21st Oct 2004

High definition television explained

High definition television (hdtv) is a new type of digital television that has come to the forefront within the last 3 years. Digital television improves on conventional TVs by producing better pictures and better sound.

Better Pictures

Digital television improves picture quality by changing the way pixels are activated. Pixels are the tiny dots on the television screen, noticeable on close inspection. Hundreds of thousands of these combine to form a picture on the television screen by lighting up in one of three primary colors – red, green or blue.

Pixels are arranged in lines from top to bottom with 480 lines being chosen as the standard for conventional analog televisions. Each row of pixels is also known as a line of resolution. In the original design, the pixels are activated when an electron gun shoots electron particles from the back of the tv and hit the screen, lighting up each pixel. Unfortunately, the electron gun was technologically limited in that it was not fast enough to shoot enough electrons at the screen to light up all 480 lines of resolution in an instant that was also not noticeable to the naked eye. Consequently, the electron gun was designed so as to light up each odd line of resolution and then each even line of resolution. To the naked eye, the picture then appeared smooth (unless compared to the new technologies). This was known as 480 interlaced.

This technology stayed the same for over 60 years until now. Now, digital television has revolutionized the technology behind the television.

Digital Equals Better

Digital tv is actually a term that encompasses a number of television formats. The two things in common amongst all these formats are that they are all broadcast digitally and that they all improve a regular television’s picture quality in some way.

The most basic of the digital television mediums is Standard Definition TV (sdtv). Sdtv still uses 480 lines of resolution and is interlaced. However, because it is digital, more pixels are lighted on each line of resolution as compared to analog broadcasts. The result is a sharper image. The improvement over regular analog television is equivalent to the improvement a dvd player has over a regular cable broadcast.

While sdtv is a major improvement over analog, there are higher digital formats capable of producing even better pictures. Enhanced digital television (edtv) is able to produce a picture by progressive scan rather than interlacing. In that case, the picture is shown at once since all the lines of resolution are lighted up sequentially rather than by interlace. This is known as 480 progressive or 480p.

Beyond SDTV and EDTV

Beyond edtv, there is the top of the line digital television, High Definition Television (hdtv). Unlike sdtv or edtv, hdtv televisions show pictures either in 720 progressive lines of resolution (720p) or 1,080 interlaced lines of resolution (1080i). Most people can’t tell the difference between the two and both are a huge improvement over both sdtv and edtv. Additional details such as the dust kicked up from a baseball player rounding third or the beads of sweat coming down a boxer’s face can clearly seen as if you are right in the action.

Wider Screen and More Action

Additionally, hdtv is shown in wide screen, 16:9 format whereas sdtv and edtv are shown in 4:3 format. This increases the “theater” experience at home. Wide screen means you’ll be able to see more of the action in a sports event, all of the stage in a music event and all of the angles in a movie.

Plug and Play

Since not all programs are broadcast in high definition, an hdtv has the ability to automatically switch to show shows that are broadcast either in analog, sdtv or edtv.

Surround Sound

In addition to increased visual detail, hdtv broadcasts are in Dolby Digital surround audio format. Coupled with the stunning pictures an hdtv is capable of producing, surround sound completes the whole home theater experience. Surround sound in Dolby Digital is incredibly realistic and clear, and truly allows you to feel a part of the show. Keep in mind that most high definition televisions don’t come with any sound system so you’ll need to separately purchase a great system, but it is well worth it. After all, why would you want to pair up a Yugo-type sound system with a Ferrari-type television?


When shopping for a new digital television, keep in mind that a TV that is simply Digital cannot display HDTV information. A Digital TV can only display 480i or 480p images (SDTV and EDTV). These TVs are perfect for watching DVDs, or Digital broadcasts, but you won’t be able to take advantage of the higher quality HDTV has to offer (unless you have a true HDTV).

Also, be aware that hdtv-ready does not mean you are able to watch high definition shows. HDTV requires an HDTV tuner or receiver. For hdtv-ready sets, you’ll need to purchase those separately. This is meant to reduce the cost of the set or for consumers wanting to wait until there is more programming available on television in HD format. Still, even without the ability to receive HD signals, an hdtv-ready set represents a good compromise and is still capable of producing pictures better than sdtv and edtv.

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