• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.12
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• pp.3653-3659
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• 2009

Inter-prediction is always the main bottleneck in H.264/AVC baseline profile. This paper describes an efficient inter-prediction hardware architecture design. H.264/AVC decoder supports various block types but reference software considers only the $4{\times}4$ block when the reference block is being fetched. This causes duplicated pixels which needs extra fetch cycles. In order to eliminate some of the duplicated pixels, the $8{\times}8$ and $4{\times}4$ blocks were considered in the previous design. If the block size is larger than or equal to the $8{\times}8$ block, it will be decomposed into several $8{\times}8$ blocks and if the block size is smaller than the $8{\times}8$ block it will be decomposed into several $4{\times}4$ blocks. Comparing with the reference software, the maximum and minimum cycle reduction of the previous design are 41.5% and 28.2% respectively. For further reduction of the fetch cycles, the various block types are considered in this paper. As a result, the maximum cycle reduction is 18.6% comparing with the previous design.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2009.05a
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• pp.112-115
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• 2009

Inter-Prediction is always the main bottleneck in H.264/AVC Baseline Profile. This paper describes an efficient Inter-Prediction hardware architecture design. H.264/AVC decoder supports various block types such as $16{\times}16$, $16{\times}8$, $8{\times}16$, $8{\times}8$, $8{\times}4$, $4{\times}8$, $4{\times}4$ block types. Reference Software(JM) only considers the $4{\times}4$ block type when the reference block is being fetched. This causes duplicated pixels which needs extra fetch cycles. In order to eliminate some of the duplicated pixels, the $8{\times}8$ and $4{\times}4$ block types were considered in the previous design. If the block size is larger than or equal to the $8{\times}8$ block type, it will be separated into several $8{\times}8$ block types and if the block size is smaller than the $8{\times}8$ block type it will be separated into several $4{\times}4$ blocks. For further reduction of the fetch cycles, the various block types are considered in this paper. As a result, the maximum cycle reduction percentage is 18.6% comparing with the previous design.

• Proceedings of the Korean Information Science Society Conference
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• 1999.10b
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• pp.580-582
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• 1999

본 논문에서는 리던던트 웨이블릿 변환을 이용한 지형메쉬(terrain mesh)의 간략화 방법을 제안한다. 기존의 MRA(Multi-Resolution Analysis) 기법을 이용한 지형메쉬의 간략화 기법은 처리과정에서 다운샘플링이 일어나게 되어 지형 데이터 중요한 특성점을 추출할 때 부분적으로 손실된 데이터를 이용한다는 단점을 갖는다. 이 논문은 전처리단계(preprocessing process)에서 지형메쉬의 간략화를 목표로 하여, 지형의 중요점 추출과정에서 리던던트 웨이블릿 변환기법을 이용하며 지형의 중요점 추출의 정확도를 높이고, 지형데이터가 갖는 중복성 (redundancy)을 제거하여 방대한 지형데이터를 간략화하는 방법을 제안한다.

• Proceedings of the Korean Information Science Society Conference
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• 2011.06b
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• pp.373-376
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• 2011

모바일 단말에서 소프트웨어의 기능을 구현할 때, 배터리 소모를 최소화 시키는 것이 매우 중요하다. 본 연구에서는 모바일 단말에서 파일 전송을 수행함에 있어서 에너지 효율적으로 처리하는 기법을 제안한다. 주요 아이디어는 클라이언트 부분에서 파일 유사도를 사용하여 대표 해시를 서버로 전송한다. 서버에서는 클라이언트에서 보내온 대표 해시와 자신이 가지고 있는 인덱스와 비교하여 유사도를 계산한다. 유사도에 따라 중복제거 파일 전송방식을 사용할지 일반적인 파일 전송을 할지 결정한다. 실험 결과 10%이상의 유사도를 가지는 파일들에 대해서 제안하는 기법이 배터리 소모를 줄일 수 있음을 보였다.

• Proceedings of the Korean Information Science Society Conference
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• 2004.04a
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• pp.445-447
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• 2004

본 논문에서는 H.263과 같은 MC-DCT방법을 사용하는 코덱에서 IDCT와 MC(Motion Compensation, 움직임보상)방법을 부분적으로 수정하여 제한된 비율의 축소영상을 디코딩 과정에서 직접 얻을 수 있는 방법을 제안한다. 제안한 방법에서는 8$\times$8 DCT 블록에 대하여 약간의 연산을 가하여 k$\times$k IDCT를 수행하고, 시간적 중복성을 제거하는 과정에서 근사적 움직임벡터를 이용한 2k$\times$2k MC 를 수행하였다. 기존의 코덱을 사용하고 후처리로 축소를 하는 경우와 비교하였을 때에 추가적인 오버헤드가 매우 경미하고 디코딩 과정이 많이 축소되어 계산효율에 있어서 대략 32%의 개선된 실험결과를 얻었고, 화질저하 현상이 개선됨을 실험적으로 보였다.

• Proceedings of the Korean Information Science Society Conference
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• 2004.10a
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• pp.529-531
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• 2004

Just-Just-in-Time 컴파일러를 이용하여 자바의 성능을 향상시키려면 여러 문제들을 극복하여야 한다. 이 문제 중 중요한 부분을 차지하는 것이 null check 코드와 array bound check코드를 어떻게 최적화하느냐는 것이다. Static한 컴파일 환경에서는 이미 많은 연구가 진행되어 매우 강력한 성능을 가지는 알고리즘이 알려져 있으나 이를 컴파일 시간이 수행시간의 일부인 Just-in-Time 컴파일 환경에 적응하기에는 컴파일 오버헤드가 너무 커서 적절하지 않다. 현재 Just-in-Time 컴파일러들은 가볍고 단순한 알고리즘을 적용하지만 중복된 array bounds check를 충분히 제거하지 못하거나 아니면 강력하지만 flow-insensitive한 SSA form을 기반으로 해야 하는 알고리즘을 사용하고 있다. SSA form의 적용은 SSA form으로의 변환과 되돌림에 의한 overhead로 가볍고 빠른 컴파일러를 지향하는 Just-in-Time 컴파일러에 부합되지 않는다. 본 논문은 변수간의 대소관계를 표현하는 그래프를 array bounds check 알고리즘에 적용해 충분한 power를 내면서도 flow-sensitive한 환경에서 동작하는 알고리즘을 제안한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.7A
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• pp.1063-1075
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• 2000

This paper proposes an adaptive error concealment technique for compressed video. Since redundancy is extracted out during compression process, compressed video is vulnerable to errors which occur during transmission of video over error prone networks such as wireless channels and Internet. Error concealment is a process of reconstructing video out of damaged video bit stream. We proved that scalable encoding is very useful for error concealment. Analysis of experiments shows that some part of image is better concealed by using base layer information and other part of image is better concealed by using previous frame information. We developed a technique which enables to decide which methodology is more effective, adaptively, based on motion vectors and regional spatial activity. We used H.263v2 for scalable encoding, but, our approach could be applied to all DCT based video codec.

• Journal of Broadcast Engineering
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• v.20 no.4
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• pp.509-520
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• 2015

A design for the merge mode of three dimensional High Efficiency Video Coding (3D-HEVC) is proposed in this paper. The proposed design can reduce the implementation complexity by removing the duplicated modules of the HEVC. For the extension codec, the implementation complexity is as crucial as coding efficiency, meaning if possible, extension codec needs to be easily implemented through by reusing the design of the legacy codec as-is. However, the existing merging process of 3D-HEVC had been built-in integrated in the inside of the HEVC merging process. Thus the duplicated merging process of HEVC had to be fully re-implemented in the 3D-HEVC. Consequently the implementation complexity of the extension codec was very high. The proposed 3D-HEVC merge mode is divided into following two stages; the process to reuse the HEVC modules without any modification; and the reprocessing process for newly added and modified merging modules in 3D-HEVC. By applying the proposed method, the re-implemented HEVC modules, which accounted for 51.4% of 3D-HEVC merge mode confirmed through the operational analysis of algorithm, can be eliminated, while maintaining the same coding efficiency and computational complexity.

• KIPS Transactions on Software and Data Engineering
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• v.1 no.1
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• pp.1-6
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• 2012

Web pages in a template-based web application (TWA) are automatically populated using a template shared by the pages with contents specific to the pages. So users can easily obtain information guided by a consistent structure of the template. Reduced duplicated code helps to increase the level of maintainability as well. However, TWA still has the interaction problem of classic web applications that each time a user clicks a hyperlink a new page is loaded, although a partial update of the page is desirable. This paper proposes a reengineering technique to transform the multi-page structure of legacy Java-based TWA to a single page one with partial page refresh. In this approach, hyperlinks in HTML code are refactored to AJAX-enabled event handlers to achieve the single page structure. In addition, JSP and Servlet code is transformed in order not to send data unnecessary for the partial update. The new single page consists of individual components that are updateable independently when interacting with a user. Therefore, our approach can improve interactivity and responsiveness towards a user while reducing CPU and network usage. The measurement of our technique applied to a typical TWA shows that our technique improves the response time of user requests over the TWA in the range from 1 to 87%.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.10 no.2
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• pp.7-12
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• 2010

In this paper, we analyze and simulate the performance of a cooperative communication system adopting a maximum likelihood (ML) equalizer. In wireless communication systems, cooperative communication schemes employing several relays can be applied for extending the communication coverage. It is assumed that both relays and user terminals can move. Therefore, coverages of two or more relays can overlap each other. If wanted and interfering signals are transmitted through the same channel and there are one terminal in the overlapped region, its performance is degraded due to interference. Hence, we use a ML equalizer for rejecting the effect of interfering signal and enhancing the communication system performance. The cooperative system performance is evaluated in terms of bit error probability. From the simulation results, it is demonstrated that the ML receiver shows good interference cancellation performance although its complexity is high.