Spatio-temporal clustering of probabilistic region trajectories

  • Authors:
  • Fabio Galasso;Masahiro Iwasaki;Kunio Nobori;Roberto Cipolla

  • Affiliations:
  • Department of Engineering, University of Cambridge, United Kingdom;Advanced Technology Research Laboratory, Panasonic Corporation, Japan;Advanced Technology Research Laboratory, Panasonic Corporation, Japan;Department of Engineering, University of Cambridge, United Kingdom

  • Venue:
  • ICCV '11 Proceedings of the 2011 International Conference on Computer Vision
  • Year:
  • 2011

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Abstract

We propose a novel model for the spatio-temporal clustering of trajectories based on motion, which applies to challenging street-view video sequences of pedestrians captured by a mobile camera. A key contribution of our work is the introduction of novel probabilistic region trajectories, motivated by the non-repeatability of segmentation of frames in a video sequence. Hierarchical image segments are obtained by using a state-of-the-art hierarchical segmentation algorithm, and connected from adjacent frames in a directed acyclic graph. The region trajectories and measures of confidence are extracted from this graph using a dynamic programming-based optimisation. Our second main contribution is a Bayesian framework with a twofold goal: to learn the optimal, in a maximum likelihood sense, Random Forests classifier of motion patterns based on video features, and construct a unique graph from region trajectories of different frames, lengths and hierarchical levels. Finally, we demonstrate the use of Isomap for effective spatio-temporal clustering of the region trajectories of pedestrians. We support our claims with experimental results on new and existing challenging video sequences.