HDTV Introduction

k@lkov

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HDTV
High-definition television (HDTV) is a digital television broadcasting system
with a significantly higher resolution than traditional formats (NTSC, SECAM, PAL).
While some early analogue HDTV formats were broadcast in Europe and Japan,
HDTV is usually broadcast digitally, because digital television (DTV) broadcasting
requires much less bandwidth if it uses enough video compression. HDTV
technology was first introduced in the United States during the 1990s by
a group of electronics companies called the Digital HDTV Grand Alliance.


How does it work?
HDTV or High Definition Television offers the highest quality picture
available in the world of home entertainment. Instead of using the
conventional 576 lines to plot a TV picture, HDTV uses 720 or 1080
lines. In addition, the pixels in each of those lines are closer. This
results in a hugely improved picture quality, clarity and colour definition.

Note: Remember that the quality of your picture depends on the source
of the broadcast as well as the quality of your TV. You can watch Freeview
(576 lines) on a Plasma or LCD screen, but the quality will not be as good
as Sky (1080 lines). A Plasma or LCD TV will actually scale whatever source
it is fed to fit the screen.


The differences between 720p, 1080i and 1080p
HDTV broadcast pictures come in two formats. The first is 720p
("p" stands for progressive), which is an image comprised of 1280
lines along the horizontal by 720 vertical lines. It shows the whole
image in a single frame – that is, progressively.

The second is 1080i, which measures 1920 x 1080 lines and is displayed
as two fields that are interlaced. You get a bit more detail with 1080i
but the interlaced image is not as smooth as a progressively scanned one.

A high-res screen with at least 720 lines will show both formats but only a
1080-line screen will show 1080i footage at its best, i.e. in an un-scaled form.

As far as Sky is concerned it will be down to the programme maker to
choose which format to use.

The 1080p format, which is the absolute best form of HD is not used by
broadcasters. Movies made in 1080p (e.g. the last three Star Wars films)
might appear in Blu-ray and/or HD DVD format. Sony's PlayStation 3
produces 1080p output.

There are more and more 'Full HD' screens (capable of displaying 1080p)
appearing. A 1080p screen can de-interlace a 1080i signal or upscale a
standard definition one. With very few 1080p sources available, the main
benefit of a Full HD screen is its ability to map a source such as Sky TV
(1080i) pixel for pixel to the screens resolution (ie 1920 x 1080).

What is the Difference Between Digital TV and HDTV?
Here is where things may start to get confusing for the consumer.
All HDTV is digital, but not all Digital TV is HDTV. As stated previously,
in the answer to question #1, the same bandwidth for digital TV
broadcasting can either used to supply a video signal (or several)
and other services, or can be used to transmit a single HDTV signal.

Although there are technically 18 different standards for digital TV
broadcasting (all Digital TV tuners are required to decode all 18
standards), the practical application of DTV has come down to 3
standards. These standards are: 480p, 720p, and 1080i.

480p
If you have a progressive scan DVD player and TV, you are familiar
with 480p (480 lines of resolution, scanned progressively). 480p is
similar to the same resolution of standard broadcast TV (and is referred
to as SDTV or Standard Definition Television), but the image is scanned
progressively, rather than in alternate fields.

480p does provide an excellent picture (especially on smaller 20-27"
screens). It is much more film-like than standard cable or even standard
DVD output, but it only provides half the potential video quality of an
HDTV picture, therefore its effectiveness is lost on larger screen sets.
Although 480p is part of the approved DTV broadcasting scheme, it is
not HDTV. This standard was included as one of the DTV broadcasting
standards to provide broadcasters the option of providing multiple channels
of programming in the same bandwidth as a single HDTV signal. In other
words, 480p is just more of what we already have with only a slight
increase in image quality.

720p
720p (720 lines of resolution scanned progressively) is also a digital TV
format, but it is also considered as one of the HDTV standards. As such,
ABC, and now FOX, have committed to 720p as their HDTV broadcasting
standard. Not only does 720p provide a very smooth, film-like image due
to its progressive scan formula, but image detail is at least 30% sharper
than 480p. As a result, 720p provides an acceptable image upgrade that
is visible on both medium (32"- 36") size screens as well as larger screen
sets. Also, even though 720p is considered high-definition, it takes up less
bandwidth than 1080i, which is covered next.

1080i
1080i (1,080 lines of resolution scanned in alternate fields consisting
of 540 lines each) is the most commonly used HDTV format, and has
been adopted by PBS, NBC, and CBS (as well as satellite programmers
HDNet, Showtime, and HBO through special feeds) as their HDTV broadcast
standard. Although there is still debate as to whether it is that much
better than 720p in the actual perception of the viewer, technically,
1080i provides the most detailed image of all the 18 approved DTV broadcast
standards. On the one hand the visual impact of 1080i is lost on smaller
screen sets (below 36"). However, with the increasing amount of large
screen projection sets and custom front projection home theater setups,
1080i provides the detail needed for such large images.

However, the two drawbacks to 1080i are:
1. It takes up the most bandwidth of all the DTV broadcast formats.
2. It is an interlaced signal, which means that the displayed image
is made up of lines that are scanned alternately instead of progressively
as in 480p and 720p. However, if you have the bucks, Faroudja markets
a processor that will actually convert a 1080i image into a 1080p image.
This essentially removes any visible scan lines present in the interlaced
1080i image, resulting in very smooth edges.

Sources: HomeTheater and HDtvorg.
 

ig0r

Administrator
Messages
7,161
Ultra-high-definition television

Ultra-high definition television includes 4K UHDTV (2160p) and 8K UHDTV (4320p), which are two digital video formats proposed by NHK Science & Technology Research Laboratories and defined/approved by the International Telecommunication Union (ITU).

4K UHDTV
4K UHDTV has a 4K resolution of 3840 × 2160 (8.3 megapixels).

8K UHDTV
8K UHDTV has a resolution of 7680 × 4320 (33.2 megapixels).
It has 16 times the number of pixels of the existing 1080p HDTV, which brings it to roughly the detail level of 15/70mm IMAX. NHK advocates the 8K UHDTV format with 22.2 surround sound as Super Hi-Vision.
 
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