Quality estimation for images and video with different spatial resolutions

Abstract

Full-reference (FR) quality estimators (QEs) for images and video are typically designed assuming that the displayed, degraded image has the same spatial resolution as the original, reference image. No-reference (NR) QEs use no knowledge about the reference image to assess quality of the displayed image. However, in many practical systems, a reference image may be available that has a different spatial resolution than the displayed image. In this paper, we explore objective quality estimation when the displayed image to be evaluated has a different spatial resolution than the reference image. We begin by identifying a range of potential weaknesses that might be present in a QE designed for this situation. Then, we create pairs of images with potential False Ties, in which a QE estimates that two images have equal quality while viewers disagree. Our subjective tests demonstrate that existing QEs do not accurately assess quality in a variety of scenarios for which images have different spatial resolutions.