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bug 635:fix generate chirp for log square no alias. Patch by Steve Daulton.

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mchinen
2013-05-19 10:00:12 +00:00
parent c51e2493eb
commit 8fd058e8ee
1 changed files with 13 additions and 8 deletions
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21
src/effects/ToneGen.cpp
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@@ -142,6 +142,8 @@ bool EffectToneGen::MakeTone(float *buffer, sampleCount len)
double throwaway = 0; //passed to modf but never used
sampleCount i;
double f = 0.0;
double a,b;
int k;
double BlendedFrequency;
double BlendedAmplitude;
@@ -187,8 +189,17 @@ bool EffectToneGen::MakeTone(float *buffer, sampleCount len)
case 2: //sawtooth
f = (2 * modf(mPositionInCycles/mCurRate+0.5f, &throwaway)) -1.0f;
break;
default:
break;
case 3: //square, no alias. Good down to 110Hz @ 44100Hz sampling.
//do fundamental (k=1) outside loop
b = (1. + cos((pre2PI * BlendedFrequency)/mCurRate))/pre4divPI; //scaling
f = (float) pre4divPI * sin(pre2PI * mPositionInCycles/mCurRate);
for(k=3; (k<200) && (k * BlendedFrequency < mCurRate/2.); k+=2)
{
//Hanning Window in freq domain
a = 1. + cos((pre2PI * k * BlendedFrequency)/mCurRate);
//calc harmonic, apply window, scale to amplitude of fundamental
f += (float) a * sin(pre2PI * mPositionInCycles/mCurRate * k)/(b*k);
}
}
// insert value in buffer
buffer[i] = BlendedAmplitude * f;
@@ -201,8 +212,6 @@ bool EffectToneGen::MakeTone(float *buffer, sampleCount len)
} else {
// this for regular case, linear interpolation
BlendedFrequency = frequency[0] + frequencyQuantum * mSample;
double a,b;
int k;
for (i = 0; i < len; i++)
{
switch (waveform) {
@@ -226,10 +235,6 @@ bool EffectToneGen::MakeTone(float *buffer, sampleCount len)
//calc harmonic, apply window, scale to amplitude of fundamental
f += (float) a * sin(pre2PI * mPositionInCycles/mCurRate * k)/(b*k);
}
break;
default:
break;
}
// insert value in buffer
buffer[i] = BlendedAmplitude * f;