ZeroCrossing

A pitch estimation UGen based on counting the zero-crossings of the input signal. This is a very crude pitch follower, but can be useful in some situations.

===Examples===

// reconstruct sine frequency
play {
 val f1 = SinOsc.kr(0.2).mulAdd(600, 700).roundTo(100)
 val a  = SinOsc.ar(f1) * 0.1
 val f2 = ZeroCrossing.ar(a)
 f2.poll(10, "estimation")
 val b  = SinOsc.ar(f2) * 0.1
 Seq(a, b)
}