What is HDTV?
HDTV is the broadcast format of the future-and of the present. More and more stations have been upgrading from NTSC to 16:9 HDTV. HDTV broadcasts will be in 16:9 formatting.
There are two types of high-definition televisions:
1. HDTV: Also known as high-definition TV. These have a built-in high-definition receiver that allows the TV to receive over-the-air high-definition broadcasts. These TVs require either an indoor or an outdoor antenna to receive high-definition over-the-air broadcasts (such as CBS or NBC).
2. HDTV Monitors: These are capable of displaying a high-definition TV signal, but require the separate purchase of a high-definition receiver and antenna to receive high-definition broadcasts.
Basically they still fall under the “Rear Projection TV” category – which means the projection cathode ray tubes, commonly known as CRTs, are found within the set and behind a plastic projection screen. The light from the CRTs strikes a mirror and is reflected onto the rear of the screen, where it forms an image you can see on the other side. Instead of the traditional direct view TVs you’re used to, where you view the picture directly on a single tube, rear projection TVs use CRTs, a series of focusing lenses, a mirror, and a display screen.
The screens on the TVs most of us are still watching today (referred to these days as “analog” or “traditional”) are roughly square and have an “aspect ratio” of 4:3. That is, they’re just slightly wider than they are tall. But widescreen HDTVs have an aspect ratio of 16:9. As you can see, they’re much wider than they are tall. So, what’s the advantage? We thought you’d never ask.
Movies shown at a theater have pictures that are wider than your TV’s screen. By the time a movie is released on video tape or shown on TV it has been “modified to fit your screen.” Unfortunately, they “modify” it by chopping off the sides of the picture. Widescreen TVs use the entire TV screen to let you see the whole picture.
The resolution for traditional TVs is of the order of 200,000 pixels whereas for HDTV it is ~2 Million. There were several resolution standards that were approved by FCC in 1996 and the most popular ones are 480i (regular analog TV), 480p, 720p and 1080i. The number is number of horizontal lines and how they are drawn (i-nterlace scanning or p-rogressive scan). The traditional TVs actually use 525 lines but some of these lines are used for things other than picture and the number is close to 480 and hence the name 480i instead of 525i. Interlacing means constructing the picture using odd-even lines and Progressive (which is only found in HDTV and HDTV Monitors since only digital broadcasts and digital sources like DVD players send the signal this way) is like computer monitors – from top to bottom in the order of lines.
The audio is CD quality sound as compared to analog sound which is like FM Radio. It supports Dolby® Digital sound that can recreate surround sound effects from five different speakers with the right kind of home theater equipment.
Source: Circuit City Knowledge base