BOLA: Near-Optimal Bitrate Adaptation for Online Videos
BOLA: Near-Optimal Bitrate Adaptation for Online Videos
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DOI：
10.1109/tnet.2020.2996964
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发表时间：
2016-01
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影响因子：
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通讯作者：
Kevin Spiteri;Rahul Urgaonkar;R. Sitaraman
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文献类型：
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作者：
Kevin Spiteri;Rahul Urgaonkar;R. Sitaraman
现代视频播放器使用复杂的算法来调整显示给用户的视频的比特率。比特率自适应需要在降低视频冻结(重新缓冲)的概率和提高视频质量之间进行权衡。码率太高会导致频繁的重新缓冲，而码率太低会导致视频质量不佳。视频提供商将视频分割成短片段，并以多个比特率对每个片段进行编码。视频播放器自适应地选择要下载的每个段的比特率，可能为连续的段选择不同的比特率。我们将码率自适应描述为效用最大化问题，并设计了一种称为BOLA的在线控制算法，该算法使用Lyapunov优化来最小化缓冲和最大化视频质量。我们证明了对于与视频缓冲器大小有关的控制参数V，BOLA实现了在最佳值的加性项$O(1/V)$内的时间平均效用。此外，与以前的工作不同，BOLA不需要预测可用网络带宽。我们使用一组网络痕迹在模拟的网络环境中经验地验证了BOLA。我们表明，BOLA达到了近乎最优的效用，并且在许多情况下显著高于当前最先进的算法。我们的工作对现实世界的视频播放器和不断发展的视频传输DASH标准产生了直接影响。我们还实现了Bola的更新版本，它现在是标准参考播放器dash.js的一部分，并被Akamai、BBC、CBS和Orange等几家视频提供商用于制作。
Modern video players employ complex algorithms to adapt the bitrate of the video that is shown to the user. Bitrate adaptation requires a tradeoff between reducing the probability that the video freezes (rebuffers) and enhancing the quality of the video. A bitrate that is too high leads to frequent rebuffering, while a bitrate that is too low leads to poor video quality. Video providers segment videos into short segments and encode each segment at multiple bitrates. The video player adaptively chooses the bitrate of each segment to download, possibly choosing different bitrates for successive segments. We formulate bitrate adaptation as a utility-maximization problem and devise an online control algorithm called BOLA that uses Lyapunov optimization to minimize rebuffering and maximize video quality. We prove that BOLA achieves a time-average utility that is within an additive term $O(1/V)$ of the optimal value, for a control parameter V related to the video buffer size. Further, unlike prior work, BOLA does not require prediction of available network bandwidth. We empirically validate BOLA in a simulated network environment using a collection of network traces. We show that BOLA achieves near-optimal utility and in many cases significantly higher utility than current state-of-the-art algorithms. Our work has immediate impact on real-world video players and for the evolving DASH standard for video transmission. We also implemented an updated version of BOLA that is now part of the standard reference player dash.js and is used in production by several video providers such as Akamai, BBC, CBS, and Orange.