Subjective quality assessment in scalable video for measuring impact over device adaptation

Multiplicity of devices used for the reproduction of video is increasing nowadays. The characteristics of the displayable video are specific for each type of device. In order to avoid using separate source streams for the different devices and use optimal delivery bit rate, it is desirable that the encoded and transmitted original is identical for all the display devices and adapted in terms of video characteristics and bit rate with techniques such as Scalable Video Coding (SVC). In this paper, an analysis of perceived quality for different devices and different video characteristics is described, consisting in subjective tests with a group of observers and analysis of results. A collection of sequences were presented to the observers at different qualities, receiving a score on the Mean Opinion Score (MOS) scale (five grades from worst to the best quality). The devices considered included tablets and mobile phones, and complemented previous studies developed with high definition televisions. The results of the tests are presented and conclusions are drawn.