• Proceedings of the Korea Multimedia Society Conference
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• 2002.05c
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• pp.449-454
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• 2002

네트워크 혼잡으로 인한 패킷 손실은 인터넷 망에서는 필수 불가결이고, 압축된 비디오 비트 스트림을 인터넷 망에 전송할 경우 공-시간적 도메인상에 에러 전파을 야기하므로 화질에 심각한 화질열화를 초래한다. 본 논문에서는 수신측에서 손상된 영상 일부분을 복구하기 위하여 새로운 에러 은닉 알고리즘인 EBMA(Edge detecting for Boundary Matching Algorithm)를 제안한다. 기존 BMA는 부호화된 인접한 블록의 움직임벡터들이 상당히 높은 유사도 혹은 상관도 (correlation)를 갖고 있다는 점과 손실블록과 인접블록 경계에 존재하는 화소간의 유사도를 이용하기 때문에 비교적 신뢰할 수 있지만, 손실블록과 정확히 복원된 인접블록 화소간의 방향성을 고려하지 않는 단점이 있다. 따라서 제안한 알고리즘은 에지영역을 검출하고, 검출된 에지영역에서 방향성을 조사하므로 기존 BMA 방법 보다 성능이 향상되었다. 실험결과는 제안한 알고리즘이 기존 BMA 방법보다 계산 및 화질측면에서 우월하였을 뿐만 아니라, PSNR 값과 주관적인 화질상에서도 좋은 결과를 나타내었다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2022.06a
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• pp.182-183
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• 2022

The large data volume of light field (LF) image has motivated much research on how to compress the data volume more efficiently. One of the approaches is to compress LF images after representing them in the form of pseudo video sequence. In this way, the pseudo temporal redundancy between views can be exploited by motion estimation and compensation. Based on our observation that images obtained by LF cameras have small range of disparity values between adjacent views, we propose to limit the motion search range to reduce the time complexity of motion estimation. Our experimental results show that a smaller motion search range reduces the encoding time while not affecting the bitrate of H.266/VVC much.

• Annual Conference of KIPS
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• 2008.11a
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• pp.175-178
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• 2008

MPEG-4 Part 2 에서 표준으로 채택된 FGS (fine granularity scalability) 코딩 기법은 전송 선로의 상태가 급변하는 경우에도 주어진 대역폭에서 최적의 화질 향상을 얻을 수 있도록 설계된 망 상태에 적응적인 스케일러블 비디오 코딩 기법이다 [1][2][9]. 본 논문에서는 기존의 FGS 향상 계층에서 영상의 잔여 신호를 다시 한 번 bit-plane 코딩을 해줌으로써 화질 확장성을 더 높인 Advanced FGS 코딩 구조를 제안하였다. 본 논문의 실험에서는 기존의 MPEG-4 VM (verification model)에서 사용된 FGS 코딩과의 비교를 통해 Advanced FGS 구조의 화질 확장성을 평가하였다. 비교는 두 부호화 기술의 PSNR 값의 분석으로 이루어졌고, 결과를 통해 Advanced FGS 구조가 고화질을 가지며, 화질 확장성이 더 높은 구조임을 알 수 있었다.

• Journal of Broadcast Engineering
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• v.15 no.4
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• pp.540-546
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• 2010

Since the stereoscopic 3-dimensional (3D) video that provides users with a realistic multimedia service requires twice as much data as 2-dimensional (2D) video, it is difficult to construct the fast system. In this paper, we propose a fast stereoscopic 3D broadcasting system based on the depth information. Before the transmission, we encode the input 2D+depth video using x264, an open source H.264/AVC fast encoder to reduce the size of the data. At the receiver, we decode the transmitted bitstream in real time using a compute unified device architecture (CUDA) video decoder API on NVIDIA graphics processing unit (GPU). Then, we apply a fast view synthesis method that generates the virtual view using GPU. The proposed system can display the output video in both 2DTV and 3DTV. From the experiment, we verified that the proposed system can service the stereoscopic 3D contents in 24 frames per second at most.

• Journal of Broadcast Engineering
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• v.24 no.6
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• pp.1053-1063
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• 2019

Recently, tile-based streaming that transmits one 360 video in several tiles, is actively being studied in order to transmit these 360 video more efficiently. In this paper, for the transmission of high-definition 360 video corresponding to user's viewport in tile-based streaming scenarios, a system of assigning the quality of tiles at each tile by applying the saliency map generated by existing network models is proposed. As a result of usage of Motion-Constrained Tile Set (MCTS) technique to encode each tile independently, the user's viewport was rendered and tested based on Salient360! dataset, streaming 360 video based on the proposed system results in gain to 23% of the user's viewport compared to using the existing high-efficiency video coding (HEVC).

• Journal of Broadcast Engineering
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• v.11 no.2 s.31
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• pp.174-180
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• 2006

H.264/MPEG-4 AVC is jointly developed by ITU-T and ISO/IEC. It provides efficient coding efficiency compared with previous video standards. It reduced the bit rate by approximately $30%{\sim}70%$ while providing the same or better image quality. And, H.264/MPEG-4 AVC supports not only lossy coding but also lossless coding. In this paper, we suggest a method to improve lossless coding efficiency. Proposed method is based on Intra residual DPCM, it has same effect with the prediction from spatially nearest pixel. Also, proposed method does not broken decoder pipe-line. Experimental results, the method reduced the bit rate by approximately 12% in comparison with the H.264 Intra lossless coding. As a result, it is adopted into the H.264/MPEG-4 AVC Advanced 4:4:4 profile.

• Journal of Broadcast Engineering
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• v.14 no.3
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• pp.271-279
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• 2009

The Moving Picture Experts Group (MPEG) and Video Coding Experts Group (VCEG) have developed a new standard that promises to outperform the earlier MPEG-4 and H.263 standards. The new standard is called H.264/AVC (Advanced Video Coding) and is published jointly as MPEG-4 Part 10 and ITU-T Recommendation H.264. In particular, the H.264/AVC intra prediction coding provides nine directional prediction modes for every $4{\times}4$ block in order to reduce spatial redundancies. In this paper, an ABS (Adaptive Bit Skip) mode is proposed. In order to achieve coding efficiency, the proposed method can remove the mode bits to represent the prediction mode by using the similarity of adjacent pixels. Experimental results show that the proposed method achieves the PSNR gain of about 0.2 dB in R-D curve and reduces the bit rates about 3.6% compared with H.264/AVC.

• Journal of Broadcast Engineering
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• v.2 no.2
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• pp.169-181
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• 1997

In this paper, we propose and discuss about image enhancement techniques for MPEG-4. which represents very low bit-rate, content-based. and object-based hierarchical audio-visual coding standard. The proposed enhancement technique removes undesired artifacts arising in the compression procedure and increase resolution in both spatial and temporal domains. In order to remove undesired artifacts. we divide the MPEG-4 video algorithm in two parts: MPEG-2 like part and the new part. For removing artifacts caused by the first part. we adopt the conventional blocking artifacts algorithm developed for MPEG-2. On the other hand for removing artifacts caused by the second part. we provide a new degradation model. and propose the corresponding image restoration method. For increasing resolution of the MPEG-4 images, we propose a general framework of multichannel image interpolation process. which includes both spatial and temporal interpolations. As the MPEG-4 standard is under development. various sophisticated techniques are considered. but research on image enhancement techniques is relatively underestimated. By this reason. additional image enhancement techniques will become very important issue in realization phase of MPEG-4.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.38 no.2
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• pp.149-159
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• 2001

The conventional block-based motion prediction suffers, especially in low bit-rate video application, from shortcomings such as blocking artifacts of motion field and unstable motion estimation. To overcome the deficiency, this paper proposes one method of adopting a new motion compensation scheme based on the irregular triangular mesh structure while keeping the current block-based DCT coding structure of H.263 as much as possible. To represent the reconstructed previous frame using minimal number of control points, the proposed method designs content-adaptive irregular triangular meshes, and then, estimate the motion vector of each control point using the affine transformation-based matching. The predicted current frame is obtained by applying the affine transformation to each triangular mesh. Experiment with the several real video sequences shows improvement both in objective and subjective picture quality over the conventional block-based H.263 method.

• 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.