Evaluating feedback devices for time-continuous mobile multimedia quality assessment

In January 2014, the new ITU-T P.913 recommendation for measuring subjective video, audio and multimedia quality in any environment has been published. This document does not contain any time-continuous subjective method. However, environmental parameter values are changing continuously in a majority of outdoor and also most indoor environments. To be aware of their impact on the perceived quality, a time-continuous quality assessment methodology is necessary. In previous standards, targeting laboratory-based test settings, a desk-mounted slider of substantial size is recommended. Unfortunately, there are many environments where such a device cannot be used. In this paper, new feedback tools for mobile time-continuous rating are presented and analysed. We developed several alternatives to the generally adopted desk-mounted slider as a rating device. In order to compare the tools, we defined a number of performance measures than can be used in further studies. The suitability and efficacy of the rating scheme based on measurable parameters as well as user opinions is compared. One method, the finger count, seems to outperform the others from all points of view. It was been judged to be easy to use with low potential for distractions. Furthermore, it reaches a similar precision level as the slider, while requiring lower user reaction and scoring times. Low reaction times are particularly important for time-continuous quality assessment, where the reliability of a mapping between impairments and user ratings plays an essential role.