• Journal of Communications and Networks
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• v.5 no.4
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• pp.374-385
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• 2003

The growing interest towards ultra-wideband (UWB) communications stems from its unique features such as baseband operation, ample multipath diversity, and the potential of enhanced user capacity. But since UWB has to overlay existing narrowband systems, multiple access has to be achieved in the presence of narrowband interference (NBI). However, existing baseband spreading codes for UWB multiple access are not flexible in handling NBI. In this paper, we introduce two novel spreading codes that not only enable baseband UWB multiple access, but also facilitate flexible NBI cancellation. We construct our codes using a single carrier or multiple carriers (SC or MC), which can be implemented with standard discrete-cosine transform (DCT) circuits. With our SC/MC codes, NBI can be avoided by simply nulling undesired digital carriers. Being digital, these SC/MC codes give rise to multiband UWB systems, without invoking analog carriers. In addition, our SC/MC codes enable full multipath diversity, and maximum coding gains. Equally attractive is their capability to reduce the number of interfering users, with simple matched filter operations. Comprehensive simulations are also carried out to corroborate our analysis.

• Proceedings of the Korean Information Science Society Conference
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• 1998.10a
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• pp.774-776
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• 1998

영상 압축의 표준인 MPEG은 대표적 비대칭 코딩방법으로 인코딩 시간이 디코딩 시간보다 훨씬 많은 시간을 소비한다. MPEG인코딩 과정은 크게 DCT, 양자화, 움직임 벡터 추출, 가변장 부호화로 구성된다. 이중에서 DCT와 움직임 벡터 추출 정도가 많은 계산량을 가지므로 병렬화의 관심이 되고 있다. 본 논문에서는 움직임 벡터의 추출에 관해서 병렬화하는 기법을 제시한다 병렬화의 단위는 fine-grained이며, 통신 오버헤드를 보다 줄일 수 있는 기법을 제시하였다. 최소한의 초기 데이터 할당으로 계산을 시작하여, 계산을 위한 초기화 과정을 줄여 속도를 증대시킨다. 통신비용 즉, 메시지 전달 수 및 메시지 전달 홉(hop) 수를 비교하고, 기존의 기법에 대해 한 프레임에 대한 움직임 벡터 추출 시간을 요소로 할 때 보다나은 결과를 나타냄을 보였다.

• Proceedings of the IEEK Conference
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• 2002.07a
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• pp.152-155
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• 2002

In this paper, a new approach is proposed for the error detection dedicated to MPEG-4 video coding by using the digital watermarking. In the process of encoding, the proposed scheme abstracts the macroblock features of headers, motion vectors, and Discrete Cosine Transform (DCT) coefficients, which are embedded in the quantized DCT coefficients as the digital watermarks. The decoder performs the accurate error detection through the watermark extraction. Simulation results demonstrate that the error detection ability of the proposed approach can be significantly enhanced, and that digital watermark embedding incurs little degradation to the picture quality.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.31B no.7
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• pp.91-100
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• 1994

The lapped orthogonal transform(LOT) has been recently proposed to alleviate the blocking effects in transform coding. The LOT is known to provide an improved coding gain than the conventional transform. In this paper, we propose a prefilter approach to design the LOT bases with the view of maximizing the transform coding gain. Since the nonlinear phase basis is inappropriate to the image coding only the linear phase basis is considered in this paper. Our approach is mainly based on decomposing the transform matrix into the orthogonal matrix and the prefilter matrix. And by assuming that the input is the 1st order Markov source we design the prefilter matrix and the orthogonal matirx maximizing the transform coding gain. The computer simulation results show that the proposed LOT provides about 0.6~0.8 dB PSNR gain over the DCT and about 0.2~0.3 dB PSNR gain over the conventional LOT [7]. Also, the subjective test reveals that the proposed LOT shows less blocking effect than the DCT.

• Journal of Korea Multimedia Society
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• v.2 no.4
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• pp.438-450
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• 1999

In this paper, a new watermaking method embedding digital watermarks in the compressed video for the copy protection of multimedia data. The proposed method segments objects and embeds independent watermarks in each objects by spread spectrum method in the bitstream domain which is compressed by DCT and motion compensated coding method like MPEG-2. And, the proposed method not only embeds watermarks but show the robustness to the attacks like average operation or statistical analysis.

• Proceedings of the Korea Contents Association Conference
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• 2007.11a
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• pp.825-828
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• 2007

오늘날 영상정보는 여러 분야에 있어 아주 큰 비중을 차지하고 있다. 다량의 정보를 가진 영상 신호의 효율적인 전송이나 저장에는 많은 제약이 따르게 되므로 고속의 영상 압축 관련 기술의 개발은 필수적이다. 본 논문은 JPEG에서 표준규격으로 채택하고 있는 DCT 및 양자화의 하드웨어에 적합한 고속연산 알고리즘을 연구하였고, JPEG 인코더에 적용 가능한 효율적인 회로 구조를 설계하였다. 연구된 DCT 및 양자화 모듈을 VHDL언어로 설계 및 합성하였으며 설계된 모듈은 영상 압축의 고속데이터 처리에 응용 가능하다.

• Journal of the Korea Computer Industry Society
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• v.2 no.11
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• pp.1465-1476
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• 2001

For the applications like video indexing, text understanding, and automatic captions localization system, real-time localization of captions is an essential task. This paper presents a algorithm for localization of captions in MPEG compression images based on I frame. In this algorithm, caption text regions are segmented from background images using their distinguishing texture characteristics and chrominance information. Unlike previously published algorithms which fully decompress the video sequence before extracting the text regions, this algorithm locates candidate caption text region directly in the DCT compressed domain.

• The Journal of the Acoustical Society of Korea
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• v.25 no.3E
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• pp.89-94
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• 2006

For audio indexing and targeted search of specific audio or corresponding visual contents, the MPEG-7 standard has adopted a sound classification framework, in which dimension-reduced Audio Spectrum Projection (ASP) features are used to train continuous hidden Markov models (HMMs) for classification of various sounds. The MPEG-7 employs Principal Component Analysis (PCA) or Independent Component Analysis (ICA) for the dimensional reduction. Other well-established techniques include Non-negative Matrix Factorization (NMF), Linear Discriminant Analysis (LDA) and Discrete Cosine Transformation (DCT). In this paper we compare the performance of different dimensional reduction methods with Gaussian mixture models (GMMs) and HMMs in the classifying video sound clips.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.3A
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• pp.249-257
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• 2002

본 논문에서는 스테레오/다시점 영상을 효율적으로 압축할 수 있는 차 영상 부호화 방법을 제안한다. 예측된 영상과 원 영상의 차이 정보를 보다 효율적으로 전송하기 위하여 DCT를 기반으로 차 영상 부호화를 하게 되는데 DCT 계수들의 방향성을 이용하여 양자화 및 스캔 방법을 각 블록의 특성에 따라 다르게 적용하였다. 특히 다시점 영상의 부호화는 첫 번째 시점 영상을 기준 영상으로 정하여 나머지 시점 영상을 기준 영상으로부터 변이를 추정하여 복원하는 방식과 다시점 영상 중 가려진 영역의 비율을 고려하여 가려진 영역이 상대적으로 제일 적은 영상을 기준 영상으로 설정하여 나머지 영상을 변이 추정하여 복원하는 방법으로 나누어 실험하였다. 실험 결과 모든 압축률에 대하여 제안 방식이 기존의 차 영상 부호화 방법보다 우수함을 확인하였고, 가려진 영역의 상대적인 비율을 고려하여 다시점 영상을 부호화한 제안 방식이 기존의 방식 및 첫 번째 시점을 기준 영상으로 설정하여 부호화한 제안 방식보다 우수함을 확인하였다.

• Journal of information and communication convergence engineering
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• v.6 no.1
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• pp.29-33
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• 2008

This paper presents the proposal and hardware design of JPEG baseline encoder. The JPEG encoder system consists of line buffer, 2-D DCT, quantization, entropy encoding, and packer. A fully pipelined scheme for JPEG encoder is adopted to speed-up an image compression. The proposed architecture was described in VHDL and synthesized in Xilinx ISE 7.1i and simulated by modelsim 6.1i. The results showed that the performance of the designed JPEG baseline encoder is higher than that demanded by real-time applications for $1024{\times}768$ image size. The designed JPEG encoder IP can be easily integrated into various application systems, such as scanner, PC camera, color FAX, and network camera, etc.