Hirokatsu KATAOKA, Ph.D.
National Institute of Advanced Industrial Science and Technology (AIST), Japan

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"Extended Co-occurrence HOG with Dense Trajectories for Fine-grained Activity Recognition"
Hirokatsu Kataoka (The Univ. of Tokyo, Keio Univ.), Kiyoshi Hashimoto (Keio Univ.), Kenji Iwata, Yutaka Satoh (AIST), Nassir Navab, Slobodan Ilic (TUM), Yoshimitsu Aoki (Keio Univ.)

  We propose Extended Co-occurrence HOG (ECoHOG) feature and integrate it with dense sampling and dense feature extraction approach in order to improve accuracy of fine-grained activity recognition. The co-occurrence feature clearly extracts an object's shape by focusing on co-occurrence of image gradients at the pairs of image pixels and in that way reduces false positives. We extend this feature by adding sum of the magnitude of the gradients as co-occurrence elements. This results in giving the importance to the object boundaries and straightening the difference between the moving foreground and static background. In addition we apply this descriptor on the dense trajectories and test it for fine grained activity recognition.

  We tested influence of our ECoHOG feature coupled with dense trajectories on two fine-grained activity recognition datasets: MPII cooking activities dataset and INRIA surgery dataset and obtained increase of performance using only this features in contrast to the use of HOG, HOF (Histograms of Optical Flow) and MBF (Motion Boundary Histograms) used in dense trajectories.

Top 50 frequent used co-occurrence elements are here.


References

- Hirokatsu Kataoka, Kiyoshi Hashimoto, Kenji Iwata, Yutaka Satoh, Nassir Navab, Slobodan Ilic, Yoshimitsu Aoki, "Extended Co-occurrence HOG with Dense Trajectories for Fine-grained Activity Recognition", Asian Conference on Computer Vision (ACCV), Nov 2014. (acceptance rate: 27.0%) [PDF]




Copyright Hirokatsu Kataoka