HD Explanation

High Definition Channels.

HD channels available are; Sky Sports 1, 2 & 3 HD, Sky Movies Premiere HD, Sky Screen 1 & 2HD, BBC HD (limited broadcast), Sky One HD, Artsworld HD, National Geographic HD, Discovery and Sky Box Office HD and more.

For more information on Sky HD boxes follow this link

On the 7th June ITV HD was launched but it is only available with a Freesat HD box by using the red interactive button.

What is HDTV?

1080i

A 1080i screen has 1080 lines from top to bottom and 1920 pixels from left to right. Our old analogue televisions used to have 576 lines from top to bottom so by increasing the lines to 1080 we achieve a much more detailed picture. The 'i' after 1080 is an abbreviation for 'Interlaced' and it refers to the way the picture is painted (or refreshed) on to the screen. The screen is painted in 2 passes (2 stages). The first pass paints the 540 even numbered lines on the screen, then the second pass paints the 540 odd numbered lines. These 2 passes together make up the picture of 1080 lines. This process is carried out 30 times every second. Because of the 2 passes per frame method in a 1080i signal, a 1080i screen is capable of producing a true sharp picture only when the image is frozen or barely moving.

720p

A 720p screen has 720 lines from top to bottom and 1280 pixels from left to right. It still has more detail than your old analogue television but not as much detail as the 1080 screen. However, the way the picture is painted differs from the 'Interlaced' method described above. The 'p' after 720 is an abbreviation for 'Progressive' scanning. Rather than painting the picture in 2 stages the screen is completely refreshed in a single pass. This happens 60 times every second and these additional scans provide a better flicker-free picture when viewing fast moving scenes such as sports, action movies or the pictures from your games console. With this in mind you could argue that a 720p screen provides a better picture than 1080i. But you should also consider that in order to display a 1080i picture on a 720p screen the resolution would be reduced from 2.07 million pixels (1080 screen) to just 0.92 million pixels (720p screen) meaning a reduction of 66% of the pixel information.

1080p

If you want the best of both worlds then a 1080p screen is what you need. It offers the full 1080 x 1920 resolution and the smooth stable progressive scanning. Unfortunately this technology comes at a premium so you may want to wait until the price comes down before you buy. Furthermore there is not much to offer at the moment (April 2007) in the way of 1080p broadcasts. Sky TV transmissions are either 720p or 1080i and unless you own a Blue-ray DVD player or a Playstation 3 then you will not notice any difference.