Browsing by Author "Hung, YP"

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A 3D predictive visual tracker for tracking multiple moving objects with a stereo vision system
(1995)
Hung, YP
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Tang, CY
;
Shih, SW
;
Chen, Z
;
Lin, WS
This paper presents a 3D feature-based visual tracker for tracking multiple moving objects by using a predictor that first partitions 3D features into different common-motion clusters and then predicts the motion of each cluster with Kalman filters. The 3D features are computed from a sequence of stereo images by combining two 2D temporal matching modules and one stereo correspondence module. To partition the 3D features into different common-motion clusters, we propose a RANSAC-based clustering method by using rigid body consensus which assumes that all the extracted 3D features on a rigid body have the same 3D motion. By using the motion estimates obtained with the RANSAC-based method as the measurements, we are able to use linear Kalman filters to predict the motion of each cluster, and then, to predict the next position of each 3D feature. Preliminary experiments showed that the proposed 3D predictive visual tracker can serve as a robust 3D feature tracker for an active stereo vision system.
A Bayesian approach to video object segmentation via merging 3-D watershed volumes
(2005-01-01)
Tsai, YP
;
Lai, CC
;
Hung, YP
;
Shih, ZC
;
資訊工程學系
In this letter, we propose a Bayesian approach to video object segmentation. Our method consists of two stages. In the first stage, we partition the video data into a set of three-dimensional (3-D) watershed volumes, where each watershed volume is a series of corresponding two-dimensional (2-D) image regions. These 2-D image regions are obtained by applying to each image frame the marker-controlled watershed segmentation, where the markers are extracted by first generating a set of initial markers via temporal tracking and then refining the markers with two shrinking schemes: the iterative adaptive erosion and the verification against a presimplified watershed segmentation. Next, in the second stage, we use a Markov random field to model the spatio-temporal relationship among the 3-D watershed volumes that are obtained from the first stage. Then, the desired video objects can be extracted by merging watershed volumes having similar motion characteristics within a Bayesian framework. A major advantage of this method is that it can take into account the global motion information contained in each watershed volume. Our experiments have shown that the proposed method has potential for extracting moving objects from a video sequence.
A method for calibrating a motorized object rig
(2006)
Huang, PH
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Tsai, YP
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Lo, WY
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Shih, SW
;
Chen, CS
Object Movies (OMs) have been successfully used in many applications. However, the techniques for acquiring OMs still need to be improved if high-quality and efficient OMs are desired. In this paper, we present a method for calibrating a motorized object rig to facilitate the acquisition of OMs. We first apply the CPC kinematic model to formulate the 3D configuration of the device, and then propose a method to estimate the parameters of the CPC model of the device. Furthermore, a visual tool is provided for users to adjust the controllable axes of the rig according to the estimated results. After this calibration, more accurate camera parameters can be obtained and then be used for different purposes. In this work, we use the parameters to reconstruct, from an OM, the 3D model of the object, and then adjust the OM according to the center of the 3D model so that a high-quality OM can be obtained for rendering.
Augmented stereo panoramas
(2006)
Chen, CW
;
Chan, LW
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Tsai, YP
;
Hung, YP
;
資訊工程學系
Panoramas and object movies are popular image-based techniques for modeling and rendering 3D scenes and objects. In this paper, we present a method which allows the authors of virtual exhibition systems to produce an augmented stereo panorama by interactively integrating stereo object movies into a stereo panorama. When navigating in the augmented stereo panorama with a stereoscopic display, the user can directly browse the stereo object movies that he is interested in. With augmented stereo panoramas, the user can enjoy more persuasive interaction with better depth perception. To our best knowledge, this paper is the first work to integrate stereoscopic image-based scenes with stereo object movies.
Automatic detection and tracking of human heads using an active stereo vision system
(2000-03-01)
Tang, CY
;
Chen, Z
;
Hung, YP
;
資訊科學與工程研究所
;
Institute of Computer Science and Engineering
A new head tracking algorithm for automatically detecting and tracking human heads in complex backgrounds is proposed. By using an elliptical model for the human head, our Maximum Likelihood (ML) head detector can reliably locate human heads in images having complex backgrounds and is relatively insensitive to illumination and rotation of the human heads. Our head detector consists of two channels: the horizontal and the vertical channels. Each channel is implemented by multiscale template matching. Using a hierarchical structure in implementing our head detector, the execution time for detecting the human heads in a 512 x 512 image is about 0.02 second in a Spare 20 workstation (not including the time for image acquisition). Based on the ellipse-based ML head detector, we have developed a head tracking method that can monitor the entrance of a person, detect and track the person's head, and then control the stereo cameras to focus their gaze on this person's head. In this method, the ML head detector and the mutually-supported constraint are used to extract the corresponding ellipses in a stereo image pair. To implement a practical and reliable face detection and tracking system, further verification using facial features, such as eyes, mouth and nostrils, may be essential. The 3D position computed from the centers of the two corresponding ellipses is then used for fixation. An active stereo head has been used to perform the experiments and has demonstrated that the proposed approach is feasible and promising for practical uses.
Comparison between immersion-based and toboggan-based watershed image segmentation
(2006-03-01)
Lin, YC
;
Tsai, YP
;
Hung, YP
;
Shih, ZC
;
資訊工程學系
Watershed segmentation has recently become a popular tool for image segmentation. There are two approaches to implementing watershed segmentation: immersion approach and toboggan simulation. Conceptually, the immersion approach can be viewed as an approach that starts from low altitude to high altitude and the toboggan approach as an approach that starts from high altitude to low altitude. The former seemed to be more popular recently (e.g., Vincent and Soille), but the latter had its own supporters (e.g., Mortensen and Barrett). It was not clear whether the two approaches could lead to exactly the same segmentation result and which approach was more efficient. In this paper, we present two "order-invariant" algorithms for watershed segmentation, one based on the immersion approach and the other on the toboggan approach. By introducing a special RIDGE label to achieve the property of order-invariance, we find that the two conceptually opposite approaches can indeed obtain the same segmentation result. When running on a Pentium-III PC, both of our algorithms require only less than 1130 s for a 256 x 256,image and 115 s for a 512 x 512 image, on average. What is more surprising is that the toboggan algorithm, which is less well known in the computer vision community, turns out to run faster than immersion algorithm for almost all the test images we have used, especially when the image is large, say, 512 x 512 or larger. This paper also gives some explanation as to Why the toboggan algorithm can be more efficient in most cases.
Improved characteristics of ultrathin CeO2 by using postnitridation annealing
(2004-02-01)
Wang, JC
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Hung, YP
;
Lee, CL
;
Lei, TF
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電子工程學系及電子研究所
This work demonstrates the improved characteristics of an ultrathin CeO2 dielectric by using the post-N2O plasma treatment with additional rapid thermal N-2 annealing. The CeO2 after the treatment exhibits superior characteristics such as a small effective oxide thickness (similar to2.25 nm), a low leakage current (5.4 x 10(-4) A/cm(2)), a high breakdown electric field (-24 MV/cm), a long projected 10 yr lifetime (-12 MV/cm), a small capacitance-voltage hysteresis (25 mV), and a high barrier height for Frenkel-Poole emission (0.55 eV). These good properties are attributed to the nitrogen incorporation into the dielectric to eliminate the traps after annealing. The postnitridation annealing appears to be a very useful treatment for future ultrathin metal-oxide gate dielectrics. (C) 2004 The Electrochemical Society.
Real-time software method for preserving eye contact in video conferencing
(2004-09-01)
Tsai, YP
;
Kao, CC
;
Hung, YP
;
Shih, ZC
;
資訊工程學系
By maintaining eye contact in visual communication, such as in video conferencing, the feeling of intimacy can be greatly enhanced. Unfortunately, due to the physical constraints on the arrangement of cameras and monitors, it is not easy to preserve eye contact in video conferencing. Most people have tried to solve this problem using hardware approaches, which usually lead to bulky or expensive solutions. In this paper, we propose a real-time software method for preserving eye contact in video conferencing. For each station involved in video conferencing, we use two pre-calibrated cameras to acquire a stereo view of the local participant. Then, we apply disparity-based view morphing to the acquired stereo view to generate the desired view that preserves eye contact with another participant. Our experiments demonstrate that the eye contact problem can indeed be solved in real-time by using our software approach. This is the first time a software approach has been shown to be practical for preserving eye contact in video conferencing.