• Journal of Broadcast Engineering
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• v.2 no.2
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• pp.94-104
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• 1997

This paper presents a new vertex-based binary shape coding scheme using one-dimensional vertex selection/encoding and vertex reordering. In compared with the conventional object-adaptive vertex encoding(OA VEL the extracted vertices are, firstly, classified into one-dimensional(lD) vertices and two-dimensional (2D) vertices in the proposed method. For lD vertices, new coding method proposed in this paper is performed. For 2D vertices, the vertex reordering and OA VE are carried out. Experimental results show that the proposed vertex-based coding scheme red.uces coding bits up to 12 % compared with the conventional one and its coding gain depends on the characteristics of contour.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.7A
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• pp.1017-1027
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• 2000

In this paper, we propose a new coding method based on the distance between vertex segments for vertex positions in the vertex-based shape coding. The pixel lines are divided into the segments of a fixed length, and the segments that have vertex pixels are called vertex segments. We analyze the probability distribution of the relative distance between vertex segments and prove that it depends only on the ratio between the number of vertices and the number of segments. Considering the coding efficiency and implementation complexity, we choose a particular ratio to make a code table. For each input image, the segment size is chosen according tothe ratio, and the relative segment distances are entropy coded. It is shown that the proposed method is efficient for the images with many vertices.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.37 no.4
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• pp.35-45
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• 2000

The vertex-based boundary encoding scheme is widely used in object-based video coding area and computer graphics due to its scalability with natural looking approximation. Existing single framebased vertex encoding algorithm is not efficient for temporally correlated video sequences because it does not remove temporal redundancy. In the proposed method, a vertex point is selected from not only the boundary points of the current frame but also the vertex points of the previous frame to remove temporal redundancy of shape information in video sequences. The problem of selecting optimal vertex points is modeled as finding shortest path in the directed acyclic graph with weight The boundary is approximated by a polygon which can be encoded with the smallest number of bits for maximum distortion. The temporal redundancy between two successive frames is efficiently removed with the proposed scheme, resulting in lower bit-rate than the conventional algorithms.

• Journal of Digital Contents Society
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• v.3 no.2
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• pp.197-209
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• 2002

If we reduce the number of vertexes to decrease bit rate in polygon-based shape coding, the distortion of approximated contour increases rapidly. On the other hand, if we reduce the distortion, the number of vertexes increases rapidly and many bits are required to encode the vertexes. To improve this problem, in this paper we propose the approximation vertex search method. The encoder in the proposed method searches the type of distortion patterns that is the most similar to the shape which polygon edge and contour segment form and then encodes it. And then, the decoder mathematically finds the approximated vertexes from decoded distortion pattern information. Therefore, the proposed algorithm results in encoding many vertexes at a low bit rate and having the smoother shape than conventional method. As shown in computer simulation, the proposed method has less distortion than conventional method. It costs less bit rate by $10{\sim}20%$ than conventional algorithm in same distortion.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 1997.11a
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• pp.123-126
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• 1997

최근에는 영역(혹은 객체)를 이용하여 비디오 시퀀스를 표현하거나 부호화하는 기법들이 많이 연구되고 있다. 이러한 부호화 기법에서는 형태정보를 효율적으로 이용하는 것이 중요함에도 불구하고, 현재 사용되고 있는 대부분의 기법에서는 기존의 블록 기반 부호화 알고리즘에서처럼 오직 PSNR 만을 고려하여 움직임 벡터를 추정하고 있다. 따라서, 형태 정보를 다루는 효율적 움직임 추정 알고리즘이 필요하다. 본 논문에서는 각 영역의 경계(contour)를 잘 피팅(fitting)시키는 움직임 추정 방법을 생각해 본다. 이를 위하여 PSNR과 영역의 모양을 함께 고려하는 비용함수를 제안하고 이를 이용한 움직임 벡터 추정을 고려해 본다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.4
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• pp.1087-1099
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• 1998

In the content-based image coding, where each object in the scene is encoded independently, the shape, texture and motion information are very important factors. Though the contours representing the shape of an object occupy a great amount of data in proportion to the whole information, they strongly affect the subjective image quaility. Therefore, the distortion of contour coding has to be minimized as much as possible. In this paper, we propose a new method for the contour coding in which the contours are approximated to polygon and the eorror signal occurring from polygonal approximation are transformed with new basis functions. Considering the facts that confour segments occurring from polygonal approximation are smooth curves and error signals have two zero-ending points, we design new basis functions based on the Legendre polynomial and then transform the error signals with them. When applied to synthetic images such as circles, ellipses and etc., the proposed method provides, in overall, outstanding results in respect to the transform coding gain compared with DCT and DST. And in the case when applied to natural images, the proposed method gives better image quality over DCT and comparable results with DST.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.40 no.1
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• pp.114-123
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• 2003

This paper proposes an efficient method for encoding the shape information of the object in the image. The polygonal approximation method is categorized into a loss coding method and is widely used for approximating object's shape information. The proposed method selects less number of vertices than IRM (iterated refinement method) or PVS (progressive vertex selection) when the maximum distortion is given, so reduces the bit-rates. The proposed method selects the vertices of a polygon with a simple and efficient method considering the rate-distortion sense. We construct the shape information coder, which shows the outstanding performance in the rate-distortion sense, based on the conventional progressive vertex selection method and the new vertex selection condition that we propose in this paper. Simulation results show that the proposed method has better performance than other conventional vertex selection methods in the tate-distortion sense.

• Journal of KIISE:Computer Systems and Theory
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• v.32 no.5
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• pp.187-195
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• 2005

A new segmentation-based image coding method which no needs transmission of contour data is proposed. The shape information acts as bottleneck in the segmentation-based video coding because it has much portion of transmission data. The proposed method segments a previous decoded frame, instead of a current frame. As a result, there is no need for transmission of contour information to a decoder. Therefore, the saved bits can be assigned to encode other information such as error signals. As shown in experiment results, if data rate is very highly increased due to abrupt motion under very low bit rate coding having limited transmission bits, PSNR of conventional block-based method go down about 20dB, while the proposed method shows a good reconstruction quality without rapid PSNR drop.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1991.04a
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• pp.91-95
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• 1991

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.6B
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• pp.1174-1182
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• 1999

Recently the shape information of the visual object in the scene is more important, as the completion of the MPEG-4 standard and the progress of the MPEG-7 standard. This paper represents the study of effective coding method of vertices that are used in the polygonal approximation to represent the feature of visual object. In the proposed method, we make the centers of gravity of triangles that are made using the vertices of polygonal approximation and encode them sequentially We can get a coding gain because the centers of the gravity of triangles have narrower dynamic ranges.