• 융합신호처리학회 학술대회논문집
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• 한국신호처리시스템학회 2001년도 하계 학술대회 논문집(KISPS SUMMER CONFERENCE 2001
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• pp.77-80
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• 2001

This paper presents a new threshold-based denoising method by using undecimated discrete wavelet transform (UDWT). It proved excellency of the UDWT compared with orthogonal wavelet transform (OWT), spatia1ly selective noise filtration (SSNF) and NSSNF added new parameter. Methods using the spatial correlation are effectual at edge detection and image enhancement, whereas algorithm is complex and needs more computation However, UDWT is effective at denoising and needs less computation and simple algorithm.

• 한국정보통신학회논문지
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• 제5권5호
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• pp.853-860
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• 2001

본 논문에서는 웨이브렛을 이용한 두 가지 새로운 잡음 제거 방법으로, 공간적 상관관계를 이용한 NSSNF(new spatially selective noise filtration)과 threshold에 기초한 UDWT(undecimated discrete wavelet transform)을 제시한다. NSSNF에서는 기존의 SSNF에 새로운 파라메타를 추가하여, 융통성 있는 SNR 이득 특성을 얻도록 하였으며, UDWT에서는 hard-threshold를 적용하여, 기존의 soft-threshold를 적용한 OWT(orthogonal wavelet transform)보다 우수한 잡음 제거 효과를 얻도록 하였다. 이러한 테스트 환경으로는 AWGN을 선택하였으며, 개선 효과의 판단 기준으로 SNR을 사용하여, 기존의 잡음 제거 방법과 비교 분석하였다.

• 한국멀티미디어학회논문지
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• 제20권10호
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• pp.1655-1661
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• 2017

A high-speed directional interpolation algorithm based on the pattern of a $2{\times}2$ pixel block is proposed in this paper. The basic concept of the proposed algorithm is started from UDWT(un-decimated discrete wavelet transform), but there are no transform operations. In order to detect the direction of the edge, 4-pixel differences of two pairs in the $2{\times}2$ block are compared. The $2{\times}2$ block patterns are grouped into total 8 classes, and thereafter the directional interpolation is executed according to the type of the pattern. Since the calculation of the proposed algorithm is very simple and needs a few additions on integer data type, the computation time is almost same as that of bilinear interpolation algorithm. However, experimental results show that the output quality of the proposed one is better than those of the conventional interpolation ones in the objective quality and the computation time.

• 한국정보통신학회논문지
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• 제6권8호
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• pp.1139-1145
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• 2002

웨이브렛 변환 데이터는 신호의 상세 정보를 포함하고 있으므로 주파수 대역별로 필터링할 수 있다. 따라서, 본 논문에서는 중요한 두 가지 잡음을 웨이브렛을 사용하여 제거하였다. AWGN 환경에 대해서 hard-threshold를 적용한 UDWT(undecimated discrete wavelet transform)를 사용하였으며, 임펄스 잡음환경에 대해서는 임계치에 의한 잡음 제거와 웨이브렛에 의한 신호의 slope를 이용하여, 잡음 제거 효과를 최대로 함과 동시에 원신호의 edge를 인식하도록 하였다. 이러한 잡음 제거 효과의 판단 기준으로 SNR을 사용하였으며, 테스트 신호로서 Blocks와 DTMF(dual tone multi frequency)를 사용하였다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1997년도 한국자동제어학술회의논문집; 한국전력공사 서울연수원; 17-18 Oct. 1997
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• pp.1387-1390
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• 1997

In this paper we propose a novel way to restore degraded image using wavelet transform & filterbank. First, we devide a degraded image into 4-suband images using UDWT(Undecimated Wavelet Transform), and then use a proper CLS (Constrained Least Square) filter in each subband. Using a proper CLS filter ineach subband, we can save high grequency components of original image. We reconstruct a restored image from the downsampled subband images using wavelet tansform. Even though there is a trade-off between ISNR and calculation loads, we reduce the calculation loads by using wavelet transform in reconstruction with a negligible degradatiion in ISNR.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 제13회 신호처리 합동 학술대회 논문집
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• pp.605-608
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• 2000

This paper introduces a new structure for the undecimated discrete wavelet transform (UDWT). This structure combines the stationary wavelet transform with a lifting scheme and its design is based on a polyphase structure .where the downsampling and split stage are removed. The suggested structure inherits the simplicity of the lifting scheme, such that the inverse transform is easily implemented. The performanace of the proposed undecimated lifting is verified on a signal denoising application.