Adaptive Live Video Streaming by Priority Drop

The reordering window in PPS introduces latency, however, and this latency might be problematic for video surveillance applications, which stream live video. In live video streaming, the latency characteristics of the streaming mechanisms partially determine the freshness of the video content. The freshness of the video content, which is measured by the end-to-end latency from a frame being captured to its display, tends to be important for video surveillance applications. In this paper we explore the use of Priority-progress streaming (PPS) for video surveillance applications. PPS is an adaptive streaming technique for the delivery of continuous media over variable bit-rate channels. It is based on the simple idea of reordering media components within a time window into priority order before transmission. The main concern when using PPS for live video streaming is the time delay introduced by reordering. In this paper we describe how PPS can be extended to support live streaming and show that the delay inherent in the approach can be tuned to satisfy a wide range of latency constraints while supporting finegrain adaptation. In this paper, we explore how much of a problem the latency in PPS is for live video streaming and determine the range of video surveillance applications it can support. We describe how PPS can be extended to support live video streaming, and evaluates the latency implications of the approach. Our implementation of the live Quasar pipeline show that even with fairly rudimentary scalable video encoding technology, the latency due to adaptation in PPS can be reduced to as little as 400ms while maintaining fine-grain adaptation. This means that applications with a latency tolerance of a half second can be supported using TCP-friendly protocols on a coast to coast link in the US (where propagation delay is typically less than 100ms).