title: BM3 E: discriminative density propagation for visual tracking.
abstract: We introduce BM3 E, a Conditional Bayesian Mixture of Experts Markov Model, for consistent probabilistic estimates in discriminative visual tracking. The model applies to problems of temporal and uncertain inference and represents the unexplored bottom-up counterpart of pervasive generative models estimated with Kalman filtering or particle filtering. Instead of inverting a non-linear generative observation model at run-time, we learn to cooperatively predict complex state distributions directly from descriptors that encode image observations - typically bag-of-feature global image histograms or descriptors computed over regular spatial grids. These are integrated in a conditional graphical model in order to enforce temporal smoothness constraints and allow a principled management of uncertainty. The algorithms combine sparsity, mixture modeling, and non-linear dimensionality reduction for efficient computation in high-dimensional continuous state spaces. The combined system automatically self-initializes and recovers from failure. The research has three contributions: (1) We establish the density propagation rules for discriminative inference in continuous, temporal chain models; (2) We propose flexible supervised and unsupervised algorithms for learning feedforward, multivalued contextual mappings (multimodal state distributions) based on compact, conditional Bayesian mixture of experts models; (3) We validate the framework empirically for the reconstruction of 3d human motion in monocular video sequences. Our tests on both real and motion capture-based sequences show significant performance gains with respect to competing nearest-neighbor, regression, and structured prediction methods.
authors.affiliation: Toyota Technological Institute-Chicago, University of Chicago, 1427 East 60th Street, Second Floor, Chicago, IL 60637, USA. crismin@nagoya.uchicago.edu
authors.forename: Cristian
authors.initials: C
authors.lastname: Sminchisescu
authors.forename: Atul
authors.initials: A
authors.lastname: Kanaujia
authors.forename: Dimitris N
authors.initials: DN
authors.lastname: Metaxas
mesh_terms: D000465:Algorithms; D001185:Artificial Intelligence; D001499:Bayes Theorem; D003198:Computer Simulation; D016002:Discriminant Analysis; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D021621:Imaging, Three-Dimensional / Q000379:methods*; D016247:Information Storage and Retrieval / Q000379:methods; D008390:Markov Chains; D015233:Models, Statistical; D009038:Motion; D010363:Pattern Recognition, Automated / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014741:Video Recording / Q000379:methods*