Skjalg Lepsoy

Statistical modelling of outliers for fast visual search

The matching of keypoints present in two images is an uncertain process in which many matches may be incorrect. The statistical properties of the log distance ratio for pairs of incorrect matches are distinctly different from the properties of that for correct matches. Based on a statistical model, we propose a goodness-of-fit test in order to establish whether two images contain views of the same object. This technique can be used as a fast geometric consistency check for visual search.

Selection of local features for visual search

In a compact descriptor for visual search only a limited number of local features may be included. The estimated probability for correct match between keypoints provides a good criterion for selection of a subset.

DynamicTV: a culture-aware recommender

A geographically homogeneous group of citizens shares much common knowledge, characteristics of their culture and history. This knowledge is captured for the use in an item-based recommender system that uses textual information, by introducing bias corpora: newspaper articles that represent the shared knowledge. We present a technique for incorporating and quickly replacing bias corpora in a case study of recommendation of TV contents on our IPTV platform. With this recommender, users watched more items and expressed satisfaction with the service.

Affine scale space for viewpoint invariant keypoint detection

The research of affine scale space is to create a more general approach to the affine invariant image scale representation by modifying the corresponding Gaussian filters in order to cope with the specific change of view point. It has the purpose to retain a linear relationship with the transiting of the view point. With this linear relationship, the affine scale space could be established as a more general approach for the affine invariant image retrieval, including affine feature detection and affine feature descriptor. The scope of this paper is to discuss the accessible to the affine scale space, its performance and a practical implementation to construct it in order to cope with the high complexity brought in by the scale space and the affine adaptation.

Loop detection in robotic navigation using MPEG CDVS

The choice for image descriptor in a visual navigation system is not straightforward. Descriptors must be distinctive enough to allow for correct localization while still offering low matching complexity and short descriptor size for real-time applications. MPEG Compact Descriptor for Visual Search is a low complexity image descriptor that offers several levels of compromises between descriptor distinctiveness and size. In this work we describe how these trade-offs can be used for efficient loop-detection in a typical indoor environment.

Enriching Search and Retrieval of Multimedia Information with DRM Services and Context-Based Content Adaptation

This paper presents a standards-based architecture for a complex and generic distributed multimedia scenario, which combines content search and retrieval, DRM, and context-based content adaptation together. The most innovative part of the proposed work comes from the integration of a flexible language for multimedia search based on MPEG query format (MPQF) standard with the application of video analysis algorithms for the automatic extraction of low-level features.