Cost-efficient and QoS-aware content management in media cloud: Implementation and evaluation

Adaptive bitrate streaming has been proposed to encode video contents into multiple versions for device heterogeneity and changing network conditions. This solution, however, could consume enormous computing and storage resource. In fact, only a small fraction of videos are frequently requested. Thus, caching multiple versions for unpopular contents is not cost efficient. In this paper, we design a cost-efficient and QoS-aware content management system for video streaming. The system consists of a set of streaming servers and a computing cluster, where streaming servers can cache video contents or transcode them in real time, and the computing cluster can perform transcoding tasks on behalf of streaming servers. Based on this architecture, to provide cost-efficient and QoS-aware video service, first, we design a cost-efficient content cache management module to minimize the operational cost, by dynamically determining whether a segment should be cached or transcoded on fly according to their popularity. Second, to reduce transcoding latency, we design a QoS-aware transcoding task delegation module to determine whether a transcoding task in streaming server should be delegated to the computing cluster according to the streaming server´s workload. We implement the system and evaluate the performance in a real environment. The results demonstrate that our method can greatly reduce the operational cost and guarantee the QoS in providing video services.