• Journal of Broadcast Engineering
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• v.5 no.2
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• pp.167-175
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• 2000

Compressed bitstreams generated by an MPEG-2 video encoder (or digital TV picture transmission are quite sensitive to channel errors. Due to the coding structure of the MPEG-2 video compression algorithm, a single bit error can affect not only the current Picture frame but also succeeding frames. Error concealment algorithms attempt to repair damaged portions of the picture by exploiting spatial and temporal redundancies in the correctly received and reconstructed video frames. In this paper, we analyze the effect of channel errors in MPEG-2 video bitstreams and estimate lost motion vectors by exploiting temporal redundancies in the video frames. Motion vectors can be estimated from the vertically adjacent extended region of lost macroblocks. Finally, we conceal the damaged macroblocks by compensating the displacement with the estimated motion vectors. Simulation results demonstrate that both the weighted sum algorithm and the extension matching algorithm achieve good performance in terms of PSNR values as well as subjective image quality.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.47 no.5
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• pp.165-174
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• 2010

The H.264/AVC standard obtained better performance than previous compression standards, but it also increased the computational complexity of CODEC simultaneously. Various techniques recently included at the KTA software developed by VCEG also were increasing its complexity. Especially adaptive interpolation filter has more complexity than two times due to development for coding efficiency. In this paper, we propose low-complexity filter bank to improve speed up of decoding and coding gain. We consists of filter bank of a fixed-simple filter for low-complexity and adaptive interpolation filter for high coding efficiency. Then we compensated using optimal filter at each macroblock-level or frame-level. Experimental results shows a similar coding efficiency compared to existing adaptive interpolation filter and decoding speed of approximately 12% of the entire decoder gained.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.10
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• pp.2563-2578
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• 1996

In this paper, channel error characteristics are investigated to alleviate the channel error propagation problem of the digital TV transmission systems. First, error propagation problems, which are mainly caused by the inter-frame dependancy and variable length coding of the MPEG-2 baseline encoder, are intensively analyzed. Next, existing channel resilient schemes are systematically classified into two kinds of schemes; one for the encoder and the other for the decoder. By comparing the performance and implementation cost, the encoder side schemes, such as error localization, layered coding, error resilience bit stream generation techniques, are described in this paper. Also, in an effort to consider the parcticality of the real transmission situation, an efficient error detection scheme for a decoder system is proposed by employing a priori information of the bit stream syntas, checking the encoding conditions at the encoder stage, and exploiting the statistics of the image itself. Finally, subsequent error concealment technique based on the DCT coefficient recovery algorithm is adopted to evaluate the performance of the proposed error resilience technique. The computer simulation results show that the quality of the received image is significantly improved when the bit error rate is as high as 10$^{-5}$ .

• Journal of the Korea Institute of Information Security & Cryptology
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• v.20 no.6
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• pp.33-42
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• 2010

With the emergence of increasingly complex networks and diverse user terminals, demand for the next generation IPTV service is rapidly growing. It enables any content to seamlessly be reused on the diverse terminals as well as be broadcasted in real-time through the complex networks. In this paper, a novel security framework is proposed for the real-time and reusable IPTV services. The proposed framework is advantageous over the conventional content protection techniques in easily producing the scalable content with lightweight, perceptual, transcodable, and adjustable security features. It does not only ensure end-to-end security over the entire service range based on a single security mechanism, but also can control a level of security while dynamically transcoding the original content. This approach basically performs selective encryption during and after the compression using scalable video coding. The suitability of the proposed approach is demonstrated through experiments with a practical service scenario. Therefore, it is expected that security technology alone could practically contribute to creating new business opportunities for IPTV services.

• The Journal of the Korea Contents Association
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• v.13 no.5
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• pp.28-36
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• 2013

Motion-compensated frame interpolation (MCFI) techniques in video signal processing have many application areas. Frame rate up-conversion (FRUC) or distributed video coding (DVC) technique needs an effective MCFI algorithm. For these applications, it is necessary to develop an effective post-processing technique to improve visual qualities or to reduce virtual channel noises, resulting in the reduced channel bit rate. This paper proposes a reliability evaluation method based on spatio-temporal characteristics for motion-compensated interpolated blocks. The proposed algorithm investigates the temporal matching characteristics for current frame and then is designed in such a way that it can measure temporal characteristics as well as the spatial ones. Through computer simulations, it is shown that the proposed method outperforms the conventional temporal matching method.

• Journal of the Semiconductor & Display Technology
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• v.13 no.1
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• pp.109-112
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• 2014

H.264/AVC is an international video coding standard that is established in cooperation with ITU-T VCEG and ISO/IEC MPEG, which shows improved code and efficiency than the previous video standards. Motion estimation using various macroblock from 44 to 1616 among the compression techniques of H.264/AVC contributes much to high compression efficiency. Generally, in the case of small motion vector or low complexity about P slice is decided $P16{\times}16$ mode encoding method. But according to circumstances, macroblock is decided $P16{\times}16$ mode despite large motion vector. If the motion vector variance is more than threshold and final select mode is $P16{\times}16$ mode, it is switched to $P8{\times}8$ mode, so this paper shows that the storage capacity is reduced. The results of experiment show that the proposed algorithm increases the compression efficiency of the H.264/AVC algorithm to 0.4%, even reducing the time and without increasing complexity.

• Journal of Broadcast Engineering
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• v.13 no.2
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• pp.172-178
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• 2008

Orthogonal Frequency Division Multiplexing (OFDM) is one of the most promising technologies for high data rate wireless communications. OFDM has been adopted in wireless standards such as digital audio/video broadcasting. The combination of OFDM and cooperative diversity techniques can provide the diversity gain and/or increased capacity. In this paper, the cooperative coding using cyclic delay diversity (CDD) for multiuser OFDM systems is introduced. To improve the beneficial effects of relays's cooperation, CDD is adopted in cooperative transmission of relays. Simulation results show the bit error rate (BER) for various consideration. The proposed scheme provides improved performance compared to delay.

• The Journal of the Korea Contents Association
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• v.12 no.12
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• pp.14-24
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• 2012

DVC (Distributed Video Coding) techniques need feedback channel for parity bit control to achieve the good RD performances, however, this causes the DVC system to have high decoding latency. In order to implement in real time environments and to accelerate commercializations, many research works have been focusing on the development of fast video decoding algorithm. As one of the real time implementations, this paper deals with a novel DVC scheme suitable for some application areas where source statistics such as motion information can be provided to the encoder side from the decoder side. That is, this paper propose a fast distributed video decoding scheme to improve the decoding speed by using the feedback of motion information derived in SI generation. Through computer simulations, it is shown that the proposed method outperforms the conventional fast DVC decoding schemes.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.3C
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• pp.247-254
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• 2008

H.264 provides a good coding efficiency compared with existing video coding standards, H.263, MPEG-4, based on the use of multiple reference frame for variable block size motion estimation, quarter-pixel motion estimation and compensation, $4{\times}4$ integer DCT, rate-distortion optimization, and etc. However, many modules used to increase its performance also require H.264 to have increased complexity so that fast algorithms are to be implemented as practical approach. In this paper, among many approaches, fast mode decision algorithm by skipping variable block size motion estimation and spatial-predictive coding, which occupies most encoder complexity, is proposed. This approach takes advantages of temporal and spatial properties of fast mode selection techniques. Experimental results demonstrate that the proposed approach can save encoding time up to 65% compared with the H.264 standard while maintaining the visual perspectives.

• Proceedings of the Korean Information Science Society Conference
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• 1999.10b
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• pp.383-385
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• 1999

본 논문에서는, 이산 웨이블릿 변환(DWT: discrete wavelet transform)에 기초한 저속 비트율 비디오 코딩 방법의 알고리즘으로써, PZTACC 방법을 제안한다. 접근 방법은 양자화된 웨이블릿 계수들이 웨이블릿 서브밴드 구조내에서 중복성을 활용하는 메커니즘에 의해서 전처리 된다면 코딩 절차가 더욱 효과적으로 작용하여 나타난다. 그러므로 본 논문에서는 partitioning, Zero-Tree aggregation, 조건적 코딩의 개념들을 기초로 하는 프리코딩 기법의 새로운 구조를 소개한다. 복원된 비디오의 주관적인 성능은 일반적으로 MPEG4의 VM 구현으로부터 획득된 성능(1.5 dB PSNR 이상)보다 우수하다. 게다가, 인트라프레임모드에 제한되어 있을 때, 제안된 코딩 알고리즘은 정지영상 압축에 대하여 최고로 보고되는 결과를 산출한다.