• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.1
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• pp.1165-1168
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• 2005

This paper proposes an digital image watermarking method based on discrete wavelet transform(DWT) and spatial perceptual properties of human visula system. first, an digital image is transformed by DWT and inserted gaussian watermark into the frequency domain. To increase the robustness and perceptual invisibility of watermark, the proposed algorithm is combined with the characteristics of digital image and human visual system. The proposed method is invisible and blind watermarking which the original image is not required to detect watermarks. Simulation results show that the proposed method is robust to the general attack such as JPEG compression, enhancement, noise, cropping, and filtering etc.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.1
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• pp.405-408
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• 2005

This paper proposed the method to images of losses using restorable wavelet transformation. The algorithm proposed in this work stars by processing the pre-quantizer on the original images to organize an image that matches the gray level. The wavelet transformation filter to the original image which is already pre-quantized in order to segment bands. Considering the lowest coding of bands influencing the most to the overall condition of the reconstructed image, it only uses the Huffman coding using prediction. Reconstructed images by proposed algorithm showed higher PSNR when coding images of JPEG or non pre-quantized images. Applying pre-quantizer can control the peak errors and is expected to be useful at mass image compression.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.1
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• pp.358-362
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• 2005

디지털 비디오 압축기술은 멀티미디어 응용분야의 핵심으로 현재 빠르게 보급되어 최근에는 디지털비디오 압축 관련 국제 표준안 중 MPEG-4와 H.264가 발표되었다. 유연성이 좋은 MPEG-4와 달리H.264는 비디오 프레임의 효율적인 압축과 신뢰성을 강조 한다. 특히 H.264의 압축 기술은 카메라폰이나 DMB등의 작은 크기의 영상에서 고품질의 영상을 보다 효율적으로 제공 한다. 이에 본 논문은 현존하는 다른 비디오 코딩 표준과 비교할 때 코딩 효율이 기준의 두 배인 새로운 비디오 코딩 표준 H.264/AVC에서 사용하는, 변환 및 양자화를 연구하고 이를 기존의 정지영상 표준안인 JPEG나 JPEG 2000과 비교 분석하여 H.264/AVC의 공간적 압축인 인트라 코딩이 더 좋은 효과를 나타낸다는 것을 검증한 후 이를 토대로 하드웨어 설계언어인 VHDL언어를 이용하여 설계하고 FPGA칩인 XCV1000E에 다운로드 하여 칩 레벨의 시뮬레이션을 수행하여 설계된 변환 및 양자화 모듈을 검증하였다. 설계된 변환 및 양자화 모듈은 DMB 및 핸드폰 카메라와 같이 작은 정지 영상 압축에 응용이 가능하다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.3
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• pp.489-497
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• 2009

Most of existent blind watermarking methods in frequency domain use coefficient relationship to detect the watermark without original image. But the change in coefficient values occurred when the original image was attacked by lossy JPEG compression or noise addition. So robustness of watermark detection was weaken. In order to solve these problems, this paper presents a robust watermarking method, which enables multiple watermark insertion. Also, in order to reduce errors in the detected value of watermarks according to small changes in the coefficient relationship when detecting watermarks, it set the change guard value for variation of the coefficients. The experimental results show that the proposed method has good image quality and is robust to various attacks such as the JPEG lossy compression, noise addition, etc.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.9B
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• pp.1616-1623
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• 1999

This paper describes error resilient coding scheme is added in WLL system and its application for robust low-bit rate still image transmission over power controlled W-CDA system Rayleigh fading channels. The baseline JPEG compressing methods are uses in image coding over wireless channel. The channel uses Reed-Solomon(RS) outer codes concatenated with convolutional inner codes, and truncated type I hybrid ARQ protocol based on the selective repeat strategy and the RS error detection capability. Simulation results are proved for the statistics of the frame-error bursts of the proposed system in comparison with conventional WLL system. it gains the 2 dB of the Eb/No in same BER.

• Annual Conference of KIPS
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• 2004.11a
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• pp.233-236
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• 2004

일반적으로 디지털 카메라나 캠코더, PC와 같은 제품에서 만들어진 이미지나 오디오 파일들은 다른 멀티 미디어 제품에서 재생하기 위하여 각종 휴대용 메모리카드에 저장된다. 본 논문에서는 이런 메모리 카드에 저장되어 있는 이미지나 오디오를 다양한 기능과 고 화질,고 음질을 제공하는 디지털 TV에 적용할 수 있는 시스템을 제안하고 있다. 제안한 시스템은 크게 JPEG 모드와 MP3 모드로 나누어지는데, JPEG 모드에서는 이미지 회전, 확대 및 화면 이동 등의 기능과 다양한 슬라이드 쇼를 제공하고 MP3 모드에서는 선택 재생, 전체 재생, 반복 재생 등의 기능을 제공함으로써 사용자들이 일반 가정에서 디지털 TV의 다양한 멀티미디어 기능을 즐길 수 있도록 하였다. 또한 사용자들에게 편리한 User Interface(UI)를 제공함으로써 PC 에 익숙하지 않은 사용자들도 쉽게 이용할 수 있을 것으로 기대된다.

• Journal of Satellite, Information and Communications
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• v.7 no.1
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• pp.48-52
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• 2012

As the growing popularity of smartphones, mobile web browsing has become one of the most important and popular applications in mobile devices. Furthermore, it is clear that the demand for PC-like full browser performance on mobile devices is increasing greatly. WebKit is an open source web browser engine adopted by Google Android. This paper proposed a technique of increasing the performance of WebKit by paralleling its libraries. This method was applied to JPEG library and the performance evaluation was conducted in PC environment. The results was used to estimate the performance prediction on multi-core mobile embedded architecture and to show the feasibility of the proposed method to estimate the performance gain on heterogeneous multi-core embedded architecture.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.4
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• pp.648-661
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• 1997

This paper presents a new method for post-processing of coded images based upon the low-pass filtering followed by the projection onto the NQCS (narrow quantization constraint set). We also investigate how the proposed method works on JPEG-coded real images. The starting point of the QCS-based post-processing techniques is the centroid of the QCS, where the original image belongs. The low-pass filtering followed by the projection onto the QCS makes the images lie on the boundary of the QCS. It is likely that, however, the original image is inside the QCS. Hence projection onto the NQCS gives a lower MSE (mean square error) than does the projection onto the QCS. Simulation results show that setting the narrowing coefficients of the NQCS to be 0.2 yields the best performance in most cases. Even though the JPEG-coded image is low-pass filtered and projected onto the NQCS repeatedly, there is no guarantee that the resultant image has a lower MSE and goes closer to the original image. Thus only one iteration is sufficient for the post-processing of the coded images. This is interesting because the main drawback of the iterative post-processing techniques is the heavy computational burden. The single iteration method reduces the computational burden and gives us an easy way to implement the real time VLSI post-processor.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.31 no.6
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• pp.1171-1179
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• 2021

Image forensic is performed to check image limpidness. In this paper, a robust scheme is discussed to detect median filtering in low quality images. Detection of median filtering assists in overall image forensic. Improved spatial statistical features are extracted from the image to classify pristine and median filtered images. Image array data is rescaled to enhance the spatial statistical information. Features are extracted using Markov model on enhanced spatial statistics. Multiple difference arrays are considered in different directions for robust feature set. Further, texture operator features are combined to increase the detection accuracy and SVM binary classifier is applied to train the classification model. Experimental results are promising for images of low quality JPEG compression.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.15 no.2
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• pp.113-122
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• 2005

In this paper, we propose a multi-watermarking algorithm to satisfy two purposes: fragility against malicious attacks and robustness against non-malicious attacks. The algorithm can be used for image authentication using coefficients of Discrete Wavelet Transform(DWT). In the proposed method, watermarks are generated by combining binary image with some features extracted from the subband LL3, and then they are embedded into both the spatial and frequency domain. That is, on the spatial domain they are embedded into the Least Significant Bit(LSB) of all pixels of image blocks, and on the frequency domain the coefficients of the subband LH2 and HL2 are adjusted according to the watermarks. Thus the algorithm not only resists malicious attack but also permits non-malicious attacks such as blurring, sharpening, and JPEG compression.