How Could I extract the signal in the below Image
Normally you could do some valley detection. Scipy does this (https://docs.scipy.org/doc/scipy/reference/generated/scipy.signal.find_peaks.html) but this requires knowing a chunk of the signal in advance so you couldn't do it real time.

For real time maybe you could look at the derivative of the signal and notice when it goes from negative to positive, it would find valleys although it may not be as smooth as your black line. Maybe also check out this: https://stackoverflow.com/questions/22583391/peak-signal-detection-in-realtime-timeseries-data