musicdsp.org source code archive - WSInf

Phase modulation Vs. Frequency modulation (click this to go back to the index)
References : Posted by Bram
Linked file : SimpleOscillator.h (this linked file is included below)
Notes :
This code shows what the difference is betwee FM and PM.
The code is NOT optimised, nor should it be used like this.
It is an EXAMPLE
See linked file.
Linked files
////////////////////////////////////////////////////
//
// this code was NEVER MEANT TO BE USED.
//
// use as EXPLANATION ONLY for the difference between
// Phase Modulation and Frequency Modulation.
// there are MANY ways to speed this code up.
//
// bram@musicdsp.org | bram@smartelectronix.com
//
// ps:
// we use the 'previous' value of the phase in all the algo's to make sure that
// the first call to the getSampleXX() function returns the wave at phase 'zero'
//
////////////////////////////////////////////////////
#include "math.h";
#define Pi 3.141592f
class SimpleOscillator
{
SimpleOscillator(const float sampleRate = 44100.f, const long tableSize = 4096)
{
this->tableSize = tableSize;
this->sampleRate = sampleRate;
phase = 0.f;
makeTable();
}
~SimpleOscillator()
{
delete [] table;
}
// normal oscillator, no modulation
//
float generateSample(const float frequency)
{
float lookupPhase = phase;
phase += frequency * (float)tableSize / sampleRate;
wrap(phase);
return lookup(lookupPhase);
}
// frequency modulation
// the fm input should be in HZ.
//
// example:
// osc1.getSampleFM(440.f, osc2.getSample(0.5f) * 5.f )
// would give a signal where the frequency of the signal is
// modulated between 435hz and 445hz at a 0.5hz rate
//
float generateSampleFM(const float frequency, const float fm)
{
float lookupPhase = phase;
phase += (frequency + fm) * (float)tableSize / sampleRate;
wrap(phase);
return lookup(lookupPhase);
}