An investigation, including subjective tests, has been carried out concerning the visibility of chrominance/luminance delay inequalities in System I (625-line PAL) video signals. The results obtained indicate that the threshold of visibility of this type of picture impairment corresponds to a delay inequality of about ±50 ns on critical pictures if it results from timing errors in a video circuit handling separate chrominance (R-Y and B-Y) and luminance (Y) signals; if, however, the delay inequality is caused by group delay distortion in a circuit handling coded PAL signals, the threshold occurs at about ±100 ns.
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