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Department of Computer Science Seminar
2008 Series

Using Ontology and Semantic Detectors for Concept-based Video Search

Dr. Chong-Wah Ngo
City University of Hong Kong

Date: March 4, 2008 (Tuesday)
Time: 2:00 - 3:00 pm
Venue: RRS628, Sir Run Run Shaw Building, Ho Sin Hang Campus

Semantic-based video retrieval has been one of the long-term goals in multimedia computing. Traditional content-based approaches of deriving semantics purely based on low-level features have proven their limitation in conquering the so-called semantic gap. Modern approaches enable the semantic search by pooling a set of concepts and thus forming a semantic space to facilitate the high-level understanding of user queries and low-level features. The search method is referred to as concept-based video search. In this talk, I will present the ideas of building large-scale concept detectors and utilizing the detectors for ontology reasoning in video search. In concept detection, the effective way of exploiting bag-of-visual-words representation will be described, including the detection of interest points, choices of word weighting, size of visual vocabulary, stop word removal, and visual linguistics. For ontology reasoning, I will introduce our works on how to construct an ontology-enriched semantic space to utilize the semantic detectors for effective query reasoning. The empirical insights based on the recent TRECVID benchmark evaluations will be presented to show the challenges of search in large-scale video database.

Chong-Wah Ngo received his PhD in Computer Science from the Hong Kong University of Science and Technology (HKUST) in 2000. He received his MSc and BSc, both in computer engineering, from Nanyang Technological University (NTU) of Singapore. Before joining City University of Hong Kong in 2002, he was with Beckman Institute of University of Illinois in Urbana Champion. He was also a visiting researcher in Microsoft Research Asia (MSRA). His recent research interests include large-scale multimedia information retrieval and video computing. He has been serving as technical program committee in various major multimedia-related conferences including ACM Multimedia (MM), International Conf. on Image and Video Retrieval (CIVR) and International Conf. on Multimedia and Expo (ICME). He is the leader of video retrieval group (VIREO): in CityU. He also serves as the chairman of ACM Hong Kong Chapter recently.

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