• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.5B
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• pp.517-525
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• 2009

We propose a quality guaranteed scalable video streaming service over the Internet using a new rate adaptation algorithm. Because video data requires much more bandwidth rather than other types of service, therefore, quality of video streaming service should be guaranteed while providing friendliness with other service flows over the Internet. To successfully provide this, we propose a framework for providing quality-guaranteed streaming service using two-channel transport layer and rate adaptation of scalable video stream. In this framework, baseline layer for scalable video is transmitted using TCP transport for minimum qualify service. Enhancement layers are delivered using TFRC transport with layer adaptation algorithm. The proposed framework jointly uses the status of playout buffer in the client and the encoding rate of layers in media contents. Therefore, the proposed algorithm can remarkably guarantee minimum quality of streaming service rather than conventional approaches regardless of network congestion and the encoding rate variation of media content.

• Proceedings of the Korea Information Processing Society Conference
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• 2004.05a
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• pp.1441-1444
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• 2004

MPEG 비디오 스트림은 소요 대역폭의 변화가 심한 군집성(bursty) 트래픽으로 망의 고정된 대역폭을 효율적으로 사용하는 전송방식을 구현하기가 매우 어렵다. 최근 ATM 망과 같이 가변으로 대역할당이 가능한 전송기술이 등장함에 따라 가변대역의 MPEG 비디오를 효율적으로 전송할 수 있게 되었다. 본 연구에서는 사용자에게 최소한의 품질을 보장하면서도 망 자원의 효율적 이용을 위하여 2 계층 구조의 새로운 대역폭 할당 기법을 제안하였다. 사용자에게 최소한의 품질을 보장하면서 망에 대역폭의 여유가 있는 경우 보다 고품질의 서비스가 가능토록 하기 위하여 ATM 망의 CBR 서비스와 VBR 서비스를 복합적으로 사용하는 방법을 제안하였다. 이의 구현을 위하여 2 계층 구조의 MPEG 부호화기를 설계하였고 모의실험으로 기존의 CBR 만을 사용하는 단일계층 방식과 비교 평가하였다.

• Journal of Broadcast Engineering
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• v.19 no.4
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• pp.468-477
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• 2014

This paper proposes a novel perceptual quality-based (PQ-based) video coding method with foveated contrast sensitivity (FCS). Conventional methods on PQ-based video coding with FCS achieve minimum loss on perceptual quality of compressed video by exploiting the property of human visual system (HVS), that is, its sensitivity differs by the spatial frequency of visual stimuli. On the other hand, PQ-based video coding with foveated masking (FM) exploits the difference of the sensitivity of the HVS between the central vision and the peripheral vision. In this study, a novel FCS model is proposed which considers both the conventional DCT-based JND model and the FM model. Psychological study is conducted to construct the proposed FCS model, and the proposed model is applied to PQ-based video coding algorithm implemented on HM10.0 reference software. Experimental results show that the proposed method decreases bitrate by the average of 10% without loss on the perceptual quality.

• KIISE Transactions on Computing Practices
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• v.20 no.11
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• pp.604-609
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• 2014

Decoding processes in portable media players have a high computational cost, resulting in high power consumption by the CPU. If decoding computations are reduced, the power consumed by the CPU is also be reduced, but such a choice generally results in a degradation of the video quality for the users, so it is essential to address this tradeoff. We proposed a new CPU power management scheme that can make use of the scalability property available in the H.164/SVC standard. We first proposed a new video quality model that makes use of a video quality metric(VQM) in order to efficiently take into account the different quantization factors in the SVC. We then propose a new dynamic voltage scaling(DVS) scheme that can selectively combine the previous decoding times and frame sizes in order to accurately predict the next decoding time. We then implemented a scheme on a commercial smartphone and performed a user test in order to examine how users react to the VQM difference. Real measurements show that the proposed scheme uses up to 34% fewer energy than the Linux DVFS governor, and user tests confirm that the degradation in the quality is quite tolerable.

• Proceedings of the KIEE Conference
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• 2008.04a
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• pp.86-88
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• 2008

지상파 방송(DMB: Digital Multimedia Broadcasting)은 음성, 영상, 데이터와 같은 다양한 멀티미디어 신호를 디지털 방식으로 변조하여 이동 중에 방송을 청취 할 수 있는 차세대 디지털방송 서비스이다. 하지만 한정된 대역폭으로 인한 비디오 전송율의 한계에 따라 최대 CIF(Common Interleaved Frame)급 화면해상도까지 서비스가 가능하다. 그러나 지상파 DMB 전송 고도화망에서는 계층 변조(Hierarchical Modulation)전송 기법을 통하여 추가의 전송대역폭을 확보할 수 있다. 또한 스케일러블 비디오 코딩(Scalable Video Coding)부호화 방식을 이용하여 고전송효율/고품질의 이동 멀티미디어 방송서비스를 제공할 수 있는 고품질 AT(Advanced Terrestrial)-DMB 시스템이 가능하다. 이러한 고품질 AT-DMB의 개발에 있어서 여러 방식들이 제시됨에 따라 시뮬레이터를 통한 다중화 시스템의 분석이 필요하다. 본 논문에서는 고품질 AT-DMB가 가능한 스케일러블 비디오 방식을 JM8.8을 사용하여 구현하였으며, 다중화 시스템의 실험을 하였다. 또한 시뮬레이터를 통하여 확보된 계층 간의 화질 차이와 엔지니어를 위해 비트스트림의 분석화면 및 PSNR을 제공 하였다.

• Proceedings of the Korea Information Processing Society Conference
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• 2017.11a
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• pp.957-960
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• 2017

디지털 비디오의 발전이 가속됨에 따라, 비디오 샷 경계 검출은 비디오 분석 및 카타로깅 등 여러 분야에 있어 필수적인 요소가 되었다. 기존 샷 경계 검출 방법들은 잠음이나 카메라 혹은 물체의 이동, 그리고 색상의 급격한 변화 등에 민감한 성능을 보인다. 본 논문에서는 개선된 지역 방향 패턴 기반(eLDP) 검출 방법을 제안한다. 제안하는 방법은 RGB 색상의 일부와 eLDP의 특징을 결합해 더욱 강인한 샷 경계 검출 성능을 보였다. 또한, 셋톱박스 품질검사 시 필요한 채널 간 동기화의 신뢰성을 높였고, 실시간으로 검사하면서도 안정적인 샷 경계 검출이 가능함을 입증하였다.

• Proceedings of the Korean Information Science Society Conference
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• 2001.04a
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• pp.130-132
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• 2001

현재 인터넷은 노력형 서비스(Best-effort service)만을 제공하며, 보장형 서비스(Guaranteed service)를 제공하지 못하는 한계를 가지고 있다. MPEG1, MPEG4, H.263과 같은 실시간 비디오 데이터를 효과적으로 제공하기 위해서는 보장형 서비스를 필요로 하며, 세션 관리, 호 허용 제어, 패킷 스케쥴링과 같은 여러 가지 기술들이 필요하다. 기존에 주로 사용되고 있는 FIFO(First-in First-out)에 의한 큐잉 정책으로는 대역폭, 지연 시간과 같은 네트워크 자원을 사용자에게 보장해 줄 수 없다. 따라서 CBQ(Class Based Queuing), WFQ(Weight Fair Queuing)아 같은 공평 큐잉 기법들에 대한 연구가 필요하다. 본 논문에서는 WFQ와 같은 공평 큐잉 기법을, 실시한 비디오 패킷 전송에 효과적으로 사용하기 위한 방법(AWF2Q+)을 제안하였다. FIFO, WFQ, AWF2Q+의 서비스 품질(PSNR)에 대한 비교, 분석을 통해 제안한 알고리즘이 실시간 비디오 서비스의 품질(PSNR)을 향상할 수 있다는 것을 보였다.

• Journal of KIISE
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• v.42 no.8
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• pp.1039-1048
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• 2015

Recently, the web-based adaptive streaming service, DASH (Dynamic Adaptive Streaming over HTTP), is receiving more attention. However, existing network-based and buffer-based video quality control schemes in DASH environments make oscillation of segment throughput, causing degradation of the quality of experience (QoE) with frequent quality changes and playback interruptions because these schemes do not consider the content characteristics. In this paper, we propose a C-DASH (Content Characteristics based Dynamic Adaptive Streaming over HTTP) scheme in order to improve the QoE in DASH environments. The C-DASH scheme performs seamless and smooth quality control based on the segment throughput, buffer status, and segment size of the content. Based on simulation results, it is confirmed that the C-DASH scheme can improve the QoE, when compared with the existing quality control schemes.

• Journal of Broadcast Engineering
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• v.23 no.1
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• pp.104-114
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• 2018

Recently, as HTTP-based video streaming traffic continues to increase, Dynamic Adaptive Streaming over HTTP(DASH), which is one of the HTTP-based adaptive streaming(HAS) technologies, is receiving attention. Accordingly, many video quality control techniques have been proposed to provide a high quality of experience(QoE) to clients in a DASH environment. In this paper, we propose a new quality control method using ANFIS(Adaptive Network based Fuzzy Inference System) which is one of the neuro-fuzzy system structure. By using ANFIS, the proposed scheme can find fuzzy parameters that selects the appropriate segment bitrate for clients. Also, considering the characteristic of VBR video, the next segment download time can be more accurately predicted using the actual size of the segment. And, by using this, it adjusts video quality appropriately in the time-varying network. In the simulation using NS-3, we show that the proposed scheme shows higher average segment bitrate and lower number of bitrate-switching than the existing methods and provides improved QoE to the clients.

• The KIPS Transactions:PartB
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• v.17B no.6
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• pp.413-420
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• 2010

In this paper, we propose a scheme for dynamic allocating network bandwidth based on the playback buffer levels of the clients in a distributed mobile multimedia system. In this scheme, the amount of bandwidth allocated to serve a video request depends on the buffer level of the requesting client. If the buffer level of a client is low or high temporarily, more or less bandwidth will be allocated to serve it with an objective to make it more adaptive to the playback situation of this client. By employing the playback buffer level based bandwidth allocation policy, fair services can also be provided to the clients. In order to support high quality video playbacks, video frames must be transported to the client prior to their playback times. The main objectives in this bandwidth allocation scheme are to enhance the quality of service and performance of individual video playback such as to minimize the number of dropped video frames and at the same time to provide fair services to all the concurrent video requests. The performance of the proposed scheme is compared with that of other static bandwidth allocation scheme through extensive simulation experiments, resulting in the 4-9% lower ratio of frames dropped according to the buffer level.