DigitalVideoAndHDTVAlgorithmsAndInterfaces.pdf

Figure 45.3 NTSC-
Encoded 100/0/75/0
colorbar waveform
The -I and +Q elements correspond
to R’G’B’ values of
[-0.3824, 0.1088, 0.4427] and
[0.2483, -0.2589, 0.6817],
respectively; and to 601 Y’C B C R
values [0, 56.96, -61.10] and
[0, 86.17, 39.68]. To produce
RGB-legal codes having the same
hue and saturation as -I and +Q,
and having minimum luma, use
R’G’B’ values [0, 0.2456, 0.4125]
and [0.2536, 0, 0.4703], respectively.
BLACK
BLACK
480i +4 IRE
-4 IRE
576i +14 mV
-14 mV
Figure 45.4 PLUGE element
of the colorbar signal enables
accurate setting of black
level. The acronym originates
with the “generating equipment,”
but nowadays PLUGE
signifies the signal element.
The lower-left quadrant of SMPTE colorbar contains
subcarrier frequency components at -I and +Q phase.
These elements were designed to exercise the encoding
and decoding axes of the original NTSC chroma modulation
method. Encoding and decoding on I and Q axes
has fallen into disuse, being replaced by encoding and
decoding on the B’-Y’ and R’-Y’ axes, so the utility of
this portion of the signal is now lost. The -I and +Q
elements contain high-magnitude chroma resting upon
black (at 0 IRE). These combinations correspond to
illegal mixtures of R’G’B’, where one or two components
are negative; so the -I and +Q elements are not
representable in the positive R’G’B’ domain.
The lower-right quadrant of colorbar contains elements
produced by picture line-up generating equipment
(PLUGE); see Figure 45.4 in the margin. Superimposed
on black are two narrow bars, one slightly more negative
than black, the other slightly more positive. If a
monitor’s black level is properly adjusted, the first of
the bars will vanish and the second will be barely
visible. The negative-going element of PLUGE cannot
be represented in positive R’G’B’.
The -I element, the +Q element, and the negative-going
element of PLUGE are generated synthetically. None of
these elements represents picture information; none is
useful in evaluating pictures; and none can be generated
in, or survives transit through, the positive R’G’B’
domain between 0 and 1 (or 0 and 255).
CHAPTER 45 SDTV TEST SIGNALS 537