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VGA Output |
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VGA is the abbreviation of Video Graphics Array. "VGA port" is also called
"D-Sub port". A standard VGA connector has 15 pins and is shaped like a
trapezoid. It arrays 3 rows, with 5 pins for each row. The image signals saved
in the digital format (frame) will be modulated to high frequency signals in
RAMDAC, and output as camera images. This can save the process of
matrix-decoding the electric circuit conversion. The VGA video frequency
transmission process is the shortest and has many advantages, such as the
crosstalk non-electric circuit synthesis separation loss.
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DVI Output |
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DVI port is used to display RGB signals by connecting to the PC graphic card
which supports digital output. DVI (Digital Visual Interface) is a digital
display interface standard introduced by the DDWG (Digital Display Working
Group) established on Intel Developer's Forum in Sep. 1998. DVI digital signals
are better than standard VGA signals. The digital jack can ensure that all the
contents will be transferred in the digital format and the signal integrity in
the process of transmission from the mainframe to your monitor to get clearer
images.
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BNC Output |
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BNC jack is a connector used for a coaxial cable. BNC stands
for "Bayonet Nut Connector" (describing the shape of this jack symbolically),
also known as"British Naval Connector" (possibly because it was firstly used by
British Navy) or "Bayonet Neill Conselman" (Neill Conselman is its inventor).
BNC cable has 5 connection pins to receive red, green, blue, horizontal
synchronization, and vertical synchronization signals. BNC tie-in is a special
monitor jack, different from a normal D-Sub 15 pin connector. It is composed of
red, green, blue, row synchronization, and field synchronization signals, and
mainly used in connecting the system that has high requirements for the scan
frequency, such as the workstation.The coaxial cable with BNC tie-in is one
kind of the shielded cable and has the advantages of long transmission distance
and stable signals to isolate the video input signals and decrease the signal
interferences. Furthermore,its signal bandwidth is larger than ordinary D-SUB
to achieve the best signal responses.
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Standard Video Output (RCA) |
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Also called the AV jack,RCA is usually paired inwhile (audio)
or yellow (video), and connected by putting the standard AV line with a male
RCA connector into the corresponding female RCA connector. The AV jack can
separate the transmission of audio and video to avoid the interference between
audio and video frequencies and prevent the decreasing of the image quality.
Because AV jack transmission is the mixed video signals of brightness /
chromaticity (Y/C), the image output devices should separate brightness /
chromaticity, and then decode the chromaticity to form an image. This process
will inevitably damage color signals, and the interference between Y/C signals
is also highly possible, which will affect the final image output. Because of
these defects, it cannot be used in some situations that excellent images are
highly demanded.
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S-Video Output |
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Super-Video, a faster video transmission with
clearer images to receive better video output. It divides Y/C signals when
video information is received and transmitted via different channels. When sent
to a television, this produces sharper images than the composite video, where
the video information is transmitted as a single signal over one wire. This is
because televisions are designed to display separate Luminance (Y) and
Chrominance (C) signals. (The terms Y/C video and S-Video are the same.)
Computer monitors, on the other hand, are designed for RGB signals.
Most digital video devices, such as digital cameras and game machines, produce
video in RGB format. The images look best, therefore, when output on a computer
monitor. When output on a television, however, they look better in the S-Video
format than in the composite format.
To use S-Video, the device sending the signals must support S-Video
output and the device receiving the signals must have an S-Video input jack.
Then, you need a special S-Video cable to connect the two devices.
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Video Chromatism Output |
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Component Video is delivered, similarly, with the color
information split up three ways. However, component video uses a
"color-difference" type signal, which consists of Luminance (the "Y" or "green"
channel, representing the total brightness of the image), Red Minus Luminance
(the "Pr" or "Red" channel), and Blue Minus Luminance (the "Pb" or "Blue"
channel). The sync pulses for both horizontal and vertical are delivered on the
Y channel. The display calculates the values of red, green and blue from the Y,
Pb and Pr signals. |
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RGB Signal |
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The representation of multicolor signal is important in
numerous video technical standards. The primary color signals are constituted
of red, green, blue which we call RGB signal. As the digital technology
develops, we're able to express any color in the world as constant or variable.
We call the method of encoding the color as number "color space" or "color
zone". As the RGB is one of numerous color spaces, each color can be expressed
as three variables 每 red, green, blue light intensity in this encoding method.
RGB is the most popular scheme of displaying and recording color image. In
order to keep compatible with the early B/W Display System, most producers
change RGB space to YUV space. To display color signal, turn YUV to RGB again. |
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YUV Signal |
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YUV (YCrCb) is a color encoding method adopted by Europe TV
System (belong to PAL). YUV is used to optimize the transmission of color
signal and keep compatible with old B/W TV System. Narrow bandwidth is a great
advantage of YUV while RGB demands three independent signals transmitting
synchronously. In YUV, "Y" is short for Luminance or Luma while "U" and "V" is
short for "Chrominance" or Chroma which is to describe the color and saturation
of the image and to specify the color of pixels. "Luminance" is created by
superposing the particular part of RGB signals while "Chrominance" defines two
parts of hue and saturation expressed by Cr and Cb. Cr reflects differences
between the red part of input RGB signals and the luminance of RGB signals
while Cb reflects differences between the blue part of input RGB signals and
the luminance of RGB signals. That is the so-called Chromatic Signal or
Component Signal (Y, R-Y, B-Y). |
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Composite Signal |
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Composing luminance signals, color signals and synchronous
signals into one signal forms the composite signal. The composing process is
called encoding. Color signals and luminance signals encoded are hard to
separate from each other without signal loss. That's the reason why we think
the quality of S-Video is higher than the composite signal. |
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