Parsing Filtering

     focuses on establishing a set of initial heartbeats, and then on using prediction and heartbeat-interval and derivative thresholding to determine the likelihood that any given point is a heartbeat. A later version also employed an output-cutoff and restart mechanism which would stop outputting the heart rate when noise started to degrade the accuracy of the output and then would restart when the heartbeat could again be established, whereas the earlier version would simply notify the user of questionable output ranges.