TV Blog

Over the last few weeks, this BBC TV blog has tried to bring you insights on a diverse selection of programmes: From the final return of Ashes To Ashes, it has travelled to new children's series ZingZillas , by way of Cracking Antiques, and Over The Rainbow.

It is a selection that highlights the breadth of programming on the BBC at any one time. But all those programmes were also made in High Definition (HD) and are shown on the BBC HD channel in addition to standard definition channels as a result.

HD is undoubtedly buzzing this spring - take a look at any advert for anyone who sells TVs and associated boxes, or wander around your local shopping centre or supermarket.

A few years ago HD was specialist television - it is now pretty much everywhere. Around 23 million HD-ready TV sets are estimated to have been sold in the UK, and 70% of the TVs sold in the last three months of 2009 were HD-ready according to the broadcasting regulator Ofcom.

But there are millions of people across the UK who mistakenly believe that once they've got their HD-ready TV they are watching HD pictures, regardless of whether they've installed an HD set-top box or Blu-ray player as well, according to the British Video Association.

So in case you are thinking of investing - either for programmes you are passionate about experiencing in true HD, or perhaps because you want to see the World Cup in June shown in full in HD for the first time - I thought it might be helpful to explain what you need to do, because getting HD pictures to the screen you want to watch them on is not absolutely straightforward.

An HD-ready TV is the first step. But you will also need an HD tuner. That could be built into your television set - the popularity of integrated TVs for general digital television viewing means that there are integrated Freesat HD TVs available, and a range of Freeview HD TVs have already arrived in shops, with more expected.

Alternatively, you will need an HD set-top box, which may or may not be combined with a hard disc recorder (like Sky Plus HD for example). And the days of the Scart lead are numbered - you will need the HD version, known as an HDMI lead - to connect your box if you have one to your television.

You can get HD from all the main digital television providers. Freesat, Sky and Virgin have had HD available for some time. Freeview has just launched a selection of HD channels, with availability across the UK increasing steadily, and a developing range of alternative equipment.

Choosing the right equipment and getting it into your home gives you the ability to watch HD television, but doesn't mean that everything you watch going forward will be HD. HD channels require more capacity than standard definition - so broadcasters need to create them specially and additionally to existing services. So BBC HD, and the other broadcasters' HD channels are separate entries on the channel guide (for the BBC Channel 50 on Freeview HD, 108 on Freesat and Virgin, and 143 on Sky).

Even then, you should not assume that everything on an HD channel is in fact in HD. The BBC HD channel only broadcasts programmes made in HD. To count as an HD programme, the vast majority of the pictures have to have been shot using broadcast-quality HD cameras (not usually the HD camcorders that you might use at home). The pictures then have to have been processed as HD too.

Within an HD programme there may be a small amount of standard definition material - the BBC, in common with most other broadcasters, allows up to 25% of a finished HD programme to be non-HD.

We don't do that to save money - but because sometimes we need to use library pictures or sections of old films which were not made in HD, or we need to use very small cameras - for example for secret filming - which have been slow to develop in HD at the quality level needed.

When the BBC started out in HD television, we wanted to use the channel we had available to offer as much HD programming as possible. We also guessed that we would find programmes we wanted to make in HD across our channels. So BBC HD does not follow the schedule of just one of our existing services but pulls in HD programmes from all of them.

This means that you can find Doctor Who (BBC One), and Doctor Who Confidential (BBC Three) on the channel, as well as Who Do You Think You Are? (BBC One), and Dragon's Den (BBC Two), and the World Cup (largely BBC One), Wimbledon (largely BBC Two) and Glastonbury (BBC Two and BBC Three) this summer.

But the majority of HD channels available in the UK are "simulcast channels". This means that they show exactly the same programmes at the same time as standard definition channels but when the programmes have been made in HD you will be able to view them in HD.

Most sport and much drama are now produced in HD, but it is still developing as a way of making programmes and therefore you will see a certain amount of "upscaled" programme. Upscaling means that the number lines in the Standard Definition (SD) picture are effectively doubled - from 576 to 1080 - to fill the HD screen.

In some people's opinion - and depending on the size of screen and the cameras used to make the programme - this can produce better pictures than on the equivalent SD channel. But it is not HD (and on BBC HD we don't do that).

So, to sum up, if you want to watch HD programmes, they need to be made in HD, shown on an HD channel, and you will need an HD TV coupled with an HD tuner inside the TV or in a box connected with an HDMI lead. There is more detailed advice on our website and trust me - you need no more technical expertise than is required to operate a remote control.

I believe - like many others who watch HD - that HD can deliver simply incredible television. I'd like every HD viewer to experience that, rather than feel let down by pictures that feel rather ordinary, and may in fact be standard definition.

Not every programme will blow you away - I've never found that to be the case in any medium with any range of content, and as programme producers I know that we're still learning how to get the best out of the technology in every situation. But I hope as you travel into HD you will find some outstanding examples of HD.

As someone once wrote to me, it can be like the excitement of the move from black and white to colour, seeing the television screen transform, and the world inside it come alive.

Danielle Nagler is controller of BBC HD