Chien-Li Chou

Pattern-Based Near-Duplicate Video Retrieval and Localization on Web-Scale Videos

With the exponential growth of web multimedia contents, the Internet is rife with near-duplicate videos, the video copies applied with visual/temporal transformations and/or post productions. Two critical issues, copyright infringement and search result redundancy, arise accordingly. To resolve these problems, this paper proposes a spatiotemporal pattern-based approach under the hierarchical filter-and-refine framework for efficient and effective near-duplicate video retrieval and localization . Firstly, non-near-duplicate videos are fast filtered out through a computationally efficient data structure, termed pattern -based index tree (PI-tree). Then, an m- pattern -based dynamic programming (mPDP) algorithm is designed to localize near-duplicate segments and to re-rank the videos retrieved. The influence of time shift misalignment can be alleviated by time-shift m-pattern similarity (TPS) measurement. Comprehensive experiments on the five datasets are conducted to verify the effectiveness, efficiency, robustness, and scalability of the proposed approach. Convincing results demonstrate that our proposed approach outperforms the state-of-the-art approaches in terms of mean average precision (MAP) and normalized detection cost rate (NDCR) on the testing datasets. Furthermore, the proposed approach can achieve high quality of near-duplicate video localization in terms of quality frames (QF) and mean F1.

Recognizing tactic patterns in broadcast basketball video using player trajectory

The explosive growth of the sports fandom inspires much research on manifold sports video analyses and applications. The audience, sports fans, and even professionals require more than traditional highlight extraction or semantic summarization. Computer-assisted sports tactic analysis is inevitably in urging demand. Recognizing tactic patterns in broadcast basketball video is a challenging task due to its complicated scenes, varied camera motion, frequently occlusions between players, etc. In basketball games, the action screen means that an offensive player perform a blocking move via standing beside or behind a defender for freeing a teammate to shoot, to receive a pass, or to drive in for scoring. In this paper, we propose a screen-strategy recognition system capable of detecting and classifying screen patterns in basketball video. The proposed system automatically detects the court lines for camera calibration, tracks players, and discriminates the offensive/defensive team. Player trajectories are calibrated to the real-world court model for screen pattern recognition. Our experiments on broadcast basketball videos show promising results. Furthermore, the extracted player trajectories and the recognized screen patterns visualized on a court model indeed assist the coach/players or the fans in comprehending the tactics executed in basketball games informatively and efficiently.

Screen-strategy analysis in broadcast basketball video using player tracking

In basketball games, screen is a blocking move performed by an offensive player, who stands beside or behind a defender, in order to free a teammate to shoot, to receive a pass, or to drive in to score. Screen is the fundamental essence that most offensive tactics are executed with. In this paper, a screen-strategy analysis system is designed, and through combining the identified screens, what tactics are executed in basketball games can be speculated. The proposed system is capable of court region detection, camera calibration and player extraction. Player trajectories are computed by a Kalman filter-based tracking method and mapped to the real-world court coordinates. The player position/trajectory information greatly assists professional-oriented applications such as screen-strategy analysis and tactic inference. The experiments on broadcast basketball videos show encouraging results.

Near-duplicate video retrieval and localization using pattern set based dynamic programming

With the exponential growth of the web multimedia contents, illegal video copies are widespread and easy to be obtained from search engines and video sharing websites. For video copyright protection, near-duplicate video retrieval becomes more and more important. In this paper, we proposed a Pattern Set based Dynamic Programming (PSDP) algorithm to retrieve near-duplicate videos efficiently and effectively. In addition, the precise positions of the near-duplicate segments in videos can also be located. To better deal with the slow/fast motion and the dropped frame problem, the Time-shift Pattern set Similarity (TPS) is then applied. Two datasets are used to evaluate the effectiveness and efficiency of the proposed method, and the experimental results show that the proposed method outperforms the compared approaches in terms of precision and execution time in both two datasets.

Spiking and Blocking Events Detection and Analysis in Volleyball Videos

In volleyball matches, spiking is the most effective way to gain points, while blocking is the action to prevent the opponents from getting scores by spiking. In this paper, we propose an intelligent system for automatic spiking events detection and blocking pattern classification in real volleyball videos. First, the entire videos are segmented into clips of rallies by whistle detection. Then, we find the court region based on proper camera calibration, and detect the location of the net for judging the positions of spiking and blocking. Via analyzing the changes of moving pixels along the net, we make a bounding box around the blocking location, so as to classify the blocking patterns into two main categories based on the width of bounding box. Finally, two important tactic patterns, delayed spiking and alternate position spiking, are recognized. With the information of spiking events and blocking locations, we can collect the statistical data and make tactics inference easily. To the best of our knowledge, no previous work is focused on spiking or blocking event detection. The experimental results on the videos recorded by a university volleyball team are promising and demonstrate the effectiveness of our proposed scheme.

Extraction and representation of human body for pitching style recognition in broadcast baseball video

In baseball games, different release points of pitchers form several kinds of pitching styles. Different pitching styles possess individual advantages. This paper presents a novel pitching style recognition approach for automatic generation of game information and video annotation. First, an effective object segmentation algorithm is designed to compute the body contour and extract the pitchers body. Then, star skeleton is used as the representative descriptor of the pitcher posture for pitching style recognition. The proposed approach has been tested on broadcast baseball video and the promising experimental results validate the robustness and practicability.

Trajectory Based Jump Pattern Recognition in Broadcast Volleyball Videos

Jump actions are typically accompanied by spiking and imply significant events in volleyball matches. In this paper, we propose an effective system capable of jump pattern recognition in player moving trajectories from long broadcast volleyball videos. First, the entire video is segmented into clips of rallies by shot segmentation and whistle detection. Then, camera calibration is adopted to find the correspondence between coordinates in the video frames and real-world coordinates. With the homographic transformation matrix computed, real-world player moving trajectories can be derived by a sequence of tracked player locations in video frames. Jump patterns are recognized from the player moving trajectory by using a sliding window scheme with physics-based validation and context constraint. Finally, the jump locations can be estimated and jump tracks can be separated from the planar moving tracks. The experiments conducted on broadcast volleyball videos show promising results.

Computer-assisted self-training system for sports exercise using kinects

Self-training plays an important role in sports exercise. However, if not under the instruction of a coach, improper training postures can cause serious harm to muscles and ligaments of the body. Hence, the development of computer-assisted self-training systems for sports exercise is a recently emerging research topic. In this paper, we propose a Yoga self-training system, entitled YogaST, which aims at instructing the user/practitioner to perform the asana (Yoga posture) correctly and preventing injury caused by improper postures. Involving professional Yoga training knowledge, YogaST analyzes the practitioners posture from both front and side views using two Kinects with perpendicular viewing directions and assists him/her in rectifying bad postures. The contour, skeleton, and feature axes of the human body are extracted as posture representation. Then, YogaST analyzes the practitioners posture and presents visualized instruction for posture rectification so that the practitioner can easily understand how to adjust his/her posture.

HMM-based ball hitting event exploration system for broadcast baseball video

With the dramatic growth of fandom population, a considerable amount of research efforts have been devoted to baseball video processing. However, little work focuses on the detailed follow-ups of ball hitting events. This paper proposes a HMM-based ball hitting event exploration system for broadcast baseball video. Utilizing the strictly-defined layout of the baseball field, the proposed system first detects the game-specific spatial patterns in the field, such as the field lines, the bases, the pitch mound, etc. Then, the play region-the currently camera-focused region of the baseball field is identified for frame type classification. Since the temporal patterns of presenting the game progress follow a prototypical order, we consider the classified frame types as observation symbols and recognize ball hitting events using HMM. Experiments conducted on broadcast baseball video show encouraging results in frame type classification and ball hitting event recognition. Three practical applications, including highlight clip extraction by user-designated query, storyboard construction, and similar event retrieval, are introduced to address the applicability of our system.

Near-duplicate video retrieval by using pattern-based Prefix tree and temporal relation forest

With the explosive growth of the social multimedia sharing, copyright protection and search result refinement are always the critical issues for the service operators. To resolve the problems, content-based near-duplicate video retrieval is developed in recent years. In this paper, we construct a condensed Pattern-based Prefix tree (PP-tree) to index the patterns of reference videos for fast retrieval. To calculate how likely a query video and a reference video are near-duplicates, a novel algorithm for discovering the temporal relations among patterns is proposed. Comprehensive experiments on public datasets are conducted to verify the effectiveness and efficiency of the proposed method. Experimental results show that the proposed near-duplicate video retrieval approach outperforms the state-of-the-art approaches in terms of precision, recall, and execution time.