High Definition TeleVision is what HDTV literally means. But high definition compared to what? In order to answer this question, we need to know a bit about the original analog TV system.
Analog TV
30 images per second (in Europe 25) are shown by normal analog TV sets. It does this by writing image lines horizontally, 525 lines in one image (In Europe 625) on the screen. The number of pixels on one line is about 500. This would be a definition of 500 pixels per line by 525 (or 625) lines. Compared to modern computer monitors this is really bad. Even the lowest resolutions monitors have higher resolutions (640 x 480) than an analog TV.
HDTV - High Definition TeleVision
HDTV is high resolution Digital TeleVision (DTV) combined with Dolby Digital Surround Sound (AC-3). There are 18 different formats defined for Digital TV of which 6 are considered to be HDTV:
| Active Lines Per Picture | Pixels Per Line | Aspect Ratio | Frame Rate | Scanning Approach |