• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.12C
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• pp.1153-1161
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• 2005

The latest standard H.264 coding methods show better efficiency compared to the former coding standards from the rate distortion point of view, but also lead to high complexity. In this paper, we propose an adaptive and fast inter/intra prediction algorithm for H.264 video coding. In the inter prediction algorithm, an effective and simple mode selection method is proposed, which can adaptively adjust to motion estimation to reduce complexity. And proposed intra prediction algorithm reduces its complexity by using calculated Minimum Rate-Distortion costs in the prediction of Intra $16{\times}16$ and $4{\times}4$ modes. From experiment using JM8.4, our algorithm can reduce about $60.9\%$ of computation time as compared to JM, with only negligible PSNR and bitrate degradation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.10C
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• pp.820-828
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• 2008

In order to achieve high coding efficiency, H.264/AVC video coding standard adopts the techniques such as variable block size coding, motion estimation with quarter-pel precision, multiple reference frames, rate-distortion optimization, and etc. However, these coding methods have a defect to greatly increase the complexity for motion estimation. Particularly, from multiple reference frame motion estimation, the computational burden increases in proportion to the number of the searched reference frames. Therefore, we propose the method to reduce the complexity by controlling the number of the searched reference frames in motion estimation. Proposed algorithm uses the optimal reference frame information in both $P16{\times}16$ mode and the adjacent blocks, thus omits unnecessary searching process in the rest of inter modes. Experimental results show the proposed method can save an average of 57.31% of the coding time with negligible quality and bit-rate difference. This method also can be adopted with any of the existing motion estimation algorithm. Therefore, additional performance improvement can be obtained.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2011.07a
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• pp.574-577
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• 2011

H.264/AVC는 휘도 신호 $4{\times}4$ 블록을 위하여 9개의 화면 내 예측모드를 사용한다. 예측 모드는 8개의 방향성을 가진 모드와 하나의 비방향성 DC 모드가 있다. 휘도 신호 $16{\times}16$ 블록에서는 4가지의 예측 모드가 있으며 색차 신호 $8{\times}8$ 에서도 4개의 예측모드를 사용한다. 이러한 예측 모드들 중 최적의 예측 모드를 선택하기 위하여, 부호화기는 선택 가능한 모든 예측 모드의 율-왜곡 비용을 계산한 후, 최적의 율-왜곡 비용을 가진 예측 모드를 사용하여 부호화를 수행한다. 따라서 H.264/AVC의 화면 내 예측 과정은 많은 계산 복잡도를 가진다. 특히 하이 프로파일에서는 휘도 신호 $8{\times}8$ 블록이 화면 내 예측을 위해서 고려되므로 더욱 많은 계산 복잡도를 요구한다. 이에 본 논문은 H.264/AVC 하이 프로파일의 화면 내 예측의 부호화 계산 복잡도를 줄이는 방법을 제안한다. 현재 매크로 블록의 분산을 계산한 후, 이를 이용하여 율-왜곡 최적화에 후보로 사용되어지는 블록 모드를 결정하고, 각 블록 모드에서 제공하는 예측 모드들을 효율적으로 선택하는 방법을 연구 개발하였다. 제안된 방법은 기존 H.264/AVC 참조 소프트웨어인 JM13.1 부호화 시간 대비 약 83%의 연산시간이 감소하는 결과를 보였다.

• Proceedings of the KIPE Conference
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• 2002.07a
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• pp.589-592
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• 2002

The CCM (Continuous Conduction Mode) boost topology is generally used in the PFC (Power Factor Correction) regulator of household air-conditioning systems. There are three kinds of power devices-bridge rectifier diodes, FRDs (Fast Recovery Diodes), and IGBTs (or MOSFETs) - used In a boost PFC regulator. Selecting the appropriate device is very cumbersome work, specially, in the case of FRDs and IGBTs, because there are several considerations as described below: 1) High frequency leakage current regulation (conducted and radiated EMI regulation) 2) Power losses and thermal design 3) Device cost. It should be noted that there are trade-offs between the power loss characteristic of 2) and the other characteristics of 1) and 3). This paper presents a detailed evaluation by using several types of power devices, which can be unintentionally used, to show that optimal selection can be achieved. Based on the given thermal resistances, thermal analysis and design procedures are also described from a practical viewpoint.

• Proceedings of the Korean Information Science Society Conference
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• 2007.10d
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• pp.564-568
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• 2007

H.264/AVC는 최신의 국제 비디오 압축 표준으로 가변블록크기 지원, 다중 참조 프레임 움직임 보상 등의 기법으로 이전의 압축 표준인 MPEG-4, H.263등에 비해 비슷한 화질에서 비트율을 거의 50%정도 줄였다. 이러한 기법들로 압축 효율성이 높아진 반면, 계산 복잡도는 증가하게 되었다. 따라서 본 논문에서는 움직임 벡터 예측인 MVP를 이용하여 시간적 상관성을 고려하고 프레임 내의 주위 매크로블록 모드정보에 가중치를 부여하여 부호화를 매크로블록의 최종 모드를 빠르게 선택하는 기법을 제안한다. 실험에서 JM10.2의 모드 선택기법과 비교한 결과, 평균 85%이상 선택한 모드가 동일함을 보여주었다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.2
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• pp.603-606
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• 2005

오늘날 컴퓨터와 데이터 통신의 급속한 발달로 인해 멀티미디어 정보통신 기술이 비약적으로 발전하고 있다 .이러한 멀티미디어 데이터 중에서 동영상은 다른 데이터 형태에 비해 정보량이 매우 방대하다. 따라서 동영상을 처리하는 시스템에서는 압축 기법이 매우 중요한 역할을 차지한다. 이에 본 논문은 H.264 Intra예측을 기반으로 고속의 움직임 탐색 모드를 미리 결정하여 최적의 움직임 탐색 모드로 움직임 예측을 시행하였고, 기존의 4$^*$4, 8$^*$8, 16$^*$16 완전블록 탐색방식과 비교 평가하였다. 뿐만 아니라 이후 이를 바탕으로 움직임 예측 모듈을 VHDL로 구현한 후 성능평가의 기준으로 이용할 것이다.

• Journal of Power Electronics
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• v.15 no.1
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• pp.190-201
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• 2015

This paper uses the switching function approach to present a simple state model of the Vienna-type rectifier. The approach introduces the relationship between the DC-link neutral point voltage and the AC side phase currents. A novel direct power control (DPC) strategy, which is based on the sliding mode control (SMC) for Vienna I rectifiers, is developed using the proposed power model in the stationary ${\alpha}-{\beta}$ reference frames. The SMC-based DPC methodology directly regulates instantaneous active and reactive powers without transforming to a synchronous rotating coordinate reference frame or a tracking phase angle of grid voltage. Moreover, the required rectifier control voltages are directly calculated by utilizing the non-linear SMC scheme. Theoretically, active and reactive power flows are controlled without ripple or cross coupling. Furthermore, the fixed-switching frequency is obtained by employing the simplified space vector modulation (SVM). SVM solves the complicated designing problem of the AC harmonic filter. The simplified SVM is based on the simplification of the space vector diagram of a three-level converter into that of a two-level converter. The dwelling time calculation and switching sequence selection are easily implemented like those in the conventional two-level rectifier. Replacing the current control loops with power control loops simplifies the system design and enhances the transient performance. The simulation models in MATLAB/Simulink and the digital signal processor-controlled 1.5 kW Vienna-type rectifier are used to verify the fast responses and robustness of the proposed control scheme.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2010.11a
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• pp.96-99
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• 2010

H.264/AVC 부호화 표준은 영상의 특성을 반영하기 위해 $16{\times}16$부터 $4{\times}4$ 크기의 가변적인 블록을 이용하여 부호화 효율을 높인다. 하지만 이로 인해 부호기의 복잡도가 증가된다. 부호기 복잡도를 증가시키는 여러 요인 중, H.264/AVC의 모드 결정은 부호기의 복잡도를 증가시키는 주요인이다. 본 논문에서는 IPPP구조에서 비트율 왜곡값을 이용하여 고속으로 매크로블록의 모드를 결정하는 방법을 제안한다. 인트라 화면에서의 인트라 $4{\times}4$, 인트라 $16{\times}16$의 비트율 왜곡 평균값으로 영상에 적응적인 최대 임계값과 최소 임계값을 결정한다. 다음, $16{\times}16$, $16{\times}8$, $8{\times}16$ 인터 모드의 비트율 왜곡값이 최대 임계값과 최소 임계값으로 분할한 범위 중 어느 곳에 해당하는지를 살펴보고, 이에 따라 인트라 모드 결정 단계를 선택적으로 결정한다. 제안하는 알고리즘은 기존의 H.264/AVC에 비해 부호화 효율의 큰 감소 없이 평균 27.42%의 부호화 시간을 감소시켰다.

• Journal of the Korea Society of Computer and Information
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• v.9 no.2
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• pp.33-40
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• 2004

According as client/server is generalized by development of computer performance and information communication technology, Servers uses local cache for extensibility and early response time, and reduction of limited bandwidth. Consistency of cached data need between server and client this time and much technique are proposed according to this. This Paper improved update frequency cache consistency in old. Existent consistency techniques is disadvantage that response time is late because synchronous declaration or abort step increases because delaying write intention declaration. Techniques that is proposed in this paper did to perform referring update time about object that page request or when complete update operation happens to solve these problem. Therefore, have advantage that response is fast because could run write intention declaration or update by sel_mode electively asynchronously when update operation consists and abort step decreases and clearer selection.

• Journal of Korea Game Society
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• v.1 no.1
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• pp.55-60
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• 2001

With rapid development of graphic hardware, researches on Virtual Reality and 3D Games have received more attention than before. For more realistic 3D graphic scene, objects were to be presented with lots of polygons and the number of objects shown in a scene was remarkably increased. Therefore, for effective visualization of large polygon models like this, view-frustum culling method, that visualizes only objects shown in the screen, has been widely used. In general, the bounding boxes that include objects are generated firstly, and the boxes are intersected with view-frustum to check whether object is in the visible area or not. Recently, an algorithm that can check in-out test of objects using OpenGL's selection mode, which is originally used to select the objects in the screen, is suggested. This algorithm is fast because it can use hardware acceleration. In this study, by implementing and applying this algorithm to large polygon models, we showed the efficiency of OpenGL assisted View-Frustum Culling algorithm. If this algorithm is applied to 3D games that have to process more complicated characters and landscapes, performance improvement can be expected.