  Video quality measurement takes an important role in many applications.
Full-reference quality metrics which are usually used in video codecs
comparisons are expected to reflect any changes in videos. In this article, we
consider different color corrections of compressed videos which increase the
values of full-reference metric VMAF and almost don't decrease other
widely-used metric SSIM. The proposed video contrast enhancement approach shows
the metric inapplicability in some cases for video codecs comparisons, as it
may be used for cheating in the comparisons via tuning to improve this metric
values.
