What is disclosed is a computationally efficient system and method for estimating a subject's cardiac pulse rate from multi-channel source video data. In one embodiment, A time-series signal is received. A sliding window is used to define overlapping segments of the time-series signal. Signal segments are processed by performing constrained independent component analysis (cICA) until convergence to obtain an estimated source signal. A frequency of each estimated source signal obtained by the cICA at convergence is determined to be the subject's estimated cardiac pulse rate for each signal segment. A seed reference signal used by the cICA is repeatedly updated. A sliding window is shifted to define a next time-series signal segment for processing. The method repeats for each signal segment until a termination criteria is met. In such a manner, the subject's cardiac pulse rate is estimated from a video of the subject on a continuous basis.