sclass PianoSampler2 > SlidingWindow {

  macro dprint { if (debug) printVars } bool debug;

  bool printFactor;

  gettable L<Frequency> frequencies;

  Double fixedFactor;

  *(int *channels, double *sampleRate, IQuerySound *sound,

    int *start, int *length) {

    init();

  }

  *() { init(); }

  void init { 

    frequencies = pianoFrequencies88();

  }

  long haarFeaturesChecked;

  // one channel

  L<Complex> measureWindow() {

    ret measureWindow(bounds());

  }

  L<Complex> measureWindow(DoubleRange timeRange, Cl<Freq> frequencies default frequencies()) {

    int channel = 0;

    moveToCenter(iround(timeRange.center()));

    ret map(frequencies(), f -> {

      var interval = f.interval()*sampleRate;

      int period1 = iceil(doubleRatio(timeRange.start, interval));

      int period2 = ifloor(doubleRatio(timeRange.end, interval))-1;

      if (period2 <= period1) ret complex(0);

      int periods = period2-period1;

      SumOfVibrations sum = new(this, channel, period1*interval, f!, periods);

      haarFeaturesChecked += periods*2;

      ret sum.complexSum();

    });

  }

  Frequency lowestFrequency() { ret first(frequencies); }

  Frequency highestFrequency() { ret last(frequencies); }

  int minWindowSizeForBase() {

    ret iceil(sampleRate*lowestFrequency().interval());

  }

  void makeWindow(DoubleRange r) {

    start = ifloor(r.start);

    length = iceil(r.end())-start;

    grab();

  }

  void makeWindowAround(double t, double size) {

    double start = max(0, t-size)/2;

    makeWindow(DoubleRange(start, start+size));

  }

  S stats() { ret renderVars(+haarFeaturesChecked); }

  IIntegralImage imageColumn(L<Complex> intensities) {

    int n = l(intensities);

    double[] col = new[n];

    for y to n: 

      col[n-y-1] = abs(intensities.get(y));

    double factor = fixedFactor != null ? fixedFactor : normalizationFactor(col, 255);

    if (printFactor) printVars(+factor, log := log10(factor));

    double[] col2 = doubleMul(col, factor);

    ret bwIntegralImageFromFunction(1, n, (x, y) -> ifloor(col2[y]));

  }

  void loadSound(IQuerySound sound, int channels) {

    this.sound = sound;

    this.channels = channels;

  }

}