Multiple hypothesis shape tracking using particle filtering and Houghbased observation models In the last years, the Particle Filter algorithm has been extensively proposed and employed for handling the problem of visual tracking of multiple moving objects under different assumptions. This wide usage is due to the capability of performing a recursive multiple hypothesis state estimation for nonlinear nonGaussian motion and observation models. In this paper a method, based on the Particle Filter framework, is proposed for multiple objects tracking, exploiting a target representation consisting of position and shape described as a fixed dimensionality vector composed by a fixed number of grouped target corners. However, usually, application domains of visual tracking algorithms are characterized by nonrigid objects and high occlusions rate entailing new corners to appear and others to disappear at each frame. In order to cope with this problem, a voting method (i.e. the Generalized Hough Transform) is employed to estimate the likelihood function to weight different propagated particles (i.e. multiple corners configurations describing shapes) by means of the corners extracted from the currently observed image. This method, in addition to the high dimensionality of the state representation, depicts the two main particularities of the presented Particle Filter. The proposed algorithm has been tested in a realworld domain and experiments indicate good results in tracking both rigid and nonrigid objects.

A Refined Particle Filter Method for Contour Tracking Traditional particle filter which uses simple geometric shapes for representation cannot track objects with complex shape accurately. In this paper, we propose a refined particle filter method for contour tracking based on a binary level set model. In contrast with other previous work, the computational efficiency is greatly improved due to the simple form of the level set function. In addition, we perform curve evolution in the update step to make good use of the observation at current time. Finally, we consider some appearance information as well as the energy function to measure the weight for particles, which can identify the target more accurately. Experiment results on several challenging video sequences have verified the proposed algorithm is efficient and effective in many complicated scenes.