What is disclosed is a system and method for extracting photoplethysmographic (PPG) signal (i.e., a cardiac signal) on a continuous basis from a time-series signals obtained from video images captured of a subject being monitored for cardiac function in a non-contact remote sensing environment involves the following. First, a time-series signal obtained from video images captured of a region of exposed skin where a photoplethysmographic (PPG) signal of a subject of interest can be registered. A sliding window is then used to define consecutive sequential segments of the time-series signal for processing. Each of the consecutive time-series signal segments is detrended such that low frequency variations and non-stationary components are removed. The detrended signals are processed to obtain, for each segment, a PPG signal. The PPG signal segments are then stitched together using a stitching method, as disclosed herein, to obtain a continuous PPG signal for the subject.