sclass SimpleBaseDrumFinder1 {
  int windowSize = 30;
  long count;
  double factor = 1.35; // how much higher max must be than avg
  int maxAscentTime = 4; // wait if it keeps ascending before triggering
  int minDownTime = 10; // don't trigger again for this long
  double minAbsoluteLoudness = 0.03;

  transient RollingAverage ra;
  transient RollingMaximum rm;
  transient double lastValue, avgAtAscendStart;
  transient long ascendingSince = 0, downSince = 0;
  transient Pair<LongRange, Double> lastBaseDrum;

  void addFrequencyImageBrightness(double b) {
    if (ra == null) ra = new RollingAverage(windowSize);
    if (rm == null) rm = new RollingMaximum(windowSize);
    ra.add(b);
    double max = rm.addAndGet(b), avg = ra!;
    ++count;
    bool ascending = b >= lastValue;
    lastValue = b;
    
    if (downSince != 0 && count < downSince+minDownTime) ret;
    
    // mark start of ascent
    if (ascending && ascendingSince == 0) {
      ascendingSince = count;
      avgAtAscendStart = avg;
    }
    
    if (ascendingSince != 0 && (!ascending || ascendingSince+maxAscentTime == count))
      if (lastValue >= minAbsoluteLoudness)
        trigger(ascendingSince, count-1, b/max(0.001, avgAtAscendStart));
    if (!ascending) ascendingSince = 0;
  }
  
  void trigger(long begin, long end, double ratio) {
    if (ratio < factor) ret;
    print("Base drum found from " + begin + " to " + end + ", ratio=" + ratio + ", last loudness: " + lastValue);
    lastBaseDrum = pair(longRange(begin, end), ratio);
    downSince = end;
  }
  
  Pair<LongRange, Double> getAndClearLastEvent() {
    try {
      ret lastBaseDrum;
    } finally {
      lastBaseDrum = null;
    }
  }
}