• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.5
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• pp.1096-1108
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• 1996

In this paper, we propose a temporal adaptive tranform 3D SBC coder with motion compensation, exploiting redundancy in the temporal domain. We propose a temporal adaptivity measure, by which the R-D optimal temporal transform can be chaosen. The base temporal subband frame is coded using H.261-like MC-DCT coder, while the higher temporal subband frames are coded using the 2D adaptive wavelet packet bases, considering the various energy distribution which results from the temporal variation. In encoding the subbands, we employ adaptive scanning methods, uniform step-size quantization with VLC, and coded/not-coded flag reduction technique using the quadtree structure. From the simulation results, the proposed adaptive 3D subband coder shows about 0.29~3.14 dB gain over the H.261 and the fixed 3D subband coder techniques.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.31B no.4
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• pp.97-105
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• 1994

Transform image coding using DCT is proved to be efficient in the absence of channel error but its performance degrades rapidly over noisy channel. In this paper, in the case of appling bit selcetive error correction coding that protects some significant bits in a codeword, an efficient allocation method of imformation bits and additive redundancy bits used for quantization and error correction coding respectively under constant transmission bit rate is proposed, and its performance is analyzed. As a result, without increasing trasmission bit rate, PSNR can be improved up to 7~8 [dB] below bit error rate $10^2$ and the image without blocking effect caused by bit error resulted from channel noise can be recostructed.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.38 no.4
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• pp.20-20
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• 2001

본 논문에서는 퍼블릭 워터마킹(public watermarking)에서 영상 블록의 유효성에 기반을 둔 상호연관성(cross-correlation property)과 관련기법을 제안하였다. 이 과정에서 워터마크의 비인식성(imperceptibility)과 깨지기 쉬운 워터마크(fragile watermark)를 보장하기 위하여 DCT(Discrete Cosine Transformation) 도메인의 고주파 영역을 사용하였다. 여러 가지 실험을 통하여 에러가 보정된 원본 영상(original image)들과 워터마크된 이미지(watermarked image)들 사이에 유효한 블록들이 동일함을 확인하였다. 그리고 이러한 상호연관성이 추후의 퍼블릭 워터마킹을 위한 응용들에 적용될 수 있음을 입증하였다.

• Journal of Korea Multimedia Society
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• v.21 no.1
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• pp.61-68
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• 2018

In this paper, we present an effective encryption algorithm for 3D printing models in the frequency domain of discrete cosine transform to prevent illegal copying, access in the secured storage and transmission. Facet data of 3D printing model is extracted to construct a three by three matrix that is then transformed to the frequency domain of discrete cosine transform. The proposed algorithm is based on encrypting the DC coefficients of matrixes of facets in the frequency domain of discrete cosine transform in order to generate the encrypted 3D printing model. Experimental results verified that the proposed algorithm is very effective for 3D printing models. The entire 3D printing model is altered after the encryption process. The proposed algorithm is provide a better method and more security than previous methods.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2009.01a
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• pp.326-329
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• 2009

This paper proposes a new video compression algorithm using an adaptive transform that is adjusted depending on the frequency contents of the input signals. The adaptive transform is based on the warped discrete cosine transform (WDCT) which is shown to provide better performance than the DCT at high bit rates, when applied to JPEG compression scheme [1, 2, 3]. The WDCT is applied to the video compression in this paper, as a new feature in the H.264/AVC. The proposed method shows the coding gain over the H.264/AVC at high bit rates. The coding gain is shown over the 35dB PSNR quality, and the gain increases as the bit rate increases. (about 1.0dB at 45dB PSNR quality at maximum)

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.05a
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• pp.818-819
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• 2013

This paper propose a contents security technique for digital holographic display service. Digital holographic video system assumes the existing service frame for 2-dimensional or 3-dimensional video, which includes data acquisition, processing, transmission, reception, and reconstruction. In this paper, we perform the encryption of RGB image and depth-map for such a system. The experimental results showed that encrypting only 0.048% of the entire data was enough to hide the constants of the RGB image and depth-map.

• The Transactions of the Korea Information Processing Society
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• v.7 no.2S
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• pp.629-637
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• 2000

The content-based information retrieval for a multimedia database uses feature information extracted from the compressed videos. This paper presents an effective method to detect scene changes from compressed videos. Scene changes are detected with DC values of DCT coefficients in MPEG-1 encoded video sequences. Instead of decoding full frames. partial macroblocks of each frame, horizontal and vertical macroblocks, are decoded to detect scene changes. This method detects abrupt scene changes by decoding minimal number of blocks and saves a lot of computation time. The performance of the proposed algorithm is analyzed based on the precision and the recall. The experimental results show the effectiveness in computation time and detection rate to detect scene changes of various MPEG-1 video streams.

• Proceedings of the Korean Information Science Society Conference
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• 2007.10c
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• pp.490-494
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• 2007

본 논문에서는, 한 장의 저해상도 영상으로부터 고해상도 영상을 생성하는 새로운 방법을 제안한다. 제안하는 방법은 고해상도 영상과 저해상도 영상의 관계를 나타내는 선형연립방정식을 푸는 원리에 기초한다. 하지만 이러한 방정식은 일의적으로 정해지지 않기 때문에 고해상도 영상을 나타내기 위챈 사용된 미지수를 축소하기 위한 이산코사인변환(DCT)의 에너지 집중특성을 이용하였다. 또한 그 구현방법으로 저해상도 영상을 일련의 작은 블록으로 나누어 각 블록영상에 적용하는 블록분할법(block division method)과 전체프레임 영상에 직접 적용하는 전 프레임법(full frame method)을 사용하였다. 최종적으로 본 제안방법의 유효성을 확인하기 위해 시뮬레이션 실험영상에 적용한 결과 양호한 결과를 나타냈다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2002.11a
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• pp.169-172
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• 2002

Embedding information into video data is a topic that recently gained increasing attention. This paper proposes a new approach for digital watermarking and secure copyright protection of video, the principal aim being to discourage illicit copying and distribution of copyrighted material. The method presented here is based on the three dimensional discrete cosine transform of video scene, in contrast with previous works on video watermarking where each video frame was marked separately, or where only intra-frame or motion compensation parameters were marked in MPEG compressed videos. The watermark sequence used is encrypted, pseudo-noise signal to the video. The performance of the presented technique is evaluated experimentally

• Journal of Digital Contents Society
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• v.6 no.2
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• pp.119-123
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• 2005

We proposed a method of effective watermarking based m HVS. To speak generally, HVS parameters are contrast sensitivity, texture degree, entropy sensitivity and standard of deviation, etc. The aim of this paper is evaluated by the experiments of imperceptibility and correctness of watermark. According to some experimental results, contrast sensitivity function is superior in smooth image. On the other hand, standard of deviation provides good results in rough images. Consequently, how to select the parameters considering image attribute is key problem in effective watermarking.