No abstract

Delay difference between the luminance and chrominance information of the NTSC color television signal causes colorr to shift to the left or right of objects in the viewed color picture. This delay difference can occur during the processing or transmission of the color signal resulting in two basic delay difference types. Flat delay is the type of delay difference that can occur when the luminance and chrominance signals are Separated, as frequently happens during signal processing, and is a function of the absolute delays of the separate luminance and chrominance signal paths. Shaped delay can occur during the transmisiion of the composite color signal and is a function of the delay characteristic of the transmission system. A series of subjective tests was designed to evaluate the effects of both flat and shaped delay on color TV pictures. Expert observers used a seven-point comment scale ranging from "not perceptible" to "extremely objectionable," to rate picture impairments resulting from various magnitudes of delay difference.T H E PIcTuwz INFORMATION in the NTSC color television signal contains both luminance and chrominance signals. The luminance signal, concentrated primarily at the lower end of the video frequency band, conveys brightness information; the chrominance signal, concentrated at the higher end of the video band, conveys hue and color saturation information. Among other things, perceived quality of color T V pictures depends on the relative time delays that are encountered by these two signals. Unequal delays result in a color shift to the left or right of objects in the viewed picture.Delay differences can occur during the processing or transmission of the NTSC color signal. During signal processing, the luminance and chrominance signals are frequently separated. Delay difference for this case is the difference between the delays of the individual circuit paths. During transmission, the luminance and chrominance signals are combined but they occupy different positions in the video frequency spectrum. Delay difference for this case is a function of the delay characteristic of the transmission facility.The effect of delay difference, i.e., color shift in the viewed picture, is subjective in nature and, thus, can only be evaluated by means of subjective tests. This effect is evaluated here by analyzing the results of a series of subjective tests that were designed to obtain observers' reactions to picture impairments resulting from various magnitudes of delay difference.These tests are part of a continuing program to acquire and periodically update information on the subjective effects of signal distortions and inter-Preaented on April 28, ferences that can occur over TV transmission facilities.

No abstract

No abstract