sbool audioSplit1_debug = true;
static float audioSplit1_threshold = 0.025f;

static L<IntRange> audioSplit1(BWImage img) {
  ret audioSplit1(img, audioSplit1_threshold);
}

static L<IntRange> audioSplit1(BWImage img, float threshold) {
  int w = img.getWidth();
  float[] f = bwImageColumnBrightnesses(img);
  
  new L<IntRange> l;
  int j = -1;
  for (int i = 0; i < l(f); i++)
    if (f[i] >= threshold) { // start / continue streak
      if (j < 0) j = i; 
    } else {
      if (j >= 0) { // end streak
        l.add(intRange(j, i));
        j = -1;
      }
    }
  if (j >= 0)
    l.add(intRange(j, w));
  if (audioSplit1_debug)
    print("audioSplit1: " + w + " => " + sfu(l));
  ret l;
}