HD - High Definition

You’ve heard the hype, and now your starting too see the products coming into the market. But just what is HDTV and what does it mean to us? This article will hopefully help put some of those questions into context and help you through the maze of terminology that surrounds the highly awaited launch.

What is HDTV?

The Analogue PAL transmission standard has served us well since the early days of BBC colour transmissions but the current 625 line system is hardly high resolution we are all used to much greater levels of detail in screen images, its more than likely that you are reading this article on a screen set to 800 x 600 or 1024 x 768. HDTV brings enhanced resolutions to the domestic TV set in two standards a vertical resolution of 720p and 1080i the P and I represent the scanning method used P is progressive scan which scans every line of the screen once, the I is for interlaced the same as the PAL system where alternate lines are scanned on each frame.

What can be confusing is that HDTV is used to refer to several things: a type of display device, a digital broadcast method, and a special way to produce TV shows and films. Viewing nirvana is achieved when all three parts of HDTV converge; a programme of film, that is produced using High Definition technology, is transmitted via a HDTV television signal (from a HDTV channel), and enjoyed on a HDTV display (preferably a projector) with a surround sound home theatre audio set up. Watching regular TV or a DVD on a HDTV is visually stunning. And that is why more and more people are getting on the HD bandwagon.

The encoders used for HDTV are complex compared to the DTV standards in use on for example the Bskyb platform, here a single encoder creates an MPEG2 transport stream of anywhere between 2.5 and 6 mbits but HDTV is far more bandwidth intensive requiring at least 15mbits possibly much more depending on the nature of the material encoded. The HDTV encoder is also increased in complexity using overlapping encoding whereby a number of encoders work together to encode the image, each encoders area to scan is overlapped to minimise artefacts around the boundaries.

HDTV Resolution

Resolution, or picture detail, is the main reason why HDTV programs look so good. The standard-definition programming most of us watch today has at most 480 visible lines of detail, whereas HDTV has as many as 1080. HDTV looks sharper and clearer than regular TV by a wide margin, especially on big-screen televisions. It actually comes in two different resolutions, called 1080i and 720p. One is not necessarily better than the other; 1080i has more lines and pixels, but 720p is a progressive-scan format that should deliver a smoother image that stays sharper during motion. Another format is also becoming more well-known: 1080p, which combines the superior resolution of 1080i with the progressive-scan smoothness of 720p. True 1080p content is extremely scarce however, and none of the major networks have announced 1080p broadcasts. Take a look at our comparison chart to see how HDTV competes up against standard TV and progressive-scan DVD.

Name	Resolution	HDTV	Wide-screen?	Progressive-scan?
1080p	1920 x 1080	Y	Y	Y
1080i	1920 x 1080	Y	Y	N
720p	1280 x 720	Y	Y	Y
Widescreen 480p (DVD)	852 x 480	N	Y	Y
Regular TV	Up to 480 lines	N	N	N

What is the benefit to me?

• HD has 2.1 million or more pixels. That is a lot more picture information and that is what makes HDTV so crisp and detailed.
• HD has an aspect ratio of 16:9 versus the 4:3 aspect ratio of analogue. You get one-third more image area and it's that much easier to watch movies in their original format. The 16:9 aspect ratio actually more closely matches the viewing angle of the human eye, making for a more immersive entertainment experience.
• HD images are made up of from 720 to 1080 horizontal scan lines. Again, a lot more detail is possible with that much more visual information on the screen.
• HDTV can provide 5.1 channel Dolby Digital sound, equal to what you hear in a cinema. Plug in a home theatre audio system and you can hear the distinctions between sound effects, dialogue and music. Analogue can't offer anything close to that!

With so much more visual information (more pixels and more scan lines), HDTV provides amazing detail. In fact, many people are startled by the amount of detail they see. And the multi-channel sound and widescreen format make the experience even more rewarding.

Why HDTV?

In order to enjoy all the future high definition programmes, you must have a HD Ready TV. Many programme makers – including the BBC – are already filming in High Definition. And HD will be available through Sky from 2006. You will be able to enjoy a host of your favourite programmes in unbelievable quality. All HD Ready screens will also work excellently with standard broadcasts until the HD broadcasts arrive. Purchasing an HD Ready TV is a way of ‘future proofing’ yourself and enhancing the picture quality and enjoyment you get from the TV.

What is HD ready?

A HD ready TV must have HDMI or DVI connectivity in order to accept a digital signal from the HD receiving equipment. It must also have a resolution of either 720 or 1080 lines. Some projectors do not have this resolution but can support it through compression. If you are unsure whether the projector you are interested in can support HDTV then please contact us.

How do I watch it?

Currently there are only 2 services available in mainland Europe both via satellite, HDTV screens are more similar to PC TFT screens in resolution so its more than likely that decoders will be provided allowing you to use you PC screen, however the refresh rates of these screens can be poor so the US model of specialist HDTV screens hitting the market is starting to be repeated in Europe. It is widely expected that these new screens will have in built HDTV tuners rather than outboard boxes, although Roku and a few other manufacturers have made outboard decoders.  Of course Sony and other large electrical manufacturers have HDTV sets waiting in the wings for European consumers but it is predicted that Europe will be even slower than the sluggish USA to take up HDTV and without government incentives we could be waiting many years.

Broadcasters are starting to shoot material in HD, many films are now edited on HD as its cheaper than film in some instances, plus many live events are now being shot in HD and relayed to the USA and Japan for the HD enabled networks, so there is content available, perhaps not enough to make a good channel.

But with signals taking 4 times more bandwidth, equipment costing much more and very few European households able to watch HD signals its going to take a big push from someone with lots of cash to burn to bring HD into European homes anytime soon.

Watch this space!