Abstract:A distortion identification technique is presented based on Hilbert-Huang transform to identify distortion model and distortion frequency of distorted real-world image sequences. The distortion model is identified simply based on Hilbert marginal spectral analysis after empirical mode decomposing. And distortion frequency is identified by analyzing the occurrence frequency of instantaneous frequency components of every intrinsic mode functions. Rational digital frequency filter with suitable cutoff frequency is designed to remove undesired fluctuations based on identification results. Experimental results show that this technique can identify distortion model and distortion frequency of displacement sequence accurately and efficiently. Based on identification results, distorted image sequence can be stabilized effectively.Video shot of a digital camera usually suffers from various distortions due to unstable random camera motion. Video stabilization technique removes undesired fluctuations, estimates intentional global motions of the camera and compensates them so that we can remove or reduce those jitter fluctuations' influence. Dynamic displacement field model is a parameterized model and provides a gradually upgraded and evolutionary process, from simple to complex, to handle image sequence distortion problems [1] . Since jitter distortion is a kind of high-frequency variation of image displacements, conventional frequency domain filter can be used to remove undesired fluctuations [1,2] . According to the relationship between distortion frequency and motion model, video stabilization becomes a facile parameter estimation process. And it is crucial to identify distortion model and distortion frequency of the acquired displacement sequence before filtering. Based on identification results, motion filtering and motion compensation can be used to suppress jitter [1][2][3][4][5][6] . However, displacement sequence is usually non-stationary because of unstable random camera motion. Conventional Fourier analysis is suitable for linear stationary signal, while it is not suitable for nonlinear non-stationary signal.This paper proposes a distortion identification technique based on Hilbert-Huang transform (HHT) [7,8] to identify distortion model and distortion frequency of realworld image sequence. Firstly, displacement sequence is decomposed into a set of intrinsic mode functions by empirical mode decomposition method. Secondly, distortion model and distortion frequency are identified based on Hilbert spectral analysis. Finally, a rational digital filter with suitable cutoff frequency is designed based on identification results. Based on these identification results, undesired fluctuation can be removed with the stabilization methods presented in Refs.[1] and [2].