title: Efficient online subspace learning with an indefinite kernel for visual tracking and recognition.
abstract: We propose an exact framework for online learning with a family of indefinite (not positive) kernels. As we study the case of nonpositive kernels, we first show how to extend kernel principal component analysis (KPCA) from a reproducing kernel Hilbert space to Krein space. We then formulate an incremental KPCA in Krein space that does not require the calculation of preimages and therefore is both efficient and exact. Our approach has been motivated by the application of visual tracking for which we wish to employ a robust gradient-based kernel. We use the proposed nonlinear appearance model learned online via KPCA in Krein space for visual tracking in many popular and difficult tracking scenarios. We also show applications of our kernel framework for the problem of face recognition.
authors.forename: Stephan
authors.initials: S
authors.lastname: Liwicki
authors.forename: Stefanos
authors.initials: S
authors.lastname: Zafeiriou
authors.forename: Georgios
authors.initials: G
authors.lastname: Tzimiropoulos
authors.forename: Maja
authors.initials: M
authors.lastname: Pantic
mesh_terms: D000465:Algorithms; D001185:Artificial Intelligence; D001699:Biometry / Q000379:methods*; D005145:Face / Q000033:anatomy & histology*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D009862:Online Systems; D010363:Pattern Recognition, Automated / Q000379:methods*; D025341:Principal Component Analysis; D013382:Subtraction Technique