Oscillation-Free Video Adaptation at Application Layer on Server Side and Experiments Using DCCP

Nowadays, video data transfers account for much of the Internet bandwidth and a huge number of users use it daily. However, despite its apparent interest, video streaming is still done in a suboptimal manner. Indeed, more and more high-definition and high-quality videos are nowadays stored on Internet but they are not accessible for everybody because a high and stable bandwidth is needed to stream them; also, during videoconferencing, the highest possible quality often exceeds the available bandwidth. Hence, a lower bitrate encoding is usually chosen but it leads to lower quality and network under-utilization too. This paper presents Video Adaptation at Application Layer (VAAL), a simple and efficient method designed to use optimally network resources and to ameliorate user video experience. It involves only the application layer on the server. The main idea of VAAL is that it checks Transmission Control Protocol-friendly transport protocol buffer overflows and adapts the video bitrate accordingly; as a result, the bitrate constantly matches the network bandwidth. It can be used together with Zigzag Avoidance Algorithm (ZAAL), a novel algorithm aiming to avoid quality oscillations. Experimental results show that the video adaptation using VAAL+ZAAL performs much better compared with the currently widely used static encoding, making it a strong candidate for hard real-time video streaming.