Title
Recognizing pair-activities by causality analysis
Abstract
In this article, beyond solo-activity analysis for single object, we study the more complicated pair-activity recognition problem by exploring the relationship between two active objects based on their trajectory clues obtained from video sensor. Our contributions are three-fold. First, we design two sets of features for representing the pair-activities encoded as length-variable trajectory pairs. One set characterizes the strength of causality between two trajectories, for example, the causality ratio and feedback ratio based on the Granger Causality Test (GCT), and another set describes the style of causality between two trajectories, for example, the sampled frequency responses of the digital filter with these two trajectories as the input and output discrete signals respectively. These features along with conventional velocity and position features of a trajectory-pair are essentially of multi-modalities, and may be greatly different in scales and importance. To make full use of them, we then develop a novel feature fusing procedure to learn the coefficients for weighting these features by maximizing the discriminating power measured by weighted correlation. Finally, we collected a pair-activity database of five popular categories, each of which consists of about 170 instances. The extensive experiments on this database validate the effectiveness of the designed features for pair-activity representation, and also demonstrate that the proposed feature fusing procedure significantly boosts the pair-activity classification accuracy.
Year
DOI
Venue
2011
10.1145/1889681.1889686
ACM TIST
Keywords
Field
DocType
pair-activity representation,novel feature fusing procedure,frequency responses,pair-activity database,length-variable trajectory pair,complicated pair-activity recognition problem,recognizing pair-activities,feedback ratio,causality ratio,activity analysis,database validate,pair-activity classification accuracy,causality analysis,digital filter,position feature,activity recognition,granger causality test,frequency response,sampling frequency
Data mining,Causality,Weighting,Digital filter,Computer science,Granger causality,Input/output,Correlation,Artificial intelligence,Machine learning,Trajectory
Journal
Volume
Issue
ISSN
2
1
2157-6904
Citations 
PageRank 
References 
10
0.51
21
Authors
4
Name
Order
Citations
PageRank
Yue Zhou1100.51
Bingbing Ni2142182.90
Shuicheng Yan39701359.54
Thomas S. Huang4278152618.42