HDTV: Are You Ready?
David Beamish provides a handy guide to help you choose the right HD screen
Anyway, enough of that blithering. High Definition is something which is going to affect us all and it seems to have been presented to the consumer so poorly that many do not know how to tell if a TV is actually High Definition or just compatible with a High Definition input. Therefore I will go over the simple checklist shortly and explain roughly what it all means and what you should look for in a new screen. Whilst pertinent to most markets, this is going to be based on the HD Ready spec developed by EICTA in Europe. The spec defines that there is more to a TV being HD Ready than just having a certain resolution. Even if not in Europe, you might want to consider these specs when looking for a new screen.
A Brief History of Time
Non-High Definition televisions are now called standard, or even low definition. This is said to reflect the resolution of the screen. Up until recently resolution was something best left for computer screens, but now it is something more of us will have to come to terms with. Basically it is a measurement of the amount of pixels on the screen usually defined as widthx height. If you’d like more info on that, check out Wikipedia. Since all high definition screens have a wide aspect ratio, I will only compare them to the standard definition widescreen sets—assuming older 4:3 sets are now obsolete. If you would like more information on aspect ratios, or are unfamiliar with the jargon, please read both of our short articles on the subject (part one here, part two here) before continuing.
Standard definition resolutions differ between countries, formats and aspect ratios, and whilst that sounds a lot it is fairly simple to follow. These are defined by the number of horizontal lines that run across the screen which is also how High Definition is measured. Whilst you might not have heard standard television resolutions described this way, it is useful to know about as a comparison tool.
As well as resolution, an image on screen is defined by how it is presented. There are two options here: Interlaced or Progressively Encoded/Scanned. An interlaced image updates alternative lines on the display every cycle—fast enough for many to not notice—and progressive scan images update every line with every refresh cycle. This gives a more solid image with less flicker, however it is twice the information to carry.
|Format||Number of horizontal lines|
|Standard Television (NTSC: USA, Japan)||480|
|Standard Television (PAL: Europe)||576|
|Standard DVD (NTSC: USA, Japan)||480|
|Standard DVD (PAL: Europe)||576|
Standard television broadcasts utilise an interlaced image. However, certain games consoles and DVD players (amongst other devices) support a progressive output. Therefore, as well as 480i and 576i, we also have 480p and 576p. Since this is a step up from standard definition, this has been termed Enhanced Definition but people seem to rarely use this description, more often than not, defining it by its content (480i, 480p etc.). Maybe it is this that will be how HD is referred to in the future—everything will be HD but the resolution will get larger.
“Dwell in the past and there will be no future”
High Definition sets have several easy to understand requirements that, for some reason, many people just do not know about. Perhaps it is to do with the current lack of HD source devices, which has meant, aside from the screens, there is nothing for the public to conceptually grasp as HD. Once HD broadcasting comes truly of age the knowledge will be more widespread, but that is going to be a bitter pill to swallow for those who have purchased ‘flat screen’ televisions only to find they are not going to be compatible with the new broadcasting systems. Incidentally, does anyone know why they are called ‘flat screen’ TVs? My old Sony CRT had a flat screen—thin screen makes more sense in defining these new toys. I digress.
The minimum number of horizontal lines that a screen must have to be classed as HD is 720, and these should be able to display a progressive format video. Therefore we can term this 720p—all HD Ready screens must have 720 horizontal lines. This is generally coupled with a width of 1280 pixels however this is not always the case. Check out the caveats section below. Since humans view in a widescreen aspect ratio (there is a debate about the actual aspect ratio, but it seems to be around 1.78:1 or 1.85:1—something close to 16x9 anyway), televisions have been moving into a wide format for several years now. The introduction of DVDs and widescreen broadcasting has helped push this concept forward and from this we realise our second HD Ready requirement—the screen must be in a wide aspect ratio.
The HD Ready specification also includes requirements for the inputs of the screen. Most of these televisions will come with such inputs as Composite, S-Video, SCART (if you live in Europe!) and even VGA for connection to a PC, but these are all additional to that defined in the specification. An HD Ready screen must have two very specific inputs and these are:
- Component: Analogue YPbPr input
- DVI or HDMI: Digital input
Not to be confused with a single composite input, a component input features three RCA type connectors and does support high definition. However, the yellow composite input is normally accompanied with a red and a white audio lead. A component lead carries video only. If the set has a DVI input then it must also support HDCP which is a form of copy protection. HDMI sockets support HDCP by default.
Finally, a small techy bit—the digital inputs have to support the following:
- 1280x720 @ 50 and 60Hz progressive scan (‘720p’)
- 1920x1080 @ 50 and 60Hz interlaced (‘1080i’)
Nb: that is not to say the component input does not need to support these. It is just assumed it does since it is required to support HD signals as industry standard. Here is the accompanying quote from the specification for that part:
HD ready displays support analogue YPbPr as a HD input format to allow full compatibility with today's HD video sources in the market.
Also, this does not mean it has to have 1080 horizontal lines—it just means it has to accept the input and then scale it to the panel’s native resolution. It is generally better to use an input signal as close to the panels native display as possible to prevent the need for any scaling.
The final requirements of an HD Ready screen
So there we have our HD Ready list of requirements:
- Have a minimum of 720 horizontal lines
- Be widescreen
- Have a component analogue input
- Have a DVI with HDCP or an HDMI digital input
- Support via the digital input 1280x720 @50 and 60Hz progressive scan (‘720p’)
- Support via the digital input 1920x1080 @50 and 60Hz interlaced (‘1080i’)
“Yes sir this is HD Ready screen I do you good deal”—caveats
Unfortunately we consumers need to have our wits about us when purchasing a new screen in Europe at least since as I just mentioned, signals can be scaled. This means it could be possible to have a screen with less than 720 horizontal lines claiming to be ready for high definition material because it can accept the input and scale it down to the screens native resolution. Therefore, whilst the screen can accept the signal, the viewer will not get the full benefit from it since it has been squashed down to fit into the smaller screen resolution.
I would also be wary of certain plasma screens. I saw one recently which had 768 horizontal lines—should be enough to display a full HD signal right? Not quite! You see it only had 1024 vertical lines instead of 1280 which would be needed to display a full 1280x720 resolution image. That also makes it sound like it is a square screen but plasmas (I heard on a forum where we were arguing on this screens legality in using the HD Ready logo) can have rectangular pixels so it did look like a widescreen set. This is just something for you to be wary of. I didn’t spend too much time on it since I don’t own a plasma screen and don’t intend to buy, one but if you do, make sure you check the entire resolution. Perhaps the spec should have been a little more explicit to cover off occurrences such as this.
One spec to rule them all!
Just when we thought we knew what was going on, those clever people at EICTA, obviously bored and needed to justify their jobs, have created another spec, which was released in March. This specification is called HDTV and you can get info on it at the EICTA website.
This defines access to the above HDTV logo and was made to identify devices that “are capable of receiving and processing High Definition television signals broadcast over terrestrial, cable and satellite or pre-recorded“ .
This makes reference to devices which can themselves receive and generate an HD signal, for instance a TV with an integrated HD tuner/receiver, or an HD set top box. It states that the HD Ready specification should be inherently implied by the use of the HDTV logo and so all HDTV logo equipped screens will follow the above guidelines from the HD Ready specification.
So there you have it. I hope that has helped to clear things up a little and that you can use this page as a reference for your HD queries.
Editorial by David Beamish
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