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Research Article An Attention-Information-Based Spatial Adaptation Framework for Browsing Videos via Mobile Devices Houqiang Li, Yi Wang, and Chang Wen Chen Department of Electronic Engineering and Information Science (EEIS), University of Science and Technology of China, Hefei 230027, China Received 1 September 2006; Revised 8 February 2007; Accepted 3 May 2007 Recommended by Chia-Wen Lin With the growing popularity of personal digital assistant devices and smart phones, more and more consumers are becoming quite enthusiastic to appreciate videos via mobile devices. However, limited display size of the mobile devices has been imposing significant barriers for users to enjoy browsing high-resolution videos. In this paper, we present an attention-information-based spatial adaptation framework to address this problem. The whole framework includes two major parts: video content generation and video adaptation system. During video compression, the attention information in video sequences will be detected using an attention model and embedded into bitstreams with proposed supplement-enhanced information (SEI) structure. Furthermore, we also develop an innovative scheme to adaptively adjust quantization parameters in order to simultaneously improve the quality of overall encoding and the quality of transcoding the attention areas. When the high-resolution bitstream is transmitted to mobile users, a fast transcoding algorithm we developed earlier will be applied to generate a new bitstream for attention areas in frames. The new low-resolution bitstream containing mostly attention information, instead of the high-resolution one, will be sent to users for display on the mobile devices. Experimental results show that the proposed spatial adaptation scheme is able to improve both subjective and objective video qualities. Copyright © 2007 Houqiang Li et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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INTRODUCTION

Recent advances in wireless networks, especially with the emergence of 3G network, have enabled a new array of applications in image and video over wireless networks beyond traditional applications in voice and text. Real-time multimedia applications, such as video streaming, have become feasible in the wireless environment. In particular, with the growing popularity of mobile devices, users can enjoy videos anyplace and anytime over wireless networks. However, for video streaming application in the wired environment, the videos stored in the video server are generally encoded at high resolution (HR) and high bitrate to guarantee users’ browsing experiences. There are two serious difficulties in enjoying these videos with mobile devices over wireless networks. One is the lower bandwidth of wireless networks. The other critical constraint is the limited display size of mobile devices, which often hinders the users to fully enjoy the video scene. I