• Journal of KIISE
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• v.41 no.10
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• pp.824-831
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• 2014

HTTP (Hypertext Transfer Protocol) Adaptive Streaming is gaining attention because it changes bitrates to adapt changing network conditions. Since HAS (HTTP Adaptive Streaming) client downloads the video data based on TCP (Transmission Control Protocol), it estimates incorrectly the available bandwidth and leads to an unnecessary video quality change in long-delay networks. In this paper, we propose a buffer-based quality control scheme in order to improve the service quality and smooth playback in the HAS. The proposed scheme estimates accurately the available bandwidth based on a modified streaming model that considers network delay. It also calculates the sustainability of the video quality to prevent an unnecessary quality change and determines the inter-request time on the basis of the buffer status. Through the simulation, we prove that our scheme improves the QoS (Quality of Service) of the HAS service and controls the video quality smoothly in long-delay networks.

• Journal of KIISE
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• v.43 no.7
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• pp.827-833
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• 2016

HTTP Adaptive Streaming (HAS) is a technique that adapts its video quality to network conditions for providing Quality of Experience. In the HAS approach, a video content is encoded at multiple bitrates and the encoded video content is divided into several video segments. A HAS player estimates the network bandwidth and adjusts the video bitrate based on estimated bandwidth. However, the segment scheduler in the conventional HAS player requests video segments periodically without considering TCP. If the waiting duration for the next segment request is quite long, the TCP connection can be initialized and it restarts slow-start. Slow-start causes the reduction in TCP throughput and consequentially leads to low-quality video streaming. In this study, we propose a TCP-aware segment scheduling scheme to improve performance of HAS service. The proposed scheme adjusts request time for the next video request to prevent initialization of TCP connection and also considers the point of scheduling time. The simulation proves that our scheme improves the Quality of Service of the HAS service without buffer underflow issue.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.3
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• pp.476-481
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• 2012

Recently, QoS/QoE technology as a part of the HTTP-based adaptive streaming technology has attracted attention. In this paper, we find out HTTP-based adaptive and dynamic streaming technology. It is based on a dynamic adaptive streaming system over HTTP, which is designed and implemented. The system consist of conversion by the bit rate of MPEG2-TS files, division of segment, creation of MPD(Media Presentation Description) and bitrate's player through analysis of MPD File between servers and clients in network environments of dynamic and adaptive. This diverse network environments, continuous and smooth playback of video will be used in various multimedia fields.

• Journal of KIISE
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• v.44 no.5
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• pp.545-552
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• 2017

Because of the explosive growth of mobile devices and development of network technologies, HTTP (Hypertext Transfer Protocol) adaptive streaming has become a new trend in video delivery to provide efficient multimedia streaming services. As interest in personalized broadcasting grows, the study of interactive multimedia has been actively pursued. The interactive multimedia service is a method of playing media according to a scenario selected by the user. Providing the interactive multimedia service with the existing HTTP adaptive streaming causes switching delay and buffer underflow according to the point in time when the user selects the scenario while the client streams the interactive multimedia and therefore decreases the user QoE (Quality of Experience). In this paper, we propose an adaptive streaming scheme for interactive multimedia service in HTTP adaptive streaming to provide seamless playback. We design the architecture and prefetching scheme for interactive multimedia streaming.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2012.05a
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• pp.488-490
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• 2012

Nowadays QoS / QoE using technology as part of HTTP, dynamic adaptive streaming technology that became a big issue. In this paper, using HTTP, dynamic adaptive streaming technology is introduced. This dynamic adaptive streaming using HTTP-based system design and implementation. In this system, a number of MPEG2-TS file bitrate's conversion of image quality, a certain amount of time by the division of Segment, standing before the final note of the files that are used in transmission MPD (Media Presentation Description) File creation and streaming between servers and clients using HTTP to a dynamic and adaptive network environment consists of bitrate's streamers. In a network environment in which an unspecified number of seamless continuous playback of video streaming for a variety of sectors and will be utilized in the field of multimedia.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2018.06a
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• pp.340-342
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• 2018

최근 네트워크 기술과 스마트 단말의 보급으로 인해 비디오 스트리밍 서비스에 대한 수요가 증가하게 되었다. 네트워크를 효율적으로 사용하여 비디오 스트리밍 서비스를 제공하기 위해 적응적으로 전송률을 조절하는 HTTP (HyperText Transfer Protocol) 적응적 스트리밍 서비스가 주목 받게 되었다. UHD (Ultra High Definition) 콘텐츠는 HD (High Definition) 콘텐츠에 비해 적어도 4 배 이상의 크기를 갖기 때문에 끊김 없는 UHD 콘텐츠 스트리밍 서비스를 제공하기 위해서는 많은 가용 대역폭이 필요하다. 기존의 HTTP 적응적 스트리밍 방식은 정상 상태 (Steady State)에서 가용 대역폭보다 낮은 품질의 비디오 세그먼트를 일정 시간마다 주기적으로 요청하여 다운로드 받는다. 정상 상태에서는 가용 대역폭과 콘텐츠의 인코딩 율에 차이에 따라 On-Off 구간의 패턴이 반복되어 발생하고, 빈번한 Off 구간에 의해서 대역폭이 낭비되는 문제점이 있다. 따라서 본 논문에서는 HTTP 적응적 스트리밍에서 UHD 콘텐츠의 효율적인 대역폭 활용을 위한 세그먼트 전송 기법을 제안한다. 제안하는 기법은 Off 구간의 빈도수를 줄이기 위한 집단 세그먼트 전송 방식과 대역폭 낭비를 최소화 하기 위한 세그먼트 품질 조절기법으로 구성되어 있다.

• Journal of KIISE
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• v.44 no.1
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• pp.95-106
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• 2017

HTTP adaptive streaming has recently emerged to handle the rapidly growing traffic and to provide high quality multimedia contents. To improve the QoE (Quality of Experience) for HTTP adaptive streaming service, the average video bitrate should be maximized, and the video switching frequency (difference of bitrate between adjacent segments) and video stalling events need to be minimized. The recently proposed quality adaptation algorithms for HTTP adaptive streaming do not provide high QoE, since detailed QoE factors such as video switching frequency and bitrate difference of adjacent segments, are not considered. In this paper, we propose a SQA (Smooth Quality Adaptation) algorithm to improve the user QoE. The proposed algorithm provides the smoothed QoE, such that it minimizes the unnecessary video switching events by maintaining the quality in a certain period, thus minimizing the bitrate difference of adjacent segments. Through simulation, we confirm that the proposed algorithm reduces the unnecessary switching events, and prevents the sudden decrease in video quality.

• Journal of KIISE
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• v.45 no.2
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• pp.175-186
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• 2018

Recently, HAS (HTTP Adaptive Streaming) has been the subject of much attention to improve the QoE (Quality of Experience). In a high latency network, HAS degrades the QoE due to the lost RTT cycle since it replies with a response of one segment to the request of one segment. The server-push based HAS schemes of downloading multiple segments in one request cause QoE degradation due to the buffer underflow. In this paper, we propose a VSSDS (Video Streaming Scheme based on Dynamic Server-push) scheme to improve the QoE in a high latency network. The proposed scheme adjust video quality by estimating available bandwidth and determine the number of segments to be downloaded for each segment request cycle. Through the simulation, the proposed scheme not only improves the average video bitrate but also alleviates the buffer underflow.

• Information and Communications Magazine
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• v.28 no.3
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• pp.19-26
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• 2011

본고에서는 스마트 TV의 대표적인 서비스인 OTT(Over-The-Top)서비스의 전송 방법 중 최근에 가장 주목을 받고 있는 HTTP에 기초한 적응적 스트리밍 기술을 알아본다. 먼저, 최근 MPEG등 각 표준단체에서 진행되고 있는 HTTP 스트리밍 기술의 표준화 범위 및 진행 상황에 대해서 살펴보고, 표준화 범위 중 핵심이 되는 메타데이타 파일 구조 및 청크 단위의 전송 포맷 및 기존 시스템 포맷의 확장 사항 등에 대해서 설명한다. 마지막으로 MPEG DASH(Dynamic adaptive streaming over HTTP)의 basic on-demand profile에 기초한 구현 내용 및 결과를 소개한다.

• Journal of KIISE
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• v.45 no.2
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• pp.187-194
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• 2018

Recently, Hypertext Transfer Protocol (HTTP) adaptive streaming service is attracting attention. The existing quality adaptive scheme of HTTP adaptive streaming service adjusts the video quality according to the network bandwidth or the client buffer size. However, the problem with the existing quality adaptive scheme is the QoE (Quality of Experience) degradation caused by the unnecessary quality change that occurs due to frequent bandwidth change or fixed buffer threshold. We propose a video quality maintenance scheme that improves average video quality and minimizes unnecessary quality change in order to improve the QoE of HTTP adaptive streaming service in the changing network environment. The proposed scheme maintains high quality for a long time by setting the quality maintenance duration to be long when buffer occupancy and video quality are high. The experimental results show that the proposed scheme improves QoE by improving the average video quality and minimizing the quality change.