New writing pointer
191  for ( unsigned int j=0; j<2*lastPeriod_; j++,M--,N-- ) {
192  sample = inputLine_.tapOut(M) * window[j] / 2.;
193  // Linear interpolation
194  outputLine_.addTo(env[0] * sample, N);
195  outputLine_.addTo(env[1] * sample, N-1);
196  }
197  outputPtr = outputPtr + lastPeriod_ * periodRatio_; // new output pointer
198  }
199  }
200  // Shifting of the pointers waiting for the new frame of length tMax_.
201  outputPtr -= tMax_;
202  inputPtr -= tMax_;
203 }

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

The Synthesis ToolKit in C++ (STK)
©1995--2014 Perry R. Cook and Gary P. Scavone. All Rights Reserved.