Composite video combines the three basic elements of a video picture
(color, brightness, and synchronization data) into a single combined
("composite") signal.
S-Video, also called Y/C, uses two separate video signals. The luminance (Y)
is the black & white portion, providing brightness information.
The chrominance, or chroma (C) is the color portion, providing
hue and saturation information.
In essence, an S-video signal is a composite signal that has been divided
into two. This video signal, transmitted with
color and brightness on two separate channels, makes for
a sharper picture image, with less granularity, on the receiving
device.
S-Video is carried on cables
terminated with 4-pin Mini-DIN connectors.
Other types of cables (such as the Apple ADB cable) also use this
same connector, although the type of wire used is different.
Since digitized granularity looks worse than analog granularity,
S-Video is preferred over composite video whenever this is an option.
TV/CATV:
Coaxial TV Cable signals are carried as a single, composite-type 75-Ohm
analog signal. Usually, RG59 or RG6 coaxial wire is used, and terminated
with a screw-locking F-type connector. RG59 wire is usually
suitable for runs up to 750 feet without boosting, and the more robust RG-6 wire
is suitable for up to 1500 feet without boosting. The maximum signal
strength allowed by the FCC is 15.5dBmV, so attenuators can be added when the
signal is too high, and tilt compensators for long-distance runs.
RGB:
Although Component Video is sometimes referred to as RGB video,
RGB is not actually a video standard, but rather a standard for
computer monitors. It requires a four conductor cable for connecting
a monitor to a CPU. In concept, it is similar to S-Video. Three
of the conductors carry color information for the red, green and
blue components of the image, while the fourth, called the "sync"
or synchronization line, carries timing information to be used
concurrently with the color information.
Because RBG separates the video signals based on color information and
not luminance/chroma, it is possible to create an
RGB to VGA cable without electronic conversions.
In this sense, RGB is not the same as component video, although component uses
cables with red, green, and blue heads. Both component and RGB use separated
signals for improved quality, but the signals themselves are fundamentally different.
Component video is the final generation of analog video, taking the
advancement from composite (1-signal) to S-Video (2-signals) one
step further. It has separated luma (brightness) and chroma (color),
but the chroma is also separated into two signals, red and blue.
The result is a triple-headed RCA cable and
an image cleaner than composite with less color bleeding that
S-Video. Although common on most DVD players and HDTV's,
component video is very rare on older TV sets and VCR's.
It is important to remember that with component video, the triple-
headed cables are often colored red, green, and blue, but they do
not carry color signals. Generally, these cables are known as YUV,
Y for luma and UV for the two chromas. On monitors and DVD players,
the connectors are usually labeled Y/Cb/Cr, for Luma (Y), Chroma Blue (Cb), and Chroma Red (Cr).
Component also can be used for high-definition output to HDTV compatible displays.
When component video is used as hi-def, it is labeled Y/Pb/Pr, to distinguish it
from standard component (Y/Cb/Cr). In this case, rather than using a YUV signal,
the video is transferred on a Progressive Scan signal, for high resolutions on
every frame.
Another group of standards combine technical and legal definitions.
These are called ATSC, NTSC, PAL, and SECAM.
ATSC
ATSC stands for Advanced Television Systems Committee, but the acronym is
synonymous with the group's standard for digital television broadcast. ATSC
is used for over-the-air transmission of HDTV signals, replacing the former
analog standard NTSC. It can support video resolutions up to 1080p and 5.1 surround
audio, and can be picked up on the same frequency UHF/VHF antennas as NTSC.
NTSC
NTSC stands for National Television Standards Committee, and is
synonymous with the video transmission standard for North and Central America, including
Mexico and Canada, and Japan. Its technical format is 525 lines per
frame at roughly 30 frames per second refresh rate. The video is interlaced over
the even and odd scanlines, for an apparent refresh rate of ~60fps.
In quality, NTSC is equivalent to a composite signal.
but is not necessarily equivalent to the output from a
video capture card that may claim to be NTSC-legal.
NTSC is no longer utilized in the United States, having been replaced with the
digital ATSC standard in 2009.
PAL
PAL (Phase Alteration Line) is the European counterpart to the NTSC
standard. It has a higher vertical resolution (625 lines per frame)
but a lower refresh rate (25 frames per second) that can cause
flickering. It is the standard for the UK, Western Europe, the Middle
East, and parts of Africa and South America.
SECAM
SECAM (Systeme Electronic Pour Couleur Avec Memoire) is very similar
to PAL. It specifies the same number of scan lines and frames per
second, but differs in that chrominance (color) is FM modulated.
It is the broadcast standard for France, Russia, and parts of Africa
and Eastern Europe.
Written by DataPro International Inc.
Unauthorized duplication strictly prohibited.
