Estimation of time-varying velocities of moving objects by time-frequency representations

An approach to the estimation of motion parameters of moving objects in a video-sequence, by using the SLIDE (Subspace- based line detection algorithm) algorithm, is considered. The proposed procedure projects video-frames to the coordinate axes, in order to obtain synthetic images containing information about the motion parameters. These synthetic images are mapped to the FM signals by using constant -propagation. The problem of velocity estimation is reduced to the instantaneous frequency (IF) estimation. IF estimators, based on time-frequency (TF) representations, are used. Three TF representations: spectrogram (SPEC), Wigner distribution (WD), and S-method (SM), are used and compared to this aim. A tradeoff between concentration of the TF representation (velocity estimation accuracy) and reduction of the cross-terms (possibility for estimation of the multiple objects parameters) is achieved by the SM. A performance analysis of the algorithm is done. Theoretical results are illustrated on several numerical examples.