MPEG-2 transport over ATM networks with best effort service.

摘要

With increasing interest in the transmission of audio-visual applications (e.g. MPEG-2) over ATM best effort services, such as Available Bit-Rate (ABR) and Unspecific Bit-Rate (UBR), efficient video-oriented control mechanisms for improving the video quality in the presence of loss have to be designed. In this thesis, we proposed and evaluated a new quality of service control framework for use with modified Unspecific Bit Rate service.; We surveyed a number of issues related to the coding and control of MPEG-2 video data streams transmitted over ATM networks, analyzed the network factors affecting the quality of service of real-time video applications and showed how this proposed video-oriented QoS control framework improve the performance for such services.; The presented framework relies on four components: a dynamic frame-level priority data partition mechanism based on MPEG-2 data structure and feedback from the network; an enhanced ATM Adaptation Layer type 5 (AAL-5) associated with a new slice-based MPEG-2 encapsulation strategy; a forward error correction (FEC) mechanism, which is implemented at the AAL-5 service specific convergence sublayer to provide the error detection and recovery capability, and a video-oriented cell discarding scheme, which adaptively and selectively adjusts discard level according to switch buffer occupancy, video cell payload types and FEC drop tolerance.; This best-effort video delivery framework is evaluated using simulation and real MPEG-2 video data. The overall objective of this proposed framework is twofold. First, ensuring a graceful picture quality degradation by minimizing cell loss probability for critical video data while guaranteeing a bounded cell transfer delay. Second, optimizing the network effective throughput by reducing the transmission of non useful data.; In comparison to previous approaches, the performance evaluation has shown a significant reduction of the bad throughput and minimization of losses of Intra- and Predictive-coded frames at the video slice layer.