CCTV Glossary
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Clipping Level - An electronic limit to avoid overdriving the video portion of the television signal.
C-mount - The first standard for CCTV lens screw mounting. It is defined with the thread of 1''
(2.54 mm) in diameter and 32 threads/inch, and the back flange-to-CCD distance of 17.526 mm
(0.69''). The C-mount description applies to both lenses and cameras. C-mount lenses can be
put on both, C-mount and CS-mount cameras, only in the latter case an adaptor is required.
CMYK - A color encoding system used by printers in which colors are expressed by the
“subtractive primaries” (cyan, magenta and yellow) plus black (called K). The black layer is added
to give increased contrast and range on printing presses.
Coaxial cable - The most common type of cable used for copper transmission of video signals. It
has a coaxial cross-section, where the center core is the signal conductor, while the outer shield
protects it from external electromagnetic interference.
CODEC - Code/Decode. An encoder plus a decoder is an electronic device that compresses and
decompresses digital signals. CODECs usually perform A/D and D/A conversion.
Color bars - A pattern generated by a video test generator, consisting of eight equal width color
bars. Colors are white (75%), black (7.5% setup level), 75% saturated pure colors red, green and
blue, and 75% saturated hues of yellow, cyan and magenta (mixtures of two colors in 1:1 ratio
without third color).
Color carrier - The sub-frequency in a color video signal (4.43 MHz for PAL) that is modulated
with the color information. The color carrier frequency is chosen so its spectrum interleaves with
the luminance spectrum with minimum interference.
Color difference signal - A video color signal created by subtracting luminance and/or color
information from one of the primary color signals (red, green or blue). In the Betacam color
difference format, for example, the luminance (Y) and color difference components (R–Y and B–Y)
are derived as follows:
Y = 0.3 Red + 0.59 Green + 0.11 Blue
R–Y = 0.7 Red – 0.59 Green – 0.11 Blue
B–Y = 0.89 Blue – 0.59 Green – 0.3 Red
The G-V color difference signal is not created because it can be reconstructed from the other three
signals. Other color difference conventions include SMPTE, EBU-N1 0 and MII. Color difference
signals should not be referred to as component video signals. That term is reserved for the RGB
color components. In informal usage, the term “component video” is often used to mean color
difference signals.
Color field - In the NTSC system, the color sub-carrier is phase-locked to the line sync so that on
each consecutive line, subcarrier phase is changed 180º with respect to the sync pulses. In the
PAL system, color subcarrier phase moves 90º every frame. In NTSC this creates four different
field types, while in PAL there are eight. In order to make clean edits, alignment of color field
sequences from different sources is crucial.
Color frame - In color television, four (NTSC) or eight (PAL) properly sequenced color fields
compose one color frame.
Color phase - The timing relationship in a video signal that is measured in degrees and keeps the
hue of a color signal correct.
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