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Version 4.3.0

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This commit is contained in:
Gary Scavone
2009-03-24 23:02:15 -04:00
committed by Stephen Sinclair
parent 2cbce2d8bd
commit 27d9b79dc7
271 changed files with 22219 additions and 8834 deletions
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47
src/BlitSquare.cpp
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@@ -8,8 +8,8 @@
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 but that is
subtracted off the output signal.
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
@@ -19,17 +19,21 @@
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).
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.
Modified algorithm code by Gary Scavone, 2005 - 2006.
*/
/***************************************************/
#include "BlitSquare.h"
#include <cmath>
#include <limits>
BlitSquare:: BlitSquare( StkFloat frequency )
{
nHarmonics_ = 0;
@@ -45,6 +49,8 @@ void BlitSquare :: reset()
{
phase_ = 0.0;
lastOutput_ = 0;
dcbState_ = 0.0;
lastBlitOutput_ = 0;
}
void BlitSquare :: setFrequency( StkFloat frequency )
@@ -56,8 +62,8 @@ void BlitSquare :: setFrequency( StkFloat frequency )
// By using an even value of the parameter M, we get a bipolar blit
// waveform at half the blit frequency. Thus, we need to scale the
// frequency value here by 2.0. (GPS, 2005).
p_ = 2.0 * Stk::sampleRate() / frequency;
// frequency value here by 0.5. (GPS, 2006).
p_ = 0.5 * Stk::sampleRate() / frequency;
rate_ = PI / p_;
this->updateHarmonics();
}
@@ -73,13 +79,12 @@ void BlitSquare :: updateHarmonics( void )
// Make sure we end up with an even value of the parameter M here.
if ( nHarmonics_ <= 0 ) {
unsigned int maxHarmonics = (unsigned int) floor( 0.5 * p_ );
m_ = 2 * maxHarmonics;
m_ = 2 * (maxHarmonics + 1);
}
else
m_ = 2 * nHarmonics_;
m_ = 2 * (nHarmonics_ + 1);
// This offset value was derived empirically. (GPS, 2005)
offset_ = 1.0 - 0.5 * m_ / p_;
a_ = m_ / p_;
#if defined(_STK_DEBUG_)
errorString_ << "BlitSquare::updateHarmonics: nHarmonics_ = " << nHarmonics_ << ", m_ = " << m_ << '.';
@@ -89,7 +94,7 @@ void BlitSquare :: updateHarmonics( void )
StkFloat BlitSquare :: computeSample( void )
{
StkFloat temp = lastOutput_;
StkFloat temp = lastBlitOutput_;
// A fully optimized version of this would replace the two sin calls
// with a pair of fast sin oscillators, for which stable fast
@@ -103,20 +108,24 @@ StkFloat BlitSquare :: computeSample( void )
if ( fabs( denominator ) < std::numeric_limits<StkFloat>::epsilon() ) {
// Inexact comparison safely distinguishes betwen *close to zero*, and *close to PI*.
if ( phase_ < 0.1f || phase_ > TWO_PI - 0.1f )
lastOutput_ = 1.0;
lastBlitOutput_ = a_;
else
lastOutput_ = -1.0;
lastBlitOutput_ = -a_;
}
else {
lastOutput_ = sin( m_ * phase_ );
lastOutput_ /= p_ * denominator;
lastBlitOutput_ = sin( m_ * phase_ );
lastBlitOutput_ /= p_ * denominator;
}
lastOutput_ += temp;
lastBlitOutput_ += temp;
// Now apply DC blocker.
lastOutput_ = lastBlitOutput_ - dcbState_ + 0.999 * lastOutput_;
dcbState_ = lastBlitOutput_;
phase_ += rate_;
if ( phase_ >= TWO_PI ) phase_ -= TWO_PI;
return lastOutput_ - offset_;
return lastOutput_;
}