Draft summary

This document specifies a subjective image quality assessment methodology that covers a range from good quality up to mathematically lossless. Good quality, here, is defined as the visual quality level corresponding to a mean opinion score of 4 on a 5-point scale in a side-by-side comparison as in ITU-R BT.500. The threshold of visually lossless quality, as determined by an AIC-2 flicker test (ISO/IEC 29170-2), is included in the range covered by this document. For mathematically lossless compression, image quality assessment does not apply, but the methods described in this document can provide meaningful differentiation (in fractional JND units) between images that are visually lossless. The methodology targets specifically the assessment of distortions due to image coding (i.e., lossy compression) and not necessarily other kinds of distortions, e.g., capture, sensor or rendering artifacts.