Spatio-Temporal phrases for activity recognition
ECCV'12 Proceedings of the 12th European conference on Computer Vision - Volume Part III
Discrete relative states to learn and recognize goals-based behaviors of groups
Proceedings of the 2013 international conference on Autonomous agents and multi-agent systems
Tracking with a mixed continuous-discrete Conditional Random Field
Computer Vision and Image Understanding
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This paper addresses the challenge of recognizing behavior of groups of individuals in unconstraint surveillance environments. As opposed to approaches that rely on agglomerative or decisive hierarchical clustering techniques, we propose to recognize group interactions without making hard decisions about the underlying group structure. Instead we use a probabilistic grouping strategy evaluated from the pairwise spatial-temporal tracking information. A path-based grouping scheme determines a soft segmentation of groups and produces a weighted connection graph where its edges express the probability of individuals belonging to a group. Without further segmenting this graph, we show how a large number of low- and high-level behavior recognition tasks can be performed. Our work builds on a mature multi-camera multi-target person tracking system that operates in real-time. We derive probabilistic models to analyze individual track motion as well as group interactions. We show that the soft grouping can combine with motion analysis elegantly to robustly detect and predict group-level activities. Experimental results demonstrate the efficacy of our approach.