text: The main task of HTTP Adaptive Streaming is to adapt video quality dynamically under variable network conditions. This is a key feature for multimedia delivery especially when quality of service cannot be granted network-wide and, e.g., throughput may suffer short term fluctuations. Hence, robust bitrate adaptation schemes become crucial in order to improve video quality. The objective, in this context, is to control the filling level of the playback buffer and maximize the quality of the video, while avoiding unnecessary video quality variations. In this paper we study bitrate adaptation algorithms based on Backward-Shifted Coding (BSC), a scalable video coding scheme able to greatly improve video quality. We design bitrate adaptation algorithms that balance video rate smoothness and high network capacity utilization, leveraging both on throughput-based and buffer-based adaptation mechanisms. Extensive simulations using synthetic and real-world video traffic traces show that the proposed scheme performs remarkably well even under challenging network conditions.
  @cite_20: Video streaming applications are a major contributor to the recent dramatic rise of data traffic in cellular networks. Mobile users in a cellular network suffer fluctuating data rates, which almost directly reflects on the quality of video they view in a streaming service. Although replacing such video streaming services with video downloading renting services could potentially allow such mobile users to enjoy consistently higher quality videos, traditionally such services cost a lot more than video streaming services because of legal copyright pricing and management issues. We propose a novel scalable video delivery service called streamloading that can potentially allow mobile users to enjoy download quality videos, while still being legally classified as a streaming service. We describe the implementation of the service and perform extensive simulations to evaluate streamloading, in comparison to traditional streaming services.
  @cite_12: Although HTTP-based video streaming can easily penetrate firewalls and profit from Web caches, the underlying TCP may introduce large delays in case of a sudden capacity loss. To avoid an interruption of the video stream in such cases we propose the Backward-Shifted Coding (BSC). Based on Scalable Video Coding (SVC), BSC adds a time-shifted layer of redundancy to the video stream such that future frames are downloaded at any instant. This pre-fetched content maintains a fluent video stream even under highly variant network conditions and leads to high Quality of Experience (QoE). We characterize this QoE gain by analyzing initial buffering time, re-buffering time and content resolution using the Ballot theorem. The probability generating functions of the playback interruption and of the initial buffering latency are provided in closed form. We further compute the quasi-stationary distribution of the video quality, in order to compute the average quality, as well as temporal variability in video quality. Employing these analytic results to optimize QoE shows interesting trade-offs and video streaming at outstanding fluency.
summary: The analysis reported in @cite_12 provides a complete characterization of BSC's performance with respect to a set of key metrics, namely the initial buffering delay, the playback interruption, and the mean video quality, which are responsible for the users' quality of experience (QoE). Also, a cost function is proposed in order to evaluate the QoE. However, the analysis proposed in @cite_12 does not account for the concurrent effect of bitrate adaptation. The scheme, combines video streaming and video downloading. Users are able to download optional enhancement layers for a tagged video. But, video streaming leverages on the base layer only. @cite_20 , numerical simulations demonstrate that system renders higher average video data rate than standard streaming schemes (HAS); the effect of adaptation part is neglected.