Forming valid scales for subjective video quality measurement based on a hybrid qualitative/quantitative methodology
Toni Virtanen, Jenni E. Radun, Paul Lindroos, Sini Suomi, Timo Säämänen, Tero Vuori, Mikko Vaahteranoksa, Göte Nyman · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 2007
This study presents a methodology of forming contextually valid scales for subjective video quality measurement. Any single value of quality e.g. Mean Opinion Score (MOS) can have multiple underlying causes. Hence this kind of a quality measure is not enough for example, in describing the performance of a video capturing device. By applying Interpretation Based Quality (IBQ) method as a qualitative/quantitative approach we have collected attributes familiar to the end user and that are extracted directly from the material offered by the observers' comments. Based on these findings we formed contextually valid assessment scales from the typically used quality attributes. A large set of data was collected from 138 observers to generate the video quality vocabulary. Video material was shot by three types of video cameras: Digital video cameras (4), digital still cameras (9) and mobile phone cameras (9). From the quality vocabulary, we formed 8 unipolar 11-point scales to get better insight of video quality. Viewing conditions were adjusted to meet the ITU-T Rec. P.910 requirements. It is suggested that the applied qualitative/quantitative approach is especially efficient for finding image quality differences in video material where the quality variations are multidimensional in nature and especially when image quality is rather high.