Qos Policy-based Video Server Design And Applications

With the development of the networks, multimedia technology has a wider and wider range of applications on the Internet, which all need the video servers to provide services.Therefore, how to improve the performance of the video server has an important impact on the application of multimedia technology and the cost of the system. Meanwhile, terminal users of multimedia information have a higher requirement on the quality of pictures, the successful rate of VOD and so on. So how to assure the QoS (quality of service) of the video server will be a key aspect to be studied.Based on the above background, this thesis has studied the improvement of the performance of the video servers and the QoS of the video transmission. Highly efficient video server refers to the one that can maximize the service to request on the condition of limited system resources, and at the same time, can provide more reliable services. So that this thesis starts research from the key technology of the video server, focuses on studying the algorithms of admission control and video streams scheduling, and proposes an admission scheme based on hierarchical QoS assurance. The scheme can provide the QoS assurance to the request with high priority, and also balance many factors such as the delay of the queue, the rate and the length of the video, resulting in a relatively small admission delay. Besides, this thesis proposes a repetitive patching streams algorithm. This algorithm will significantly improve the common share property of the system resources, and consequently increase the number of the concurrent streams which are supported by the server.And then, from the point of video stream transmission, this thesis investigates how to promote QoS of video stream transmission, and proposes a multicast congestion control scheme based on the application of multicast, with dynamic FEC error control. Multicast application is regarded as the best way to solve the VOD service. This scheme can enable UDP application to solve congestion problem in the way of adjusting transmission rate on the condition of assurance of TCP-friendly. In addition, the scheme provides a dynamic FEC, error control mechanism, making stream media transmission more effective.At last, this thesis has applied all the above schemes into the actual project called the Network Video Surveillance System with very good performance results.