Creation & Assessment of a Video Quality Ruler
Abstract: Image quality has always been a matter of great importance for anyone working with or consuming images and videos. Images and videos are, in general, for human consumption. Thus, image quality is essentially a subjective attribute of an image. Though there exist both objective and subjective approaches to assessing image quality, objective results may not correlate well with subjective results. On the other hand, pre-existing subjective methods for evaluating video quality can be time-consuming, resource-consuming, or unreliable. The aim of this thesis was to create and analyse a method for sub- jectively determining video quality. Based on a previously established method for assessing still image quality prescribed in ISO 20462, this method, the Video Quality Ruler, establishes an absolute scale of per- ceptive video quality. The Video Quality Ruler consists of a series of 31 ordered video clips, varying solely in sharpness. Each of the 31 video clips are one perceptual unit apart. Users are able to determine the overall level of quality of a video through comparison against the Ruler. The method provides an easy, universal analysis of video quality that correlates well to human opinions, and is not as time- nor resource- consuming as many other subjective methods. The creation of the Video Quality Ruler was, on the whole, successful. The calibration of the ruler videos differs slightly from the calibration of the Image Quality Ruler from ISO 20462, particularly for images on the blurrier end of the Ruler. Assessment of the Video Quality Ruler deter- mined that a few levels of the Ruler may need to be adjusted, and that the software and laboratory used for the experiment should be improved slightly, to eliminate bias and reduce the variance of results.
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