OC: An Optimal Cache Algorithm for Video Staging

The video content for on-demand services is generally stored and streamed in a compressed format. The compressed video is naturally with the VBR (variable-bit-rate) property and the stream traffic is highly burst. Subject to the QoS-guaranteed playback, the WAN bandwidth needs to allocate the video's peak bit rate if there is no client buffer for regulating the video delivery [7][8][9][10][11]. To reduce the requirement of WAN bandwidth, Video Staging [2], first proposed by Zhang et al., caches parts of a video content in the video proxy closed to clients. Therefore, the video can be streamed across the WAN with CBR (constant-bit-rate) services and its bandwidth requirement is significantly reduced. In this paper, we propose an Optimal Caching (OC) algorithm to handle the Video Staging problem. We also prove that the cache storage computed by our OC algorithm is minimal. Relatively, if the same cache size is given, OC requires less WAN bandwidth than [2] does to provide streaming services. By doing experiments on several benchmark videos [12], we show that the OC algorithm can reduce the cache storage requirement by over 30% while comparing to [2]. With the same proxy cache storage of [2], we can reduce the WAN bandwidth requirement with more than 50%. Additionally, the WAN bandwidth utilization can also be increased by over 30%. Index terms – Video Staging, VBR (variable-bit-rate), CBR (constant-bit-rate), Video Proxy, and Optimal Caching (OC).