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Enhanced two-bit transform based motion estimation via extension of matching criterion
Changryoul Choi,Jechang Jeong IEEE 2010 IEEE transactions on consumer electronics Vol.56 No.3
<P>Improved two-bit transform-based motion estimation algorithms are proposed in this paper. By extending the typical two-bit transform (2BT) matching criterion, the proposed algorithms enhance the motion estimation accuracy with almost the same computational complexity, while preserving the binary matching characteristic. Experimental results show that the proposed algorithm achieves peak-to-peak signal-to-noise ratio (PSNR) gains up to 0.42 dB compared with the conventional 2BT-based motion estimation.</P>
Modified rate distortion optimization using inter-block dependence for H.264/AVC intra coding
Jongmin You,Changryoul Choi,Jechang Jeong IEEE 2008 IEEE TRANSACTIONS ON CONSUMER ELECTRONICS - Vol.54 No.3
<P>H.264/AVC allows several prediction schemes including variable modes for intra and inter predictions. To take full advantage of all allowed modes, H.264 employs rate distortion optimization (RDO) as its mode decision method. However, RDO incorporated into the H.264 encoder assumes block independence because calculating rate distortion (RD) cost for all possible mode sets requires a huge number of computations. In contrast to this assumption, coding efficiency of intra prediction in the H.264 encoder is affected by reference pixels in neighboring blocks. Thus, RDO in the H.264 encoder has potential to improve coding performance by considering the accuracy of intra prediction for the next blocks during the mode decision process of the current block. In this paper, we propose new criteria for I4 times 4 mode decision and by using this criteria, the proposed method considers more mode sets to improve RD performance compared to the original RDO. Although the proposed method requires more computations compared to the original RDO, experimental results indicate that the proposed method noticeably improves coding efficiency compared to the original RDO.</P>
특이값 분해와 영상 피라미드를 이용한 대비 향상 알고리듬
하창우(Changwoo Ha),최창렬(Changryoul Choi),정제창(Jechang Jeong) 한국통신학회 2013 韓國通信學會論文誌 Vol.38 No.11(통신이론)
본 논문은 특이값 분해와 영상 피라미드를 이용한 새로운 대비 개선 방법을 제안한다. 제안된 방법은 다음과 같이 네 단계로 진행 된다. 먼저 전역 명암대비와 지역적 디테일을 향상시키기 위해 영상 피라미드를 이용하여 영상을 기저영상과 세부영상들로 분해한다. 전역 명암대비 향상은 특이값 분해를 이용하여 영상 전체의 명암대비를 향상시키고, 지역적 디테일 향상은 가중치를 이용하여 개선시킨다. 영상 합성은 영상의 컬러 일관성을 유지하기 위해 컬러와 명암성분들을 결합한다. 실험 결과를 통해 제안된 방법은 기존의 방법들보다 영상의 세부 정보를 강화하면서 전체적인 명암대비 개선을 보인다. This paper presents a novel contrast enhancement method based on singular value decomposition and image pyramid. The proposed method consists mainly of four steps. The proposed algorithm firstly decomposes image into band-pass images, including basis image and detail images, to improve both the global contrast and the local detail. In the global contrast process, singular value decomposition is used for contrast enhancement; the local detail scheme uses weighting factors. In the final image composition process, the proposed algorithm combines color and luminance components in order to preserve the color consistency. Experimental results show that the proposed algorithm improves contrast performance and enhances detail compared to conventional methods.