• Journal of the Institute of Electronics Engineers of Korea SP
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• v.38 no.4
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• pp.38-38
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• 2001

본 논문에서는 웨이브릿 영역에서의 영역 분류와 대역간 예측 및 선택적 벡터 양자화를 이용한 다분광 화상테이타 압축 기법을 제안하였다. 이 방법에서는 각 대역을 웨이브릿 변환 후, 각 대역의 기저밴드의 대역별 특성을 이용하여 영역 분류를 행하였다. 그리고, 다른 대역과 해상도가 동일하고 공간적 분산이 작으며 분광적 상관성이 큰 기준대역 (reference channel)을 결정한 뒤, 이를 영역별 스칼라 및 분류별 가변 벡터 양자화를 행하여 부호화 하였다. 또한 기준대역과의 대역간 상관성이 큰 대역들에 대해서는 영역별 대역간 예측을 행한 후, 활동도가 높은 블록에 대해서만 선택적 벡터 양자화로 부호화를 행하였다. 이때, 활동도가 높은 블록들의 위치정보는 기준대역으로부터 얻어지는 임계치 지도 (threshold map; THMAP)를 이용하였다. 즉, 제안한 방법에서는 각 대역에 대해 웨이브릿 영역에서의 영역 분류 후 영역별 대역간 예측을 행함으로써 다분광 화상데이타에 존재하는 대역간 중복성을 제거하고 선택적 벡터 양자화를 행함으로써 대역내 중복성을 효과적으로 제거하여 압축효율을 향상시킨다. 실제 원격 센싱된 인공위성 화상데이타에 대한 실험을 통하여 제안한 기법의 부호화 효율이 기존의 기법에 비하여 우수함을 확인하였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.2C
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• pp.100-109
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• 2003

A differential index assignment scheme is proposed for the image encoding system in which a variable-length tree-structured vector quantizer is adopted. Each source vector is quantized into a terminal node of VLTSVQ and each terminal node is represented as a unique binary vector. The proposed index assignment scheme utilizes the correlation between interblocks of the image to increase the compression ratio with the image quality maintained. Simulation results show that the proposed scheme achieves a much higher compression ratio than the conventional one does and that the amount of the bit rate reduction of the proposed scheme becomes large as the correlation of the image becomes large. The proposed encoding scheme can be effectively used to encode R images whose pixel values we, in general, highly correlated with those of the neighbor pixels.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.2A
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• pp.86-95
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• 2003

With the advent of future mobile communication systems, the wireless transmission of the huge amount of multimedia data over the error-prone multipath fading channel has to overcome the inherent sensitivity to channel errors. To alleviate the effect of the channel errors, hosts of techniques based on the forward error correction(FEC) has been proposed at the cost of overhead rate. Among the FEC techniques, turbo code, whose performance has been shown to be very close to the Shannon limit, can be classified as a block-based error correction code. In this paper, considering the variable packet size of the multimedia data, we analyzed turbo codes employing the variable-sized interleaver. The effect of the various parameters on the BER performance is analyzed. We show that the turbo codes can be used as efficient error correction codes of multimedia data.

• The Transactions of the Korea Information Processing Society
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• v.4 no.4
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• pp.1121-1131
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• 1997

In video coding at high compression rate, factal compression schemes in spatial domain have outstanding blocking artifacts and compression schemes in wavelet transform domain have rinfing artifacts at edges. In order to compensate these disadvantages, we propose a fractal video coding in wavelet transrorm domain which leads to clear edges without blocking atrifacts even at high bompression rate. The proposed method performs variable block sized motion estimation by using correlation among different subbands. Then the wavelet coefficients which are not enoded dffectively by the motion estimation are compressed by inter-frame fractal coding which predicts fine scale subbands hierarchically from the next coarser scale subbands. Computer sumulations with sev-eral test images wequences show that the proposed method shows better performance than the conventional video coding methods using fractal and wavelet.

• Journal of the Korean Institute of Intelligent Systems
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• v.10 no.3
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• pp.179-187
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• 2000

Fractal theory has strengths such as high compression rate and fast decoding time in application to image compression, but it suffers from long comparison time necessary for finding an optimally similar domain block in the encoding stage. This paper proposes a neural network based block classifier which enhances the encoding time significantly by classifying domain blocks into 4 patterns and searching only those blocks having the same pattern with the range block to be encoded. Size of a block is differently determined depending on the image complexity of the block. The proposed algorithm has been tested with three different images having various featrues. The experimental results have shown that the proposed algorithm enhances the compression time by 40% on average compared to the conventional fractal encoding algorithms, while maintaining allowable image qualify of PSNR 30 dB.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2010.07a
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• pp.335-336
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• 2010

H.264/AVC 비디오 압축 표준은 압축 효율을 높이기 위해 다양한 크기의 블록을 사용하여 화면 사이의 움직임 예측을 수행한다. 세밀한 움직임 예측으로 인해 기존의 동영상 표준보다 압축 효율을 높일 수 있었지만, 복잡도도 증가하는 단점이 있다. 따라서, H.264/AVC의 고속 움직임 추정 기법은 필수적이다. H.264/AVC에서 사용하는 움직임 예측 방법은 고정된 탐색 영역 안에서 모든 정수 화소 단위로 최적의 움직임 벡터를 계산한다. 불필요한 정수 화소까지 움직임을 예측하므로 계산양이 증가한다. 본 논문에서는 움직임 벡터의 시간적 상관도와 공간적 상관도를 이용하여 가변적으로 탐색 영역의 크기를 조절하는 방법과 적응적인 초기 시작점 결정 방법을 제안했다. 현재 매크로블록과 참조 화면 사이의 거리를 고려하여 시간적 상관도와 공간적 상관도의 탐색 영역 비중을 가변적으로 조절했다. 또한 참조 화면과 현재 매크로블록 사이의 거리가 멀어질수록 초기 시작점의 정확도를 높이기 위해 초기 시작점을 예측 움직임 벡터와 이전 참조 화면에서 결정된 최적의 움직임 벡터의 평균으로 결정했다. 제안하는 방법은 기존의 전 영역 탐색 방법과 유사한 부호화 성능을 보이면서 움직임 예측 시간이 평균 53.98% 감소하는 것을 확인할 수 있다.

• Journal of Broadcast Engineering
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• v.13 no.1
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• pp.128-136
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• 2008

In this paper, we propose a variable step search fast motion estimation algorithm using local statistics of neighboring motion vectors. Using the degree of correlation between neighboring motion vectors, motion search range is adaptively adjusted to reduce unnecessary search points. Based on the adjusted search range, motion vector is obtained by variable search step. Experimental results show that the proposed algorithm has the capability to dramatically reduce the search points and computing cost for motion estimation, comparing to fast full spiral search motion estimation and other fast motion estimation.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.47 no.6
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• pp.1-9
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• 2010

In this paper, we propose an efficient compression method of the integral images. The integral imaging is a well-known technique to represent and record three-dimensional images. The proposed method is based on three dimensional discrete cosine transform (3D-DCT). The 3D-DCT techniques for the integral images have been reported as an efficient coding method for the integral images which reduces the redundancies between adjacent elemental images. The proposed method is a compression method efficient to integral images using adaptive block mode(ABM), based on the 3D-DCT technique. In the ABM, 3D-DCT blocks adaptive to the characteristics of integral images are constructed, which produces variable block size 3D-DCT blocks, and then 3D-DCTs for the 3D blocks are performed. Experimental results show that the proposed method gives significant improvement in coding efficiency. Especially, at the high bit-rates, the proposed method is more excellent since the overhead incurred by the proposed method take less part of the total bits.

• Journal of Broadcast Engineering
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• v.22 no.1
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• pp.15-27
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• 2017

CRA(Conditional Replenishment Algorithm) was proposed to improve the visual quality of SC-MMH(Service Compatible 3DTV using Main and Mobile Hybrid delivery) which is a kind of hybrid 3DTV system and has been standardized by ATSC. In SC-MMH system, reference view and additional view may have different resolutions and/or encoding methods. To reconstruct 3D view, additional view needs to be enlarged as same as reference view. Although the performance of CRA is quite satisfactory, there may exist some blocky artifacts in the enlarged view since it adopts block-shaped processing unit with quad-tree structure. In this paper, we analyze the main causes of blocky artifacts in CRA and show these artifacts can be successfully suppressed by applying the deblocking filter at receiver side.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.10C
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• pp.820-828
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• 2008

In order to achieve high coding efficiency, H.264/AVC video coding standard adopts the techniques such as variable block size coding, motion estimation with quarter-pel precision, multiple reference frames, rate-distortion optimization, and etc. However, these coding methods have a defect to greatly increase the complexity for motion estimation. Particularly, from multiple reference frame motion estimation, the computational burden increases in proportion to the number of the searched reference frames. Therefore, we propose the method to reduce the complexity by controlling the number of the searched reference frames in motion estimation. Proposed algorithm uses the optimal reference frame information in both $P16{\times}16$ mode and the adjacent blocks, thus omits unnecessary searching process in the rest of inter modes. Experimental results show the proposed method can save an average of 57.31% of the coding time with negligible quality and bit-rate difference. This method also can be adopted with any of the existing motion estimation algorithm. Therefore, additional performance improvement can be obtained.