• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2017.06a
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• pp.133-134
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• 2017

본 논문에서는 차세대 방송 표준 ATSC (Advanced Television Systems Committee) 3.0 기반 LDM (Layered Division Multiplexing) 및 스케일러블 비디오 코덱 (Scalable Video Codec) 을 활용한 지상파 방송시스템 기술을 살펴보고 그 성능을 비교 분석한다. 코어 레이어 (Core Layer)와 인핸스드 레이어 (Enhanced Layer)로 구성된 LDM 기반 PLP (Physical Layer Pipe)에, 스케일러블 비디오 코딩이 적용된 베이스 레이어 (Base Layer)와 인핸스먼트 레이어 (Enhancement Layer) 스트림을 각각 전송함으로써 하나의 RF 채널에 두 개 이상의 서비스를 전달할 경우 채널 효율을 극대화 할 수 있다. 본 논문에서는 이동 및 고정용 서비스, 즉 두 개의 서비스를 전송할 때 제안된 LDM 및 스케일러블 비디오 코덱을 사용한 기술과 TDM (Time Division Multiplexing) 및 Simulcast 를 적용한 기술과의 성능 비교를 통해 제안된 기술의 우수성을 검증하고자 한다.

• Proceedings of the Korean Information Science Society Conference
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• 2006.10d
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• pp.193-198
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• 2006

멀티미디어 데이터를 이종의 수신자에게 안정적으로 전달하고자 하는 것은 인터넷에서 중요한 주제 중의 하나이다. 특히, 최근에 소개된 계층형 MDC(Layered Multiple Description Coding) 기법은 오버레이 멀티캐스트에서 이 문제를 효율적으로 해결하는데 중요한 접근방법이다. 그러나, 이 과정에서 저속 수렴(slow convergence)과 참가 실험(join experiment) 동안에의 손실과 같은 문제가 새롭게 발생하게 되었다. 본 논문에서는 비디오 스트리밍 서비스에서 위의 문제를 해결할 수 있는 효율적인 계층형 멀티캐스트 혼잡 제어 기법을 소개한다. 여기서 제시하는 기법의 가장 특징적인 점은 사용자가 수신할 계층(layer)의 수를 결정하기 위하여 패킷페어(packet-pair)방식에 기반한 수신률 조절 메커니즘을 사용하는 것이다. 결과적으로 본 논문에서는 수신자가 최적의 전송률에 빠르게 수렴하면서도 손실을 최소화할 수 있는 종단-대-종단간 혼잡 제어 기법을 제시한다.

• Journal of Broadcast Engineering
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• v.14 no.5
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• pp.561-572
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• 2009

In this paper, we propose an efficient layer-separable PES packetization and processing scheme for DVB-S2 satellite broadcasting service based on SVC video. Unlike the conventional single layer-based video coding such as MPEG-2, MPEG-4 and H.264, SVC can combine numerous number of video layers, which are aggregated to a single bitstream. Therefore, it is necessary to devise a new PES packetization scheme that can efficiently separate multiple video layers of SVC. In order to combine the layered characteristics of the SVC video and the robust channel coding capability of LDPC (Low Density Parity Check) of DVB-S2 for unequal error protection, we propose an efficient PES packetization in the transmitter side and PES packet processing scheme in the receiver side of DVB-S2. We prove the effectiveness of the proposed scheme in terms of processing speed and time delay required for processing of the separated layers of SVC video in the satellite broadcasting service.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.5
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• pp.435-446
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• 2014

Even if it is important to transmit high rate multimedia information without any transmission errors for surveillance systems, it is difficult to achieve error-free transmission due to infra-less adhoc networks. In order to reduce the transmission errors furthermore, additional signal overheads or retransmission of signals should be required, but they may lead to transmission delay. This paper represents a study on low delay and adaptive video transmission for the unmanned surveillance systems by developing system protocols. In addition, we introduce an efficient and adaptive control algorithm using system parameters for exploiting unmanned surveillance system properly over multi-channels.

• Journal of Broadcast Engineering
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• v.20 no.5
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• pp.756-769
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• 2015

In this paper, we propose a scalable coding method for high dynamic range (HDR) and standard dynamic range (SDR) videos based on Scalable High Efficiency Video Coding (SHVC). The proposed method has multi-layer coding architecture that consists of base layer for SDR videos and enhancement layer for HDR videos to support the backward compatibility with legacy codec and display devices. Also, to improve coding efficiency of enhancement layers, a global inverse tone mapping is applied to the reconstructed SDR video and the compensated frames are referred for coding of the enhancement layer. The proposed method is found to achieve BD-Rate gain of 43.0% on average (maximum 76.3%) for the enhancement layer and 15.7% on average (maximum 31%) for dual-layer against the SHM 7.0 reference software.

• Journal of Digital Contents Society
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• v.8 no.4
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• pp.441-449
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• 2007

In video coding, motion estimation is a process to estimate the pixel of the current frame from the reference frame, which affects directly the predictive quality and the encoding time. This paper is related to AHHS(Adaptive Hierarchical Hexagon Search) using spatio-temporal motion activity for fast motion estimation. The proposed method defines the spatio-temporal motion activity of the current macroblock using the motion vectors of its spatio-temporally adjacent macroblocks, and then conventional AHS(Adaptive Hexagon Search) is performed if the spatio-temporal motion activity is lower, otherwise, hierarchical hexagon search is performed on a multi-layered hierarchical space constructed by multiple sub-images with low frequency in wavelet transform. In the paper, based on computer simulation results for multiple video sequences with different motion characteristics, the performance of the proposed method was analysed and assessed in terms of the predictive quality and the computational time. Experimental results indicate that the proposed method is both suitable for (quasi-) stationary and large motion searches. The proposed method could keep the merit of the adaptive hexagon search capable of fast estimating motion vectors and also adaptively reduce the local minima occurred in the video sequences with higher spatio-temporal motion activity.

• Journal of Engineering Education Research
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• v.24 no.1
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• pp.34-45
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• 2021

This research is a case study about "Critical Thinking and Debate Education" class which was done for freshmen at the engineering college of "S" Women's University. Real time remote classes through LMS and ZOOM were the most effective tools under on-line circumstances, considering the fact that video lectures only cannot cultivate students' capabilities of critical thinking and communication. Throughout the analysis on students' self-reflection journals and lecture evaluations, this paper examined considerable future points and the pros and cons of "Critical Thinking and Debate Education" under online presentation and discussion situation. As research outputs, students told they could feel less nervousness and anxiety when they exercise and have a presentation because they could choose familiar space for them. In addition, students also told that they feel comfortable about both self-feedback and peer evaluation, repeatedly seeing the recorded video clip. However, on the contrary, sometimes students felt uncomfortable due to unstable internet connection through the online classes, and they also were regretful about the missing chances of interaction between a teacher and students and of intimate exchanges among students. They also told they had felt a kind of limit of enhancing their presentation skills just in front of the monitor. Considering these outcomes, this research paper points out that online education needs to be proceeded by strengthening multi layered feedback to students with the build-up of a non-face-to-face stable educational infrastructure, application of online instructional strategy, and utilization of YouTube platform and video contents. Through this research paper, I hope the new system of encompassing on/off line "Critical Thinking and Debate Education" and effective teaching and learning method can be developed soon by strengthening the strength of online education.

• Journal of KIISE:Information Networking
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• v.27 no.4
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• pp.476-481
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• 2000

멀티캐스트 데이터의 기밀성을 유지하기 위해서는 멀티캐스트 데이터를 그룹의 공동키로 암호화하여 전송하여야 한다. 그러나 멤버가 멀티캐스트 그룹에 동적으로 가입하거나 탈퇴하는 경우에는 그룹의 공통키를 변경하기 위해 필요한 계산량과 메시지의 수가 그룹의 크기에 비례해 커지는 규모확장성 문제에 봉착하게 된다. 이러한 문제를 해결하기 위해 그룹의 멤버나 키에 계층 구조를 두는 여러 가지 방법들이 제안된바 있으나 계층 멀티캐스트에 적용할 수 있는 방법은 아직 제안된 바가 없다. 본 논문에서는 계층 비디오 멀티캐스트 환경에 적용할 수 있는 두가지의 그룹 키 분배 방법을 제안한다. 첫 번째 방법은 각 계층에 대해 별도의 키 계층 구조를 유지하는 계층별 키트리 방법이며 두 번째 방법은 하나의 공통 키트리를 유지하고 각 계층을 공통 키트리상의 서브트리로 유지하는 통합 키트리 방법이다. 성능분석결과 멤버가 그룹에 가입해 있는 동안 계층 상승을 자주하는 경우는 계층별 키트리 방법이 유리하며 계층의 개수가 많고 계층 상승이 잦지 않은 경우는 통합 키트리 방법이 효율적이다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2010.11a
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• pp.78-81
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• 2010

In this paper, we propose an efficient and effective selective protection scheme to SVC that exploit the propagation of protection effect by protecting significant frames that can give the maximum visual quality degradation. We model SVC dependency coding structure as a directed acyclic graph which is characterized with an estimated visual quality value as the attribute at each node. The estimated visual quality is calculated by using our model based on the proportions of intra- and inter-predicted MBs, amounts of residual, and estimated visual quality of reference frames. The proposed selective protection scheme traverses the graph to find optimal protection paths that can give maximum visual quality degradation. Experimental results show that the proposed selective protection scheme reduces the required number of frames to be protected by 46.02% compared to the whole protection scheme and 27.56% compared to the layered protection scheme.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37C no.11
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• pp.1054-1063
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• 2012

In this paper, we introduce basic theories, effects and applications of the unequal error protection (UEP) system that is expected to play a major role in the future multi-layered broadcast system. Also we show results of surveys on the various previous studies and standards about the UEP systems, and we give prospects of standardizations and future applications of UEP based on the surveys.