Backward-Shifted Strategies Based on SVC for HTTP Adaptive Video Streaming

TL;DR

This paper introduces Backward-Shifted Coding (BSC), a novel SVC-based strategy that pre-fetches future video frames to enhance streaming quality and reduce interruptions under variable network conditions.

Contribution

The paper proposes BSC, a new SVC-based method that adds time-shifted redundancy to improve QoE in HTTP adaptive streaming, supported by analytical models of buffering and quality variability.

Findings

BSC reduces initial buffering and re-buffering times.

BSC maintains higher average video quality under network fluctuations.

Analytical models effectively predict QoE metrics and guide optimization.

Abstract

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.