• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2014.06a
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• pp.26-27
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• 2014

This paper presents an adaptive interpolation filtering scheme for the High Efficiency Video Coding (HEVC) standard. In regards to interpolation for motion estimation and compensation, the conventional HEVC employs 8-tap and 4-tap filters for luma and chroma samples, respectively. Coefficients in such filters are determined by discrete cosine transform (DCT). In the proposed scheme, boundary strength values are stored after the execution of the deblocking filter. For each block, the sum of boundary strength values is calculated to indicate whether its region is complex or simple. Consequently, based on the region classification, 12-tap and 8-tap interpolation filters are used for complex and simple regions, respectively. This process is applied to luma sample interpolation only. Simulation results show 1.8% average BD-rate reduction compared to the conventional method.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.7
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• pp.891-897
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• 2013

The power system frequency plays an important role in monitoring and controlling the power system. The frequency can be measured through discrete Fourier transform (DFT) coefficients of its positive fundamental frequency. The accuracy of the frequency estimate is severely affected by noise in the power system signal and the leakage effect of the negative fundamental frequency in DFT. This paper proposes a DFT-based frequency estimation algorithm to cope with the noise as well as the leakage effect. In this algorithm, two suitable digital filters are introduced to reduce efficiently frequency estimate error due to the noise. These filters are designed to use a digital bandpass filter and a second-degree integrator. The effectiveness of the proposed algorithm in reduction of frequency estimate error is verified through simulations on noise, harmonics and frequency deviation.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 2000.04a
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• pp.138-143
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• 2000

In order to investigate the relationship between fabric sound parameters and subjective sensation, each sound from 60 fabrics was recorded and analyzed by Fast Fourier transform. Level pressure of total sound (LPT), three coefficients (ARC, ARF, ARE) of auto regressive models, loudness (Z), and sharpness (Z) by Zwickers model were estimated as sound parameters. For subjective evaluation, seven sensation (softness, loudness, sharpness, clearness, roughness, highness, and pleasantness) was rated by both semantic differential scale (SDS) and free modulus magnitude estimation (FMME). As the results, the ARC values were positively proportional to both LPT and loudness (Z) values. In both of SDS and FMME, softness, clearness, and pleasantness were negatively correlated with loudness, sharpness, roughness, and highness. In regression models, softness and clearness by FMME were negatively affected by LPT뭉 ARC, while loudness, sharpness, roughness, and highness were positively expected. Regression models for pleasantness showed low values for R2.

• Journal of Electrical Engineering and Technology
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• v.10 no.5
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• pp.2149-2154
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• 2015

This paper proposes a novel watermarking method to discover the tampers and localize it in digital image. The image which is to be used to generate a watermark is first wavelet decomposed and the edge feature from the sub bands of high frequency coefficients are retrieved to generate a watermark (Edge Feature Image) and which is to be embed on the cover image. Before embedding the watermark, the pixels of cover image are disordered through the Arnold Transform and this helps to upgrade the security of the watermark. The embedding of generated edge feature image is done only on the Least Significant Bit (LSB) of the cover image. The invisibleness and robustness of the proposed method is computed using Peak-Signal to Noise Ratio (PSNR) and Normalized Correlation (NC) and it proves that the proposed method delivers good results and the proposed method also detects and localizes the tampers efficiently. The invisibleness of proposed method is compared with the existing method and it proves that the proposed method is better.

• Proceedings of the Korea Multimedia Society Conference
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• 2002.11b
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• pp.283-286
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• 2002

본 논문에서는 보다 효과적이고 강인한 워터마크 은닉을 위한 방법으로 웨이브릿 변환 영역에서 영상의 통계적 특성에 기초한 비정상상태(non-stationary)에서와 정상상태(stationary) 일반화 가우스(generalized Gaussian: GG)모델을 이용한 적응 워터마크 은닉 기술을 제안한다. 워터마크는 고주파 영역에서 연속 부대역 양자화(successive subband quantization: SSQ)를 이용하여 다해상도 영상의 웨이브릿 계수 중에서 시각적 중요 계수(perceptual significant coefficients: PSC)를 선택하여 삽입한다. 워터마크 은닉을 위한 지각 모델은 NVF(noise visibility function)함수에 의해 계산된다. 이것은 비정상상태와 정상상태의 통계적 특성을 이용하고, 국부영상 특성을 가진다. 은닉모델은 다해상도내의 각 부대역별 분산과 형상계수(shape parameter)를 사용한다. Stirmark benchmark test에 근거하여 여러 가능한 왜곡에 대한 실험에서 강인성과 비가시성에서의 우수함을 확인하였고, 비정상상태의 경우와 정상상태의 경우를 비교하였다.

• Proceedings of the Korea Multimedia Society Conference
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• 1998.10a
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• pp.237-242
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• 1998

본 논문에서는 임의 형태 영상 영역에 대한 새로운 변환 부호화 방법을 제안한다. 제안된 방법에서는 영상 영역을 구성하는 각 열의 화소들을 변환 블록의 상단으로 이동시킨 후, 비어 있는 부분을 각 열의 화소 평균값으로 외삽한다. 그리고 수직 방향 1차원 변환을 실행한 후 외삽된 부분의 변환 계수들을 삭제한다. 수평 방향 1차원 변환은 각 행의 변환 계수들을 변환 블록의 좌측단으로 이동시킨 후, 수직 방향 1차원 변환에서와 동일한 과정을 실행함으로써 이루어진다. 복호화를 위해서는 먼저 삭제된 변환계수들을 복원한 후에 수평 방향 1차원 역변환 과정을 수행하며, 역변환 계수들 중 복원된 부분의 계수들을 삭제한다. 그리고 수평방향의 1차원 역변환 과정은 수직 방향 1차원 역변환 과정과 동일한 방식으로 수행한다. 역변환으로 만들어진 재생 영상은 변환 계수와 함께 전송된 형태 정보를 이용하여 원 위치로 이동된다. 모의 실험 결과는 제안된 방법의 압축 성능이 낮은 비트율에서 특히 우수함을 보여준다.

• Proceedings of the KIEE Conference
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• 2005.07a
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• pp.341-343
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• 2005

This paper introduces a compression algorithm for power quality disturbance signal via the discrete wavelet transform, DWT. Algorithm to estimate a time delay from the power quality disturbance signal is proposed. Pseudo-stationary signal is constructed from the estimated time delay. A difference signal or nonstationary signal is obtained by removing a pseudo-stationary signal from a disturbance signal. DWT is applied to a difference signal. The threshold is applied to reduce a number of coefficients. Simulation results show the resonable compression ratio while keep low signal distortion.

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.12
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• pp.1940-1946
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• 1990

In this paper, we are proposed a 2-D zero-phase IIR second-order filter which have separable denominators. The filter combines the advantages of the separable denominator and the simplicity of the McClellan transform. Generally, the McClellan transformation is not suitable for IIR filter because the 1-D to 2-D substibution can not be achieved easily in most of denominators. So we have designed the second order denominator using a separable condition via a first order McClellan transformation. The implementation of a higher order filter can be achieved by cascading such second order parts with different coefficients in denominator. As a result, we have suppressed the ripples in stopband and obtained the narrow transition band.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.39 no.6
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• pp.616-623
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• 1990

This paper includes the analysis and formulation of a new model for studying scattering from wire meshes that is more efficient and simpler to apply than the previous methods. In the new method, the conjugate gradient method is employed to improve each previous iterative and the fast Fourier transform (FFT) technique is utilized. A numerical computation of mesh scattering algorithm has been carried out in the Spectral Domain. A study on the electromagnetic properties such as reflection coefficients, induced currents and aperture fields has been presented and compared with data calculated by other methods to support the validity of the algorithm.

• IEIE Transactions on Smart Processing and Computing
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• v.2 no.1
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• pp.20-26
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• 2013

Image noise reduction in the frequency domain by thresholding is simple, but quite effective. Wavelet domain thresholding has been an active area of research but relatively little work has been published on DCT domain denoising. A novel method for determining the hard threshold for the DCT domain denoising is proposed. The low amplitude DCT coefficients are discarded until the cumulative sum of the discarded signal energy is comparable to that of noise in each DCT block. Cycle spinning is also applied to reduce block artifacts. The proposed method is quite effective and simple enough to be used in portable devices.