• The KIPS Transactions:PartB
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• v.12B no.7 s.103
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• pp.755-760
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• 2005

To transmit a video bit stream over low bandwith, such as mobile, channels, encoding algorithms for high bit rate like H.263+ are used. In transmitting video bit-streams, packet losses cause severe degradation in image quality. This paper proposes a new algorithm for the recovery of missing or erroneous motion vectors when H.263+ bit-stream is transmitted. Considering that the missing or erroneous motion vectors are closely related with those of neighboring blocks, this paper proposes a temporal-spatial error concealment algorithm. The proposed approach is that missing or erroneous Motion Vectors(MVs) are recovered by clustering the movements of neighboring blocks by their homogeneity. MVs of neighboring blocks we clustered according to ALA(Average Linkage Algorithm) clustering and a representative value for each cluster is determined to obtain the candidate MV set. By computing the distortion of the candidates, a MV with the minimum distortion is selected. Experimental results show that the proposed algorithm exhibits better performance in subjective and objective evaluation than existing methods.

• Journal of Broadcast Engineering
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• v.10 no.3
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• pp.286-296
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• 2005

This paper presents a stereo-based image compression and transmission system for 3D realistic television. In the proposed system, a disparity map is extracted from an input stereo image pair and the extracted disparity map and one of two input images are transmitted or stored at a local or remote site. However, correspondences can not be determined in occlusion areas. Thus, it is not easy to recover 3D information in such regions. In this paper, a reconstruction image compensation algorithm based on error block concealment and in-loop filtering is proposed to minimize the reconstruction error in generating stereo image pair. The effectiveness of the proposed algorithm is shown in term of objective accuracy of reconstruction image with several real stereo image pairs.

• Proceedings of the IEEK Conference
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• 2007.07a
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• pp.255-256
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• 2007

We propose a frame loss concealment algorithm for multi-view video sequences based on correspondence matching, which can hide the effects of frame losses efficiently. To achieve high PSNR performances, we employ a block error concealment scheme to refine the concealed results. Simulation results demonstrate that the proposed algorithm effectively protects the quality of reconstructed videos against transmission errors.

• International Journal of Internet, Broadcasting and Communication
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• v.12 no.1
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• pp.111-115
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• 2020

In this paper, I proposed an effective technique for accurately predicting pixel values using edge components. Adjacent pixel values are similar to each other. That is, generally, similarity exists between adjacent pixels in an image. In the proposed algorithm, edge components are detected using the surrounding pixels in the first step, and pixel values are estimated using the edge components in the second step. Therefore, the prediction accuracy of the pixel value is improved and the prediction error is reduced. Pixel value prediction is a necessary technique for various applications such as image magnification and confidential data concealment. Experimental results show that the proposed method has higher prediction accuracy and fewer prediction error. Therefore, the proposed technique can be effectively used for applications such as image magnification and confidential data concealment.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2014.06a
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• pp.209-210
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• 2014

최근 인터넷 상에서 제공되는 영상 서비스에 대한 요구가 증가하고 있다. 하지만 네트워크 환경에서 전송되는 데이터는 오류로 인하여 쉽게 손실될 수 있다. 특히 HEVC(High Efficiency Video Coding)와 같이 높은 압축률로 압축된 정보에 대한 전송 오류는 영상 복원에 심각한 영향을 끼친다. 따라서 네트워크 환경에서 일정한 화질을 유지하기 위한 오류 은닉(Error Concealment : EC) 방법이 필요하다. 본 논문은 HEVC EC 를 위한 PU(Prediction Unit) 기반 움직임 벡터 외삽법(Motion Vector Extrapolation : MVE) 모델을 제안한다. PU 는 예측의 기본 단위로써 PU 내에 동일한 물체가 포함될 확률이 높다. 따라서, 이 모델은 손실된 프레임의 이전 프레임이 갖는 PU 정보를 이용하여 PU 단위로 외삽(extrapolation)을 실시한다. 또한, 손실된 블록과 외삽 블록간의 관계를 고려하여 겹쳐진(overlapped) 외삽 블록 중 가장 작은 PU 크기를 EC 기본 단위로 결정한다. 이 방법은 PU 정보를 반영함으로써 블록 경계 오류(block artifact)를 감소시킨다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.8
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• pp.1776-1784
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• 2003

In this paper, we propose the architecture of stream producer for MPEG­4 Video encoding. This module receives the quantized coefficient from DCT and Quantization module in macroblock unit and performs the VLC coding according to the encoding mode, and supports the error concealment mode of MPEG­4 and data partitioning mode. Using the VHDL, we designed the module using this architecture and performed the evaluations of this module by performing the post­-simulation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.5
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• pp.1107-1115
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• 1997

In this paper, we propose an error concealment method to recovre damaged block-based image coding schemes. Channel errors during transmission of image data such as bit errors or cell loss result in damaged image blocks in the reconstructed images. To recover damaged blocks is to estimate them using the correctly received or undamaged neighborhood information. In the proposed method, an overcomplete basis for a large block containing a damaged block at its center is introduced and damaged blocks are recovered by sequentially projecting the known neighborhood information onto the overcomplete basis function. Computer simulations show that the proposed algorithm outperforms the conventional method in subjectie recovery qualities as well as objective ones.

• Proceedings of the Korea Information Processing Society Conference
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• 2007.05a
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• pp.341-344
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• 2007

In this paper, a new temporal error concealment method for the new coding standard H.264/AVC is presented, which uses the high correlation between the motion vectors of neighboring blocks. By using the motion vector of neighboring MB of the lost MB, the MV of the lost MB are recovered. It is shown that under FMO coding method of H.264/AVC, the proposed method increases PSNR gain up to 2.85dB compared to build-in algorithm in the H.264/AVC test model and 2.59dB compared to Lagrange interpolation.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.42 no.3 s.303
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• pp.91-98
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• 2005

In this paper, we propose a temporal error concealment method based on the edge adaptive masking. In the method, four regions around the corrupted block - top, bottom, left, and right - are defined and the edge features of the regions are extracted by applying an edge operator for each direction. The size of a mask for the boundary matching is determined by the edge information, which can be considered as a criterion to measure the activity of the boundary region. In other words, it is determined such that the size of the mask is proportional to the amount of edge-component extracted from each region in order to yield the higher reliability on boundary matching. This process is equivalent to applying weights depending on the edge features, which leads the improved motion vector. In experiments, it is verified that the proposed method outperforms the conventional methods in terms of image quality, and then its merits and demerits are discussed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.5C
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• pp.503-511
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• 2006

H.264 adopts new coding tools such as intra-prediction, loop filter, etc. The adoption of these tools enables an H.264-coded bitstream to have more information compared with previous standards. In this paper we proposed an effective spatial error concealment method for H.264. Among the information included in an H.264-coded bitstream, we use intra-mode for recovering a damaged block. This is because prediction direction in intra-mode is highly correlated to the edge direction of a lost macroblock. We first estimate the edge direction using intra-modes of blocks adjacent to a lost macroblock, and classify the area in a damaged macroblock into the edge and the flat area. And then our method 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 the proposed method yields better video quality than conventional approaches by 0.35 to 5.48 dB.