static VF1<double[]> stereoSamplesIterator(final short[] samples) {
  ret samples == null ? null : new VF1<double[]>() {
    int sampleIndex = 0;
    public void get(double[] pair) {
      pair[0] = samples[sampleIndex];
      pair[1] = samples[sampleIndex+1];
      sampleIndex = (sampleIndex+2) % l(samples);
    }
  };
}