BOLA: Near-optimal bitrate adaptation for online videos
BOLA: Near-optimal bitrate adaptation for online videos
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DOI：
10.1109/infocom.2016.7524428
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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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作者：
Kevin Spiteri;Rahul Urgaonkar;R. Sitaraman
现代视频播放器采用复杂的算法来调整向用户显示的视频的比特率。比特率自适应需要在降低视频冻结的概率和增强向用户显示的视频的质量之间进行权衡。太高的比特率导致频繁的视频冻结（即，重新缓冲），而太低的比特率导致差的视频质量。视频提供商将视频分割成短块，并以多个比特率对每个块进行编码。视频播放器自适应地选择下载的每个块的比特率，可能为连续的块选择不同的比特率。虽然比特率自适应是用户获得良好体验的关键，但当前的视频播放器使用的是人们知之甚少的ad-hoc算法。我们制定比特率自适应作为一个效用最大化的问题，并设计了一个在线控制算法称为BOLA，使用李雅普诺夫优化技术，以尽量减少再缓冲和最大限度地提高视频质量。我们证明，BOLA实现的时间平均效用是在一个附加项O（1/V）的最佳值，对于一个控制参数V相关的视频缓冲区的大小。此外，与以前的工作不同，我们的算法不需要任何可用网络带宽的预测。我们经验验证我们的算法在模拟的网络环境中使用广泛的收集网络痕迹。我们表明，我们的算法实现了接近最佳的效用，在许多情况下显着更高的效用比目前最先进的算法。我们的工作对现实世界的视频播放器有直接的影响，BOLA是不断发展的DASH视频传输标准的参考播放器实现的一部分。
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 and enhancing the quality of the video shown to the user. A bitrate that is too high leads to frequent video freezes (i.e., rebuffering), while a bitrate that is too low leads to poor video quality. Video providers segment the video into short chunks and encode each chunk at multiple bitrates. The video player adaptively chooses the bitrate of each chunk that is downloaded, possibly choosing different bitrates for successive chunks. While bitrate adaptation holds the key to a good quality of experience for the user, current video players use ad-hoc algorithms that are poorly understood. We formulate bitrate adaptation as a utility maximization problem and devise an online control algorithm called BOLA that uses Lyapunov optimization techniques 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, our algorithm does not require any prediction of available network bandwidth. We empirically validate our algorithm in a simulated network environment using an extensive collection of network traces. We show that our algorithm 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 BOLA is part of the reference player implementation for the evolving DASH standard for video transmission.