| The news report is an important information carrier. Users pay attention to the news based on some specific events. Therefore a kind of intelligent services, which can automatically analyzing and tracking the news are in urgent need. The research of event-based news tracking is developed in text. Compared with the report based on text media, news video is faced with some problems, such as complexity of structure and multiplicity of media modals. Tracking reports in news video across different event-based sources is a challenging work.News video can be represented by a hierarchical structure consisting of 4 levels: frame, shot, story and video, in which story is the unit relating news events. Based on news video database, the research on the technique of identifying and tracking the stories which report the same news event is becoming the frontier topic in news video research field. Therefore, this thesis explores the topic on event-based news video story tracking technology, which is a research issue with great significance in theory and wide perspective in application. The goal of this thesis is to find a possible way to solve the problems of analyzing and utilizing information in news video database based on event by probing into the key technologies of tracking news stories.Firstly, the architecture of tracking news stories is proposed in this thesis. Secondly, the related key techniques of story segmenting, story correlation analyzing and story tracking are discussed. Feasibility and effect of these techniques are validated by experiments. The original contributions of this thesis can be described as follows:1. A frame of event-based news video story tracking is proposed. Firstly, relevant concepts and terms are defined. Then, describing modals of news video and story are investigated. And, this thesis proposes a pattern named"story space"for describing news video database. These works provide theoretical basis for tracking news stories. On this basis, this thesis proposes technology frame of tracking news stories, which discusses the approaches and key techniques to realize event-based news story tracking, and points out the problems this thesis concentrates on.2. A news video story segmentation method is proposed and improved. In view of characters of news video's edition, this thesis presents a novel strategy for selecting video and audio candidate points as segmentation boundaries, in which an adaptive method to detect anchorperson shot is studied prominently. Different set operating methods are developed to fuse diverse modal candidate points and get story boundaries efficiently.3. News video story correlation analyzing method is proposed. This thesis investigates internal relations and domain knowledge between near duplicate keyframes and correlation analysis. To increase matching speed of keyframes essentially, approach for constructing sub-database and pruning local keypoints is studied. Then a hierarchical approach for identifying near duplicate keyframes based on matching local keypoints is proposed. Finally, this thesis presents a method to identify correlations of related stories based on near duplicate keyframes and transitivity of correlations.4. A method for tracking news video stories with"multithreading"is proposed. In order to incarnate"multithreading"of news event reporting, a method for calculating similarity of news stories is presented in detail. It fuses information of all semantic levels and all media modals, in which methods to calculate similarity of local feature in lower visual feature, similarity of keyframe scene class in middle caption, similarity of text in high-level semantic and fusion strategy of these similarities are researched prominently.Then, this thesis studies validity of graph theory for tracking news stories and proposes an approach for tracking the similarity of news stories with"multithreading"based on digraph.5. A system for tracking news stories is designed and implemented. The design idea and each functional module of system NStoryThread are described in detail, and the implementation of prototype system is also presented, which provides a support to the applications of the frame and relevant methods.As a general, the thesis focuses on the key techniques of tracking news video stories, such as story segmentation, story correlation analysis, story tracking and so on, and each method is validated by experiments. The achievements of this thesis promote the development of news video analyzing and data mining, and also have great theoretic and realistic significance in multimedia information analysis.
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