Stochastic Systems Group  

Leonid Taycher  CSAIL, MIT
Stochastic tracking of structured models in monolithic state spaces often requires modeling complex distributions that are difficult to represent with either parametric or samplebased approaches. However, multiple simpler models are often available, each of which captures some aspect of the complex behavior. For example, human body parts may be robustly tracked individually, but the resulting pose combinations may not satisfy articulation constraints. Conversely, the results produced by fullbody trackers satisfy such constraints, but such trackers are usually fragile due to the presence of clutter.
We propose a method for combining such redundant models to improve individual state estimates. The constituent models are combined in a manner similar to a Product of HMMs model. Hidden variables are introduced to represent system appearance. While the resulting model contains loops, making the inference hard in general, we present an approximate nonloopy filtering algorithm based on sequential application of Belief Propagation to acyclic subgraphs of the model.
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