HDTV
High-Definition television (HDTV) means broadcast of television signals with a higher resolution than traditional formats (NTSC, SECAM, PAL) allow. Except for early analog formats in Europe and Japan, HDTV is broadcasted digitally, and therefore its introduction sometimes coincides with the introduction of digital television (DTV).
HDTV is defined as 1080 active lines, 16 x 9 aspect ratio in ITU-R BT.709. However, in the ATSC broadcast standard used in the United States and other countries, any ATSC resolution with 720 or more active lines is considered HDTV.
HDTV has at least twice the resolution of SDTV, thus allowing much more detail to be shown compared to analog television or regular DVD. In addition, the technical standards for broadcasting HDTV are also able to handle 16:9 aspect ratio pictures without using letterboxing, thus further increasing the effective resolution for such content.
Advantages of HDTV
1. All commercial HD is digital, so the signal will either deliver an excellent picture, a picture with noticeable pixelation, a series of still pictures, or no picture at all. You would never get a snowy or washed out image from a weak signal, effects from signal interference, such as herringbone patterns, or vertical rolling.
2. Most HD programming and films will be presented in the 16x9 proportioned, semi-widescreen format (though some films created in even wider ratios will still display "letterbox" bars on the top and bottom of even 16:9 sets.) Older films and programming that retain their 4:3 ratio display will be presented in a version of letterbox commonly called "pillar box", displaying bars on the right and left of 16:9 sets (rendering the term "fullscreen" a misnomer). Or, one can usually choose to enlarge the image to fill the screen, however this option will display a distorted, stretched-out picture.
3. The colors will generally look more realistic, due to their greater bandwidth.
4. The visual information is about 2-5 times more detailed overall. The gaps between scanning lines are smaller or invisible. Legacy TV content that was shot and preserved on 35 mm film can now be viewed at nearly the same resolution as that at which it was originally photographed.
5. Two new pre-recorded disc formats support HDTV resolutions. One is the currently available HD DVD, and the other is the as yet unreleased Blu-ray (expected June 2006). Players for both systems are expected to be backward-compatible with DVDs, however the two formats are not compatible with each other.
6. The increased clarity and detail make larger screen sizes more comfortable and pleasing to watch.
7. Dolby Digital 5.1 sound is broadcast along with standard HDTV video signals allowing full surround sound capabilities. (standard television signals broadcast basic stereo audio signals)
Be part of the HDTV revolution...
Could you ever imagine that watching a special effects film in your home could be as enjoyable as going to the cinema? Or, if you are a football fanatic, a movie addict or simply passionate about true picture definition then HDTV is a must – and will blow your mind!
HDTV is more than a new technology... HDTV is a new experience different to what you have ever seen before on TV.
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 625 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.
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 details 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. DVD decks and standalone scalers are starting to appear that upscale standard definition footage to HD. Movies made in 1080p (e.g. the last three Star Wars films) might appear in Blu-ray and/or HD DVD format.
There are very few 1080p screens and projectors around at the moment as the technology is young and expensive. A 1080p screen can de-interlace a 1080i signal or upscale a standard definition one.
What is HDMI/DVI?
HDMI or High Definition Multimedia Interface provides an interface between any audio/video sources over a single cable.
DVI or Digital Visual Interface is a high-bandwidth video connection that carries digitalised picture information. It can also support copy-protection methods.
The DVI specification allows for the presentation device and display device to agree on an optimal picture size and resolution to ensure the highest quality picture automatically.
It is necessary for an HD-ready TV to have HDMI or DVI connectivity in order for it to receive the digital signal.
All TVs on the market sporting the new HD-Ready logo will be able to produce at least a true 720p image.
HD Ready or not?
The HD Ready logo appears on all TV screens and projectors that are compatible with HDTV signals. HD Ready screens must meet the following specification:
Minimum 720 vertical lines (the latter figure when a resolution is written out, e.g. 1280 x 720)
Analogue component video and either
DVI or HDMI inputs
Support for HDCP content protection
Able to display 720p
(1280 x 720 at 50Hz and 60Hz progressive)
Able to display 1080i
(1920 x 1080 at 50Hz and 60Hz interlaced