DigitalVideoAndHDTVAlgorithmsAndInterfaces.pdf

Luminance, relative
Details will be presented in Setup
(pedestal), on page 327.
1.0
0.8
0.6
0.4
0.2
0
0 mV Analog video, zero setup, 7:3 (EBU N10; HDTV) 700 mV
0 mV Analog video, zero setup, 10:4 (NTSC, NTSC-J) 714 mV
54 mV Analog video, 7.5% setup
714 mV
16 Rec. 601 digital video (interface levels)
235
0 Rec. 601 digital video (processing levels) 219
0 Typ. computer framebuffer code 255
Figure 23.6 CRT signal levels and luminance. An analog video signal may be coded between 0
and 700 mV, between 0 and 714 mV, or between 54 mV and 714 mV. A digital signal may be
coded from 16 to 235 (for Rec. 601 studio video interface), from 0 to 219 (for Rec. 601-related
studio video signal processing), or from 0 to 255 (as is typical in computer graphics).
electrical interface between a computer framebuffer
and a monitor.
Figure 23.6 illustrates the function that relates signal
input to a CRT monitor to the light luminance produced
at the face of the screen. The graph characterizes
a grayscale monitor, or each of the red, green, and blue
components of a color monitor. The x-axis of the graph
shows the input signal level, from reference black to
reference white. The input signal can be presented as
a digital code, or as an analog voltage according to one
of several standards. The y-axis shows the resulting
relative luminance.
For analog voltage signals, three standards are in use.
The range 54 mV to 714 mV is used in video systems
that have 7.5% setup, including composite 480i
systems such as NTSC, and computer video systems
that conform to the levels of the archaic EIA RS-343-A
standard. Computer framebuffer digital-to-analog
converters often have 7.5% setup; these almost
CHAPTER 23 GAMMA 271