Technology: HDTV explained

What is HDTV, what does HDTV mean?

HDTV High definition Television is the first major change to TV since color was introduced in the 1950's. HDTV signals are digital instead of analog like 'standard' TV's, digital HDTV images are much clearer, and HDTV sound is far superior to standard television.

4:3 TV screen

The difference between HDTV and regular TV

Standard TV

  • A standard TV breaks up each image into 480 lines. It very quickly draws these lines on the screen in two passes of 240 lines each. It first draws all the even-numbered lines, then draws the odd-numbered lines. This odd/even drawing is called an interlaced image. Because the TV draws these lines so quickly, they appear as one image. This interlacing of the 480 lines that makes up each image on a standard TV is known as 480i. 480i means the picture is made up of 480 lines that are interlaced.
  • Standard television is broadcast over the air with an analog signal. Because of this analog broadcast signal, the image is susceptible to interference. If you have ever seen TV "snow" or TV "ghosts" you know how poorly an analog TV signal can look.
  • Standard TV signals have an analog sound signal. Sometimes the sound is transmitted in stereo.
  • Standard TV's have an aspect ratio of 4:3. This means a standard television screen is nearly perfectly square.

High Definition Television (HDTV)

  • A true HDTV image is transmitted in 1080i format. This means that each image is broken up into 1080 lines, and the HDTV draws them interlaced between odd and even lines, 540 lines at a time. Because the image is made up of far more image lines than standard TV, the image is far more clear and colorful. Most HDTV's also support 720p which is an image made up of 720 lines drawn progressively or, all at once. Some newer HDTV's also support 1080p, 1080 lines, drawn progressively (at the same time). As a comparison, a DVD is recorded in a format 480p, but if you watch it on a standard TV, it will display as 480i. If you think that a DVD is clear and colorful, it is nothing compared to a good 720p or 1080i HDTV image!
  • High Definition Television signals are transmitted digitally. Because the nature of digital is either "on" or "off", there is no snow and no static with HDTV. You either have a 100% digitally perfect image, or you have no image at all. Sometimes, if the signal is fluctuating between good and bad, you may encounter digital "blocks" or "tiling" in the image. This is as close to digital static that you will find.
  • HDTV sound can transmit in stereo or digital 5.1 surround
  • High Definition TV's have an aspect ratio of 16:9, making them rectangular. Because of the wider image format, HDTV's display movies as they were intended to be displayed in the theater.

HDTV screen

All HDTV is digital, but not all digital is HDTV!

HDTV is, by definition digital, but this does not mean that all digital is High Definition! Most cable companies and all satellite TV services offer digital transmission and digital TV channels, but this does not necessarily mean these channels are HDTV! Most digital channels are simply a standard 480i television signal transmitted through the cable, or via the satellite digitally. This amounts to a very clear image, and no snow or static, but the image is still a standard, 480i, 4:3 television image. Most cable and satellite TV companies charge more to enable HDTV service. In most cases you also need an HDTV cable or satellite box made to work with your particular cable or satellite provider in order to receive their HDTV channels.

Is HDTV service free?

YES! Television stations in most of the United States now transmit in both standard TV and HDTV. If you live within range of the HDTV signals you can put an antenna on your roof and connect to your HDTV and watch HDTV for free. Note that your television must be an HDTV Television and not a HD READY TV. The difference between and HDTV television and and HD Ready TV is a built-in HDTV tuner. If you have an HD-Ready TV, you must then purchase a HDTV tuner box to receive over the air (OTA) HDTV transmissions. Today, most HDTV's have built-in HD tuners.

What is EDTV?

EDTV, or Enhanced Digital Television is a slight twist on standard TV, offering 480p image resolution and wide-screen (16:9) format. EDTV cannot display 1080i or 720p true HDTV. Many people mistakenly purchase EDTV's thinking they are low-priced HDTV's. Don't be fooled by an EDTV. Be sure to compare all the features of EDTV to HDTV before purchasing an EDTV. After making the comparison, you will probably agree EDTV's are a bad choice.

More about 1080P

There are already a large number of 1080p HDTV sets on the market, which upconvert all incoming signals, including standard-definition TVs, DVDs, HDTVs and PCs, to their panels’ native resolution of 1920x1080 pixels. Ironically, these 1080p televisions can not accept a 1080p signal. Yes, you read that correctly.

If you already own a 1080p HDTV, it is highly probable that you won’t be able to provide it with a 1080p signal from a PlayStation 3 or a Blu-ray Disc or an HD-DVD player. The good news is that the first 1080p input capable televisions are on the way and if you are planning to get a big screen HDTV, this is the perfect time to invest in a future-proof television.

Read the entire article here: Facts about 1080P HDTV