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HIGH DEFINITION TELEVISION (HDTV) EXPLAINED

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For consumers shopping for a new TV set, HDTV has become an incredibly popular choice for television buyers who want a superb picture quality with extremely detailed images and full, rich colours. If you have seen HDTV programming you will already know that the comparison of image quality between a high definition (high def) television and one displaying a regular analog TV signal is very different.

Most consumers want a HDTV because they look so good, but not everyone understands the technology behind HD television and how it works. This Projector Source Canada article will help you to understand why the picture quality in high definition is so much better than "standard definition".

We will also explain the different HD TV resolutions (such as 1080i and 1080p). The different HD resolutions will be explained in the following sections, together with the implications of HDTV for the future of television signals.

What is HD television?


In today''s market place, large Plasma and LCD television screens and television signals and movies displayed by projectors are becoming increasingly more common. This has made the limitations of Standard Definition Television more noticeable.

HDTV, or high-def TV stands for High Definition Television. It displays TV images in four times as much detail as the current analog "standard definition" NTSC (National Television Standards Committee) format.

Resolution is the main reason why TV pictures look so much better in HDTV than in Standard Definition. On a High Definition television displaying a High Definition signal source, over two million pixels are utilized to create images. As a result, TV pictures displayed in High Definition appear clearer, more vibrant, and have much greater depth. If you are watching a movie in your home theatre system, High Definition can add an extra layer of immersion, while sporting events appear in incredible detail. A recent survey actually revealed that nearly 50% of HDTV owners cited the fantastic quality of HD sports as the reason for their purchase.

The Differences between HDTV and NTSC standards


NTSC is the current analog "standard definition" television format used in the USA, Canada, Mexico, Japan and several other countries. NTSC stands for the National Television Standards Committee which is the standardization body from United States that adopted it.

HDTV, however, is the television signal of the future and over the coming years will gradually overtake NTSC as the standard used to output videos. The HD television format differs from NTSC in three main ways:

Aspect ratio


HDTV displays content using a widescreen aspect ratio of 16:9 where as NTSC uses a 4:3 aspect ratio.

Signal type


Data in HDTV format is transmitted via digital signal instead of an analog signal that NTSC images use (this is because digital television, or DTV, requires less bandwidth if the video signal is compressed sufficiently). As a result, much more information can be transmitted in an HDTV signal, such as a multi-channel digital audio.

Resolution


The resolution on a HDTV image is shown at either 1280 x 720 or 1922 x 1080. Comparatively, NTSC uses a relatively low 640 x 480 resolution.

It is important to note that because of the resolution HDTV signals use, if you are thinking of purchasing a projector to display HD television you should ensure that you buy a projector that can support these resolutions. For example, a SVGA resolution projector is unable to output High Definition content because of the way it maps images. Instead it will display an image with a resolution compatible to NTSC. If you wish to view HDTV images then a XGA resolution projector is advisable, as it will output an image closely matching an HDTV resolution.

The Different HDTV Resolutions


When discussing HDTV resolutions, the terms 720p or 1080i are frequently used. These terms refer to the two HDTV resolution output mentioned above, 1280 by 720 and 1922 by 1080. Simply put, the larger the resolution, the sharper and more detailed the image will appear.

The letter "i" or "p" after the number 720 or 1080 refers to the way in which the image is displayed. The "p" signifies that the device uses a "progressive scan" technique. An "i" means the image will be displayed using an "interlaced" technique.

A progressive scans redraws every line of the picture each time it is refreshed, meaning a smoother picture will result that will remain sharper in motion scenes. Comparatively, an interlaced image only redraws every second line, resulting in an image of slightly higher resolution, but an image that displays more image artefacts. Consequently, progressive scan is the most popular image renderer.

What is the best HDTV Resolution?


The best resolution HDTV can output in is 1080p, meaning that the HD display device portrays an image with a resolution of 1922 x 1080 pixels using a progressive scan image rendering technique. 1080p will be the most expensive choice of HD television, but many consider it worth the extra money due to the extremely high quality image produced.

Television signals in the near future


Multiple governments are now setting mandates to replace analog TV signals with High Definition digital TV signals. Following the Digital Television Transition and Public Safety Act of 2005, all analog transmissions will be turned off as of February 17th 2009.

HD or HD Ready?


As a result of television signals switching to digital transmission in the near future, there has become an increasing demand for High Definition TV sets. To meet such demand a television standard known as "HD Ready" has come into production. To achieve the HD Ready logo of approval the television must be capable of displaying resolution of 720p, 1080p, or 1080i via component or digital input. These televisions provide a way to "future proof" yourself. You can enjoy current broadcasts perfectly, and ensure that when the switch to HDTV occurs your television will be capable of displaying them.

Benefits of HDTV


There are numerous reasons why HDTV is worth upgrading to:

  • Millions of extra pixels are used to displays images, resulting in a far sharper, better quality picture.
  • The aspect ratio of HDTV signals is 16:9, meaning the displayed image area is increased by a 1/3.
  • Films use the same aspect ratio as HDTVs, meaning that the image can be displayed without black borders.
  • The audio quality that the majority of HDTV signals broadcast in is Dolby Digital 5.1, which enables users to experience full surround sound.
  •  The option to have an image rendered using progressive scan is available, meaning images can be displayed to look smoother.
  • Unlike analog television broadcasts, there is no ghosting or fuzzy images when using HTDV signals.
  • The graphics in the latest videogames look far superior when rendered in High Definition.

Blu-ray


Blu-ray is the next generation of DVD format used for playing high definition content, named after the blue laser used to write the data. Blu-ray discs and DVDs look identical, Blu-ray disks are capable of storing up 46 gigabytes of data where as a DVD can only hold a maximum of 7 gigabytes. All film studios produce both high definition Blu-ray and a standard definition DVD discs when a film is release. Be aware that Blu-ray discs are not playable on standard DVD players. Therefore if you ever want to watch a high definition film at home, you will need to own a separate Blu-ray player.

HDTV Cabling


The two types of cables that carry High Definition signals are HDMI (High-Definition Multimedia Interface) and DVI (Digital Visual Interface) cables. HDMI signals are superior in that they are substantially smaller and contain both audio and visual information, where as a DVI signals only carry visual data and so separate audio cables are needed.
HDMI signals incorporate a digital rights management technology known as High-bandwidth Digital Content Protection. Indeed HDMI is viewed as the evolution of DVI due to the extra functionality it offers.


We hope you enjoyed this article by Projector Source Canada.  For more information, or to purchase a display and projector for your business or home, visit us online at http://www.projectorsourcecanada.ca or contact us at 1-800-821-3021.

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