real-time zero-crossing detection with sample-rate precision.
this is something that is super simple to implement.
it's like:
if (incomingSignal > 0 && previousIncomingSignal < 0 || incomingSignal < 0 || previousIncomingSignal > 0) return 1; else return 0;
i also don't understand why such an easy tool has never been put into vanilla pd.