Mobile video perception: New insights and adaptation strategies

It is now a common knowledge for mobile users to notice that the video viewing experience for the same device and same content can be dramatically different. The main reason for such difference is the dynamic viewing environment of mobile device which may change from indoor to outdoor or from walking to riding in a traveling vehicle. In this paper, we report our recent study on how mobile video perception is different from conventional TV viewing experiences in the living room and on which adaption strategy we can take to generate video bitstreams that matches better with the dynamic viewing environment. We first identify several key factors that would impact the mobile video perception, including display size and viewing distance, surrounding luminance, and body movement. These factors will be evaluated by context-aware subjective tests specifically designed to quantify the correlations between these factors and the viewing experience. Based on such evaluation, we develop a mobile video quality assessment tool to measure the just noticeable distortion in a given viewing environment. With appropriate rate adaptation to viewing context parameters, we show that an environment-aware video bit-stream preparation is able to enhance mobile video experience by exploiting inherent video signal redundancy under a given viewing context. Such adaptation can also reduce the bitrate requirement by an average of 30%.