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Motion estimation using regions
Sull, Sanghoon The Korea Institute of Information and Commucation 1998 韓國通信學會論文誌 Vol.23 No.9
We present a two step approach for estimating the motionand sturcture parameters from region orrespondences in two frames. Given four or more region corresondences on the same planar surface, the motion and planar orientation parameters are first linearly estimated based on second-order approximation of the displacement field of the image plane. Then, using this linear estimate as an initial guess, a nonlinear estimate is obtained by iteratively minimizing an objective function using the exact experession of the displacement field. The objective function involves the centroids of corresponding regions and relationships among low-order moments. Through simulations, we show that the two-step region-based approach gives robust estimates. The performance of nonlinear region-based estimation is compared with that of linear region-based and point-based methods. Experimental results for two image pairs, on esynthetic and one real, ar epresented to show the practical applicability of our approach.
Keypad Navigator : Rendering Web Pages in Mobile Devices
Guilherme Dreossi,Sanghoon Sull 한국정보과학회 2009 한국정보과학회 학술발표논문집 Vol.36 No.1
Displaying web content in mobile devices still represents a great challenge for mobile device developers, because there are no standards and no general solution. In this work we propose a general way to navigate the web using a mobile device. Our approach consists of segmenting the screen into nine blocks and according to where the desired information is; we zoom in into that specific block, as many times as necessary. To accomplish this, we make use of the DOM Tree generated by the browser to calculate the exact location where to zoom. The method is robust, works with all types of contents and at the same time is very simple and intuitive, which is a requirement for any mobile user interface.
Lee, Hoonjae,Sull, Sanghoon [Institute of Electrical and Electronics Engineers 2012 IEEE transactions on broadcasting Vol.58 No.1
<P>During consecutive large picture information changes under limited bandwidth, the use of constant bit rate (CBR) encoding for high definition television (HDTV) broadcasting systems often causes serious picture quality degradation due to the tight constraint on small buffering delay, whereas a variable allocation of bits depending on the picture information changes results in large buffering delay. In this paper, we propose a frame-layer variable bit rate (VBR) video encoding method for maintaining locally consistent picture quality of an encoded video with small buffering delay, which can be used for a video on demand (VOD) system which streams an encoded video file to a client device under limited bandwidth or a real-time streaming application allowing a small delay. An objective function defined as a sum of the local distortion variation of the encoded pictures and the underflow levels at the decoder buffer is minimized with respect to the discrete frame-layer quantization step sizes subject to a constraint on the target number of bits within a temporal sliding window. Then, the constrained discrete minimization problem is converted to an unconstrained continuous minimization problem by introducing a Lagrange multiplier and is solved by applying the first-order necessary condition for local minima with respect to the quantization step sizes. Experimental results demonstrate that the proposed method provides a lower local standard deviation of PSNR comparing with the recent VBR method by 29.2% on average with small buffering delay.</P>
Frame loss concealment for stereoscopic video plus depth sequences
Tae-Young Chung,Sanghoon Sull,Chang-Su Kim IEEE 2011 IEEE transactions on consumer electronics Vol.57 No.3
<P>In this work, an efficient frame loss concealment algorithm for stereoscopic video plus depth sequences is proposed. To conceal an erroneous left color frame, we extrapolate motion vectors for the temporal error concealment. To conceal a left depth frame, we exploit the motion vectors of the corresponding left color frame. To conceal a right color frame, we employ a 3D image warping technique to determine matching pixels between inter-views, and perform the reconstruction based on the similarities of the motion vectors and the intensity differences of matching pixels. Finally, to conceal a right depth frame, we use the motion vectors of the right color frame and the left color frame. Simulation results show that the proposed algorithm is more effective than conventional algorithms in recovering erroneous color and depth frames. Moreover, it is also demonstrated that the proposed algorithm can be used for efficient virtual view synthesis in error prone environments.</P>
조용래(Cho Yongrae),설상훈(Sull Sanghoon) 한국방송·미디어공학회 2005 한국방송공학회 학술발표대회 논문집 Vol.2005 No.-
본 논문은 디지털 방송에서 다양한 부가 정보 제공 및 관련 기기의 기능을 효과적으로 활용하기 위한 연구로서, 방송 시스템에서의 방송이나 편집 등을 고려하여 색인 정보를 재사용하는 알고리즘에 관한 것이다. 이를 위해 본 논문에서는 비주얼 리듬을 이용한 원본 영상과 목표 영상의 매칭을 제안하며, 비주얼 리듬의 히스토그램을 특징 벡터로 사용하여 유사도를 계산한다. 검색 시 목표 영상에 대해 우선 검색 구간을 설정하여 검색 시간을 줄이고자 하였으며, 실제 이 알고리즘을 적용한 결과 약 97%의 정확도의 매칭 결과를 보였다. 또한 결과를 시각적으로 쉽게 알 수 있었기에 오류를 수정하는데 수월하였다. 이를 통해 기존의 색인화 정보를 목표 영상의 복호화 작업 없이 쉽게 재사용 할 수 있어, 불필요한 비용의 증가를 방지하는 효과를 기대할 수 있다.
Fast thumbnail generation in integer DCT domain for H.264/AVC
Myounghoon Kim,Hoonjae Lee,Sanghoon Sull IEEE 2011 IEEE transactions on consumer electronics Vol.57 No.2
<P>In this paper, we propose a simple and efficient method for generating a thumbnail or 1/4 reduced-size image in integer Discrete Cosine Transform (DCT) domain for H.264/AVC video streams. To accomplish this, we first obtain the integer DCT coefficients of a prediction residual using a newly-defined re-scaling operation of inverse quantization, and then perform a transform domain intra prediction in integer DCT domain through simplified matrix multiplication by using only shift operation and integer addition. Finally, we generate a thumbnail directly from a H.264/AVC intra frame. Experimental results demonstrate that the proposed algorithm can reduce the total computational complexity about 16% on average, while maintaining almost the same image quality as compared to the existing method.</P>
Hanje Park,Hoonjae Lee,Sanghoon Sull IEEE 2014 IEEE transactions on multimedia Vol.16 No.2
<P>This paper presents an efficient method for adjusting the 3D depth of an object including as much as a whole scene in stereo 3D images by utilizing a virtual fronto-parallel planar projection in the 3D space perceived by a viewer. The proposed method just needs to establish object correspondence instead of the accurate estimation of the disparity field or point correspondence. We simulate the depth adjustment of a 3D point perceived by a viewer through a corresponding pair of points on the stereo 3D images by moving the virtual fronto-parallel plane on which the left and right points are projected. We show that the resulting transformation of image coordinates of the points can be simply expressed by three values of a scale factor and two translations that depend on one parameter for the depth adjustment. The experimental results demonstrate the feasibility of the proposed approach that yields less visual fatigue and smaller 3D shape distortion than the conventional parallax adjustment method. The overall procedure can be efficiently applied to each frame of a stereo video without causing any artifact.</P>