A no reference metric for the quality assessment of videos affected by exposure distortion

Abstract

In the field of still and moving pictures digital imaging one of the most important factors affecting the quality of the acquisition is a correct exposure. This factor is especially important for video surveillance. It is particularly applicable in the case of CCTV cameras often operating in low-light conditions or blinded by an external light source. It is quite common that the lighting conditions are well below the adaptive capacity of a camera. Therefore, it is necessary to continuously monitor the level of exposure to determine image quality. It should be noted that the level of exposure is not expressed using quantitative parameters of acquisition (being sometimes meaningless from the perceived quality assessment point of view) but is measured directly on the image. The purpose of the presented research was to develop a No Reference (NR) metric assessing video Quality of Experience (QoE) affected with the exposure distortion. It was presumed that both over- and under-exposure degrade QoE, so the research task was to derive a proper mapping function between QoE and exposure. The presented exposure metric is unique and no similar research was found in the literature.