Subjective Impairmnt Units in Relation With Oscilloscope Graticules for Evaluating Short-Time Linear Waveform Distortion of the Luminance Signal in 525-Line Television

Objective ratings (for example, the K-rating) for waveform distortion are assessed customarily by using oscilloscope graticules. They are based on subjective evaluations of television picture impairments. As the impairment unit (imp) is a unit which expresses subjective impairments quatitatively, it is used here as a means to check whether the graticules proposed for the assessment of short-time linear distortion of the luminance signal in television in North America comply with the principle that a given rating factor should correspond to a single value of subjective impairment. This is accomplished by converting to imps the results of published North American evaluations of subjective picture quality and utilizing a computer, in connection with a specially devised algorithm, to derive the imp value corresponding to any given point on a rating outline of the graticules examined. In addition, imp-to-rating relations are derived where feasible.