Comparing fixed and variable segment durations for adaptive video streaming: a holistic analysis
Comparing fixed and variable segment durations for adaptive video streaming: a holistic analysis
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比较自适应视频流的固定和可变片段持续时间：整体分析
DOI：
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发表时间：
2020
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通讯作者：
A. Raake
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作者：
Susanna Schwarzmann;N. Hainke;T. Zinner;Christian Sieber;W. Robitza;A. Raake
HTTP自适应流（HAS）是互联网上视频传输的事实标准。它通过将视频分割成小片段并为每个片段提供多个质量级别来实现视频质量的动态自适应。到目前为止，HAS服务通常利用固定的段持续时间。这减少了编码和流可变性，并且因此允许视频内容的更快编码和自适应比特率算法的降低的预测复杂度。由于I帧在每个段的开始处的内容不可知的放置，引入了额外的编码开销。为了减轻这种开销，最近已经提出了可变段持续时间，其考虑编码器放置的I帧。因此，需要较低数量的I帧，从而实现较低的视频比特率而不降低质量。虽然存在利用可变段持续时间的几个提议，但是还没有进行突出这种技术对编码效率和自适应流传输性能的影响的比较研究。本文在自适应视频流生态系统中进行了这样一个整体的比较。首先，它提供了一个广泛的调查视频编码效率的可变段持续时间。其次，测量研究使用三种适应算法和dash.js参考实现评估了段持续时间可变性对HAS性能的影响。我们的研究结果表明，可变段持续时间提高了54%的评估流媒体会话的体验质量，同时平均降低了7%的整体比特率。
HTTP Adaptive Streaming (HAS) is the de-facto standard for video delivery over the Internet. It enables dynamic adaptation of video quality by splitting a video into small segments and providing multiple quality levels per segment. So far, HAS services typically utilize a fixed segment duration. This reduces the encoding and streaming variability and thus allows a faster encoding of the video content and a reduced prediction complexity for adaptive bit rate algorithms. Due to the content-agnostic placement of I-frames at the beginning of each segment, additional encoding overhead is introduced. In order to mitigate this overhead, variable segment durations, which take encoder placed I-frames into account, have been proposed recently. Hence, a lower number of I-frames is needed, thus achieving a lower video bitrate without quality degradation. While several proposals exploiting variable segment durations exist, no comparative study highlighting the impact of this technique on coding efficiency and adaptive streaming performance has been conducted yet. This paper conducts such a holistic comparison within the adaptive video streaming eco-system. Firstly, it provides a broad investigation of video encoding efficiency for variable segment durations. Secondly, a measurement study evaluates the impact of segment duration variability on the performance of HAS using three adaptation heuristics and the dash.js reference implementation. Our results show that variable segment durations increased the Quality of Experience for 54% of the evaluated streaming sessions, while reducing the overall bitrate by 7% on average.