Home
List of Articles
|
 |
How to Avoid the HDTV Resolution Trap
There's a great deal of nonsense talked about HDTV and much of
the noise comes from manufacturers' and retailers' advertising
which in some cases is extremely misleading.
One of the areas of greatest confusion is resolution. Resolution
is defined as the number of pixels - the elements which make up
a digital image - in an image and is usually quoted as a x b,
where a is the number of pixels across the screen (horizontal)
and b is the number of pixels up and down (vertical, also
referred to as the number of lines). In this article we'll
explain everything you need to know about the number of pixels
required for HDTV.
HDTV Specification
The HDTV specification provides for three different types of
HDTV, denoted by the number of lines of resolution and the
signal type. They are:
1080p (1080 lines, progressive scan)
1080i (1080 lines, interlaced)
720p (720 pixels, progressive)
Any TV not capable of displaying at least 720 lines is not
'HDTV ready' and any signal with fewer than 720 lines is not an
HDTV signal.
Interlaced or Progressive?
The 'i' and 'p' in the HDTV specification refer to interlaced
and progressive scan. The analog TV we've been watching for
years is interlaced. That simply means that each frame of video
(of which there are 30 per second in NTSC and 24 per second in
PAL) is split into two fields. Each field contains alternate
lines of the signal (one has the odd, the other the even) and is
displayed for 1/60th of a second (1/48th for PAL). Because it
happens so fast, your brain interprets each frame as a single
image. Progressive scan signals have no fields, they simply
display each frame in its entirety for 1/30th (or 1/24th) of a
second. This results in a higher quality image, particularly
noticeable in fast-action broadcasts such as sporting events.
So every TV that can display 720 lines is HDTV ready?
No, and this is one of the key areas of confusion. The other
important element of the HDTV specification is that signals must
be broadcast in 16:9 widescreen. This is known as the aspect
ratio, where '16' refers to the width of the image and '9' to
the height. In other words, the height of the picture is 9/16ths
of the width.
Some manufacturers promote TVs with a maximum resolution of 1024
x 768 pixels as HDTV ready. This is incorrect. Although the
total number of vertical pixels is greater than the 720 minimum
necessary for HDTV, at an aspect ratio of 16:9 it would need
1280 pixels horizontally to display a 720-line HDTV picture. The
only solution is to either squash or crop the picture, neither
of which is satisfactory.
So, in order to be properly HDTV capable, a TV needs to be able
to display at least 1280 pixels horizontally as well as at least
720 vertically.
About the author:
Kenny Hemphill is the editor and publisher of The HDTV Tuner.
Visit him at http://www.the-hdtv-tuner.com and discover why HDTV
is the most exciting thing to happen to television since the
advent of color TV. Better still, keep up to date with the
latest developments in HDTV and high definition DVD by
subscribing to the news feed. Click the link for details.
Written by: Kenny Hemphill
|
|
Recent Articles
Free Satellite TV deals -- Myth or for Real?
Free satellite TV is the biggest myths on the internet, is this statement true? I would say it’s true if you DON’T understand correctly the word ‘FREE’ in this offer! Free satellite TV doesn’t mean you can get a TV for free. Free satellite TV...
The Start of Television
A six year-old commented, "TV is so necessary. What would I do
without it?" I told him TV is a rather new invention and the
idea of it dawned on its makers about a century ago. It is a
stirring thought that something playing such an important...
What is PocketDISH?
PocketDish by Dish Network is an ingenious video, music, game
and photo device that's compact enough to fit into a pocket or
purse. You can store TV programs, music, your favorite games and
photos on PocketDish.
PocketDish was created by...
Why Go To The Theater When You Can Bring The Theater To You
So, have you gone to the movies lately? Let's face it, in
this day and age, going to the movies isn't what it's
cracked up to be. Recent studies have shown that box office
ticket sales have steadily declined over the years and the
...
|
