Fuzzy Temporal Segmentation and Probabilistic Recognition of Continuous Human Daily Activities

摘要

Understanding human activities is an essential capability for intelligent robots to help people in a variety of applications. Humans perform activities in a continuous fashion, and transitions between temporally adjacent activities are gradual. Our Fuzzy Segmentation and Recognition (FuzzySR) algorithm explicitly reasons about gradual transitions between continuous human activities. Our objective is to simultaneously segment a given video into a sequence of events and recognize the activity contained in each event. The algorithm uniformly segments the video into a sequence of nonoverlapping blocks, each lasting a short period of time. Then, a multivariable time series is formed by concatenating block-level human activity summaries that are computed using topic models over local spatiotemporal features extracted from each block. Through encoding an event as a fuzzy set with fuzzy boundaries to represent gradual transitions, our approach is capable of segmenting the continuous visual data into a sequence of fuzzy events. By incorporating all block summaries contained in an event, our algorithm determines the activity label for each event. To evaluate performance, we conduct experiments using six datasets. Our algorithm shows promising continuous activity segmentation results on these datasets and obtains the event-level activity recognition precision of 42.6%, 60.4%, 65.2%, and 78.9% on the Hollywood-2, CAD-60, ACT $4^2$, and UTK-CAP datasets, respectively.