Ensemble Designs 7555 HD / SD Video Processing Frame Synchronizer - Manual (Page 62)

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7555 HD/SD, 9550 3G/HD/SD, and 9550-XA 3G/HD/SD Video Processing Frame Synchronizers
signal with more detail or fidelity. Thus, a video digitizer with 12 bits of resolution will capture 4 times
as much detail as one with 10 bits.
Blanking
The Horizontal and Vertical blanking intervals of a television signal refer to the time periods between
lines and between fields. No picture information is transmitted during these times, which are required
in CRT displays to allow the electron beam to be repositioned for the start of the next line or field.
They are also used to carry synchronizing pulses which are used in transmission and recovery of the
image. Although some of these needs are disappearing, the intervals themselves are retained for
compatibility purposes. They have turned out to be very useful for the transmission of additional
content, such as teletext and embedded audio.
CAV
Component Analog Video. This is a convenient shorthand form, but it is subject to confusion. It is
sometimes used to mean ONLY color difference component formats (SMPTE or Beta), and other times
to include RGB format. In any case, a CAV signal will always require 3 connectors – either Y/R-Y/B-Y,
or R/G/B.
Checkfield
A Checkfield signal is a special test signal that stresses particular aspects of serial digital transmission.
The performance of the Phase Locked-Loops (PLLs) in an SDI receiver must be able to tolerate long
runs of 0’s and 1’s. Under normal conditions, only very short runs of these are produced due to a
scrambling algorithm that is used. The Checkfield, also referred to as the Pathological test signal, will
“undo” the scrambling and cause extremely long runs to occur. This test signal is very useful for testing
transmission paths.
Chroma
The color or chroma content of a signal, consisting of the hue and saturation of the image.
See also Color Difference.
Component
In a component video system, the totality of the image is carried by three separate but related
components. This method provides the best image fidelity with the fewest artifacts, but it requires
three independent transmission paths (cables). The commonly used component formats are
Luminance and Color Difference (Y/Pr/Pb), and RGB. It was far too unwieldy in the early days of color
television to even consider component transmission.
Composite
Composite television dates back to the early days of color transmission. This scheme encodes the
color difference information onto a color subcarrier. The instantaneous phase of the subcarrier is the
color’s hue, and the amplitude is the color’s saturation or intensity. This subcarrier is then added onto
the existing luminance video signal. This trick works because the subcarrier is set at a high enough
frequency to leave spectrum for the luminance information. But it is not a seamless matter to pull
the signal apart again at the destination in order to display it or process it. The resultant artifacts of
dot crawl (also referred to as chroma crawl) are only the most obvious result. Composite television is