HDTV
frequently asked questions

Answers to questions about HDTV

More affordable products. That means a more viable choice. Sky satellite services and Cable TV providers are continuing to provide an increasing number of High Definition feeds.

But the issues surrounding HDTV can easily confuse the selection/buying decision. Many new models are appearing with various badges, abbreviations and letters which look and sound high-tech and they are. But you'll still need to understand what they actually mean and if they really will add something to your viewing
experience.

After reading the answers here, you'll be better informed and you'll be able to make your own decision.

What's the difference between digital TV and analogue TV?

The video signal of analogue television is transmitted in AM, whilst the audio is transmitted in FM. Analogue TV is subject to interference, such as ghosting and snow, depending on the distance and location of the TV receiving the signal.

Also, the amount of bandwidth assigned to an analogue TV channel restricts the resolution and overall quality of the image. The current analogue signal standard (in the UK) is referred to as PAL. It's based on a 625 line system for transmission and display of video images.

Digital TV, on the other hand, is transmitted as data bits of information, just as computer data is written or the way music is written on a CD.

This digital signal is basically "on" or "off". To put it another way, you either see an image or nothing at all. There is no gradual signal loss as distance from the transmitter increases. If the you are too far from the transmitter or in an odd location, there is nothing to see.

On the other hand, unlike analogue, digital TV has been designed from the ground up to take all the main factors of the television signal into consideration: B/W, colour, and audio and can be transmitted as an interlaced (lines scanned in alternate fields) or progressive (lines scanned in linear sequence) signal. As a result, you have is a far better picture.

Since the Digital signal is made up of "bits" (the same bandwidth size that takes up a current analogue TV signal) it can handle not only a higher quality image in digital form, but the extra space not used for the TV signal can be used for extra video, audio, and text signals.

Broadcasters can supply more features, such as surround sound, multiple language audio, text services, and more in the same space now taken by a standard analogue TV signal. There is one more advantage to the ability of a Digital TV channel's space; the ability to transmit a High Definition signal.

Finally, another difference between Digital TV and Analogue TV is the ability to broadcast in true widescreen (16x9) format. The shape of the picture more closely resembles the shape of a cinema screen, which allows you to see a film as the film maker intended. In Sports, you can get more of the action in one camera shot, such as viewing the entire length of a football pitch without making look like it is a long distance away from the camera.

A 16x9 TV can display widescreen images without a large amount of picture space taken up by black bars on the top and bottom of a widescreen image, which is what you see with images on a standard TV. Even non-HDTV sources, such as DVD can also take use 16x9 TV.

Is there a Difference between Digital TV and High Def TV?

This is where things can become confusing. All HDTV is digital, but not all Digital TV is HDTV. The same bandwidth for digital TV broadcasting can either used to supply a video signal (or several) and other services, or can be used to transmit a single High Def signal. Although there are several standards for digital TV, Digital TV has come down to these standards: 720p, and 1080i.

720p

720p (720 lines of resolution scanned progressively) is also a digital TV format. Not only does 720p give a very smooth, film-like image due to its progressive scan formula, but image detail is at least 30% sharper than standard. And so 720p brings very good image upgrade that is visible on both medium (32"- 36") size screens as well as larger screen sets. Also, even though 720p is considered high-definition, it takes up less bandwidth than 1080i, which is covered next.

1080i

1080i (1,080 lines of resolution scanned in alternate fields consisting of 540 lines each) is the most commonly used HDTV format. 1080i provides the most detailed image of all the broadcast standards. On the one hand the visual impact of 1080i is lost on smaller screen sets (below 36"). However, with the increasing amount of large screen projection sets and custom front projection home cinema setups, 1080i delivers the detail needed for large images.

Two drawbacks to 1080i are:

1. It takes up the most bandwidth of all the Digital TV broadcast formats.

2. It is an interlaced signal, which means that the displayed image is made up of lines that are scanned alternately instead of progressively as in 480p and 720p.

But, if you have the money, there are processors that will actually convert an image all the way into a 1080p image. This essentially removes any visible scan lines, so you see very smooth edges.

The results of this conversion are totally impressive.

What do I actually need to buy to watch HDTV?

Basically you need to get several things:

1. A source of High Def programming: Broadcast, Satellite, or Cable.

Before you make any decision on whether to buy an HDTV of any type, check to see if High Def service is available in your area.

2. An HD-aerial, HD-satellite box, or HD--cable box, or HD-Set-top box.

You need to find out about High Def programme sources. That determines what you'll need to receive signals.

Make sure you know the costs of their service, and whether you need to pay a fee to hire or to buy their High Def TV box. Ask if a generic High Def TV set-top box can be used instead of their box. Lastly, make sure you understand which channels are offered.

3. An integrated High Def TV or an HD-upgradable (or HD-ready, HD-compatible) TV.

An integrated HDTV is one that has a built-in High Def tuner built in to the TV. The advantage is that you don't have to spend more money for an external box to receive High Def. But, the downside is that if you subscribe to a cable or satellite service, their box may be required to receive their HD channel service. Also, if standards or technology do change, you are stuck with the tuner you have in the set.

An HD-upgradable, HD-ready, or HD-compatible TV has everything you need to watch HDTV once your High Def signal is acquired, but you must add an additional set-top box to actually receive High Def signals.

The good thing about this is that you have the flexibility to add the type of set-top box that suits your needs, such as broadcast, satellite, or cable. But then you may have to pay, hire, or lease the set-top box on top of paying for the TV itself.

A growing number of HD-ugradeable televisions will have a special slot that allows Cable TV providers to simply insert a special card, referred to as a Cable Card, that enables your TV to receive cable television channels, including HDTV channels.

Of course, you still have to pay subscription fees, and the card would have to be removed if you move to another area with a different service. Since the Cable Card is inserted into the TV directly, you may still need a separate cable box for you to be able to record cable TV channels on your VCR or DVD recorder. You must check all this out.

Will my current TV still work after Digital and High Def take over in the UK?

The original target date for full UK use of digital and High Def has moved. The process of switchover will take place gradually between 2008 and 2012 (ITV region by ITV region). The UK analogue TV signal will totally cease in 2012.

Many people are under the impression that when the change to total Digital TV Broadcasting occurs that all current TVs will be "obsolete". However, external set-top boxes are available now (and will be at reasonable cost in the future) that will mean that older TVs could still be used.

The set-top box just converts a DTV/HDTV signal to an Analogue TV signal that can be linked to any TV. You won't get any of the higher resolution pictures of Digital TV or High Def TV and all widescreen programmes will appear as letterboxed on your analogue set. But at least it extends useful life of an older, but still functioning TV.

Most of the same set-top boxes designed to be used as tuners for High Def TVs can also downconvert High Def TV signals for use with an analogue TV. The big plus about this is that the same box you may need to use to downconvert HDTV for viewing on an analogue TV, can also be used as your HDTV tuner, once you decided to make the move to HDTV.

Also, if you want to go all out now and buy a High Def set, all currently available sets can also be used to watch normal TV programmes, because all of them (except some flat panel monitors) have standard analogue TV tuners built-in, regardless of whether or not they also include an HD tuner or require and external set-top box for receiving HD programming.

With prices of the digital TVs coming down to affordable levels and sales of digital TVs continuing on a steady pace, the vast majority of TVs in UK households by the end of the decade will be digital. That's when the analogue-or-digital issue will be put to rest.

Why are black bars sometimes still on a 16x9 High Def screen?

In some cases, when watching films - you may still see black bars to the top and bottom of a 16x9 image, as some films were and are made in wider ratios than 16x9.

For example: Original High Def programming is made in the 16x9 (1.78) as aspect ratio, which fits the dimensions of High Def TVs. But, many cinema films are made in either the 1.85 or 2.35 aspect ratio, which is even wider than the 16x9 (1.78) aspect ratios of High Def TVs. So, when viewing these films on an HDTV (if in their original aspect ratio) - you will see black bars on your 16x9 screen. However, the bars will be less noticeable than if the same film was letterboxed on a standard 4x3 set.

It's not whether image fills the screen, but that you are seeing everything in the image that was originally filmed. Being able to view the entire image as originally filmed is certainly the more important issue, rather than be concerned about how thick the black bars are, especially if you are looking at the image on projection screen, which is a large image to begin with.

On the other hand, when viewing a standard 4x3 image on a 16x9 set, you will see black or grey bars on the left and right side of the screen, since there is no information to fill that space.

However, you can stretch the image to fill the space, but you will distort the proportions of the 4x3 image in doing so. This results in objects appearing wider horizontally. Once again, the important issue is that you able to view the entire image, not whether the image fills the entire screen.

Depending on how the images are formatted, the entire image may or may not fill the entire screen surface. However, the screen surface on a 16x9 Television is able to allow for more variations in image aspect ratio than the traditional 4x3 analogue televisions.

Why do analogue TV signals often look worse on a High def than on an analogue TV?

In most cases, an analogue video signal will not look as good as it would on an analogue TV set. There are two basic reasons for this:

1. The video processing circuitry upscales the image, which can improve the good aspects of the image. At the same time, however, the video processing also will magnify the defective parts of the image, such as interference and video noise that is not as noticeable on a lower resolution analoue set.

In this case, the quality of the video processing in the TV can have either a positive or negative effect on the degree of correction for poor analogue signals.

2. If you have upgraded from a 26-inch (as an example) analogue television, to a large screen Plasma (lets say 42-inches) - the lower resolution analogue image will degrade somewhat since you are blowing the image up to a larger size. This is particularly noticeable on VHS recordings as VHS is such a poor quality source to begin with.

In some cases, it may not only be the TV that is a fault. If you receive your television channels through the air, it may be simply a matter of geography as to the quality of your incoming signal, however, you may be able upgrade your aerial.

If you get poor analogue reception on your High Definition Television and you subscribe to a digital service, switching to digital or HD cable or having the cable service come out and check your line may also help to improve things.

Just be aware that by 2012 (as it stands now), all broadcast signals are scheduled to go digital and the poor analogue broadcast issue should then be just a thing of the past.

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