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Reference
WFM700 Series Waveform Monitors User Manual
3-43
Luminance Gain Measurement. The signal is driven along the vertical axis above
and below the center box by the luminance signal. The luminance gain is correct
when the center dot (clamped black level) is centered in the target box and the
positive and negative excursions end at the top and bottom of the graticule.
Perfect monochrome signals appear as a thin vertical line. Any deviation or
bending off the center line indicates a color variation from the monochrome
setup of the display monitor.
Interchannel Timing Measurement. The scale (sequence of dots) between the green
and magenta targets provides a way to check interchannel timing (CH-2 to CH-1
and CH-3 to CH-1) or signal delay. If the color difference signal is not coincident
with luminance, the transitions between color dots will bend. The amount of this
bending represents the relative signal delay between luminance and the color
difference signal. The upper half of the display measures the Pb-to-Y timing,
while the bottom half measures the Pr-to-Y Timing. If the transition bends in
toward the vertical center or black region, the color difference signal is delayed
with respect to luminance. If the transition bends out toward white, the color
difference signal is leading the luminance signal.
Figure 3--13 shows a signal with proper interchannel timing. In Figure 3--14, the
Lightning display shows that the signal has Y--Pb and Y--Pr timing errors.
Pr and Pb Gain Measurement. The horizontal deflection of the top half of the
display is an indication of the Pb gain and the lower half indicates the Pr gain. If
the color bar signal dots are within the horizontal dimensions of the appropriate
graticule targets, the Pb and Pr gains are within 2% of the correct amplitude.
Since the vertical and horizontal dimensions of the graticule target boxes indicate
2% luminance and color difference gain errors, respectively, you can evaluate
each color bar for encoding accuracy with these limits.