• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권11호
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• pp.4068-4086
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• 2014

Due to the prevalence of powerful mobile terminals and the rapid advancements in wireless communication technologies, the wireless video streaming service has become increasingly more popular. Recent studies show that video streaming services via Transmission Control Protocol (TCP) are becoming more practical. TCP has more advantages than User Diagram Protocol (UDP), including firewall traversal, bandwidth fairness, and reliability. However, each video service shares an equal portion of the limited bandwidth because of the fair sharing characteristics inherent in TCP and this bandwidth fair sharing cannot always guarantee the video quality for each user. To solve this challenging problem, an Adaptive Multiple TCP (AM-TCP) scheme is proposed in this paper to guarantee the video quality for mobile devices in wireless networks. AM-TCP adaptively controls the number of TCP connections according to the video Rate Distortion (RD) characteristics of each stream and network status. The proposed scheme can minimize the total distortion of all participating video streams and maximize the service quality by guaranteeing the quality of each video streaming session. The simulation results show that the proposed scheme can significantly improve the quality of video streaming in wireless networks.

• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송공학회 2009년도 IWAIT
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• pp.668-672
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• 2009

In wireless ad-hoc network, knowing the available bandwidth of the time varying channel is imperative for live video streaming applications. This is because the available bandwidth is varying all the time and strictly limited against the large data size of video streaming. Additionally, adapting the encoding rate to the suitable bit-rate for the network, where an overlarge encoding rate induces congestion loss and playback delay, decreases the loss and delay. While some effective rate controlling methods have been proposed and simulated well like VTP (Video Transport Protocol) [1], implementing to cooperate with the encoder and tuning the parameters are still challenging works. In this paper, we show our result of the implementation experiment of VTP based encoding rate controlling method and then introduce some techniques of our parameter tuning for a video streaming application over wireless environment.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제4권6호
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• pp.1209-1221
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• 2010

Three dimensional (3D) video is expected to be an important application for broadcast and IP streaming services. One of the main limitations for the transmission of 3D video over IP networks is network bandwidth mismatch due to the large size of 3D data, which causes fatal decoding errors and mosaic-like damage. This paper presents a novel selective frame discard method to address the problem. The main idea of the proposed method is the symmetrical discard of the two dimensional (2D) video frame and the depth map frame. Also, the frames to be discarded are selected after additional consideration of the playback deadline, the network bandwidth, and the inter-frame dependency relationship within a group of pictures (GOP). It enables the efficient utilization of the network bandwidth and high quality 3D IPTV service. The simulation results demonstrate that the proposed method enhances the media quality of 3D video streaming even in the case of bad network conditions.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2004년도 한국우주과학회보 제13권2호
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• pp.308-311
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• 2004

This paper describes design, implementation and functional test of on-board flight analog video system. Video system is the part of the telemetry system as a means of providing flight vehicle's image data. Adopting analog video transmission technique, we could design and test the system in a short time and implement the prototype model with simpler circuits. As results of the functional test, we have made the verification and validation of two cameras' switching in time, and frequency modulation and demodulation of NTSC color signals successfully.

• ETRI Journal
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• 제37권6호
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• pp.1096-1107
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• 2015

This paper presents a dynamic retry adaptation scheme for H.264 HD video, called DRAS.264, which dynamically adjusts the retry limits of frames at the medium access control (MAC) layer according to the impact those frames have on the streamed H.264 HD video. DRAS.264 is further improved with a bandwidth estimation technique, better prediction of packet delays, and expanded results covering multi-slice video. Our study is performed using the Open Evaluation Framework for Video Over Networks as a simulation environment for various congestion scenarios. Results show improvements in average peak signal-to-noise ratios of up to 4.45 dB for DRAS.264 in comparison to the default MAC layer operation. Furthermore, the ability of DRAS.264 to prioritize data of H.264 bitstreams reduces error propagation during video playback, leading to noticeable visual improvements.

• ETRI Journal
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• 제33권3호
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• pp.454-457
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• 2011

In this letter, we propose a new quality measurement method to identify the causes of video quality degradation for IP-based video services. This degradation mainly results from network performance issues and video compression. The proposed algorithm identifies the causes based on statistical feature values from blocky block distribution in degraded IP-based videos. We found that the sensitivity and specificity of the proposed algorithm are 93.63% and 91.99%, respectively, in comparison with real error types and subjective test data.

• 방송공학회논문지
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• 제24권1호
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• pp.132-141
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• 2019

매우 제한된 전송 대역을 이용하여 비디오 데이터를 전송해야 하는 필요성은, 광대역을 통한 비디오 서비스가 활성화되어 있는 현 시점에서도 꾸준히 존재한다. 본 논문에서는 초협대역 네트워크를 통한 저해상도 비디오 전송을 위해, 공간 확장형 스케일러블 비디오 코딩 프레임워크에서 기본 계층의 부호화된 프레임을 심층 신경망 기반 초해상화 기법을 이용하여 업스케일링 하여 향상 계층 부호화 시에 예측 영상으로 활용하여 부호화 효율을 높이는 방법을 제안한다. 기존의 스케일러블 HEVC (High efficiency video coding) 표준에서는 고정된 필터로 업스케일링을 하는데 비해, 본 논문에서는 초해상화 수행을 위해 학습된 심층신경망을 기존의 고정 업스케일링 필터를 대체하여 적용하는 스케일러블 비디오 코딩 프레임워크를 제안한다. 이를 위해 스킵 연결과 잔차 학습 기법 등이 적용된 심층 콘볼루션 신경망 구조를 제안하고, 비디오 코딩 프레임워크의 실제 응용 상황에 맞추어 학습시켰다. 입력 해상도가 $352{\times}288$이고 프레임율이 8fps인 영상을 110kbps로 부호화 하는 응용 상황에서, 기존의 스케일러블 HEVC 프레임워크에 비해 제안하는 스케일러블 비디오 코딩 프레임워크의 화질이 더 높고 부호화 효율이 우수함을 확인할 수 있었다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권1호
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• pp.374-395
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• 2017

Users quite often experience volatile channel conditions which negatively influence multimedia transmission. HTTP adaptive streaming has emerged as a new promising technology where the video quality can be adjusted to variable network conditions. Nevertheless, the new technology does not remain without drawbacks. As it has been observed, multiple video players sharing the same network link have often problems with achieving good efficiency and stability of play-out due to a mutual interference and competition among video players. Our investigation indicates that there may be another cause for under-performance of the streamed video. In an emulated environment, we implemented three algorithms of adaptive video play-out based on bandwidth or buffer assessment. As we show, traffic generated by players employing the same or similar play-out strategies is positively correlated and synchronised (clustered), whereas traffic originated from different play-out strategies shows negative or no correlations. However, when some of the parameters of the play-out strategies are randomised, the correlation and synchronisation diminish what has a positive impact on the smoothness of the traffic and on the video quality perceived by end users. Our research shows that non-correlated traffic flows generated by play-out strategies improve efficiency and stability of streamed adaptive video.

• 산업공학
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• 제11권2호
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• pp.39-48
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• 1998

It is strongly believed that Video on Demand(VOD) will become one of the most promising services for Broadband Integrated Services Digital Network(B-ISDN). VOD service can be classified into two types of services: Near VOD(NVOD) and Interactive VOD(IVOD). Although VOD network requires many kinds of resources, we only consider video servers, programs. and storages. In the network. some video servers should be installed at some nodes(especially, at the root node for NVOD service). so that each node with video server stores video programs and distributes stored programs to customers. We take into account three kinds of costs related with the above resources: a program transmission cost, a program storage cost, and a video server installation cost. There exists a trade-off relationship among those three costs according to the locations of video servers and the kinds of programs stored at each video server. Given a multi-level VOD network and the total number of programs being served in the network. the resource. optimization problem for providing both IVOD and NVOD services is to determine where to install video servers, and which and how many programs should be stored at each video server, in order to minimize the total cost. In this paper we develop an efficient dynamic programming algorithm to solve the problem. We also implement the algorithm based on two different service policies assumed in this paper.

• 디지털콘텐츠학회 논문지
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• 제18권1호
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• pp.133-139
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• 2017

기존 서버 기반의 클라우드 시스템에서의 높은 설치 및 유지비용 문제를 해결하기 위해 최근 P2P 클라우드 스토리지에 대한 연구가 진행되었다. 본 논문에서는 비디오 전송을 위한 P2P 클라우드 스토리지 시스템에서 재생 품질을 향상시키는 계층적인 오버레이 구조를 제안한다. 이 구조에서는 현재 접속 중인 피어들의 유사성을 기반으로 피어들을 클러스터링해서 하나의 그룹을 생성한 후 각 그룹 내에서 물리적인 인접성을 고려해서 피어들을 지역별로 서브그룹으로 다시 구성한다. 따라서 특정 비디오에 대한 재생이 요청되면 지역성을 고려해서 소스 피어들을 선택하여 전송 지연 시간을 최소화할 수 있다. 마지막으로 실험을 통해서 본 논문에서 제안하는 지역성을 고려한 계층적 오버레이 구조가 임의로 소스 피어를 선택하는 구조에 비해 성능이 우수한다는 것을 보인다.