• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2002.11a
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• pp.57-62
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• 2002

전송선로와 저장공간의 제약을 극복할 수 있는 영상압축기술이 발달함에 따라 인터넷과 멀티미디어 통신이 비약적으로 발전할 수 있었으며, 앞으로도 보다 높은 효율의 압축기술이 요구되고 있다. 현재 영상압축표준은 대부분 블록 DCT(Discrete Cosine Transform)를 기반으로 하고 있지만, 압축 이전에 영상을 블록으로 나누어 처리하게 되므로 블록효과가 발생하게 된다 본 논문에서는 이러한 블록효과를 제거하기 위해 확산을 이용한 방법을 제시한다. 확산의 정도를 자유로이 조절할 수 있는 새로운 형태의 이방성 확산 방정식을 제안하여 이를 블록효과를 제거하는데 적용한다. 이는 평탄한 영역에서의 경계에 대해서는 등방성 확산으로, 그렇지 않은 영역에 대해서는 경계에 수직인 방향으로만 확산이 일어나는 이방성 확산으로 자유로이 조절하여 적용할 수 있는 장점이 있다. 이를 이용하여 원 영상정보의 손실을 최소화하기 위해 영역에 따라 확산속도와 방향을 적응적으로 조절할 수 있는 알고리즘을 제안하고 기존의 블록효과 제거 알고리즘과 비교 실험을 통하여 제안한 알고리즘의 성능을 평가한다.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.55 no.8
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• pp.369-374
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• 2006

Due to development of internet network environments and data compression techniques, the size and amount of multimedia data has greatly increased. They are compressed before transmission or storage. Dealing with these compressed data such as video retrieval or indexing requires decompression procedure in most cases. This causes additional computations and increases the processing time. In various applications a histogram is one of the most frequently used tools. Efficiency of extracting such histograms will drop down if decompression is involved. We propose a novel scheme for extracting histograms from images that are transformed into the compressed domain by 8x8 DCT(Discrete Cosine Transform). In this scheme an averaged version of original image is obtained by a simple linear combination of DCT coefficients with the sets of coefficients we designed.

• Proceedings of the IEEK Conference
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• summer
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• pp.114-117
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• 2004

This paper proposes a novel algorithm for hybrid lossless audio coding, which employs integer discrete cosine transform. The proposed algorithm divides the input signal into frames of a proper length, decorrelates the framed data using the integer DCT and finally entropy-codes the frame data. In particular, the adaptive Golomb-Rice coding method used for the entropy coding selects an optimal option which gives the best compression efficiency. Since the proposed algorithm uses integer operations, it significantly improves the computation speed in comparison with an algorithm using real or floating-point operations. When the coding algorithm is implemented in hardware, the system complexity as well as the power consumption is remarkably reduced. Finally, because each frame is independently coded and is byte-aligned with respect to the frame header, it is convenient to move, search, and edit the coded data.

• Proceedings of the IEEK Conference
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• 2000.07a
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• pp.19-22
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• 2000

In this paper, we propose a watermarking method for still images using Discrete Cosine Transform (DCT). Watermarking is a copyright protection technique for digital contents by hiding secret information into the contents. The proposed method embeds the watermark information into DCT coefficients. To obtain a watermarked image that is not only high quality but also has robustness for compression, we considered a method to change the degree of embedding by utilizing the activity of each DCT block. The simulation results show that the proposed scheme can obtain huh quality watermarked images and we can extract most of the embedded data even if they are compressed by JPEG scheme.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.359-360
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• 2006

Magnetic Flux Leakage (MFL) methods are widely employed for the non-destructive testing of gas pipelines. In the application of MFL pipeline inspection technology, corrosion anomalies are detected and identified via their leakage filed due to changes in wall thickness. This paper presents discrete cosine transform (DCT) based MFL signal analysis for defect feature extraction of natural gas pipelines. The original MFL signals are transformed into new ones based on the analysis. The usefulness of the approach has been shown by the experimental results.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.395-396
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• 2006

본 논문에서는 얼굴 인식의 성능을 효율적으로 향상시키기 위하여 Discrete Cosine Transform (DCT)와 Principal Component Analysis(PCA)에 기반한 새로운 특징 추출 방법을 제안한다. 얼굴 영상의 공간 영역은 DCT를 이용하여 주파수 영역으로 변환되며, DCT 도메인에서 얼굴 영상이 갖는 고유한 주파수 특성을 최적화 하는 주파수 밴드 영역을 추출한다. 차원이 축소된 데이터는 PCA 를 이용하여 데이터의 변별력에 가장 적합한 얼굴의 특징을 추출하고 Nearest Neighbor Classification 을 통해 본인여부를 확인 한다. 실험 결과 제안된 방법은 데이터의 차원을 효과적으로 축소하면서 기존의 얼굴 인식 방법에 비해 높은 인식률 향상을 보였다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2020.07a
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• pp.553-556
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• 2020

최근 이미지 인식을 위한 Convolutional Neural Network(CNN) 모델의 경량화에 관한 연구가 활발하게 이루어지고 있다. 그중 양자화는 모델을 구성하는 가중치의 크기를 낮추는 방법이다. 기존의 CNN 모델에서 가장 큰 비중을 하는 Fully Connected Layer(FCL)는 내부적으로 32 Bit의 실수 행렬로 표현된다. 본 논문에서는 미리 학습된 실수 가중치를 더 작은 비트의 정수 행렬로 양자화한다. 양자화된 행렬에 대해서 영상 압축 등에서 사용하는 Discrete Cosine Transform(DCT)을 통해 주파수 영역으로 변환한 후 고주파 영역을 생략하는 손실압축 방법을 제안한다. 실험을 통해 그 과정에서 손실에 따른 정확도의 변화를 나타낸다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.11C
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• pp.1053-1059
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• 2005

The computer generated hologram (CGH) designs and produces digital information for generating 3-D (3-Dimension) image using computer and software instead of optically-sensed hologram of light interference, and it can synthesis a virtual object which is physically not in existence. Since digital hologram includes an amount of data as can be seen at the process of digitization, it is necessary that the data representing digital hologram is reduced for storing, transmission, and processing. As the efforts that are to handle hologram with a type of digital information have been increased, various methods to compress digital hologram called by fringe pattern are groped. Suitable proposal is encoding of hologram. In this paper, we analyzed the properties of CGH using tools of frequency transform, assuming that a generated CGH is a 2D image by introducing DWT that is known as the better tool than DCT for frequency transform. The compression and reconstruction result which was extracted from the wavelet-based codecs illustrates that it has better properties for reconstruction at the maximum 2 times higher compression rate than the Previous researches of Yoshikawa[2] and Thomas[3].

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.6 no.2
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• pp.65-70
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• 2013

In this paper, we proposed color image watermarking using human visual system. A watermark is embedded by transforming a color image of RGB coordinate into a color image of HSI coordinate with considering that chromatic components are less sensitive than achromatic components. Watermark is embedded in the frequency domain of the chromatic channels by using discrete cosine transform. Watermark is extracted from watermarked image by using inverse discrete cosine transform. To verify the proposed method, a standard image and a fingerprint image are used for the original image and the watermark image, respectively. Simulation results are satisfied with invisibility and robustness from attacks as image compression.

• Nuclear Engineering and Technology
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• v.43 no.4
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• pp.343-354
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• 2011

It is critically important to identify unexpected loose parts in a nuclear reactor pressure vessel, since they may collide with and cause damage to internal structures. Mass estimation can provide key information regarding the kind as well as the location of loose parts. This study proposes a mass estimation method based on an artificial neural network (ANN), which can overcome several unresolved issues involved in other conventional methods. In the ANN model, input parameters are the discrete cosine transform (DCT) coefficients of the auto-power spectrum density (APSD) of the measured impact acceleration signal. The performance of the proposed method is then evaluated through application to a large-sized plate and a 1/8-scaled mockup of a reactor pressure vessel. The results are compared with those obtained using a conventional method, the frequency ratio (FR) method. It is shown that the proposed method is capable of estimating the impact mass with 30% lower relative error than the FR method, thus improving the estimation performance.