What is HDTV?
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).
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).
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