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The 25th International Conference on Machine Learning (ICML 2008)

Robust Matching and Recognition using Context-Dependent Kernels

author: Hichem Sahbi, CNRS - LTCI UMR 5141 Telecom ParisTech

Description

The success of kernel methods including support vector machines (SVMs) strongly depends on the design of appropriate kernels. While initially kernels were designed in order to handle fixed-length data, their extension to unordered, variable-length data became more than necessary for real pattern recognition problems such as object recognition and bioinformatics. We focus in this paper on object recognition using a new type of kernel referred to as "context-dependent". Objects, seen as constellations of local features (interest points,regions, etc.), are matched by minimizing an energy function mixing (1) a fidelity term which measures the quality of feature matching, (2) a neighborhood criteria which captures the object geometry and (3) a regularization term. We will show that the fixed-point of this energy is a "context-dependent" kernel ("CDK") which also satisfies the Mercer condition. Experiments conducted on object recognition show that when plugging our kernel in SVMs, we clearly outperform SVMs with "context-free" kernels.

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Slides
0:00 Robust Matching and Recognition Using Context-Dependent Kernels
0:25 Outline
0:51 Outline - Issues and Contribution.
0:54 Holistic vs Subset Kernels
2:39 Methods
3:23 Contribution
3:58 Outline - Subset Kernels
4:00 Subset Kernels
4:52 Subset Kernels (Minor Kernel De ciency)
4:54 Subset Kernels
4:57 Subset Kernels (Minor Kernel De ciency)
6:26 Outline - Context Dependent Kernel Design
6:28 Kernel Design - 1
9:13 Kernel Design - 2
10:02 Kernel Design - 1
10:06 Kernel Design - 2
10:10 Kernel Design - 1
10:14 Kernel Design - 2
10:18 Neighborhood Parameter
11:20 Mercer Condition
12:20 Mercer Condition (Sketch of the Proof)
12:54 Kernel Design - 2
13:02 Mercer Condition (Sketch of the Proof)
13:03 Convergence - 1
13:53 Convergence - 2
14:15 Convergence - 3
14:17 Convergence - 4
14:17 Outline - Experiments and Take-Home Message
14:20 Results
16:00 Conclusion and Extensions
17:12 Machine Translation
20:00 - Questions

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