Velocity-adaptation of spatio-temporal receptive fields for direct recognition of activities: An experimental study

Ivan Laptev and Tony Lindeberg

Technical report CVAP264, ISRN KTH NA/P--02/04--SE. Department of Numerical Analysis and Computer Science, KTH (Royal Institute of Technology), SE-100 44 Stockholm, Sweden, March 2001.

Shortened version in Proc. ECCV'02 workshop on Statistical Methods in Video Processing, Copenhagen, Denmark, June 2002, pp.61-66.

Extended version in Image and Vision Computing, volume 22, number 2, pages 105--116, 2004.

Abstract

This article presents an experimental study of the influence of velocity adaptation when recognizing spatio-temporal patterns using a histogram-based statistical framework. The basic idea consists of adapting the shapes of the filter kernels to the local direction of motion, so as to allow the computation of image descriptors that are invariant to the relative motion in the image plane between the camera and the objects or events that are studied. Based on a framework of recursive spatio-temporal scale-space, we first outline how a straightforward mechanism for local velocity adaptation can be expressed. Then, for a test problem of recognizing activities, we present an experimental evaluation, which shows the advantages of using velocity-adapted spatio-temporal receptive fields, compared to directional derivatives or regular partial derivatives for which the filter kernels have not been adapted to the local image motion.

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Related publications: (Time-recursive velocity-adapted spatio-temporal scale-space filters) (Linear spatio-temporal scale-space) (Separable scale-space with causal time direction) (Automatic selection of temporal scales in time-causal scale-space) (Monograph on scale-space theory)