• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2017.06a
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• pp.63-65
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• 2017

This paper proposes a detection algorithm of video tampering by investigating the change of HEVC coding pattern. When a part of video is deleted and re-compressed, the characteristic patterns are generated by forgery. The proposed algorithm uses these patterns to classify whether video is forged. Experimental results show that the proposed method detects video forgery effectively.

• Journal of Korea Multimedia Society
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• v.21 no.10
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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.

• The Transactions of the Korea Information Processing Society
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• v.7 no.7
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• pp.2254-2263
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• 2000

This paper proposes an efficient predictive image-compression technique based on vector quantization of blocks of pels. In the proposed method edge contents of blocks control the selection of predictors and block shapes as well. The maximum number of bits assigned to quantizers has been in creased to 3bits/pel from 1/5bits/pel, the setting employed by forerunners in predictive vector quantization of images. This increase prevents the saturation in SNR observed in their results in high bit rates. The variable block shape is instrumental in eh reconstruction of edges. The adaptive procedure is controlled by means of he standard deviation ofp rediction errors generated by a default predictor; the standard deviation address a decision table which can be set up beforehand. eh proposed method is characterized by overall improvements in image quality over A-VQ-PE and A-DCT VQ, both of which are known for their efficient use of vector quantizers.

• The Transactions of the Korea Information Processing Society
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• v.7 no.6
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• pp.1956-1963
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• 2000

In this paper, a wavelet image coding scheme exploiting the correlation of neighboring VQ indices in eh wavelet domain is proposed. the codewords in each sub-codebook are re-ordered in terms of their energies in order to increase the correlation of he indices. Then, the generated indices after VQ can be further encoded by non-adaptive DPCM/Huffman method. LBG algorithm and a fast-PNN algorithm using k-d trees are used for generating a multiresolution codebook. Experimental results show that or scheme outperforms the ordinary wavelet VQ and JPEG at low bit rates.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2011.07a
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• pp.278-280
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• 2011

본 논문은 이미지가 갖는 R, G, B 비율의 분산을 이용하여, 공간 영역에서 정보를 은닉하는 알고리즘을 제시한다. 웹 상에서 Jpeg, bmp, gif 등의 포멧을 갖는 이미지를 raw 파일로 변환한 후, R,G,B 비율을 구한다. 그 중 사람의 눈에 가장 둔감한 B 비율 분산을 조작하여 정보를 은닉하는데 이용한다. 또한 오류율을 낮추기 위하여 (15,7)BCH Code 를 사용한다. 제안된 알고리즘이 JPEG(Joint Photographic coding Experts Group) compression, scale(이미지의 크기 변화), Mediancut 과 같은 이미지 변화에 강한 특성과 정보은닉 후에도 화질열화가 발생하지 않는 특성을 실험을 통해 보인다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2013.06a
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• pp.173-175
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• 2013

In this paper, we propose a fast and low-complexity Motion Estimation (ME) algorithm for High Efficiency Video Coding (HEVC). Motion estimation occupies 77~81% of the amount of computation in HEVC. After all, the main key of codec implementation is to find a fast and low-complexity motion estimation algorithm and architecture. The proposed algorithm uses only 1% of the amount of operations compared to full search algorithm while maintaining compression performance with slight loss of 0.6% (BDBR).

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.20-23
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• 1996

The block matching algorithm for the motion estimation is relatively simple to implement, and thus widely applied in image sequence coding such as H.261, MPEG- I and MPEG-2. Most techniques of the block matching method use fixed-size blocks for the motion estimation. And their success relies on the assumption that the motion within each block is uniform. But if the block size is increased to reduce the number of motion vectors for high data compression, the estimated image brings about many errors. In this paper, the variable-sized blocks are used to solve this problem. And the top down method is used to select the block size.

• Journal of the Korea Society of Computer and Information
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• v.3 no.3
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• pp.99-106
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• 1998

This Paper proposes a novel fractal image method for image communication to shorten time to take on fractal encoding by using limited search area method and scaling method First, the original image is contracted respectively by half and by quarter with the scaling method. And then, the corresponding domain block of the quarter-sized image which is most similar with one range block of the half-sized image is searched within the limited area in order to reduce the encoding time extremely As the result of the evaluation, the proposed algorithm provided much shorter encoding time and better compression ratio with a little degradation of the decoded image quality than Jacquin's method.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.12A
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• pp.2085-2091
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• 2001

In lossy compression method, the transformed coefficients are quantized. This results in the quantization noise. The video image quality and bit rate is closely related with the quantization step. In this paper, we proposed a new quantization function for the improved performance. The DC value of each macroblock is compensated depending on the magnitude of DC quantization error. It is implemented very low bit-rate video coding, i.e., H.26L. The experimental result is useful when the object motion is not severe.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.12
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• pp.3033-3045
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• 1996

In this paper, we propse an object-oriented coding method in low bit-rate channels using pyramid structure and residual image compensation. In the motion estimation step, global motion is estimated using a set of multiresolution images constructed in a pyramid structure. We split an input image into two regions based on the gradient value. Regions with larte motions obtain observation points at low resolution level to guarantee robustness to noise and to satisfy a motion constraint equation whereas regions with local motions such as eye, and lips get observation points at the original resolution level. Local motion variations and intesity variations of an image reconstructed by the golbal motion are compensated additionally by using the previous residual image component. Finally, the model failure (MF) region is compensated by the pyramid mapping of the previous displaced frame difference (DFD). Computer simulation results show that the proposed method gives better performance that the convnetional one in terms of the peak signal to noise ratio (PSNR), compression ratio (CR), and computational complexity.