• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2009.11a
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• pp.107-110
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• 2009

본 논문에서는 무손실 위성 영상 압축의 효율을 높이기 위해 H.264/AVC의 무손실 화면내 부호화에 기반한 새로운 문맥기반 적응적 가변 길이 부호화 (CAVLC) 방법을 제안한다. 기존의 H.264/AVC의 CAVLC는 손실 압축에 적합하게 설계되었기 때문에, 변환과 양자화 과정을 수행하지 않는 무손실 압축에서 최적의 압축 성능을 제공하지 못한다. 본 논문에서는 손실 압축과 무손실 압축 환경에서 잔여 영상 신호의 통계적 차이가 있음을 확인하고, 무손실 위성 영상 압축 환경에서 잔여 신호의 통계적 특성을 고려하여 향상된 CAVLC 기반의 무손실 위성 영상 압축 방법을 제안한다. 제안한 방법을 사용하여 위성 영상을 압축한 결과 기존의 대표적인 무손실 영상 압축 방법인 JPEG-LS와 CALIC 보다 약 12% 정도 비트 수를 감소시켰다.

• Proceedings of the Korea Contents Association Conference
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• 2009.05a
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• pp.861-864
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• 2009

디지털 콘텐츠는 원본을 훼손하지 않고 복제 및 인터넷을 통한 배포가 가능하기 때문에 콘텐츠에 대한 지적 재산권 보호 할 수 있는 장치는 필수적이다. 본 논문에서는 디지털 콘텐츠의 지적 재산권을 보호할 수 있는 강인한 워터마킹 방법을 제안한다. 제안한 방법은 최신의 비디오 압축방법인 H.264에서 GOP(group of picture)내에서 시각적으로 민감하지 않고, 에러 전파를 할 수 없는 GOP의 프레임에 워터마크 강도를 크게 하고, 그렇지 않은 프레임에는 워터마크 강도를 상대적으로 낮추어 적은 화질열화에 비해 상대적으로 검출율이 높아 질 수 있도록 하였다. 실험 결과 H.264의 압축에서 높은 검출률을 보였고, 프레임별 화질 열화는 존재하지만 비디오를 재생하여 시각적인 테스트를 할 경우 화질 열화가 숨겨짐을 보였다. 제안하는 방법은 콘텐츠의 지적 재산권을 보호하기 위한 응용프로그램을 필요로 하는 DVD 제작자, IPTV 방송국과 같은 곳에 필요로 할 것이다.

• Proceedings of the Korean Information Science Society Conference
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• 2008.06d
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• pp.268-271
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• 2008

본 논문에서는 H.264/SVC(Scalability Video Coding)를 기반으로 한 ROI(Region Of Interest) 화질 개선 방법을 제안한다. H.264/SVC는 공간적, 시간적, 화질적 확장성을 지원하고 있다. 이로 인해 네트워크 환경과 모바일 기기에 더욱 적합하게 되었다. 하지만 이러한 확장성은 객관적인 화질 개선을 고려하여 설계되었다. 본 연구는 주관적인 화질 개선을 위해 관심 영역을 설정하였으며, 이를 위하여 관심 영역을 설정하기 위한 방법과 이를 효율적으로 전송하기 위한 효과적인 전송 방법을 제안한다. 또한 기존 SVC 확장성까지도 활용하는 화질 개선 방법을 제시 한다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2012.07a
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• pp.37-39
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• 2012

ITU-T와 ISO/IEC의 공동 작업으로 제정된 H.264/AVC는 기존 비디오 표준들에 비해 동일한 화질에서 약 30%~70%의 비트 량을 절감할 수 있으며, 동일한 비트 량으로 PSNR이 2~3dB 가량 우수한 영상을 제공할 수 있다. H.264/AVC는 인트라 부호화 효율을 높이기 위해 공간 영역에서 주변 화소를 이용하여 $4{\times}4$ luma 예측의 9가지 모드와 $16{\times}16$ luma 예측의 4가지 모드에 대한 비트율-왜곡 최적화 기법을 사용하여 최적의 인트라 예측 모드를 선택한다. 본 논문에서는 $4{\times}4$ luma 예측에서 발생하는 정보량을 줄이기 위해 사용하는 MPM을 기존의 방법과는 다르게 연산을 통해 상관도를 높임으로써 보다 정확한 MPM 결정으로 부호화 효율을 높이는 방법을 제안하였다. 실험결과, 제안한 방법은 기존의 방법과 비교하여 BD-RATE 평균 약 -1.4%의 성능 개선 효과를 보였다.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.1
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• pp.103-110
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• 2011

This study is to comparatively analyze the characteristics of pH decrease in recycled fine aggregates for embankment and landfill produced from waste concrete by using natural process and artificial process. The result was as follows In case of recycled fine aggregates left outdoor, it was found that pH level was decreased if the thickness of embankment becomes thinner, or the materials left outdoors owing to high concentration of $CO_2$ in atmosphere caused by respirations of people. When the air was permeated, pH level was decreased more effectively. It was analyzed that this phenomenon was caused by efficient supply of $CO_2$ in the recycled fine aggregates owing to high-pressure ventilators. In case of water spraying treatment, sprayed water facilitated hydration of unhydrated cement to dissolve calcium hydroxides which neutralized $CO_2$ in the atmosphere during desiccation process and decrease pH level by a considerable margin. In case of Immersed treatment, decrease of pH was not sufficient. When facilitating the supply of $CO_2$, pH level of the recycled fine aggregates was decreased by the largest margin. It was analyzed that this phenomenon was caused by efficient supply of $CO_2$. From the above results, it was analyzed that the most effective method of reducing pH level of the recycled fine aggregates from the aspects of pH reduction performance, economic efficiency and workability was repeated wet-dry cycles of spraying water to the aggregates in the proportion of 1:0.5 by weight and then treating by forcefully blowing $CO_2$ gas into the aggregates.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.1C
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• pp.37-47
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• 2009

When H.264 encoded video streams are transmitted over wireless network, packet loss is unavoidable. Responding on this environment, we propose methods to recover missed motion vector in the decoder: At first, A candidate vector set for missing macroblock is estimated from high correlation coefficient of neighboring motion vectors and missing block vectors the algorithm clusters candidate vectors through distances amongst motion vectors of neighboring blocks. Then the optimal candidate vector is determined by the median value of the clustered motion vector set. In next stage, from the candidate vector set, the final candidate vector of missing block is determined it has minimum distortion value considering directions of neighboring pixels' boundary. Test results showed that the proposed algorithm decreases the candidate motion vectors $23{\sim}61%$ and reduces $3{\sim}4sec$ on average processing(decoding) time comparing the existing H.264 codec. The PSNR, in terms of visual quality is similar to existing methods.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.46 no.2
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• pp.48-56
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• 2009

We propose a fast intra mode skip decision algorithm for H.264/AVC video encoding. Although newly added MB encoding algorithms based on various prediction methods increase compression ratio, they require a significant increase in the computational complexity because we calculate rate-distortion(RD) cost for all possible MB coding modes and then choose the best one. In this paper, we propose a fast mode decision algorithm based on an adaptive motion vector map(AMVM) method for H.264/AVC video encoding to reduce the processing time for the inter frame. We verify that the proposed algorithm generates generally good performances in PSNR, bit rates, and processing time.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.12C
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• pp.1039-1045
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• 2008

The H.264/AVC video coding standard shows extremely higher coding efficiency, but it causes high computational complexity. Especially, the intra mode decision using the rate-distortion method requires many computations. Thus, the efficient intra mode decision methods have been proposed by decreasing the encoding complexity. In this paper, we propose an efficient intra mode decision algorithm using $4{\times}4$ integer transform coefficients in the conversion of MPEG-2 to H.264 standard. It is shown that the proposed algorithm reduces encoding time and complexity compared to the conventional algorithm, while showing similar PSNR performance.

• The Journal of the Korea Contents Association
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• v.8 no.5
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• pp.29-37
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• 2008

To transmit video bit stream over low bandwidth such as wireless channel, high compression algorithm like H.264 codec is exploited. In transmitting high compressed video bit-stream over low bandwidth, packet loss causes severe degradation in image quality. In this paper, a new algorithm for recovery of missing or erroneous motion vector is proposed. Considering that the missing or erroneous motion vectors in blocks are closely correlated with those of neighboring blocks. Motion vector of neighboring blocks are clustered according to average linkage algorithm clustering and a representative value for each cluster is determined to obtain the candidate motion vector sets. As a result, simulation results show that the proposed method dramatically improves processing time compared to existing H.264/AVC. Also the proposed method is similar to existing H.264/AVC in terms of visual quality.

• Journal of KIISE:Software and Applications
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• v.31 no.4
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• pp.505-515
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• 2004

In a newspaper, 5W1H information is the most fundamental and important element for writing and understanding articles. Focusing on such a relation between a newspaper article and the 5W1H, we propose a summarization method based on the activation degree of 5W1H. To overcome problems of the lead-based and the title-based methods, both of which are known to be the most effective in newspaper summarization, sufficient 5W1H information is extracted from both a title and a lead sentence. Moreover, for each sentence, its weight is computed by considering various factors, such as activation degree of 5W1H, the number of 5W1H categories, and its length and position. These factors make a great contribution to the selection of more important sentences, and thus to the improvement of readability of the summarized texts. In an experimental evaluation, the proposed method achieved a precision of 74.7% outperforming the lead-based method. In sum, our 5W1H approach was shown to be promising for automatic summarization of newspaper articles.