High-math behind high-definition

General

Learning math sucks. Unless, of course, it helps you understand high definition TV, which doesn’t suck if you get to watch hockey on it, right? So to better understand how you can actually see the sweat fly when a player is checked, let’s do some TV math. In the words of Mrs. Pengelley, my Grade 8 math teacher: “Pay attention, people! This stuff’s important.”

  1. 480i: Until HDTV came along, television in North America used a standard called NTSC, named after the National Television System Committee. NTSC is also known as 480i. 480 is the number of scan lines that make up the picture. (Actually, there are 525 lines in an NTSC signal, but only 480 are visible.)
    The lines draw across the screen starting at the top, cascading downward. The ‘i’ in 480i stands for ‘interlaced’, which means 240 odd lines (lines 1,3,5, etc.) draw first on the screen in 1/60 of a second. Then the even lines, the other 240 of the 480 (lines 2,4,6, etc.), draw next in the next 1/60 of a second. Your brain sews these alternating sets of lines together to perceive a picture.
  2. 480p: When DVDs came along, developers had to come up with a standard called 480p. P is for progressive, which means that all 480 lines are drawn at once in 1/60 of a second. The picture is sharper because there’s twice as much information delivered to the screen.
  3. 720p and 1080i: In the HD world, there are two common standards. The first is called 720p. That’s 720 lines of picture all drawn at once (progressive). Then, there is 1080i, where 540 odd lines draw first, and 540 even lines draw next. Some say 720p is better. Hockey sweat looks pretty good on both.
  4. 1080p: There’s another emerging HD standard called 1080p. That’s 1080 lines drawn progressively in 1/60 of a second. It’s the most detailed HD format and (of course) the most expensive.

      5. So which standard you should choose when you buy a TV?

      Most HDTVs handle 480i, 480p as well as both 720p and 1080i. They convert whatever signal they receive to show you a great picture. Not all display a 1080p picture; but a 1080p video source will be converted to either 720p or 1080i. No broadcaster uses 1080p, yet. However, next generation high-definition DVD formats produce a 1080p picture.

      See, TV math is fun! Mrs. Pengelley would be proud.

      Here are a few choices of where to find high definition televisions online: