Subjective comparison of temporal and quality scalability

In video streaming applications, it is necessary to choose the rate of the encoded stream to match the available transmission channel capacity. To provide flexible means for rate adaptation, different scalable video coding schemes have been proposed. For example, if necessary the bitrate can be reduced either by downscaling the frame rate (temporal scalability) or the image quality (quality scalability). However, the user preferences between different scalability types are not well known in different scenarios. In this paper, we present a methodology for subjective comparison between temporal and quality scalability. The practical experiments with low resolution video sequences show that in general, distortion is a more crucial factor for the perceived subjective quality than frame rate. However, the results also depend on the content. Moreover, we discuss the role of other different influence factors on perception.