Avoiding quality oscillations during adaptive streaming of video
Résumé
A high number of videos, encoded in several bitrates, are nowadays available on Internet. A high bitrate needs a high and stable bandwidth, so a lower bitrate encoding is usually chosen and transferred, which leads to lower quality too. A solution is to adapt dynamically the current bitrate so that it always matches the network bandwidth, like in a classical congestion control context. When the bitrate is at the upper limit of the bandwidth, the adaptation switches constantly between a lower and a higher bitrate, causing an unpleasant oscillation (zigzag) in quality on the user machine. This paper presents a solution to avoid such oscillations. It uses an EWMA (Exponential Weighted Moving Average) value for each bitrate, which reflects its history. The evaluation of the algorithm shows that loss rate is much smaller, bitrate is more stable, and so received video quality is better.