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Queueing Theoretic Approach to Playout Buffer Model for HTTP Adaptive Streaming
( Jiwoo Park ),( Kwangsue Chung ) 한국인터넷정보학회 2018 KSII Transactions on Internet and Information Syst Vol.12 No.8
HTTP-based adaptive streaming (HAS) has recently been widely deployed on the Internet. In the HAS system, a video content is encoded at multiple bitrates and the encoded video content is segmented into small parts of fixed durations. The HAS client requests a video segment and stores it in the playout buffer. The rate adaptation algorithm employed in HAS clients dynamically determines the video bitrate depending on the time-varying bandwidth. Many studies have shown that an efficient rate adaptation algorithm is critical to ensuring quality-of-experience in HAS systems. However, existing algorithms have problems estimating the network bandwidth because bandwidth estimation is performed on the client-side application stack. Without the help of transport layer protocols, it is difficult to achieve accurate bandwidth estimation due to the inherent segment-based transmission of the HAS. In this paper, we propose an alternative approach that utilizes the playout buffer occupancy rather than using bandwidth estimates obtained from the application layer. We start with a queueing analysis of the playout buffer. Then, we present a buffer-aware rate adaptation algorithm that is solely based on the mean buffer occupancy. Our simulation results show that compared to conventional algorithms, the proposed algorithm achieves very smooth video quality while delivering a similar average video bitrate.
Park Jiwoo,Kim Dae Young 대한화학회 2022 Bulletin of the Korean Chemical Society Vol.43 No.7
A photoredox-catalyzed selenylation and ring closure sequences of alkenoic acid derivatives are achieved. This transformation is efficiently accelerated using an inexpensive Rhodamine 6G as an organophotocatalyst under visible light irradiation. The present method affords efficient and practical access to structurally diverse selenated γ-lactones in moderate to high yields.