• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.417-420
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• 2000

점진적 영상 전송과 저해상도에서도 높은 PSNR를 나타내는 방법으로 EZW(Enbeded Zerotree Wavelet)과 SPIHT(set partitioning in hierarchical tree)를 사용한 보다 향상된 영상 압축방법이 제안되어졌다. 특히 SPIHT는 적응 산술부호화(adaptive arithmetic coding)를 사용하지 않고도 EZW보다 뛰어난 압축률과 효과를 얻을 수 있다. 하지만 부대역(subband)간의 유사성(similarity)을 이용한 제로트리 부호화에서 계층을 나누는 일은 계수 사이의 연결관계를 깰 수 있기 때문에 간단한 일은 아니다. 본 논문에서는 SPIHT의 비트열을 여러개의 계층으로 나누고 각각의 해상도로 복원하는 새로운 정렬 방법을 제안하고, 계층간의 비트열을 균일하게 나눔으로써 보다 효율적으로 전송 할 수 있는 방법을 제안하였다. 또한 복호시에 낮은 해상도일수로 복원시간의 이득을 볼 수 있는 향상된 방법을 제안한다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.6
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• pp.1089-1093
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• 2001

A H$\infty$ control theory is applied to the design problem of synthesis filters in a mutirate filter bank. We select a desired pure time-delay system as reference model, and then consider the error system between the mutirate filter bank and the reference model. 1'he synthesis filters minimize the ι$_2$-induced norm of the error system.

• The Journal of the Acoustical Society of Korea
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• v.15 no.4E
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• pp.53-57
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• 1996

An extension of the well-known Fourier transform is developed in this paper. It is denoted as the generalized Fourier transform(GFT), since it encompasses the Fourier transform as its special case. The first idea of this extension can be found on [1]. In the definition of the N-point discrete GFT, it first construct a passband in time which functions as a window in the time domain. An appropriate interpretation of each variables are introduced during the definition of the GFT, followed by the formal derivation of the inverse GFT. This transform pair is similar to the windowing in the frequency domain such as the subband coding technique (or filter bank approach) and could be extended to the wavelet transform.

• Proceedings of the IEEK Conference
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• 2002.07b
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• pp.1015-1018
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• 2002

We show how any discrete wavelet transform or two band subband filtering with finite filters can be decomposed onto a finite sequence of simple filtering steps, which we call lifting steps but that are also known as ladder structures, We present a self-contained derivations, building the decomposition from the basic principles such as the Euclidean algorithm, with a focus on a applying it to wavelet filtering. This factorization provides an alternative for the lattice factorization, with the advantage that it can also be used in the bi-orthogonal, i.e, non-unitary case. Lifting leads to a speed-up when compared to the standard implementation. We show that this lifting scheme can be applied in image compression efficiently

• Journal of the Korean Institute of Telematics and Electronics S
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• v.36S no.5
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• pp.56-69
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• 1999

본 논문에서는 움직임 보상 차영상 ( motion compensated difference image; MCDI)을 대역 분할한 뒤, 움직임 정보를 이용하여 에너지가 큰 부분만을 선택하여 적응적으로 벡터 양자화를 행함으로써 효율적으로 동영상을 부호화 할 수 있는 기법을 제안하였다. 제안한 기법에서는 MCDI의 특성들을 고려하여 에너지가 낮은 부분은 부호화를 행하지 않고, 에너지가 높은 부분에 대하여서만 움직임 벡터의 크기에 따라 클래스를 분류한 뒤 각 클래스에 맞는 코드북을 설계하여 벡터 양자화를 행한다. 이를 위해서는 부호화 되는 에너지가 높은 부분에 대한 정보와 클래스 부분에 대한 정보가 필요하다. 본 논문에서는 이러한 부가 정보의 양을 움직임 벡터를 이용하여 최소화함으로써 비트율을 크게 줄이면서도 우수한 화질의 복원 영상을 얻을 수 있었다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2018.06a
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• pp.166-168
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• 2018

다양한 분야에서 홀로그램을 서비스하기 위해 다양한 수신 환경을 반영한 전송기술이 필요하다. 따라서 프레넬릿 변환을 이용한 홀로그램을 위한 스케일러블 코딩 기법을 제안한다. 또한 프레넬릿 필터의 특성을 분석하여 각 서브밴드별 중요도 및 서비스된 서브밴드의 수에 따른 복원된 홀로그램을 분석하였다. 분석 결과, 주로 좋지 못한 수신환경에 서비스되는 응용분야에서는 (3,1)이중직교 필터를 이용하는 것이 유리하며, 반대의 경우 (5,5)필터를 이용하는 것이 유리하다.

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.1
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• pp.80-87
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• 2017

This paper proposes a pre-processing algorithm to improve perceptual video coding efficiency which decomposes an input frame via a sub-band decomposition, and suppresses only high frequency band(s) having low visual sensitivity. First, we decompose the input frame into several frequency subbands by a linear sub-band decomposition. Next, high frequency subband(s) which is rarely recognized by human visual system (HVS) is suppressed by applying relatively small gain(s). Finally, the high frequency suppressed frame is compressed by a specific video encoder. We can find from the experimental results that if comparing before-use and after-use of the proposed pre-processing prior to the encoder, no visual difference is shown. Also, the proposed algorithm achieves bit-saving of 13.12% on average in a H.264 video encoder.

• Journal of Broadcast Engineering
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• v.1 no.2
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• pp.118-132
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• 1996

This paper proposes a wavelet transform- based image compression method using the energy distribution. The proposed method Involves two steps. First, we use a wavelet transform for the subband decomposition. The original image Is decomposed into one low resolution subimage and three high frequency subimages. Each high frequency subimages have horizontal, vertical, and diagonal directional edges. The wavelet transform is luther applied to these high frequency subimages. Resultant transformed subimages have different energy distributions corresponding to different orientation of the high pass filter. Second, for higer compression ratio and computational effciency, we discard some subimages with small energy. The remaining subimages are encoded using either DPCM or quantization followed by entropy coding. Experimental results show that the proposed coding scheme has better performance in the peak signal to noise ratio(PSNR) and higher compression ratio than conventional image coding method using the wavelet transform followed by the straightforward vector quantization.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.40 no.6
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• pp.106-113
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• 2003

The modified discrete cosine transform (MDCT) and inverse MDCT (IMDCT) are employed in subband/transform coding schemes as the analysis/synthesis filter bank based on time domain aliasing cancellation (TDAC). And the MDCT and IMDCT are the most computational intensive operations in layer III of the MPEG audio coding standard. In this paper, we propose a new efficient algorithm for the MDCT/IMDCT computation in various audio coding systems. It is based on the MDCT/IMDCT computation algorithm using the discrete cosine transforms (DCTs), and It employs two discrete cosine transform of type II (DCT-II) to compute the MDCT/IMDCT In addition, it takes advantage of ability in calculating the MDCT/IMDCT computation, where the length of a data block Is divisible by 4. The Proposed algorithm in this paper requires less calculation complexity than the existing method does. Also, it can be implemented by the parallel structure, therefore its structure is particularly suitable for VLSI realization

• Journal of Broadcast Engineering
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• v.1 no.1
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• pp.67-73
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• 1996

In general, the high quality audio coding(HQAC) has the structure of the convertional data compression techniques combined with moodels of human perception. The primary auditory characteristic applied to HQAC is the masking effect in the spectral domain. Therefore spectral techniques such as the subband coding or the transform coding are widely used[1][2]. However no effort has yet been made to apply the temporal masking effect and temporal redundancy removing method in HQAC. The audio data compression method proposed in this paper eliminates statistical and perceptual redundancies in both temporal and spectral domain. Transformed audio signal is divided into packets, which consist of 6 frames. A packet contains 1536 samples($256{\times}6$) :nd redundancies in packet reside in both temporal and spectral domain. Both redundancies are elminated at the same time in each packet. The psychoacoustic model has been improved to give more delicate results by taking into account temporal masking as well as fine spectral masking. For quantization, each packet is divided into subblocks designed to have an analogy with the nonlinear critical bands and to reflect the temporal auditory characteristics. Consequently, high quality of reconstructed audio is conserved at low bit-rates.