// @title Free2.ck

SndBuf rec => blackhole;
"E:/Google Drive/Stanford/Senior Year/Music220A/HW5/guitar.wav" => rec.read;

// pipe input into analysis audio graph:
// track amplitude for gain of an FM patch
// frequency will be max bin amplitude from the spectrum
rec => FFT fft  =^ RMS rms => blackhole;

// setup FFT: choose high-quality transform parameters
4096 => fft.size;
Windowing.hann(fft.size() / 2) => fft.window;
20 => int overlap;
0 => int ctr;
second / samp => float srate;

// actual audio graph and parameter setting
// NOTE: gain 'g' prevents direct connection bug
rec => Gain g => dac.left;
// creating hammond organ-like FM instrument
TriOsc b3 => dac.right; 
// set initial frequency
100 => Std.mtof => b3.freq; 
// instantiate a smoother to smooth tracker results (see below)
Smooth sma, smf;
// set time constant: shorter time constant gives faster 
// response but more jittery values
sma.setTimeConstant((fft.size() / 2)::samp);
smf.setTimeConstant((fft.size() / 5)::samp);


// setGainAndFreq()
spork ~ setGainAndFreq();
fun void setGainAndFreq() {
    while (true) {
        // apply smoothed values
        b3.gain(sma.getLast()); 
        b3.freq(smf.getLast());
        1::samp => now;
    }   
}


// main inf-loop
while(true) {
    // hop in time by overlap amount
    (fft.size() / overlap)::samp => now; 
    // then we've gotten our first bufferful
    if (ctr > overlap) {
        // compute the FFT and RMS analyses
        rms.upchuck(); 
        rms.fval(0) => float a;
        Math.rmstodb(a) => float db;
        // boost the sensitity
        30 + db * 15 => db;
        // but clip at maximum
        Math.min(100, db) => db; 
        sma.setNext(Math.dbtorms(db));      
        
        0 => float max;
        0 => int where;
        // look for a frequency peak in the spectrum
        // half of spectrum to save work
        for(0 => int i; i < fft.size()/4; ++i) {
            if(fft.fval(i) > max) {
                fft.fval(i) => max;
                i => where;
            }
        }
        // get frequency of peak
        (where $ float) / fft.size() * srate => float f; 
        // then convert it to MIDI pitch
        f => Math.ftom => float p;
        // plus a major third
        4 +=> p; 
        // set lower boundary: prevents note too low
        Math.max(20, p) => p;
        // new freq if not noise
        if(db > 10.0) {
            smf.setNext(Math.mtof(p));
        }
    }
    ctr++;
}


// @class Smooth
// @desc contral signal generator for smooth transition
class Smooth
{
    // audio graph
    Step in => Gain out => blackhole;
    Gain fb => out;
    out => fb;
    
    // init: smoothing coefficient, default no smoothing
    0.0 => float coef;
    initGains();
    
    // initGains()
    fun void initGains() {
        in.gain(1.0 - coef);
        fb.gain(coef);
    }
    
    // setNext(): set target value
    fun void setNext(float value) { 
        in.next(value); 
    }
    
    // getLast(): return current interpolated value
    fun float getLast() {
        1::samp => now; 
        return out.last(); 
    }
    
    // setExpo(): set smoothing directly from exponent
    fun void setExpo(float value) { 
        value => coef;
        initGains();
    }
    
    // setTimeConstant(): set smoothing duration
    fun void setTimeConstant(dur duration) {
        Math.exp(-1.0 / (duration / samp)) => coef;
        initGains();
    }
} // END OF CLASS: Smooth