Research On Adaptive Multimedia Transmission In Mobile Internet

In recent years mobile Internet has emerged as one of the largest sector of the global information industry and the demand of multimedia services in the mobile Internet is increasing. The key to the success of wireless multimedia services is the transmission quality. However, the transmission quality of multimedia stream will degrade greatly in low bandwidth, high error rate and time-variant wireless channel.In additional, limited terminal capability and various mobile user requirements also bring challenges to wireless multimedia transmission. Wireless multimedia should be adapted to the transmission network, the terminal and mobile users'requirements. To solve the above problems, this thesis addresses on adaptive multimedia transmission in mobile Internet. The objective of this work is to enable multimedia resources adapted to different network bandwidth, effectively fight against all kinds of transmission errors, and optimize the transmission quality of wireless multimedia. The research of this thesis mainly focuses on wireless image and video transmission, and includes four issues: (1) transmission property model of JPEG2000 encoded image over wireless channel and design of error protection schema; (2) property model of H.264/AVC video and design of error protection schema; (3) network bandwidth adaptation technology for wireless H.264/AVC video transmission; (4) multimedia learning resource adaptation and delivery framework. The work in this thesis has been supported by the National Science Foundation of China "Investigation of Wireless Multimedia Techniques based on Multimedia Transmission Property "(No.60202005) and international academic (Nanyang Technological University in Singapore) cooperation project "Push-Pull Extraction Tool For DistributEd AudioVIsual Content Terminal "respectively, and also supported by the project "Learning Resource Management System"(No.2001BA101A07), which is a sub-project of the "Key Technology and Demonstration Project of Network Learning "project in the 10th National Five Year Plan for Key Problem Tackling in Science and Technology. The contributions of this thesis include: 1. The transmission property model of JPEG2000 image over wireless channel and error protection schema: Existing researches on rate-distortion optimization and error-resilient schema are mainly based on simulation approaches requiring large amounts of computation time. This thesis proposed an analytical model to estimate statistical distortion for the transmission of JPEG2000 encoded image over wireless channel. Based on this model, we design effective and accurate unequal error protection schema for JPEG2000 image transmission over wireless channel with better transmission quality. 2. Property Model of H.264/AVC video and error protection schema: Current unequal error protection schemas are based on heuristic approaches and take no account of the characteristics of human visual system. According to the sensitive characteristics to video motions of human eyes, this thesis utilized perceived motion energy model by taking account to the new encoding features of H.264/AVC standard to analyze and model the motions in H.264/AVC encoded video. The bit stream of the video is divided into several quality layers and an unequal error protection has also been designed to protect this layered bit stream for the transmission over wireless channels. Experiment results show that higher video transmission quality is obtained. 3. H.264/AVC video adaptation model and system: Towards the limited bandwidth and time-variant characteristics of wireless channel, we proposed an adaptation model based on MPEG-21 Digital Item Adaptation framework for wireless H.264/AVC video transmission. The proposed system not only ensures the viewers'perceived qualities as high as possible but also realizes format-independent video adaptation mechanism and enhances the flexibility and scalability of multimedia adaptation system. 4. Multimedia learning resource adaptation and delivery framework: For the terminal adaptation and learner requirements adaptation in mobile learning, this thesis proposedan adaptation and delivery framework for multimedia learning resource. By integrating the adaptation of learning object and the adaptation of multimedia content together, this framework ensures higher general transmission quality of learning resource than other approaches which only consider one type of the adaptation.