Signal Processing Ideas

Below: signal amplitude, signal envelope, estimated signal onset.

Below:
R: bpm estimated from the first 3 seconds of signal,
G: bpm estimated from the second 3 seconds of signal,
B: bpm estimated from the third 3 seconds of signal,
Black: Avg. of the three previous estimations.

Remark: There is no real bpm fluctuation over the frames, as the peaks keep their position.

Code here. Please contribute.