Work-in-Progress: Version-Aware Video Caching Strategy for Multi-version VoD Systems

Recently, many video-on-demand (VoD) providers store multiple versions of the same videos to offer multiple-quality video services with different bitrates to users, called as multi-version VoD. To decrease the start-up delay for users, it is a good idea to cache videos at caching server that is in close proximity. However, how to decide which versions of which videos should be cached and replaced in caching server is still one major challenge for multi-version VoD systems because of limited caching storage. In this paper, we propose a version-aware video caching strategy for multi-version VoD systems, which aims to reduce start-up delay and improve cache hit ratio. First, we take into account the transcoding delay among versions and transmit delay from content server to caching server to calculate version-aware caching profit when caching a certain version or multiple versions of a video. It is the basis for the following caching replacement algorithm. Second, we propose version-aware video caching (VaVC) algorithm to decide which versions of which videos will be replaced based on the version-aware caching profit dynamically. In this way, VaVC can reduce start-up delay and improve the cache hit ratio. Our simulation results have shown that VaVC outperforms the others in both the start-up delay and the cache hit ratio.