stupid question

Discussion in 'Playback Devices' started by PeterK, Sep 3, 2004.

  1. PeterK

    PeterK Supporting Actor

    Jan 14, 2004
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    when you are talking resoulution like 480i or 720p, is that horizontal lines or vertical lines? [​IMG]
  2. Steve Schaffer

    Steve Schaffer Producer

    Apr 15, 1999
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    480i or 720p are not "resolutions". They are scanrates, meaning the number of lines used to scan the picture and whether all the lines are scanned in one pass or only half of them. The lines are scanned from left to right on the screen in the horizontal direction.

    480i=480 Interlaced lines=480 total lines but only half of them are scanned per pass of the electron beam-they alternate on every pass. Even numbered lines will scan on one pass, odd numbered on the next, then even numbered then odd and so on.

    480p=480 lines progressive=480 lines but each line is drawn on every pass of the electron beam instead of them alternating as with 480i.

    720p=720 lines progressive=720 lines each one of which is scanned on every pass of the electron beam.

    "Resolution" usually refers to "horizontal resolution" which leads to lot's of confusion with scanrates due to the word "horizontal" What it "horizontal resolution" really means is how many vertical lines (as in a picket fence) the monitor can display across it's horizontal dimension.

    The above is applicable to crt displays, those using cathode ray guns to display the picture either directly or by rear or front projection.

    Fixed pixel displays (LCD, DLP, Plasma) have a fixed number of pixels each one of which can display a different color. Typically an HD-capable fixed pixel display will have about 720-780 pixels in the vertical dimension and 1000+ in the horizontal dimension and are usually referred to as having a "native scanrate" of 720p because they are capable of showing 720 horizontal lines from top to bottom of the screen, though they don't really do any scanning like a crt based display does. The "horizontal resolution" would be equivalent to the number of pixels the display has running from one side of the screen to the other.

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