• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.8
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• pp.1677-1690
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• 1997

Block-transform coding is one of the most popular approaches for image compression. For example, DCT is widely used in the internaltional standards standards such as MPEG-1, MPEG-2, JPEG, and H.261. In the block-based transform coding, blocking artifacts may appear along block boundaries, and they can cause severe image degradation eqpecially when the transform coefficients are coarsely quantized. In this paper, we propose a new method for blocking artifacts reduction in transform-coded images. For blocking artifacts reduction, we add a correction term, on a block basis, composed of a linear combination of 28 basis images that are orthonormal on block boundaries. We select 28 DCT kernel functions of which boundary values are linearly independent, and Gram-Schmidt process is applied to the boundary values in order to obtain 28 boundary-orthonormal basis images. A threshold of bolock discontinuity is introduced for improvement of visual quality by reducing image blurring. We also investigate the number of basis images needed for efficient blocking artifacts reduction when the compression ratio changes.

• Journal of Broadcast Engineering
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• v.15 no.1
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• pp.133-143
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• 2010

This paper proposes a quadtree image compression method which encodes images efficiently and also makes unartificial compressed images. The proposed compression method uses edge-based quadtree decomposition to preserve the significant edge-lines, and it utilizes the predictive coding scheme to exploit the high correlation of the leaf node blocks. The simulation results with $256\times256$ grayscale images verify that the proposed method yields better coding efficiency than the JPEG by about 25 percents. The proposed method can provide more natural compressed images as it is free from the ringing effect in the compressed images which used to be in the images compressed by the fixed block based encoders such as the JPEG.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.36S no.1
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• pp.70-80
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• 1999

In this paper, a new hierarchical image segmentation algorithm based on human visual system(HVS) characteristic is proposed which can efficiently reduce and control transmission information quantity without the degradation of the subjective and objective image quality. It consists of image segmentation based on mathematical morphology and region merging considering HVS characteristic for the pairs of two adjacent regions at each level of the hierarchy. Image segmentation is composed of 3-level hierarchical structure. In the region merging structure of each level, we extract the pairs of two adjacent regions which human vision can't discriminate, and then merge them. The proposed region merging method extracts pairs of two neighbor regions to be merged and performs region merging according to merging priority based on HVS characteristics. The merging priority for each adjacent pair is determined by the proposed merging priority function(MPF). First of all, the highest priority pair is merged. The information control factor is used to regulate the transmission information at each level. The proposed segmentation algorithm can efficiently improve bottleneck problem caused by excessive contour information at region-based very low bit rate coding. And it shows that it is more flexible structure than that of conventional method. In experimental results, though PSNR and the subjective image quality by the proposed algorithm is similar to that of conventional method, the contour information quantity to be transmitted is reduced considerably. Therefore it is an efficient image segmentation algorithm for region-based very low bit rate coding.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.8
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• pp.1740-1747
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• 2004

In this paper, we proposed an effective method for detecting fingerprint ridge direction based on the run-length and chain codes. First, a fingerprint image is normalized, and it is thresholded to obtain binary image with foreground and background regions. The foreground regions is composed of fingerprint ridges, and the ridges is encoded with the run-length and chain codes. To detect directional information, the boundary of ridge codes is traced, and curvature is calculated at ecah point of boundary. And the detected direction value is smoothed with appropriate window locally. The proposed method is applied to NIST and FVC2002 fingerprint database to evaluate performance. By the experimental results, the proposed method can be used to obtain ridge direction value in fingerprint image.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.6A
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• pp.510-516
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• 2005

In this paper, we discuss parameters of line code and simulate a same optical ethernet having minimum bandwidth(MB810) and non-minimum bandwidth line code(8B/10B) to present the possibility of improving of transmission performance using minimum bandwidth line code on the high speed optical ethernet. We design the high speed optical ethernet using Serial type LAN PHY 10GBASE-E(WDM type LAN PHY 10GBASE-LX4) for the single(multi) channel link. To compare the transmission performance of MB810, 8B/10B line code we measure the bit error rate(BER) according to the received optical power of single and multi channel link.

• Proceedings of the IEEK Conference
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• 2000.11d
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• pp.97-100
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• 2000

This paper presents a new approach to the vertex based shape coding technique. The conventional approaches encode objects using a spline method with the same distortion coefficients. The proposed approach, however, classifies the objects based on the object's features, and then applies different distortion values depending on the classified object types. Using this pre-classifying technique, this paper reduces the bit rate and the computational complexity necessary for the encoding process. The performance of the proposed method has been proved by experiments on the various sample Images.

• Proceedings of the IEEK Conference
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• 1998.10a
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• pp.915-918
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• 1998

Region based coding consistsof image segmentation contour and texture coding. Contour coding techniques can be classified into contour or shape-oriented approaches. In this paper, geodesic skeleton based on shape-oriented approach is used for contour coding. Efficient application of geodesic skeleton for contour coding based on the characteristics of regions in segmented image will be discussed.

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.153-156
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• 2004

Spatial Audio Coding (SAC)은 낮은 대역폭에서 다채널/다객체 오디오 신호를 전송하기 위해 제안된 기술이다. 본 논문에서는 MPEG 에서 SAC 기술의 평가 방법으로 채택된 Multi-Stimulus test with Hidden Reference and Anchor (MUSHRA) 실험 절차에 대해서 설명한다. 또한 제 69 차 MPEG 회의에서 제안된 4 개 기관의 SAC 기술에 대한 청취실험을 수행하고 그 결과를 분석한다.

• Proceedings of the Korea Institute of Convergence Signal Processing
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• 2001.06a
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• pp.261-264
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• 2001

논문에서는 S+P 웨이브릿 변환과 정수 웨이브릿 필터들을 비교 분석하고, 9/7텝 정수 웨이브릿 필터를 이용하여 웨이브릿 변환을 하고, 점진적 전송에 적합 하고, 다중 분해능 구조의 종속성과 방향성에 대한 고려와 예측오차의 피드백을 이용한 컨텍스트 모델링 예측과 적응산술부호화에 의한 엔트로피 코딩 방법을 제안하였다. 다양한 영상들에 대한 실험을 통해 본 논문에서 제안한 무손실 영상 압축알고리즘을 S+P 웨이브릿을 이용한 결과와 비교하였다.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.8 no.1
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• pp.39-52
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• 1998

본 논문에서는 모듈러 지수승시에 요구되는 모듈러 곱셈의 반복 횟수를 줄이기 위해 SM(m)기법을 제안하며 지수를 SM(m)표현과 시스톨릭 SM(m) 표현으로 변환한다.그리고 변환된 스스톨릭 SM(m) 표현으로부터 모듈러 지수연산을 위한 선형시스톨릭 어레이를 제시한다. 제안된 기법은 기존의 방법보다 소프트웨어로 구현시에 선 계산기에 필요한 기업 장소의 크기를 줄였으며, 선형 시스톨릭 어레이로 구현시에 기존의 방법들보다 처리기의 개수를 감소시키며, 처리기내에 필요한 기억 장소의 크기를 줄였다. 수정된 부호화 디지트 기법과 비교하면 처리기의 개수를 24%정도 줄일 수 있다.