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HDMI has the capacity to support
existing high-definition video formats (720p, 1080i, and even
1080p). It also has the flexibility to support enhanced
definition formats such as 480p, as well as standard definition
formats such as NTSC or PAL.
First we need to look at the types
of video available and how they work, then look at whether they
are compatible with HDMI.
The format of composite video is that of a picture only analog
television signal before any sound signal is combined in and
both signals are modulated onto an RF Carrier. Composite video
is so named because it is usually a composite of three source
signals, named Y, U, and V. Composite video uses an analog
interface. Composite video uses one signal line to carry the
entire set of signals.
S-video stands for separate video and may also be known as Y/C
video. S-video uses two separate signals, color and brightness,
to carry video data. It does not use the same cable to carry
audio signals. S-video uses an analog interface and is video
signal in analog. S-video is one type of component video.
S-video is not like composite video, which carries the entire
set of signals in one signal line. S-Video, as it is usually
implemented, carries high-bandwidth 480i or 576i resolution
video, for example, standard definition video. It doesn't carry
audio on the same cable.
Component video consists of a video signal that has been split
into at least two components. The types of analog component
video include RGB analog component video, Y'PbPr analog
component video, and S-video analog component video. The various
RGB (Red, Green, Blue) analogue component video standards
typically offer the best analogue video signals available in
consumer electronics. RGB uses no compression and offers no real
limit in color depth or resolution. Many televisions, especially
in Europe and Japan, utilize RGB via the SCART connector. All
arcade games, excepting early vector and black and white games,
use RGB monitors. Analog RGB is slowly falling out of favor as
computers obtain better clarity using Digital Video Interface,
DVI, and home theater moves towards HDMI.
Digital Video Interface, or DVI, is actually a predecessor of
HDMI. Digital Video Interface was made by the Digital Display
Working Group (DDWG). The original design for DVI included
conversion of analog signals by converting analog into a digital
signal. This was done so that both analog and digital signal
monitors could be accommodated by DVI. Data is transmitted by
the use of transition minimized differential signaling (TMDS)
protocol and provides a digital signal from a PC's graphics
subsystem to the display unit. There are actually three types of
DVI. There is DVI-A and this type of DVI is used for analog
signals like VGA. The second type of DVI is DVI-D. This type of
DVI is used for digital signals, and this type of signal is the
one that all home theater products use and that are intended for
consumer home use. DVI-I is the third type of DIV. This type is
a combination of DVI-A and DVI-D. There are two levels of
performance are supported by DVI-I. These levels are single link
and dual link. Currently all home electronics products are
designed around the single link standard. A dual link cable,
however, is 100 % compatible with a single link cable plus the
dual link cable offers the benefit of adaptability in the future
for any wide band width applications. DVD-I is a complete, fully
digital video transport protocol that is supportive of all
digital video formats including 480p, 480i, 540p, 720p,1080p,
and 1080i.
HDMI technology uses a digital interface instead of an analog
interface. With an analog interface the digital signal is
converted to an imperfect analog signal, sent to the display
unit, then the signal is converted back to digital so it can
display the signal. When the cable is translated into analog,
some of the signal's quality is lost. HDMI uses a digital
interface which means that the signal starts out digital, stays
digital through the transmission, and is received as a digital
signal by the receiving display. Because there are no signal
conversions this keeps the digital signal strong with no
degradation.
Whether the video source is a PAL, NTSC or ATSC standard, HDMI
will fully support it. The creators behind HDMI claims that it
supports every video format in the consumer electronics
industry. Due to the three TMDS channels each capable of 3.4Gbps
bandwidth, HDMI supports video resolutions from 480p to 1080p
and even higher, 1440p, and supports 48bit color resolutions in
the RGB or YCbCr color space, with HDMI 1.3 adding support for
xvYCC color space. |
