• Proceedings of the Korean Society of Computer Information Conference
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• 2009.01a
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• pp.241-244
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• 2009

최근 모바일폰에 500만 화소 이상의 카메라 모듈이 장착되는 등 모바일 장치에서 고해상도 영상의 인코딩 및 디코딩에 대한 요구가 크게 늘어남에 따라 저성능 시스템에서 실시간으로 동작하는 영상 코덱 구현에 대한 필요성이 증대되고 있다. 본 논문은 JPEG 디코딩의 마지막 단계인 컬러변환 과정에 대해 계산 복잡도를 최적화하는 기법을 제안하고 성능을 평가하였다. 제안된 기법은 JPEG 디코딩 과정에서 IDCT(Inverse Discrete Cosine Transform) 변환과 컬러변환 간의 선형성을 바탕으로 이들 연산 순서를 재배열함으로써 컬러변환 과정에서 요구되는 계산 횟수를 줄이고, 재배열된 부동소수점 연산에 대해 정수 맵핑을 적용하여 계산 복잡도를 줄임으로써 실행시간을 최적화하였다. 임베디드 시스템 개발 플랫폼에서의 성능 평가를 통해 제안된 기법이 기존의 컬러변환 기법들과 비교하여 실행시간을 크게 단축함을 얄 수 있었으나 복원 영상의 화질이 상대적으로 저하됨을 확인하였다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.5
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• pp.1134-1138
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• 2008

In this paper, the synthesis of distributed impedance transformers is presented that is essential for power divider design, whereby a broadband power divider is designed. Transfer functions of distributed transformers are synthesized with Chebyshev approximation, and their element values are calculated for various minimum insertion losses(MIL) and ripples. Desired performance of transformers is obtained by optimizing MIL's and ripples of a transfer function. As an application example, a four-way power divider is designed that operates over 2 to 8GHz frequency range. Experimental results are shown to approach the design performance, so transformer design by distributed network synthesis proves to be useful to power divider design.

• Journal of the Korean Institute of Telematics and Electronics T
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• v.36T no.1
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• pp.1-7
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• 1999

We present VLSI architecture for a high performance 2-D DCT processor which is used compressing system of real time image processing or HDTV using fast computational algorithm of the Optimized Integer Cosine Transform(OICT). The coefficients of the OICT are integer, so the OICT performs only the integer operations for both forward and inverse transform. Therefore the proposed architecture could be greatly enhanced in improving the speed, reduced the hardware cost considerably by replacing the multiplication operations with shift and addition operations compared with DCT which performs floating-point operations.

• Journal of KIISE
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• v.44 no.5
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• pp.537-544
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• 2017

As a special form of the signed-digit representation, the NAF(non-adjacent form) minimizes the hamming weight by reducing the average density of the non-zero bits from the binary representation of the positive integer k. Due to this advantage, the NAF is used in various fields; in particular, it is actively used in cryptology. The existing NAF-conversion algorithm, however, is problematic because the conversion speed decreases when the LSB(least significant bit) frequently becomes "1" during the binary positive integer conversion process. This paper suggests a method for the improvement of the NAF-conversion speed for which the problems that occur in the existing NAF-conversion process are solved. To verify the performance improvement of the algorithm, the CPU cycle for the various inputs were measured on the ATmega128, a low-performance 8-bit microprocessor. The results of this study show that, compared with the existing algorithm, the suggested algorithm not only improved the processing speed of the major patterns by 20% or more on average, but it also reduced the NAF-conversion time by 13% or more.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.12C
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• pp.1182-1191
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• 2003

In this paper, we propose a new hardware architecture for integer transform, quantizer, inverse quantizer, and inverse integer transform of a new video coding standard H.264/JVT. We describe the algorithm and derive hardware architecture emphasizing the importance of area for low cost and low power consumption. The proposed architecture has been verified by PCI-interfaced emulation board using APEX-II Alters FPGA and also by ASIC synthesis using Samsung 0.18 um CMOS cell library. The ASIC synthesis result shows that the proposed hardware can operate at 100 MHz, processing more than 1,300 QCIF video frames per second. The hardware is going to be used as a core module when implementing a complete H.264 video encoder/decoder ASIC for real-time multimedia application.

• Journal of the Korea Society of Computer and Information
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• v.14 no.1
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• pp.135-143
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• 2009

Recently, in the mobile device, the increase of the need for encoding and decoding of high-resolution images requires an efficient implementation of the image codec. This paper proposes a time-optimized color conversion method for the JPEG decoder, which reduces the number of calculations in the color conversion by the rearrangement of arithmetic operations being possible due to the linearity of the IDCT and the color conversion matrices and brings down the time complexity of the color conversion itself by the integer mapping replacing floating-point operations to the optimal fixed-point shift and addition operations, eventually reducing the time complexity of the JPEG decoder. And the proposed method compensates a decline of image quality incurred by the quantification error of the operation arrangement and the integer mapping by using the multi-mode chrominance reconstruction. The performance evaluation performed on the development platform of embedded systems showed that, compared to previous color conversion methods, the proposed method greatly reduces the image decoding time, minimizing the distortion of decoded images.

• Proceedings of the Korea Institute of Convergence Signal Processing
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• 2001.06a
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• pp.261-264
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• 2001

논문에서는 S+P 웨이브릿 변환과 정수 웨이브릿 필터들을 비교 분석하고, 9/7텝 정수 웨이브릿 필터를 이용하여 웨이브릿 변환을 하고, 점진적 전송에 적합 하고, 다중 분해능 구조의 종속성과 방향성에 대한 고려와 예측오차의 피드백을 이용한 컨텍스트 모델링 예측과 적응산술부호화에 의한 엔트로피 코딩 방법을 제안하였다. 다양한 영상들에 대한 실험을 통해 본 논문에서 제안한 무손실 영상 압축알고리즘을 S+P 웨이브릿을 이용한 결과와 비교하였다.

• Proceedings of the KIEE Conference
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• 2003.07d
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• pp.2537-2539
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• 2003

본 논문에서는 의료 영상에 대한 저작권보호를 위한 새로운 워터마킹 알고리즘을 제안한다. 본 알고리즘에서는 이산 웨이블릿 변환 대신에 계산량이 적은 정수 웨이블릿 변환을 이용하였다. 본 논문에서는 정수 웨이블릿 공간에서 유사-잡음 수열을 워터마크로 삽입 하였다. 워터마크를 추출할 때 확산스펙트럼 기법을 이용하고 유사도는 공분산 수열에서 결정한다. 실험을 통하여 제안한 알고리즘이 노이즈, 압축 등 공격에 강인함을 보임을 확인하였다.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.15 no.6
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• pp.82-88
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• 2001

This paper considers the problem of the identification of the time invariant parameters of distributed systems. In general, the parameters are identified by using the CBPOM(Conventional Block Pulse Operational Matrices), but in this paper, the parameters ard identified by using the EBPOMS(Extended Block Pulse Operational Matrices) which can reduce the burden of operation md the volume of error caused by matrices multiplication. The simulation cloves the effectiveness of the proposed method.

• Journal of the Institute of Convergence Signal Processing
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• v.1 no.1
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• pp.82-88
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• 2000

In this paper, We compare the Harr wavelet of the S+P transform with various integer coefficient filter banks and apply 9/7 ICFB to the wavelet transform. In addition, we propose a entropy-coding method that exploits the multiresolution structure and the feedback of the prediction error, and can efficiently compress the transformed image for progressive transmission. Simulation results are included to compare to the compression ratio using the S+P transform with different types of images.