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—A novel unsupervised video object segmentation algorithm is presented, aiming to segment a video sequence to objects: spatiotemporal regions representing a meaningful part of the sequence. The proposed algorithm consists of three stages: initial segmentation of the first frame using color, motion, and position information, based on a variant of the(More)
A learning approach to knowledge-assisted image analysis and classification is proposed that combines global and local information with explicitly defined knowledge in the form of an ontology. The ontology specifies the domain of interest, its subdomains, the concepts related to each subdomain as well as contextual information. Support vector machines(More)
In this paper, we provide an overview of the Social Event Detection (SED) task that is part of the MediaEval Benchmark for Multimedia Evaluation 2013. This task requires participants to discover social events and organize the related media items in event-specific clusters within a collection of Web multimedia. Social events are events that are planned by(More)
Intravascular ultrasound (IVUS) constitutes a valuable technique for the diagnosis of coronary atherosclerosis. The detection of lumen and media-adventitia borders in IVUS images represents a necessary step towards the reliable quantitative assessment of atherosclerosis. In this work, a fully automated technique for the detection of lumen and(More)
The detection of lumen and media-adventitia borders in intravascular ultrasound (IVUS) images constitutes a necessary step for the quantitative assessment of atherosclerotic lesions. To date, most of the segmentation methods reported are either manual, or semi-automated, requiring user interaction at some extent, which increases the analysis time and(More)
This paper presents a GPU-assisted version of the LIB-SVM library for Support Vector Machines. SVMs are particularly popular for classification procedures among the research community, but for large training data the processing time becomes unrealistic. The modification that is proposed is porting the computation of the kernel matrix elements to the GPU, to(More)
This paper introduces an algorithm for fast temporal segmentation of videos into shots. The proposed method detects abrupt and gradual transitions, based on the visual similarity of neighboring frames of the video. The descriptive efficiency of both local (SURF) and global (HSV histograms) descriptors is exploited for assessing frame similarity, while(More)
This paper provides an overview of the Social Event Detection (SED) task, which is organized as part of the MediaEval 2011 benchmarking activity. With the convergence between social networking and multimedia creation and distribution being experienced on a regular basis by hundreds of millions of people worldwide, this task examines how new or state of the(More)
This paper provides an overview of the Social Event Detection (SED) task, which is organized as part of the MediaEval 2012 benchmarking activity and examines how social events can be detected by automatically analyzing social multime-dia content. The 2012 edition of the SED task follows the successful completion of the first edition of SED, in 2011. This(More)
—An approach to knowledge-assisted semantic video object detection based on a multimedia ontology infrastructure is presented. Semantic concepts in the context of the examined domain are defined in an ontology, enriched with qualitative technologies are used for knowledge representation in the RDF(S) metadata standard. Rules in F-logic are defined to(More)