The Research On Scheduling Algorithms For Distributed Video Transcoding Service

By the continue developing of distributed network technology and its expansion form the Cloud technique, diversification service based on distributed mode has become more and more popular. With the advantages of low-cost,good flexibility of foundation and independent from physical area, the distributed service system has become the most potential researching area among today's network technology study. So that how to work out the stream video service under distributed mode is a significant issue to research.The difficulty of distributed video service is not on the video operation itself but how can we give out a rational control to the whole process of distributed video service. The common"scheduling—feedback—modification"for dynamic real-time scheduling algorithms is quite suitable and effective to solve the problem of unstable and un-uniform of node resource build up in distributed networks. This passage first give a description of distributed system and the principle of its service implement, while also show the problem and challenge of real-time distributed scheduling. Then use distributed video transcoding service as a study object, through analyzing the figure of PC resource occupy of video transcoding, we proposed a novel node resource computing method. Based on the node resource information obtained through this method, combine the classical Knapsack-Approx problem and Greedy Assignment ideology, we give the Double-Priority Knapsack-Approx(DPKA) algorithm for task requirement selection and Resource Information Based Greedy-Loadbance algorithm for Close-GOP level task assignment. Meanwhile , by analyzing the condition which segment data transmission should satisfied for fluency stream video service, we proposed the video segment transmission control algorithm the implement of fluency stream video service for the client.Finally, we proved the effective of our algorithms through s series of experiment. The experiment result showed that the DPKA algorithm will make the system access more clients under the same limited resource condition and the RIBGL algorithm can lower the overflow rate of node payload according to its available resource when it hold the average usage of resource of all the nodes. Video segment transmission algorithm can give a good effect to reduce the interval of Close-GOP playing and give a better video watching quality to the client with an acceptable additional delay.