Are you too mystified and intrigued by this new kid
on the TV block: high-definition television (HDTV). Expectations
run high, but so is the uncertainty - what is really different
about it, when compared with standard-definition television (SDTV)?
In simplest terms, while both use digital signal, HDTV uses more pixels
(pix-el/ement, physical display unit of image-forming television
screen) per given screen area than standard digital television. This results in finer resolution,
as well as smoother motion and better color definition. This is
especially advantageous with larger TV screen formats, which
with standard pixel number have them enlarged enough to cause
picture granulation. Due to smaller pixel size, high-definition
TV screen has 2-5 better resolution than standard TV.
Compared to a standard (analog) TV, standard digital TV
(SDTV) has the same 720x480 pixels resolution, but has the
advantage of progressive (continuous) scanning (denoted 480p), as opposed to
inferior alternate line scanning (480i, for "interlaced"
scanning) of the analog TV. But even more, digital TV owes its
quality to the properties of a digital TV signal, which
is code based (binary code, 0,1), thus much less affected by the
amplitude loss in transmission. Unlike it, analog TV signal
is flow based, and needs to be re-enforced in transmission by a
number of amplifiers, creating electronic noise and distortions.
Digital TV signal also can be compressed much
more efficiently, allowing for significantly higher channel
For TV screens smaller than 27" DTV
is as good as HDTV. Larger screens, however, benefit from higher
density resulting in smaller pixel size.
High-definition television begins with 1
million pixel level, or 1280x720 pixel screen (also
progressive scanning, thus 720p format). The next larger
format is 1920x1080, which comes either as 1080i (with
interlaced scanning), or 1080p (progressive scanning)
format. There are intermediate formats, such as one used in
Australia, which is termed HDTV there, and "enhanced digital TV"
While interlaced scanning has the advantage of
using only half the bandwidth required by progressive scanning,
allowing it to achieve higher resolution than progressive
scanning for given bandwidth (due to a higher pixel count
possible), its alternate line refreshing mode produces
undesirable artifacts and effects, tending to cause eye strain
and fatigue. Due to this disadvantage, it was quickly abandoned
by the PC industry, and will likely be eclipsed by progressive
scanning in the area of HDTV as well.
HDTV comes with wider screen format. Its
16:9 screen ratio is between the nearly square 4:3 ratio of
standard television, but not as wide as format used for most
movies (from 5:3 to 3:1 screen ratio). It will still some cause
cropping, and display black top/bottom bars when playing such
movies, although less than standard television. On the other
hand, HDTV format will show vertical side bars with some older
TV shows and movies.
Although not inherently part of HDTV, it comes
with top-notch audio quality (Dolby Digital), superior to
standard TV audio. Also, being using digital technology, HDTV
offers steady quality and higher reliability.
So, what do you need to be able to watch HDTV?
Other than high-definition TV set with high-definition screen
and built-in or set-top HD tuner for HD signal processing, you
need - of course - HDTV signal itself. This signal can be
received either by a standard UHF antenna (for local HDTV
broadcasts not transmitted through cable or satellite TV), TV
cable (for HDTV from cable TV service) or HDTV-capable satellite
While non-HDTV set still can receive HDTV
channels, if hooked up with HDTV decoder, you will only have a
partially improved picture quality. And vice versa, HD TV set
often has standard (analog) signal picture showing worse than on
standard TV sets. Part of it is that HDTV sets generally have
larger screens, magnifying picture defects, which are rather
numerous in the analog mode. Adding to that, the superior screen
resolution of an HD television set will often show such defects
more clearly than lower resolution standard TV screens.
Nothing is perfect, and that includes HDTV. But
if you want large screen television, HDTV is the way to go.
Available HD programming is booming, and some technical problems
still plaguing the execution will likely be soon remedied. If
you are for HDTV, the time is on your side.
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