HDTV or not 

1 July 2006 tbs.pm/1146

I wonder if you invested in an HDMI/HDCP-equipped flat panel display and an HD box to watch the World Cup in Hi-Def? Well, let’s not talk about that then. But have you seen Wimbledon in HD? The World Cup looks pretty amazing (if the system is set up correctly and dodgy HDMI chips in the box haven’t blown up your plasma), but Wimbledon looks even more amazing.

The reason is that in this country, broadcasters have decided to use 1080i (1080 lines, interlaced) as the standard for HDTV. Certainly, it’s one of the two most popular formats. The other is 720p (720 lines, progressive scan). Interlaced television divides each image into two fields, one with the even-numbered lines and the other with the odd-numbered lines. With progressive, the whole frame – with all the lines – is shown in one go, so the complete image is shown twice as often (this takes up more bandwidth, and this is why they transmit fewer lines). In fact, all flat panel displays, like computer screens, are progressive, even if you’re watching interlaced broadcasts (where something in the chain will de-interlace it for you).

Because it has more lines, 1080i (which was originally designed for CRTs, not flat panels) is great for static scenes, where the camera moves slowly or not at all, little is moving and you can enjoy details like being able to count the blades of grass in the Centre Court.

720p, however, because there are more complete pictures per unit time, is great for sporting events where the camera as well as the personnel zip around the field – such as football for example. With progressive scan, motion artefacts are minimised and the fact that there aren’t so many lines is not so apparent.

That, then, is one reason that Wimbledon looks better than the World Cup in Hi-Def – and cricket will probably be the same. (Another reason is that the BBC have been doing Wimbledon in HD for donkey’s years, even though most of us have never had the gear to see it.)

But if the powers that be decided to use the World Cup as the peg to hang HD on, why did they choose to employ 1080i for it when 720p would be visibly better – and sets are required to do both anyway?

A Transdiffusion Presentation

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