• 전자공학회논문지B
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• 제33B권8호
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• pp.81-95
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• 1996

In this paper, we propose a motio estiamtion algorithm using low-resolution quantization to reduce the computation of the full search algorithm. The proposed algorithm consists of the low-resolution search which determins the candidate motion vectors by comparing the low-resolution image and the full-resolution search which determines the motion vector by comparing the full-resolution image on the positions of the candidate motion vectors. The low-resolution image is generated by subtracting each pixel value in the reference block or the search window by the mean of the reference block, and by quantizing it is 2-bit resolution. The candidate motion vectors are determined by counting the number of pixels in the reference block whose quantized codes are unmatched to those in the search window. Simulation results show that the required computational cost of the proposed algorithm is reduced to 1/12 of the full search algorithm while its performance degradation is 0.03~0.12 dB.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 ITC-CSCC -2
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• pp.843-846
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• 2000

An optical flow-based motion estimation algorithm is proposed for video coding. The algorithm uses block-matching motion estimation with an adaptive search region. The search region is computed from motion fields that are estimated based on the optical flow. The algorithm is based on the fact that true block-motion vectors have similar characteristics to optical flow vectors. Thereafter, the search region is computed using these optical flow vectors that include spatial relationships. In conventional block matching, the search region is fixed. In contrast, in the new method, the appropriate size and location of the search region are both decided by the proposed algorithm. The results obtained using test images show that the proposed algorithm can produce a significant improvement compared with previous block-matching algorithms.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 추계종합학술대회 논문집(4)
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• pp.109-112
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• 2000

Bitstrems corrupted by channel errors are not only difficult to be decoded but also propagate error to other part of the bitstreams when highly compressed video is transmitted over channels with noise such as mobile communication channels. In this paper, error concealment algorithm performed in decoder is proposed when errors occur for transmission. Proposed algorithm searches moving area with homogeneous movement in neighbored blocks when motion vectors are damaged, then recovers motion vectors of missing blocks considering where missing blocks are belong to. Experiment result shows that proposed algorithm exhibits better performance in PSNR than existing error concealment method.

• 한국멀티미디어학회논문지
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• 제21권9호
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• pp.1052-1061
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• 2018

In this paper, we propose a new algorithm that is robust against the effects of objects that are relatively unaffected by camera motion and can accurately detect camera motion even in high resolution images. First, for more accurate camera motion detection, a global motion filter based on entropy of a motion vector is used to distinguish the background and the object. A block matching algorithm is used to find exact motion vectors. In addition, a matched filter with the angle of the ideal motion vector of each block is used. Motion vectors including 4 kinds of diagonal direction, zoom in, and zoom out are added additionally. The experiment shows that the precision, recall, and accuracy of camera motion detection compared to the recent results is improved by 12.5%, 8.6% and 9.5%, respectively.

• 한국정보통신학회논문지
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• 제10권8호
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• pp.1373-1379
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• 2006

움직임 객체의 추출은 비디오 서비스 등에서 주요한 연구목적 중의 하나이다. 본 논문은 블록 움직임 벡터를 이용하여 움직임 객체를 추출하는 새로운 기법을 제시한다. 이를 위하여, 1) 사후 확률 밀도와 Gibbs 랜덤필드의 이용하여 블록 움직임 벡터를 결정하고, 2) 2-D 히스토그램을 바탕으로 전역 움직임을 구하고, 3) 경계 블록 분할 단계를 통해 객체 추출을 달성한다. 제안된 알고리듬은 특히 압축된 비디오 신호의 움직임 객체에 특히 유용하게 이용될 수 있다. 제안된 알고리듬을 여러 가지 영상에 적용한 결과 양호한 결과를 얻을 수 있었다.

• 한국통신학회논문지
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• 제24권8B호
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• pp.1438-1443
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• 1999

In this paper, we propose detection methods for gradual scene changes such as dissolve, pan, and zoom. The proposal method to detect a dissolve region uses scene features based on spatial statistics of the image. The spatial statistics to define shot boundaries are derived from squared means within each local area. We also propose a method of the camera motion detection using four representative motion vectors in the background. Representative motion vectors are derived from macroblock motion vectors which are directly extracted from MPEG streams. To reduce the implementation time, we use DC sequences rather than fully decoded MPEG video. In addition, to detect the gradual scene change region precisely, we use all types of the MPEG frames(I, P, B frame). Simulation results show that the proposed detection methods perform better than existing methods.

• 대한전자공학회논문지SP
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• 제46권4호
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• pp.108-115
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• 2009

본 논문에서는 에러에 강인한 동영상 압축을 위해서 효과적인 에러 은닉을 제공하는 새로운 움직임 예측기법을 제안한다. 일반적으로 전송 에러에 의해 손실된 프레임을 효율적으로 복원하기 위해서는 영상 내에서 객체의 실제 움직임을 정확하게 아는 것이 중요하다. 하지만 현재 블록과 움직임 보상된 블록에 있는 화소의 차의 절대값의 합 (sum of absolute different, SAD)을 기준으로 이용하는 기존의 움직임 예측 (motion estimation, ME)기법이 객체의 실제 움직임을 항상 정확하게 반영하는 것은 아니다. 이러한 문제를 해결하기 위해서, 본 논문에서 현재 블록과 움직임 보상된 블록의 움직임 벡터들의 차이의 절대값 (absolute different of motion vectors, ADMV)을 새로운 부가적인 기준으로 소개한다. 본 논문에서 제안하는 ME 기법은 SAD와 ADMV의 가중 합을 최소화시킴으로써 실제 움직임과 거리가 먼 움직임 벡터들을 효과적으로 제거할 수 있다. 또한, 제안하는 ADMV을 이용하면 영상의 전송 과정에서 손실된 프레임의 정보를 전혀 사용하지 않고도 손실된 움직임 정보를 효과적으로 복원할 수 있으므로 복호기에서의 에러 은닉 성능을 크게 향상시킬 수 있다. 실험을 통하여 본 논문에서 제안하는 기법이 기존의 ME기법과 유사한 압축 효율을 갖으면서 기존의 에러 내성 기법보다 성능이 더 우수하다는 것을 확인하였다.

• 전자공학회논문지S
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• 제35S권5호
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• pp.68-74
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• 1998

Block-based interframe interpolation algorithms cause severe block effect because the algorithm interpolates the skipped frame by using block based motion vector. Therefore, in this paper, we propose an algorithm that reduces the block effect in the interpolated frames. First, we propose an algorithm that obtains backward motion vector by using forward motion vector received from the transmitter. In order to predict well covered and uncovered region, backward motion vector is needed as well as forward motion vector. Second, we propose the algorithm which segments the motion boundary blocks into regions and obtains the motion vector of each region from candidates that consist of the motion vectors of neighbor blocks. This algorithm makes it possible that the moving object and the background, in spite of being in the same block, have different motion vectors from each other so that the block effect can be reduced. According to the results of simulation, the proposed algorithm is superior to conventional algorithm in subjective quality a swell as in objective quality.

• 방송공학회논문지
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• 제16권1호
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• pp.108-122
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• 2011

본 논문은 저복잡도 및 고효율 분산 비디오 코딩에서 H.264/AVC로의 변환을 위한 트랜스코딩 방법을 제안한다. 제안한 방법은 낮은 복잡도로 높은 부호화 성능을 유지하기 위하여, 보조정보 생성을 위하여 측정된 움직임 벡터를 Wyner-Ziv (WZ) 프레임뿐만 아니라 키 프레임에서도 적용하여 부화화를 수행한다. 보조정보 생성을 위하여 측정된 움직임 벡터는 키 프레임에서 이전의 키 프레임으로의 움직임 추정에 의해 결정된 움직임 벡터임으로, 이 움직임 벡터를 이용하여 인트라 키 프레임을 예측 프레임으로 변환압축하는 방법을 제안한다. 또한, 제안한 방법은 두 예측 움직임 벡터를 기반으로 측정된 두 움직임 벡터 중, 비트율-왜곡 최적화를 수행하여 최적의 움직임 벡터를 선택한다. 보조정보의 움직임 벡터는 보조정보를 생성하기 위하여 수행된 움직임 추정을 통하여 측정된 움직임 벡터임으로, 적은 탐색 영역을 적용하여도 높은 부호화 효율을 얻을 수 있다. 따라서, 제안한 방법은 예측 움직임 벡터와 보조정보 기반의 예측 움직임 벡터로 적용하여 적은 탐색 영역에서 움직임 추정을 수행함으로써, 저복잡도로 높은 부호화 효율을 가질 수 있다. 실험결과는 기존 변환 방법과 대비하여, 트랜스코더의 복잡도가 2.82%로 감소하고 비트율 성능은 23.06% 상향되었다.

• 한국멀티미디어학회논문지
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• 제21권10호
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• pp.1131-1141
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• 2018

Motion Estimation which is used to reduce the redundant data plays an important role in video compressions. However, it requires huge computational complexity of the encoder part. And therefore many fast motion estimation methods has been developed to reduce complexity. Multi-view video is obtained by using many cameras at different positions and its complexity increases in proportion to the number of cameras. In this paper, we proposed a fast motion estimation method for multi-view video. The proposed method predicts a search start point by using correlated candidate vectors of the current block. According to the motion size of the start search point, a search start pattern of the current block is decided adaptively. The proposed method proves to be about 2 ~ 5 times faster than existing methods while maintaining similar image quality and bitrates.