Hierarchical representation of the motion of a walker and motion reconstruction for model-based image coding

We apply a model-based image coding scheme to the scene of a human walker. In our scheme, the motion of a whole human body is represented in 3-D stick motion. We concentrate on the following subjects: modeling of a walker by a stick model, the motion analysis algorithm based on the stick model, and the scheme to reconstruct continuous stick motion by the analyzed results. We determine both the form of a 3-D human stick model and how the model walks, and define the parameters of the model to represent the real motion in the scene. Then, we propose a three-layer motion representation scheme by using three stick models with different degrees of coarseness. Also, we present an algorithm for estimating the parameters of these stick models from monocular moving pictures. With this algorithm, the parameters of each model are estimated efficiently in the order of coarseness of model. We have applied his scheme to two experimental scenes where the identical walker is walking straight to the different direction. While the estimated 3-D motion has included some errors, the availability of this motion representation scheme to the model-based image coding system has been confirmed.