Research On Key Techniques Of Video Adaptation For Heterogeneous Networks

With the development of Internet and multimedia technologies, net-based multimedia has been applied in a wide range of applications. There are three main characteristics in the current multimedia application environment: heterogeneous networks, diverse terminals and diversity of user tasks. These limitations lead to difficulties and challenges in Universal Media Access (UMA). Video adaptation is one of the most promising ways to solve these problems in UMA and is the hot spot in video processing and communication research area.Under the framework of video adaptation based on Meta-data sub-space, this thesis investigates key techniques in video adaptation and mainly focuses on overcoming difficulties in UMA which is brougnt by heterogeneous networks. The main contents and nolvelties of this paper are as follows:1. This thesis proposes a general video adaptation framework based on Meta-data sub-space.In this framework, efficient description of video signals is investigated in order to facilitate adaptation operations. As a set of feature descriptions of videos, meta-data subspace servers as an efficient representation of video signals. Furthermore, this thesis proposes to address video adaptation problems on three levels: signal level, structural level and semantic level.2. On signal level, this thesis investigates video adaptation techniques based on error control.One feature of the heterogenous networks is that various propabilities of communicating error may exist. This thesis aims to provide flexible error robustness for heterogeneous networks, by adaptively extracting redundant information from compressed videos. Specifically, a non-interactive adaptive error resilient video coding scheme is proposed combining redundant picture coding, reference picture selection and temporal error tracking. In this scheme, redundant information is extracted as the Meta-data of compressed video features to efficiently prevent temporal error propagation in video coding and communication.3. On structural level, this thesis proposes a video adaptation scheme based on image inpainting techniques.Another feature of heterogeneous networks is their fluctuating bandwidths. To improve compression ratio, traditional video coding schemes tend to use coarse quatization accuracy, which results in the degradation of visual quality. Considering that traditional video coding schemes cannot fully exploit visual redundancies in video signals, this thesis employs computer vision techniques such as texture synthesis and image/video inpainting to make use of visual redundancies. Moreover, texture, structure and motion information of the original video signals are extracted as Meta-data and incorporated into conventional video coding, in order to enhance compression efficiency without loss of visual quality.In conclusion, this thesis investigates video adaptation techniques based on extracting and building-up Meta-data and developing corresponding adaptation operations. Some useful and encouraging results have been obtained. However, up to now, the proposed framework is still at the initial stage. The video adaptation framework based on Meta-data sub-space is a potential research field which is worthy of further studies.