• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.225-228
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• 2005

According to a popularization of the Internet and digital lifestyle, digital watermarks have been proposed for protection of copyrighted multimedia content. In blind watermark detection, which an original image is not provided, robustness against geometric distortion and compression remains challenging. In this paper, we propose a new perceptual blind discrete wavelet transform - discrete Fourier transform (DWT-DFT) composite watermarking scheme that is robust against both general linear transform and JPEG compression. This algorithm constructs an image-dependent watermark in the most significant DWT coefficients, which is determined by using a hierarchical tree structure. Strength of watermark is determined from a just-noticeable difference (JND) profile of a perceptual model. Furthermore, a desired template is inserted into DFT domain of the watermarked image. In new manner, a cross-ratio of four collinear points is used for detecting the template. Experimental results have showed that the proposed scheme is robust against general linear distortion, JPEG compression and various general kinds of attacks in the Stirmark 3.1 watermark evaluation tool.

• Journal of Broadcast Engineering
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• v.3 no.2
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• pp.155-163
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• 1998

본 논문에서는 DCT를 기반으로 영상의 지역적인 특성에 따라 워터마크를 삽입하는 위치와 워터마크의 크기를 조절하며 영상에 워터마크를 삽입하는 기법을 소개하고자 한다. 영상의 속성에 따라 워터마크의 크기를 조정할 수 있는 JND(Just Noticeable Difference)와 워터마크가 삽입될 위치를 정하는 기준이 되는 Variance를 사용함으로써 워터마크를 영상에 삽입하였을 때, 원래 영상의 질(Qualtiy)을 저하시키지 않고도 영상변형에 강인하도록 한다. 또한, 전체 영상의 JND특성을 함께 고려해 줌으로써 영상에 삽입할 수 있는 워터마크의 크기를 지역적인 영상의 JND를 통해서 구해진 한계치보다 크게 조정하여 워터마크의 강인성을 증가시킨다. 실험 결과에 의하면 본 알고리즘은 워터마크가 삽입된 영상을 필터링(blurring, sharpening) 처리하거나 압축, 또는 노이즈를 첨가하는 등의 영상변형을 가안 후에도 워터마크를 검출함으로써 영상변형에 강인한 알고리즘을 확인할 수 있다.

• Proceedings of the Korea Institute of Convergence Signal Processing
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• 2003.06a
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• pp.54-57
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• 2003

본 논문에서는 멀티웨이브릿 변환영역에서 통계적 모델과 지각적 동조특성을 이용한 적응적 디지털 워터마킹 기법을 제안한다. 워터마크는 4레벨로 분해된 멀티웨이브릿 변환영역에서 최저주파 영역과 최고주파 대역들을 제외한 중간 및 고주파 영역에, 인간 시각 시스템(human visual model BWS)을 이용한 JND(just noticeable difference) 특성과 NVF(noise visibility function)를 이용한 통계적 특성을 기반으로 정상상태 가우시안 모델과 비정상상태 가우시안 모델에 따라 지각적 동조 특성을 이용하여 적응적으로 삽입된다. 실험 결과 제안한 방법에서 에지나 텍스쳐 영역에 더 강하게 삽입할 수 있었고, 평탄영역에서 보다 적응적으로 은닉할 수 있었으며 정상상태 가우시안 모델에서 지각적 동조특성을 이용한 방법이 더 우수한 비가시성과 강인성을 확인하였다.

• Proceedings of the Korea Multimedia Society Conference
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• 2003.05b
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• pp.334-337
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• 2003

본 논문에서는 멀티웨이브릿 변환영역에서 스토케스틱 모델과 지각적 동조특성을 이용한 적응 디지털 워터마크 은닉 방법을 제안한다. 워터마크는 4레벨로 분해된 멀티웨이브릿 변환영역에서 최저주파 영역과 최고주파 대역들을 제외한 중간 및 고주파 영역에, 인간 시각 시스템(human visual model ： HVS)을 이용한 JND(just noticeable difference) 특성과 NVF(noise visibility function)를 이용한 통계적 특성을 기반으로 정상상태 가우시안 모델에 따라 지각적 동조 특성을 이용하여 적응적으로 은닉된다. 실험 결과 제안한 방법에서 에지나 텍스쳐 영역에 더 강하게 삽입할 수 있었고, 평탄영역에서 보다 적응적으로 은닉할 수 있었으므로 우수한 비가시성과 강인성을 확인하였다

• Fashion & Textile Research Journal
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• v.21 no.1
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• pp.88-95
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• 2019

The purpose of this study was to figure out the various characteristics of the thickness sensation among elements of tactile sensation using psychophysical method. Firstly, panel screening was processed to select sensitive thickness panel using the triangle test. As a result of discriminating the paper thickness difference from 1 to 4 pieces, the female students perceived the thickness difference more sensitively than the male students (p<.05). Secondly, JND (Just Noticeable Difference) was obtained at percentage of stimulus detection rate in order to detect the degree of thickness difference by psychophysical method. It was found that the difference threshold of the entire group was about 0.125mm, with male group being about 0.178mm and female group being about 0.095mm. Thirdly, Weber's law was used to find the minimum discrimination difference between the stimuli. The experiments were conducted by increasing the paper's base thickness from 1.950mm to 1.330mm, and it was found that the difference tendency increased when the size of the basic stimulus increased. At this time, the minimum discrimination difference increased, but the Weber' fraction was not proportional to the magnitude of the stimulus. The significance of this study was that sensory evaluation was applied to research in the fields of clothing science and it seems effective to further screen and train sensitive students as material discrimination experts.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.43 no.6 s.312
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• pp.65-84
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• 2006

In this paper, we present an improved image formation model and propose a color image enhancement based on the model. In the presented image formation model, an input image is represented as a product of global illumination, local illumination, and reflectance. In the proposed color image enhancement, an input RGB color image is converted into an HSV color image. Under the assumption of white-light illumination, the H and S component images are remained as they are and the V component image only is enhanced based on the image formation model. The global illumination is estimated by applying a linear LPF with wide support region to the input V component image and the local illumination by applying a JND (just noticeable difference)-based nonlinear LPF with narrow support region to the processed image, where the estimated global illumination is eliminated from the input V component image. The reflectance is estimated by dividing the input V component image by the estimated global and local illuminations. After performing the gamma correction on the three estimated components, the output V component image is obtained from their product. Histogram modeling is next executed such that the final output V component image is obtained. Finally an output RGB color image is obtained from the H and S component images of the input color image and the final output V component image. Experimental results for the test image DB built with color images downloaded from NASA homepage and MPEG-7 CCD color images show that the proposed method gives output color images of very well-increased global and local contrast without halo effect and color shift.

• Journal of Broadcast Engineering
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• v.21 no.6
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• pp.929-943
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• 2016

This paper proposes the rate control algorithm based on the S-JND (Saliency-Just Noticeable Difference) model for considering perceptual visual quality. The proposed rate control algorithm employs the S-JND model to simultaneously reflect human visual sensitivity and human visual attention for considering characteristics of human visual system. During allocating bits for CTU (Coding Tree Unit) level in a rate control, the bit allocation model calculates the S-JND threshold of each CTU in a picture. The threshold of each CTU is used for adaptively allocating a proper number of bits; thus, the proposed bit allocation model can improve perceptual visual quality. For performance evaluation of the proposed algorithm, the proposed algorithm was implemented on HM 16.9 and tested for sequences in Class B and Class C under the CTC (Common Test Condition) RA (Random Access), Low-delay B and Low-delay P case. Experimental results show that the proposed method reduces the bit-rate of 2.3%, and improves BD-PSNR of 0.07dB and bit-rate accuracy of 0.06% on average. We achieved MOS improvement of 0.03 with the proposed method, compared with the conventional method based on DSCQS (Double Stimulus Continuous Quality Scale).

• The Journal of the Acoustical Society of Korea
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• v.34 no.2
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• pp.146-156
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• 2015

This study investigated how the location of sound absorptive materials and sound diffusers affects the acoustic performance of small auditoriums. It was conducted for a standard model established with the averaged dimension of 36 auditoriums which had opened since 2000 in Daehak-ro, Seoul. In this study, the installation area of finishing materials was calculated upon a back wall which had the smallest installation effective area of finishing materials. To analyze the changes of acoustic performance according to installation location of finishing materials, experiments were carried out using the 1/10 down scale models for 8 cases which were made by classifying the installation location of ceiling and side wall into the front, middle and rear part.The used acoustic parameters were reverberation time (RT), early decay time (EDT), clarity (C80), definition (D50) and speech transmission index (STI). In result, the index related to the amount of reverberant sound (RT, EDT) showed the great changes when evaluating it through just noticeable difference (JND), but the one related to clarity (C80, D50, STI) hardly indicated the changes. In case to obtain short reverberation time, it was most effective to control reverberation time through the side walls when installing sound absorptive and diffusive materials, and side wall front was the location which could get the shortest reverberation time.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.9
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• pp.853-860
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• 2012

This paper identifies a cause of pick up noise in a laser printer and a relationship between pick up noise and major components related to pick up noise. A pick up sound is affected by many components such as spring force, spring constant, and friction coefficient. Objective evaluation for the pick up sound is difficult because of back ground sound such as operating sound. Especially, a sound between a friction pad and a paper in the process of printing has become an essential issue in an aspect of quality evaluation. However the existing criteria for determining the above sound have solely relied on human's subjective judgments; which highlights the requirement to objectify these criteria. In this paper, the standard of existing pick up noise is established by finding the tonality, which is a psychoacoustic parameter, of noticeable limit sound level. Based on the findings of the method, the study has found factors which cause pick up noise and suggests the substitution of following components of printers such as spring constants, spring force, and the quality of friction pads. As a result, it is confirmed that the proposed pick up noise index has usefulness to classify whether existence of pick up noise with an objective evaluation and not to occur the noise based on design optimized combination of laser printer components.

• Proceedings of the Korea Information Processing Society Conference
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• 2003.11a
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• pp.23-26
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• 2003

디지털로 신호를 표현하는 방법은 기존 아날로그 표현하는 방법에 비해 많은 장점을 가지고 있다. 하지만 디지털로 된 데이터는 언제 어디서든 대단위 복제가 가능하다. 즉, 저작권 침해, 불법 복제 및 배포, 손쉽게 위조할 수 있다는 점이 그것이다. 디지털 영상 정보의 보호를 위해 디지털 영상의 불법적인 내용 조작을 막고, 영상의 소유권을 보장할 수 있는 방법으로 디지털 워터마크(Digital Watermark)가 있다. 디지털 워터마크는 공개키 알고리즘이나 방화벽 등으로 해독된 영상에 대하여 부가적인 보호를 제공한다. 본 논문에서는 디지털 영상 데이터의 정보 보호를 위해 주파수 영역에서의 웨이브릿 변환(Wavelet Transform)을 이용한 이미지 적용 디지털 워터마킹(Image-Adaptive Digital Watermarking) 방법을 제안한다. 이미지 적용 웨이브릿(Image-Adaptive Wavelet)은 영상을 주파수적으로 분해하면서 각 대역들의 공간 영역에서의 정보를 함께 지니고 JND(Just noticeable difference)을 포함한다. 이미지 적응 웨이브릿의 이러한 특성을 이용하여 다해상도 분해하고, 손실 압축(Loss Compression)이나 필터링(Filtering), 잡음(Noise)등에 크게 영향받는 저주파 성분과 인간의 시각적으로 큰 의미를 갖는 고주파 성분의 특성을 이용하여 워터마크를 삽입한다.