• Journal of IKEEE
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• v.25 no.1
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• pp.139-147
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• 2021

This paper introduces an image decomposition-based deep learning method and loss function to improve low-light images. In order to remove color distortion and halo artifact, illuminance channel of an input image is decomposed into reflectance and luminance channels, and a decomposition-based multiple structural deep learning process is applied to each channel. In addition, a mixed norm-based loss function is described to increase the stability and remove blurring in reconstructed image. Experimental results show that the proposed method effectively improve various low-light images.

• Journal of Broadcast Engineering
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• v.25 no.3
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• pp.353-361
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• 2020

VVC (Versatile Video Coding) is a new video compression technique that is being standardized, and it supports HD / UHD / 8K video, and High Dynamic Range (HDR) video with a goal of approximately 2 times higher coding efficiency than the conventional HEVC. It also aims to support a variety of functionalities such as screen content coding, adaptive resolution changes, and independent sub-pictures. In this paper, we investigate the signaling process of intra prediction mode first, and develop an effective coding method of the chroma intra prediction mode. In case of the DM mode, the proposed method simplifies the prediction mode of the chorma intra prediction mode when referring to the angular mode of the luminance block. It can improve coding efficiency of the chroma intra prediction mode, and the proposed process can also consider the size of the block in order to further improve its coding efficiency.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2011.11a
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• pp.172-175
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• 2011

높은 효율을 가진 비디오 압축 코덱인 H.264/AVC는 예전보다 압축 성능을 향상 시키기 위한 방법 중 하나로 율-왜곡 최적화 기법이라는 것을 사용한다. 이 기법은 압축된 결과를 가지고 손실과 압축률 두 가지를 모두 고려하여 어떤 경우가 더 최적의 압축인가 하는 것을 판별하는데, 여기서 모든 경우에 대해 압축을 수행해야 함으로 이전 보다 몇 배나 높은 복잡도를 가질 수 밖에 없다. 이러한 문제를 해결하고자 하는 노력으로 본 논문에서는 SAHTD(Sum of Absolute Hadamard Transform Difference)라는 기준을 사용하여 이를 이용해 율-왜곡 최적화 기법을 사용하지 않거나, 사용을 최소화 하면서 압축 효율을 유지하는 방법을 제시하였다. 본 논문에서는 휘도 신호 $8{\times}$8과 $4{\times}4$블록을 위한 방법을 제시하고 있다. 이 두 가지 크기의 블록에 대해서 SAHTD값을 구해 SAHTD가 낮은 순으로 모드들을 정렬하고, 이것이 가장 낮은 3개의 모드를 선택해 이것 중에 MPM이 포함되지 않았을 경우에 대해서는 MPM을 포함해 4개의 모드를 선택해 압축을 수행하도록 한다. 여기서 얻은 모드들 중에 SAHTD값이 일정 값 이상 더 낮은 모드가 존재할 경우, 그 모드들에 대해서만 율-왜곡 최적화 기법을 수행한다. 이를 통해 최적의 모드일 가능성이 낮은 모드들에 대한 부가적인 연산 수행을 방지하게 된다. 휘도신호 16x16이나 색차 신호 압축의 경우에는 SAHTD를 사용하여 가장 낮은 SAHTD값을 갖는 모드를 최적의 모드로 결정한다. JM 참조 소프트웨어를 통한 실험결과 제안된 기법은 기존 JM의 방식에 비해 화면 내 프레임의 부호화 시간의 82.2% 감소와 0.042dB의 PSNR 감소율, 0.527%의 비트 증가율을 보여주었다.

• Journal of the Institute of Convergence Signal Processing
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• v.9 no.3
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• pp.195-200
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• 2008

To compress the moving picture data effectively, it is needed to reduce spatial and temporal redundancy of input image data. While motion estimation! compensation methods is effectively able to reduce temporal redundancy but it is increased computation complexity because of the prediction between frames. So, the study of algorithm for computation reduction and real time processing is needed. This paper is presenting quantizer effectively able to quantize DCT coefficient considering the human visual sensitivity. As quantizer that proposed DCT-based H.263 could make transmit more frame than TMN5 at a same transfer speed, and it could decrease the frame drop effect. And the luminance signal appeared the difference of $-0.3{\sim}+0.65dB$ in the average PSNR for the estimation of objective image quality and the chrominance signal appeared the improvement in about 1.73dB in comparision with TMN5. The proposed method reduces $30{\sim}31%$ compared with NTSS and $20{\sim}21%$ compared to 4SS in comparition of calculation quantity.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.36S no.11
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• pp.112-119
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• 1999

TMN5 has been used to evaluate the performance of H.263, the ITU-T/LBC standard of moving picture coding. As DCT is used as transform coding methods in TMN5, blocking effect exists seriously in reconstruction picture at low bit rate. In this pater, DWT is substituted for DCT and adaptive quantizer is designed while the structure of TMN5 is maintained to be excellent in the transplantation of conventional system. It has shown that average PSNR is reduced by 0.35dB in luminance but increased by 2dB in chrominance comparing with that of TMN5. As block effect is reduced in reconstruction picture, the subjective picture quality is better than that of TMN5. Picture drop is, also, reduced because much more frames are transmitted at same bit rate.

• The Journal of the Acoustical Society of Korea
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• v.18 no.6
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• pp.77-83
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• 1999

H.263 is an international standard of ITU-T that can makes the service such as video phone, video conference in the transmission line less than 64Kbps. This recommendation draft has used motion estimation/compensation, transform coding and quantizing methods. TMN5 used for the performance estimation of H.263 has fundamentally used DCT in transform coding method and presented quantizer for quantizing the DCT transform coefficient. This paper is presenting adaptive quantizer effectively able to quantize DCT coefficient considering the human visual sensitivity while the structure of TMN5 is maintaining. As quantizer that proposed DCT-based H.263 could make transmit more frame than TMN5 in a same transfer speed, it could lower the frame drop effect. And the luminance signal appeared the difference of -0.3 ～ +0.7dB in the average PSNR for the estimation of objective image quality and the chrominance signal appeared the improvement in about 1.5dB in comparision with TMN5. As a result it can attain the better image quality compared to TMN5 in the estimation of subjective image quality.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.45 no.5
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• pp.72-78
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• 2008

Although the H.264 video coding scheme is popular, it is not efficient for high-definition (HD) video coding because the size of its macroblock is relatively small for the HD video resolution. In this paper, we propose a new intra coding scheme based on the enlarged macroblock size. For the luminance component, intra $4{\times}4$ prediction and intra $16{\times}16$ prediction in H.264 are scaled into intra $8{\times}8$ prediction and intra $32{\times}32$ prediction, respectively. For the chrominance components, intra $8{\times}8$ prediction is extended to intra $16{\times}16$ prediction. Along with the $8{\times}8$ basic coding block size, an $8{\times}8$ integer discrete cosine transform (DCT) is used. Experimental results show that the proposed algorithm improves coding efficiency of the intra coding for HD video: PSNR gain by 0.23dB and bit-rate reduction by 5.32% on average.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.42 no.4 s.304
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• pp.31-38
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• 2005

In this paper, we propose the chromatic adaptation models (CAM) for the variations of the luminance levels. A chromatic adaptation model, CAM$\Delta$Y , is proposed according to the change of luminance level under the same illuminants. The proposed model is obtained by the transform the test colors of the high luminance into the corresponding colors of the low luminance. In the proposed model, the optimal coefficients are obtained from the corresponding colors data of the Breneman's experiments. In the experimental results, we confined that the chromaticity errors, $\Delta$u'v', between the predicted colors by the proposed model and the corresponding colors of the Breneman's experiments are 0.004 in u'v' chromaticity coordinates. The prediction performance of the proposed model is excellent because this error is the threshold value that two adjacent color patches can be distinguished. Additionally, we also propose equal-whiteness CCT curves (EWCs) by CAM$\Delta$Y according to the luminance levels of the surround viewing conditions. And the proposed EWCs can be used as the theoretical standard which determines the reference white of the color display devices.

• Journal of Broadcast Engineering
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• v.17 no.6
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• pp.1029-1039
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• 2012

In this papar, we propose a new motion estimation and coding technique using adaptive motion vector resolution. Currently, HEVC encodes a video using 1/4 motion vector resolution. If there are high texture regions in a picture, HEVC can't get a performance enough. So, we insert additional 1-bit flag meaning whether motion vector resolution is 1/4 or 1/8 in PU syntax. Therefore, decoder can recognize the transmitted motion vector resolution. Experimental results show that maximum coding efficiency gain of the proposed method is up to 5.3% in luminance and 7.9% in chrominance. Average computional time complexity is increased about 33% in encoder and up to 5% in decoder.

• Journal of Korea Multimedia Society
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• v.13 no.5
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• pp.710-721
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• 2010

Recently, for the advancement of embedded technology about mobile device, a new kind of service, mash-up is appeared. It is service or application combining multimedia content making tool or device and web-GIS(geographic information system) service in the mobile environment. This service can be ease to use for casual user and can apply in various ways. So, It is served in web 2.0 environment actively. But, in the mashup service, because generated multimedia contents linked with web map are new type of multimedia contents which include user's migration routes in the space such as GPS coordinates. Thus, there are no protection ways for intellectual property created by GIS web-map service users and user's privacy. In this paper, we proposed a location and user information hiding scheme for GIS web-map service. This scheme embeds location and user information into a picture that is taken by camera module on the mobile phone. It is not only protecting way for user's privacy but is also tracing way against illegal photographer who is peeping person through hidden camera. And than, we also realized proposed scheme on the mobile smart phone. For minimizing margin of error about location coordinate value against contents manipulating attacks, GPS information is embedded into chrominance signal of contents considering weight of each digit about binary type of GPS coordinate value. And for tracing illegal photographer, user information such as serial number of mobile phone, phone number and photographing date is embedded into frequency spectrum of contents luminance signal. In the experimental results, we confirmed that the error of extracted information against various image processing attacks is within reliable tolerance. And after file format translation attack, we extracted embedded information from the attacked contents without no damage. Using similarity between extracted one and original templete, we also extracted whole information from damaged chrominance signal of contents by various image processing attacks.