OLAC: An Open-Loop controller for low-latency adaptive video streaming

Dynamic video streaming performs video rate selection based on streaming client's throughput estimate. In practice, the accuracy of the estimated throughput is limited due to feedback delay and unawareness of the dynamics of the underlying HTTP/TCP transport layer. Furthermore, state-of-the-art rate selection methods inherently introduce a two-fold quantization error, as will be detailed in this paper. As a result, streaming adaptation is often erroneous and causes client buffer instability such that conventional streaming applications require an extensive buffering on the order of tens of seconds. In this paper, we present Open-Loop rAte Control (OLAC), an adaptive streaming architecture designed to support low-latency streaming applications. The key components of our architecture are a server-side simulation of the streaming client's buffer, which provides a low-delay feedback for the video rate selection, and a hybrid adaptation logic based on throughput and buffer information, which stabilizes the adaptive response to dynamics of transport and application layers. We evaluate the performance of OLAC with respect to impairment functions that model user-perceived video quality and compare it against two well-known streaming architectures, QAC and vlc-plugin DASH. The results show that our approach achieves a very low initial delay, 64% lower impairment of stalls and 20% lower impairment of quality variation in dynamic streaming with buffering delays as low as the chunk duration.