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Abstract: The application of different downsampling filters in video coding directly models visual information at lower resolutions and influences the compression performance of a chosen coding system. In wavelet-based scalable video coding the spatial scalability is achieved by the application of wavelets as downsampling filters. However, characteristics of different wavelets influence the performance at targeting spatio-temporal decoding points. An analysis of different downsampling filters in popular wavelet-based scalable video coding schemes is presented. Evaluation is performed for both intra- and inter-coding schemes using wavelets and standard downsampling strategies. On the basis of the obtained results a new concept of inter-resolution prediction is proposed, which maximises the average performance using a combination of standard downsampling filters and wavelet-based coding.
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1 Introduction
Increasing developments in technologies for transmission of and access to multimedia content over heterogeneous networks are setting new requirements for multimedia systems, which cannot be reached by conventional coding and streaming techniques. Here, a key challenge relates to the fact that content needs to traverse network paths supporting different transmission bandwidths: from very low bandwidths such as dial-up to high bandwidths on fibre optic networks. Furthermore, the same content has to be accessible from a variety of devices at the user side that have different displaying and computational capabilities. In this context two highly desirable features have to be met by the content compression technology used in the transmission system. First, it has to be highly efficient in terms of compression, and second, it has to provide flexible low-complexity real-time content adaptation to the network and user's device properties. In case of video content, conventional coding systems can provide content adaptation by transcoding or by storing different instances of the same content at the server and transmitting appropriate content instance based on the network and/or display device properties. Since transcoding is computationally expensive, it does not meet the requirements for low-complexity adaptation, while the storing of different content instances at the server provides an ineffective solution in terms of storage. An emerging technology, scalable video coding, appears to be the most suitable technology to achieve the required high compression and efficient adaptation functionalities. The scalable video-coding technologies evolved from two different branches of video coding - 3D wavelet-based...