DTV is not the same as HDTV!

The D in DTV stands for “digital” while in HDTV it stands for “definition”. HDTV is based on DTV as it is only transmitted only in digital format. There is no analog HDTV.

But if you have a digital TV it only means that you are save when all analog broadcasting ceases at the end of 2006. It doesn’t automatically mean that you can view programming in high definition. You need a HD-ready TV or a HD-capable TV with an external tuner.

DTV comes with a standard resolution of 640 : 480 or 704 : 480. That is the picture consists of 640 or 704 vertical and 480 horizontal lines. The aspect ratio therefore is 4 : 3 as we are used to since the beginning of TV.

HDTV comes with resolutions of either 1920 : 1080 or 1280 : 720 which means an aspect ratio of 16 : 9. This resembles the screen proportions of a movie theatre screen and makes for a 5x to 10x sharper picture.

Note: often the description of TV resolutions is shortened to giving only the number of horizontal lines. So 1080 would mean the highest available HDTV resolution of 1920 : 1080.
720 describes the lower resolution of 1280 : 720.

Then the aspect of frame rate enters in, This describes how often within 1 second the entire picture is created on the screen. Actually employed frame rates today are 24p, 30p, 60i and 60p.

“I” means interlaced which means that not the whole picture is created in one scan but alternately the odd lines in one and then the even lines in the next scan etc.

“P” means that the whole picture is created in one scan. I.e. with a frame rate of 60p there are 60 complete pictures created in 1 second. The progressive mode provides a smoother picture but of course double the data volume to be transmitted.