I. Introduction
Ground truth is one of the most important and useful components for the evaluation and benchmarking of new algorithms. In the field of image and video quality, ground truth means databases of test clips annotated with subjective ratings. The lack of annotated databases used to be a major hurdle for researchers working on quality assessment algorithms. Even uncompressed video content was hard to find. In recent years, an increasing a number of databases have been released into the public domain, to the point where it has become be hard to keep track of them or to choose the most suitable one. For this paper, we have compiled a list of 27 image and video databases that are publicly available and relevant to quality assessment.