DaisySP_TeensyDaisySP_Teensy/DaisySP/Synthesis/formantosc.cpp

#include "../utility/dsp.h"
#include "formantosc.h"
#include <math.h>

using namespace daisysp;

void FormantOscillator::Init(float sample_rate)
{
    carrier_phase_ = 0.0f;
    formant_phase_ = 0.0f;
    next_sample_   = 0.0f;

    carrier_frequency_ = 0.0f;
    formant_frequency_ = 100.f;
    phase_shift_       = 0.0f;

    sample_rate_ = sample_rate;
}

float FormantOscillator::Process()
{
    float this_sample = next_sample_;
    float next_sample = 0.0f;
    carrier_phase_ += carrier_frequency_;

    if(carrier_phase_ >= 1.0f)
    {
        carrier_phase_ -= 1.0f;
        float reset_time = carrier_phase_ / carrier_frequency_;

        float formant_phase_at_reset
            = formant_phase_ + (1.0f - reset_time) * formant_frequency_;
        float before        = Sine(formant_phase_at_reset + phase_shift_
                            + (ps_inc_ * (1.0f - reset_time)));
        float after         = Sine(0.0f + phase_shift_ + ps_inc_);
        float discontinuity = after - before;
        this_sample += discontinuity * ThisBlepSample(reset_time);
        next_sample += discontinuity * NextBlepSample(reset_time);
        formant_phase_ = reset_time * formant_frequency_;
    }
    else
    {
        formant_phase_ += formant_frequency_;
        if(formant_phase_ >= 1.0f)
        {
            formant_phase_ -= 1.0f;
        }
    }

    phase_shift_ += ps_inc_;
    ps_inc_ = 0.f;

    next_sample += Sine(formant_phase_ + phase_shift_);

    next_sample_ = next_sample;
    return this_sample;
}

void FormantOscillator::SetFormantFreq(float freq)
{
    //convert from Hz to phase_inc / sample
    formant_frequency_ = freq / sample_rate_;
    formant_frequency_ = formant_frequency_ >= .25f ? .25f : formant_frequency_;
    formant_frequency_
        = formant_frequency_ <= -.25f ? -.25f : formant_frequency_;
}

void FormantOscillator::SetCarrierFreq(float freq)
{
    //convert from Hz to phase_inc / sample
    carrier_frequency_ = freq / sample_rate_;
    carrier_frequency_ = carrier_frequency_ >= .25f ? .25f : carrier_frequency_;
    carrier_frequency_
        = carrier_frequency_ <= -.25f ? -.25f : carrier_frequency_;
}

void FormantOscillator::SetPhaseShift(float ps)
{
    ps_inc_ = ps - phase_shift_;
}

inline float FormantOscillator::Sine(float phase)
{
    return sinf(phase * TWOPI_F);
}

inline float FormantOscillator::ThisBlepSample(float t)
{
    return 0.5f * t * t;
}

inline float FormantOscillator::NextBlepSample(float t)
{
    t = 1.0f - t;
    return -0.5f * t * t;
}