==== The EG HDTV Guide ====|
High Definition is set to be the TV buzzphrase of 2006. With next generation consoles, Satellite Broadcasting and next gen DVD formats set to launch in the next 12 months, it's all a bit of a minefield out there - and there is a hell of a lot of misinformation being spread (understandably). I hope this guide helps a little. It's very very WIP, and I really appreciate any commenst / correction as most of what's written is from memory - the rest is munged off the web where needed. Enjoy!
== HDTV - What resolution counts as High Definition? ==
720p = 1280 x 720 progressive
1080i = 1920 x 1080 interlaced. The standard for most US and Japanese High Definition broadcasting.
1080p = 1920 x 1080 progressive.
== HDTV - What resolutions don't count? ==
480i or p = US (NTSC) DVD / Digital TV format.
576i or p = UK (PAL) DVD / Digital TV format.
== So, what shape should the screen be? ==
All HDTV formats are 16:9 (thats a 16 units wide by 9 high ratio). What is known generically as 'widescreen'. Or, erm .. oblong!
== Key: ==
All TV displays and their drawing methods use the term 'lines' to refer to horizontal picture elements:
- An interlaced image draws alternate odd and even lines (known as fields) in quick succession a certain number of times a second. Disadvantages are a noticeable flicker and line twitter.
- A progressive image is displayed 'progressively' by drawing all lines of the picture from top to bottom. The advantage being a much more solid / stable / watchable image.
== Refresh Rates: ==
A term for describing how often a display is updated:
50hz - Used across europe and Australia. Display is updated 50 times a second. With
60hz - Commonly used in US displays (and many countries around the world). Display is updated 60 times a second. For interlaced displays this means 60 fields (interlaced line groups), for progressive the entire screen.
100hz - Not actually a TV / Video standard. In fact a post processing technique (invented by Philips) which attempts to reduce flicker in interlaced displays by effectively updating the screen (repeating every frame twice) every second. Disdvantages include motion artifacts such as judder, and many complain of smearing due to poor processing. Can be found on many modern CRT TV's.
== Key: ==
Hz = "The unit of frequency; one Hertz has a periodic interval of one second". In english this means how many times per second a display is updated. So for a 720p image at 50hz the screen is updated progressively 50 times a second.
== What does High Definition ready mean? ==
It's an industry initiative to improve consumer understanding and help prospective buyers know what they are gettingfor their money.
Put simply, if the TV has an HD Ready label it SHOULD support:
What this usually means is that the screen will 'accept' and display images of the above format. Usually it means that the screen will upscale and downscale images where necessary. e.g. 1080i will be downsized to fit the native resolution of the screen in question.
The unit SHOULD also support HDCP over HDMI (see Jargon below) - which will be cricial once High Definition broadcasting and copy protected material becomes availake over the air and via cable / satelite providers.
== Screen Tech (what is there out there?): ==
Below you'll find a list of specific screen technology, with accompanying variations that utilise it.
CRT - Cathode Ray Tube: "A CRT works by moving an electron beam back and forth across the back of the screen. Each time the beam makes a pass across the screen, it lights up phosphor dots on the inside of the glass tube, thereby illuminating the active portions of the screen. By drawing many such lines from the top to the bottom of the screen, it creates an entire screenful of images."
-Standard Televisions: Everyone's probably got one somewhere. Disadvantages include low definition (image blurring), crosstalk and line twitter / unstable images. CRT is considered 'older' technology these days and are generally undesirable due to their bulky nature. However, there are many excellent CRT screens being produced, and in fact High Definition CRT's are still very popular in the US.
-Front Projectors: Uses a series of Red, Green and Blue guns to fire a convergent image onto a projection screen. Generally regarded as one of the best home projection methods. However they are very expensive, massively bulky and require professional levels of maintenance and calibration.
Plasma - Gas Plasma: "Plasma technology is different from that used in other display systems in that red, green and blue lights are created in every pixel, reducing the need for space. Charged electrodes between glass panels cause tiny pockets of inert gas to change a state of plasma. This process causes UV light to be produced, which in turn reacts with the red, green, and blue phosphors in each pixel to produce visible light.
Unlike traditional displays, where the image is scanned across the screen, in plasma displays all pixels are "lit" at once. Having no electron beam, back lighting or light polarization, the image is inherently sharper and brighter. Perfect from edge to edge. "
- Plasma televisions: Offer sharp and vivid images with good colour registration. Disadvantages include ppor screen life (screen burn susceptible with images static for long periods of time), images can lack contrast and many early screens had problems registering blacks well causing a lack of depth in most images.
LCD - Liquid Crystal Display:
- standard Televisions: The current darling of the high-street, boasting excellent colour fidelity, but poor contrast.
- Front Projectors: Use LCD panels mounted in series, light is projected through panels onto a projection screen. Advantages include, great image size, colour fidelity and clarity. Disadvantages include: low brightness in ambient lighting conditions, poor contrast on lower end models.
DLP - Digital Light Processor: Tecnology uses an array of tiny spinning mirrors to reflect light at specific times in order to make an image. Far better explanation of the technology can be found here.
- Rear Projection TV: DLP source image is bounced off a mirro onto the reverse of a forward facing screen. Advantages, outstanding brightness, excellent viewing angles. Disadvantages, colour wheel used in DLP tech can cause headaches.
- Front Projectors: As LCD but usig DLP tech. Advantages, outstanding brightness and contrast - even in ambient lighting conditions. Disadvantages - see colour wheel headaches above.
== Near Future Tech: == ***WIP***
SED (Surface-Conduction Electron-emitter Display) from Toshiba. Benefits include sharper, brighter, faster displays with the low profile sizes of LCD and Plasma panels.
SXRD (Silicon X-tal Reflective Display) - Projection specific technology used in Sony's high-end 'Qualia' projection systems. More info here.
3-Chip DLP - Actually present / past technology this but prices are dropping, currently used mainly for HighEnd cinema projection systems. This system uses 3 DLP chips for Red, Green and Blue (RGB) elements of the image. Standard DLP projectors only use one chip which essentially produces a monochrome image, colour is added by use of a colour wheel in front of the assembled image. This can cause headaches as the colour 'spin' speed can be detected by the human eye and brain. This is not a problem with a 3 Chip solution, as no colour wheel is involved. More info at the bottom of this page.
== What about the games? ==
The new generation of consoles are set to push HD gaming into the public's perception at last. Whilst both the PS2 and the X-Box supported both 720p and 1080i, they lacked the muscle to make use of them accross the board. With Xbox 360 and PS3 boasting heaving masses of powerful graphics power, most games are expected to be presented in 720p.
== Cables and connectors: ==
VGA / HiD 15 Pin - Carries high quality analogue signals. Commonly used for connecting PC graphics cards to monitors.Can also be used to connect Plasmas, LCD monitors and Projectors.
DVI / HDMI / HiD Centronics - Digital video carrier. Currently the best way to transport High Definition TV signals from source to display. Compatible with HDCP.
M1 Universal - "M1 cables (also known as EVC or P&D cables) work with projectors and other devices with the new universal M1 connector. M1 can carry both digital and analog signals as well as USB. Many new projectors on the market utilize this new technology to provide the flexibility of connecting to either VGA or DVI inputs.
". More here.
Component - Analogue, usual comprising 3 RCA terminated coaxial cables. Commonly used to carry High Defnition and Standard Definition progressive signals.
More accurate technical explanations along with diagrams can be found here.
== General Jargon: ==
Deinterlacing / Reinterleaving: The process of displaying a once interlaced in a progressive format. Very complex area, I suggest reading more here if you are interested.
HDCP - High Definition Copy Protocol. Protection applied to broadcast and consumer HD material. More here
DRM - Digital Rights Managment. A way of licensing and protecting copyrighted diditally distributed material. More here
== DVD and BluRay: ==***WIP***
== What can I expect from my Current Standard Definition Material: ==
Buying an HD Ready display will NOT make low resolution standard definition material look magically better. Digital terrestrial and Satellite TV currently suffers from an incredibly poor bandwidth allocation. What that means effectively is that although you can receive a genuine 16:9 anamorphic image, due to compression artifacts (the worst known as macroblocking) the image quality is often far worse than that of a standard analogue image.
However, this is not to say you cannot enjoy improved quality from your regular definition sources. Apart from Progressive Scan (which is mentioned above) if you own a medium specced PC, it is likley you have the equipment necessary to enhance your DVD's. Home Cinema PC's excel in image quality for many reasons - one of the biggest is utlilising the PC's power to accurately upscale from standard DVD resoltuon (see above for reference) to a higher resolution (for example 720p). Although you might simply say "but theres no more detail on show - why is it any better". Well, as far as actual detail on show - you'd be right, as far as presenting your HiDef unit with the best possible source image to display (essentially bypassing the often inferior upscaling / deinterlacing onbaord the display) the PC offers advanced scaling calculations, and also offers post processing on the image (you can sharpen, soften AND process the image to remove certain compression artifacts).
So, a warning - don't expect miracles from your shiny new HiDef ready set - it won't be able to (on it's own at least) make your bog standard TV and DVD's look better.
Edited by silentbob at 22:19:23 11-12-2005
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