Synchronization of oscillations for machine perception of gaits

Substantial evidence supports a relationship between gait perception and gait synthesis. Furthermore, passive mechanical systems demonstrate that the jointed leg systems of humans have innate oscillations that form a gait. These observations suggest that systems may perceive gaits by synchronizing an internal oscillating model to observed oscillations. We present such a system in this paper that uses phase-locked loops to synchronize an internal oscillator with oscillations from a video source. Arrays of phase-locked loops, called video phase-locked loops, synchronize a system with the oscillations in pixel intensities. We then test the perception of the resulting synchronized-oscillator model in various gait recognition tasks. Tools based on Procrustes analysis and directional statistics provide the computational mechanism to compare patterns of oscillations. We discuss the possibility of an alternative model for motion perception based on synchronization with the transient oscillations of temporal band-pass filters that is consistent with other proposed models for human perception. Synchronization of a kinematic model to oscillations also suggests a path to bridge the gap between the model-free and model-based domains. 2004 Published by Elsevier Inc.