A Comparison Framework for walking performances using aSpaces .

In this paper, we address the analysis of human actions by comparing different performances of the same action executed by different actors. Specifically, we present a comparison procedure applied to the walking action, but the scheme can be applied to other different actions, such as bending, running, etc. To achieve fair comparison results, we define a novel human body model based on joint angles, which maximizes the differences between human postures and, moreover, reflects the anatomical structure of human beings. Subsequently, a human action space, called aSpace, is built in order to represent each performance (i.e., each predefined sequence of postures) as a parametric manifold. The final human action representation is called p-action, which is based on the most characteristic human body postures found during several walking performances. These postures are found automatically by means of a predefined distance function, and they are called key-frames. By using key-frames, we synchronize any performance with respect to the p-action. Furthermore, by considering an arc length parameterization, independence from the speed at which performances are played is attained. As a result, the style of human walking can be successfully analysed by establishing the differences of the joints between female and male walkers.