What is HDTV?

HDTV, or High Definition Television, is a new set of standards for television resulting in a significant increase of picture quality.

Regular color television is scanned at 480i, which means there are 480 vertical lines that are scanned in an Interlaced format. This means that at any given time, only half of the picture is on the screen at a time. While one frame will only display the odd lines (1, 3, 5), the next frame will only display the even lines (2, 4, 6). This happens so fast that the human eye is tricked into thinking that it is only seeing one picture.

This is the opposite of progressive scanning, which means each frame is displayed all at one time. Instead of interlacing the lines, each frame is displayed as you would guess, being line 1, line 2, line 3, etc. The end result is a much sharper image and looks much better. Although the difference in an interlaced signal and a progressive signal is the way the picture is scanned, it does have a big difference on the resulting image.

True HDTV signals are signals that are broadcast in a format of 720p or 1080i. 720p means that there are 720 horizontal lines that are scanned progressively and 1080i means there are 1080 horizontal lines that are scanned in an interlaced format. Although there is a big difference in the number of horizontal lines, the fact that 720p is progressive and 1080i interlaced means that the resulting pictures are very similar.