• The Transactions of the Korea Information Processing Society
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• v.6 no.8
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• pp.2271-2280
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• 1999

In this paper, a variable motion estimation scheme based on HBMA(Hierarchical Block Matching Algorithm) to improve the performance and to reduce heavy computational and transmission load, is presented. The proposed algorithm is composed of four steps. First, block activity for each block is defined using the edge information of differential image between two sequential images, and then average block activity of the present image is found by taking the mean of block activity. Secondly, camera pan compensation is carried out, according to the average activity of the image, in the hierarchical pyramid structure constructed by wavelet transform. Next, the LUT classifying each block into one among Moving, No Moving, Semi-Moving Block according to the block activity compensated camera pan is obtained. Finally, as varying the block size and adaptively selecting the initial search layer and the search range referring to LUT, the proposed variable HBMA can effectively carries out fast motion estimation in the hierarchical pyramid structure. The cost function needed above-mentioned each step is only the block activity defined by the edge information of the differential image in the sequential images.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.45 no.6
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• pp.1-8
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• 2008

This paper introduces three efficient frame selection schemes to reduce the computation complexity for the multi-reference and variable block size Motion Estimation (ME). The proposed RSP (Reference Selection Pass) scheme can minimize the overhead of frame selection. The MFS (Modified Frame Selection) scheme can reduce the number of search points about 18% compared with existing schemes considering the motion of image during the reference frame selection process. In addition, the TPRFS (Two Pass Reference frame Selection) scheme can minimize the frame selection operation for the variable block size ME in H.264/AVC using the character of selected reference frame according to the block size. The simulation results show the proposed schemes can save up to 50% of the ME computation without degradation of image Qualify. Because the proposed schemes can be separated from the block matching process, they can be used with any existing single reference fast search algorithms.

• Proceedings of the IEEK Conference
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• 2002.06d
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• pp.37-40
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• 2002

MPEG-4 부호화기는 16×16 픽셀로 이루어진 매크로 블록을 기본 단위로 하는 비디오 객체에 대해 움직임 추정과 움직임 보상을 수행한다. 이때 이전 블록과 현재 블록간의 차이를 8×8 블록으로 BCT하여 압축한다. DCT는 영상 신호의 에너지를 낮은 대역으로 집중시켜 낮은 에너지를 갖는 고주파 성분을 제거하여 정보를 압축하므로 복원된 영상은 블록의 경계선이 표시되는 블록킹 현상이 발생한다. 본 논문에서는 4×4 블록과 8×8 블록을 이용하여 DCT하는 가변 블록 변환 방식을 사용한다. 이는 작은 크기의 블록을 사용하므로 블록내 주파수의 분포를 비교적 좁은 영역으로 변환할 수 있어 블록킹 현상을 줄일 수 있다. 또한 INTRA 프레임의 DCT 과정에서 4개의 DCT 변환 블록중 하나를 이웃하는 블록의 DC 계수와 화소값들을 이용하여 그 값을 예측하여 DCT계수를 결정하고 INTER 프레임에서는 간략화된 정수 DCT의 사용과 작은 블록단위의 작업으로 인한 부호화의 부담을 줄인 다.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.8
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• pp.47-54
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• 1998

With the increasing popularity of the use of large-volume image database in various application, it becomes imperative to build an efficient and fast retrieval system to browse through the entire database. We present a new method for a content-based image retrieval by using a variable block size and block matching algorithm. Proposed approach is reflecting image features that exploit visual cues such as color and space allocation of image and is getting the fast retrieval time by automatical convergence of retrieval times which adapt to wanting similarity value. We have implemented this technique and tested it for a database of approximately 150 images. The test shows that a 1.9 times fast retrieval time compare to J & V algorithm at the image retrieval efficiency 0.65 and that a 1.83 times fast retrieval time compare to predefined fixed block size.

• Proceedings of the Korea Information Processing Society Conference
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• 2001.10b
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• pp.823-830
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• 2001

본 논문에서는 데이터 의존 회전 기법과 프로그램 셀룰라 오토마타 기법을 사용한 블록 암호 알고리즘인 가칭 Pkc128(PuKyong Code 128) 암호 알고리즘을 제안한다. 제안한 암호 알고리즘의 블록 크기는 128 비트이고, 키의 치기는 128 비트 이상 가변이며 Feistel Network 구조를 취하였다. 제안한 알고리즘의 안전성을 검정하기 위하여 출력 스트림에 대한 통계적 검정을 실시하였다. 그 결과 16 회전 시에 모든 검정과정을 통과하여 제안된 알고리즘이 통계적으로 안전함을 확인하였다.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.40 no.5
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• pp.417-425
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• 2003

H.264, which is the latest video coding standard of both ITU-T(International Telecommunication Union-Telecommunication standardization sector) and MPEG(Moving Picture Experts Group), adopts new video coding tools such as variable block size motion estimation, multiple reference frames, quarter-pel motion estimation/compensation(ME/MC), 4${\times}$4 Integer DCT(Discrete Cosine Transform), and Rate-Distortion Optimization, etc. These new video coding tools provide good coding of efficiency compared with existing video coding standards as H.263, MPEG-4, etc. However, these new coding tools require the increase of encoder complexity. Therefore, in order to apply H.264 to many real applications, fast algorithms are required for H.264 coding tools. In this paper, when encoder MacroBlock(MB) mode is decided by rate-distortion optimization tool, fast mode decision algorithm by skipping variable block size ME/MC and spatial-predictive coding, which occupies most encoder complexity, is proposed. In terms of computational complexity, the proposed method runs about 4 times as far as JM(Joint Model) 42 encoder of H.264, while the PSNR(peak signal-to-noise ratio)s of the decoded images are maintained.

• The Journal of the Korea Contents Association
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• v.10 no.4
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• pp.28-35
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• 2010

The variable block size motion estimation (ME) and compensation (MC) using multiple reference frames is adopted in H.264/AVC to improve coding efficiency. However, the computational complexity for ME/MC increases proportional to the number of reference frames and variable blocks. In this paper, we propose a new efficient reference frame selection algorithm to reduce the complexity while keeping the visual quality. First, a motion vector reference map is constructed by SAD of $4{\times}4$ block unit for multi reference frames. Next, the variable block size motion estimation and motion compensation is performed according to the motion vector reference map. The computer simulation results show that the average loss of BDPSNR is -0.01dB, the increment of BDBR is 0.27%, and the encoding time is reduced by 38% compared with the original method for H.264/AVC.

• Proceedings of the Korea Information Processing Society Conference
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• 2001.04b
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• pp.847-850
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• 2001

영상과 같은 다양하고 복잡한 데이터 검색은 기존의 키워드를 이용한 검색이 아닌 내용 기반 검색 방법이 요구된다. 본문은 JPEG/MPEG 과 같은 영상 압축 기법에서 사용되는 DCT 변환 부호화를 이용하여 각 블록의 평균인 DC 성분을 얻어 이 정보를 이용하여 영상을 검색하는 방법을 제시한다. 기존의 방법은 단순히 DCT 전체 성분을 이용하는 방법으로, 영상 전체의 DCT 정보를 처리하여야 하므로 시간과 메모리의 낭비가 있을 수 있다. 본문에서는 이러한 처리시간과 메모리의 낭비를 막기 위해 DC 성분만을 이용하여 영상 검색을 하며, 영상이 실제로 있는 부분에서는 블록의 크기를 가변적으로 변경하여 검색의 오류를 줄일 수 있다. 또한 검색을 전체 영상에 대한 빠른 1 차 검색과 동일 패턴을 가진 영상의 2 차 세부 검색으로 나누어 실행함으로써 보다 빠른 검색을 할 수 있다. 한편, 겹쳐진 영상에 대해서도 검색이 가능하다.

• 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.