[Univ of Cambridge] [Dept of Engineering]
Thomas Woodley

Tracking Using On-line Feature Selection and a Local Generative Model

Abstract

This paper proposes an algorithm for online  feature selection which improves robustness to occlusions by referring to a localized generative appearance model. Discriminative classifiers based on feature extraction have classically either prepared a fixed prior model by training offline, or continually adapted their classification parameters to any apparent appearance changes. By combining the attractive qualities of each approach, our framework can cope with appearance changes of a target object and will maintain proximity to a static appearance model. Our main contribution is the use of a generative model to guide the online feature selection to regions of an image which maintain a valid appearance. The generative model exhibits the properties of non-negativity, localization and orthogonality. We demonstrate the system in a tracking framework
to show improved tracking performance through occlusions.


People

Thomas Woodley
Björn Stenger
Roberto Cipolla


Resources

Paper (pdf)

Demo Video


Sample Results

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Tracking Through Occlusion. Red regions indicate the outlier map, as determined from the generative appearance model. White overlay indicates the location of features used in the classifier.


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Tracking Through Total Occlusion. By referring to the appearance model we prevent the on-line feature selection from locking on to the occluding object.


Hindsights/Future Work

  • Being able to localize occlusions in an image is useful technique for preventing drift in an on-line learning tracker.
  • However, the appearance model takes away too much of the flexibility afforded by the on-line learning approach; a model which admits more flexibility in appearance (e.g pose changes) would better complement the tracker.