Towards Scalable Retrieval of Human Motion Episodes

With the increasing availability of human motion data captured in the form of 2D/3D skeleton sequences, more complex motion recordings need to be processed. In this paper, we focus on the similarity-based retrieval of motion episodes - medium-sized skeleton sequences that consist of multiple semantic actions and correspond to some logical motion unit (e.g., a figure skating performance). We examine two orthogonal approaches to the episode-matching task: (1) the deep learning approach that is traditionally used for processing short motion actions, and (2) the motion-word technique that transforms skeleton sequences into a text-like representation. Since the second approach is more promising, we propose a two-phase retrieval scheme that combines mature text-processing techniques with application-specific refinement methods. We demonstrate that this solution achieves promising results in both effectiveness and efficiency, and can be further indexed to implement scalable episode retrieval.