The video image is recorded one horizontal line at a time. These lines are called scan lines and the process is known as scanning. If you look closely at a TV screen you will see the scan lines. You probably can’t see them on your computer monitor because the lines are narrower than on a TV.
Standard Definition (SD)
The term “definition” basically means the visible detail in the video image. It is measured by the number of horizontal scan lines in a single frame. In the United States and Japan, standard definition video is 525 lines. In most European countries, standard definition is 625 lines. (The former is known as NTSC; the latter is PAL).
High Definition (HD)
Although much hype has been made about HD, the concept itself is simple to understand.
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