>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.