• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2008년도 하계종합학술대회
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• pp.927-928
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• 2008

In this paper, a interpolation error concealment algorithm of motion compensated interpolated frame for motion compensated frame rate conversion to reduce the block artifacts caused by failure of conventional motion estimation based on block matching algorithm is proposed. Experimental results show good performance of the proposed scheme with significant reduction of the block artifacts.

• 대한원격탐사학회지
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• 제33권5_1호
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• pp.495-506
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• 2017

본 연구는 동일 촬영시기 정사영상에 대한 색상보정을 효과적으로 수행하기 위하여 실시되었다. 이를 위하여, 인접 영상 간 상대적인 지상좌표 위치오차를 분석하였다. 위치오차를 저감시키기 위한 방법으로 block sum 방법을 제시하였다. 각각 block sum 크기에 따라 결정된 회귀계수를 이용하여 상대색상보정을 수행하였다. 그 결과 시각적으로 상대색상보정이 잘 수행되었음을 확인하였다. 정량적인 분석은 히스토그램 유사성 분석을 통해 수행되었다. 이로부터 block sum 방법이 상대색상보정에 유용함이 증명되었다. 특히 상대적인 지상좌표 위치오차의 양에 따라 block sum 크기의 선정이 매우 중요한 것으로 나타났다. 위치오차가 클수록 높은 크기에서의 block sum 적용이 유용한 것으로 확인되었다.

• 한국통신학회논문지
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• 제22권8호
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• pp.1691-1697
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• 1997

This paper presents a new motion compensated error coding method suitable for region based image coding system. Compared with block based conding, the region based coding improves subjective quality as it estimates and compensates 2D (or 3D) translantional, rotational, and scaling motion for each regions. although the region based coding has this advantage, its merit is reduced as bock-DCT (2D-DCT) is used to encode motion-compensated error. To overcome this problem, a new region adaptive motion compensated error coding technique which improver subjective and objective quality in the region boundary is proposed in this paper. In the proposed method, regions with large error are estimated using contour of the regions and contrast between the regions. The regions estiated as those with large error are coded by arbitrarily shaped image segment coding method. The mask information of the coded regions is not transmitted because it is estimated as the same algorithm in the encoder and the decoder. The proposed region adaptive motion conpensated error coding method improves about 0.5dB when it is compared with conventional block based method.

• 한국전자통신학회논문지
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• 제17권1호
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• pp.31-40
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• 2022

본 논문은 기존 QSBC(Quantum Short-Block Code)의 기능은 보전하면서 파울리 X 및 Y 오류에 의한 단일 비트플립 오류정정 기능을 부가한 증강된 QSBC를 제안한다. 증강된 QSBC는 기존 QSBC에 정보워드 수만큼의 추가적인 보조 큐비트와 Toffoli 게이트를 삽입해 단일 파울리 X 오류의 진단과 자동정정 기능을 부여한 것이다. 본 논문은 종자 벡터를 이용한 증강된 QSBC의 일반적 확장 방법과 확장성을 반영한 단일 비트플립오류 자동정정 함수의 Toffoli 게이트 실현 방법도 제시하였다. 본 논문이 제안한 증강된 QSBC는 보조 큐비트 삽입으로 인해 코딩률이 최소 1/3과 최대 1/2인 trade-off를 갖는다.

• ETRI Journal
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• 제30권4호
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• pp.506-515
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• 2008

The H.264/AVC standard has adopted new coding tools such as intra-prediction, variable block size, motion estimation with quarter-pixel-accuracy, loop filter, and so on. The adoption of these tools enables an H.264/AVC-coded bitstream to have more information than was possible with previous standards. In this paper, we propose an effective spatial error concealment method with low complexity in H.264/AVC intra-frame. From information included in an H.264/AVC-coded bitstream, we use prediction modes of intra-blocks to recover a damaged block. This is because the prediction direction in each prediction mode is highly correlated to the edge direction. We first estimate the edge direction of a damaged block using the prediction modes of the intra-blocks adjacent to a damaged block and classify the area inside the damaged block into edge and flat areas. Our method then recovers pixel values in the edge area using edge-directed interpolation, and recovers pixel values in the flat area using weighted interpolation. Simulation results show that the proposed method yields better video quality than conventional approaches.

• 한국멀티미디어학회논문지
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• 제6권1호
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• pp.78-88
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• 2003

본 논문에서는 연산 영역 가변 알고리즘을 적용한 MPEG-4 부호화 기반의 적응적 오류 은닉 (error concealment) 기법을 제안하였다. 이 알고리즘에서는 손실 블록을 그의 주변 정보를 이용하여 이들을 평탄블록 (flat block) 및 에지 블록 (edge block)으로 분류한다. 즉, 손실된 블록의 주변 블록들에 대해서 블록 경계 영역의 인접 화소들의 차를 이용하여 평탄 블록을 분류하고, 평탄 블록으로 분류되지 않은 블록들에 대해서는 인접 화소의 차가 정해진 임계값을 넘어서는 개수에 따라 가변적인 연산 영역 (variable operating region, VOR)을 설정한 후, Sobel 연산자를 적용하여 우세 에지 방향 성분을 추정한다. 이렇게 분류된 각 블록에 대하여 적응적 오류 은닉을 수행한다. 평탄 블록에 대해서는 시각적 성능 향상을 위해 평균값을 기반으로 한 가중치에 따른 양선형 보간(mean based weighted bilinear interpolation, MWBLI) 방법을 적용하고, 에지 블록에 대해서는 8가지 방향에 대하여 경계 픽셀을 이용한 방향성 보간 (boundary directional interpolation, BDI) 방법을 적용하여 오류 은닉을 수행한다. 모의 실험 결과를 통하여 제안한 방법이 객관적 화질 및 주관적 화질 측면에서 기존의 방법보다 그 성능이 우수함을 확인하였다.

• Journal of Communications and Networks
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• 제12권1호
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• pp.5-10
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• 2010

This paper introduces a new fast motion estimation based on estimating a block matching error (i.e., sum of absolute difference (SAD)) between blocks which can eliminate an impossible candidate block much earlier than a conventional partial distortion elimination (PDE) scheme. The basic idea of the proposed scheme is based on predicting the total SAD of a candidate block using its partial SAD. In particular, in order to improve prediction accuracy and computational efficiency, a sub-sample based block matching and a selective pixel-based approaches are employed. In order to evaluate the proposed scheme, several baseline approaches are described and compared. The experimental results show that the proposed algorithm can reduce the computations by about 44% for motion estimation at the cost of 0.0005 dB quality degradation versus the general PDE algorithm.

• ETRI Journal
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• 제27권1호
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• pp.53-63
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• 2005

A compressed video bitstream is sensitive to errors that may severely degrade the reconstructed images even when the bit error rate is small. One approach to combat the impact of such errors is the use of error concealment at the decoder without increasing the bit rate or changing the encoder. For spatial-error concealment, we propose a method featuring edge continuity and texture preservation as well as low computation to reconstruct more visually acceptable images. Aiming at temporal error concealment, we propose a two-step algorithm based on block matching principles in which the assumption of smooth and uniform motion for some adjacent blocks is adopted. As simulation results show, the proposed spatial and temporal methods provide better reconstruction quality for damaged images than other methods.

• 전기전자학회논문지
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• 제2권2호
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• pp.285-293
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• 1998

This paper presents unequal error protection and error concealment techniques far robust H.263 video transmission over mobile channels. The proposed error protection scheme has three major features. First, it has the capability of preventing the loss of synchronization information in H.263 video stream as much as possible that the H.263 decoder can resynchronize at the next decoding point, if errors are occurred. Secondly, it employs an unequal error protection scheme to support variable coding rates using rate compatible punctured convolutional (RCPC) codes, dividing the encoded stream into two classes. Finally, a macroblock-interleaving scheme is employed in order to minimize the corruption of consecutive macroblocks due to burst errors, which can make a proper condition for error concealment. In addition, to minimize the spatial error propagations due to the variable length codes, a fast resynchronization scheme at the group of block layer is developed for recovering subsequent error-free macroblocks following the damaged macroblock. futhermore, error concealment techniques based on both side match criterion and overlapped block motion compensation (OBMC) are employed at the source decoder so that it can not only recover the lost macroblock more accurately, but also reduce blocking artifacts. Experimental results show that the proposed scheme can be an effective error protection scheme since proper video quality can be maintained under various channel bit error rates.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제15권9호
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• pp.3458-3481
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• 2021

Existing methods for blind identification of linear block codes without a candidate set are mainly built on the Gauss elimination process. However, the fault tolerance will fall short when the intercepted bit error rate (BER) is too high. To address this issue, we apply the reverse algebra approach and propose a novel "two-step-screening" algorithm by solving the linear error equations on the binary Galois field, or GF(2). In the first step, a recursive matrix partition is implemented to solve the system linear error equations where the coefficient matrix is constructed by the full codewords which come from the intercepted noisy bitstream. This process is repeated to derive all those possible parity-checks. In the second step, a check matrix constructed by the intercepted codewords is applied to find the correct parity-checks out of all possible parity-checks solutions. This novel "two-step-screening" algorithm can be used in different codes like Hamming codes, BCH codes, LDPC codes, and quasi-cyclic LDPC codes. The simulation results have shown that it can highly improve the fault tolerance ability compared to the existing Gauss elimination process-based algorithms.