• Journal of KIISE:Computer Systems and Theory
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• v.33 no.8
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• pp.547-553
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• 2006

We present a new geometry coding method for 3D meshes, an adaptive subdivision. Previous localized geometry coding methods have demonstrated better compression ratios than the global approach but they are considered hard to use in practice partly due to time - consuming quantization. Our new localized scheme replaces this quantization with an adaptive subdivision of the localized range. The deeper level a user chooses, the closer to the original the mesh will be restored. We also present an improved connectivity coder upon the current leading Angle-Analyzer's by applying a context-modeling. As a result, our new coder provides reliable and intuitive controls between bit-rate and distortion without losing efficiency.

• Journal of the Institute of Convergence Signal Processing
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• v.17 no.2
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• pp.67-70
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• 2016

This paper discusses a graphic user interface(GUI) for the concealed target segmentation. The human subject hiding a metal gun is captured by the passive millimeter wave(MMW) imaging system. The imaging system operates on the regime of 8 mm wavelength. The MMW image is analyzed by the multi-level segmentation to segment and identify a concealed weapon under clothing. The histogram of the passive MMW image is modeled with the Gaussian mixture distribution. LBG vector quantization(VQ) and expectation and maximization(EM) algorithms are sequentially applied to segment the body and the object area. In the experiment, the GUI is implemented by the MFC(Microsoft Foundation Class) and the OpenCV(Computer Vision) libraries and tested in real-time showing the efficiency of the system.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.44 no.11
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• pp.1-8
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• 2007

A wideband continuous-time sigma delta modulator for wireless application is implemented in 130nm CMOS. The SNR for small input signal is improved using a proposed adaptive quantizer which can effectively scale the quantization level. The modulator comprises a second-order loop filter for low power consumption, 4-bit quantizer and DAC for low jitter sensitivity and high linearity. Designed circuit achieves peak SNR of 51.36B with 10MHz signal Bandwidth and 320MHz sampling frequency dissipating 30mW.

• The Transactions of the Korea Information Processing Society
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• v.3 no.4
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• pp.938-946
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• 1996

Hierarchical subband codec has been widely promoted in the field of data compression/decompression because of their simplicity and modular nature. Over the past years, the study has received great attention to the perfect reconstruction (PR)system which perfectly recovers the original input signal at the reconstructed output. However, in the actual subband codec system, the signals that passed through the analysis filter bank are quantized before transmission to the receiver side and reconstructed by the synthesis filter bank. Thus the PR system is impossible and the quantization effects must be carefully considered in the system design such that the system recovers the reconstructed output as possible to the the original input signal with minimum quantization error.In this paper, we propose an optimum hierarchical subband codec structure in the presence of quantizer. The optimality criteria of the code is given to the deign of the hierarchical analysis/synthesis subband filter bank and the quantizer that minimize then output mean square error due to the quantizer in the codec. Specific opti-mum design esamples are shown with level-1, level-2 hierarchical structure. The optimal designs are verified by computer simulation.

• Journal of KIISE
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• v.42 no.6
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• pp.699-706
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• 2015

In recent years, as near-duplicate image has been increasing explosively by the spread of Internet and image-editing technology that allows easy access to image contents, related research has been done briskly. However, BoF (Bag-of-Feature), the most frequently used method for near-duplicate image detection, can cause problems that distinguish the same features from different features or the different features from same features in the quantization process of approximating a high-level local features to low-level. Therefore, a post-verification method for BoF is required to overcome the limitation of vector quantization. In this paper, we proposed and analyzed the performance of a post-verification method for BoF, which converts SIFT (Scale Invariant Feature Transform) descriptors into 128 bits binary codes and compares binary distance regarding of a short ranked list by BoF using the codes. Through an experiment using 1500 original images, it was shown that the near-duplicate detection accuracy was improved by approximately 4% over the previous BoF method.

• Journal of Korea Multimedia Society
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• v.6 no.3
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• pp.436-443
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• 2003

A digital video watermarking algorithm is proposed that uses HVS and DWT. In this algorithm, each video frame is decomposed into four-level by DWT which reveals the characteristics of the human eyes and watermark is embedded into DWT coefficients using HVS. For robustness, the lowest level subbands which represent the highest frequency component are excluded in watermark embedding step and watermark is embedded into the perceptually significant coefficients (PSCs) of the rest subbands. PSCs of the baseband are selected according to the amplitude of the coefficients and PSCs of the high frequency subbands are selected by successive subband quantization (SSQ). Watermark is embedded into the PSCs of the baseband and high frequency subbands by Weber's law and spatial masking effect, respectively, for the invisibility and robustness. We tested the performance of the proposed algorithm compared with the conventional watermarking algorithm by computer simulation. Experimental results show that the proposed watermarking algorithm produces a better invisibility and robustness than the conventional algorithm.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.12A
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• pp.2100-2108
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• 2001

A digital image watermarking algorithm is proposed that uses human visual system (HVS) and discrete wavelet transform (DWT). In this algorithm, an image is decomposed into four-level by DWT which reveals the characteristics of the human eyes and watermark is embedded into DWT coefficients using HVS. For robustness, the lowest level subbands which represent the highest frequency component are excluded in watermark embedding step and watermark is embedded into the perceptually significant coefficients (PSCs) of the rest subbands. PSCs of the baseband are selected according to the amplitude of the coefficients and PSCs of the high frequency subbands are selected by successive subband quantization (SSQ). Watermark is embedded into the PSCs of the baseband and high frequency subbands by Weber\`s law and spatial masking effect, respectively, for the invisibility and robustness. We tested the performance of the proposed algorithm compared with the conventional watermarking algorithm by computer simulation. Experimental results show that the proposed watermarking algorithm produces a better invisibility and robustness than the conventional algorithm.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.39 no.2
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• pp.45-53
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• 2002

A wavelet-based digital watermarking algorithm is proposed that uses the successive subband quantization and human visual system (HVS). After an original image is decomposed into 4-level by the discrete wavelet transform, perceptually significant coefficients (PSC) of each subband excluding the lowest level subband are utilized to embed the watermark. PSC of the baseband ate chosen according to their amplitude and they are slightly modified to embed the watermark by a conventional embedding method. By the successive subband quantization, PSC of the high frequency subband are chosen and slightly modified according to the HVS. We tested the performance of the proposed algorithm compared with the conventional watermarking algorithm by computer simulation. Experimental results show that the proposed watermarking algorithm produces a better invisibility and robustness than the conventional algorithm.

• Korean Journal of Remote Sensing
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• v.30 no.1
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• pp.137-147
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• 2014

We proposed and verified the methods to maintain data qualities as well as to reduce data volume for the Geostationary Ocean Color Imager (GOCI), the world's first ocean color sensor operated in geostationary orbit. For the GOCI level-2 data, 92.9% of data volume could be saved by only the data compression. For the GOCI level-1 data, however, just 20.7% of data volume could be saved by the data compression therefore another approach was required. First, we found the optimized number of bits per a pixel for the GOCI level-1 data from an idea that the quantization bit for the GOCI (i.e. 12 bit) was less than the number of bits per a pixel for the GOCI level-1 data (i.e. 32 bit). Experiments were conducted using the $R^2$ and the Modulation Transfer Function (MTF). It was quantitatively revealed that the data qualities were maintained although the number of bits per a pixel was reduced to 14. Also, we performed network simulations using the Network Simulator 2 (Ns2). The result showed that 57.7% of the end-toend delay for a GOCI level-1 data was saved when the number of bits per a pixel was reduced to 14 and 92.5% of the end-to-end delay for a GOCI level-2 data was saved when 92.9% of the data size was reduced due to the compression.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2009.01a
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• pp.612-617
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• 2009

In a DCT coding, degradations called block artifact and mosquito noise are appeared in reconstructed pictures. They should be reduced in post processing after decoding without superabundant processing. However, an estimation of mosquito noise is rare because of its difficulty. To realize an estimation of mosquito noise level, we extract a block that mosquito noise will be easy to occur. Mosquito noise level is calculated at a selected side of the block. In this processing, only the sides of high probability block are used. Then, a block value is taken by averaging. Finally, the picture value is calculated by averaging of this. Estimation method is evaluated by using the MPEG-4 decoded pictures. Quantization scale of coding and the estimated mosquito noise level are compared. As the results, we recognize the proposed method gives almost reasonable mosquito block and absolute level. Father, adaptive filter is controlled by the estimated mosquito noise level. It is recognized that the high quality of decoded picture is kept and the mosquito noise is reduced effectively at the picture with degradation.