I need some help explaining an answer to a question.

Discussion in 'Archived Threads 2001-2004' started by Dean Cooper, Aug 16, 2001.

  1. Dean Cooper

    Dean Cooper Supporting Actor

    Oct 23, 2000
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    Someone just asked me to explain the difference between an input resolution and his TV’s resolution and I’m having a hard time coming up with a good way to describe the answer. Does anyone know a link that has a good description or can describe the details in layman’s terms?
  2. Allan Jayne

    Allan Jayne Cinematographer

    Nov 1, 1998
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    Input horizontal resolution -- if digital it means that the video signal representing the picture is organized in terms of pixels, say, 1/640'th the screen width occupying fixed positions 1/640'th, 2/640'th, 3/640'th, etc. from the left side of the screen. If analog it means that details can be as small as say 1/640'th the screen width and not have blurred to gray but not constrained to positions 1/640'thj, 2/640'th etc. from the left of the screen.
    Horizontal resolution of the TV means how small details can be reproduced for viewing. If video that was once digital at, say, 640 max pixels across is fed in but if the TV is analog (like most) and only has, say, 500 max pixels across for resolution, it can still reproduce the pixels in any of the 640 positions (1/640'th, 2/640;th, etc. from the left edge) across but not all at the same time; three dissimilarly shaded ones in a row anywhere will be blurred together.
    For a digital TV the display itself consists of pixels with fixed spacing. Regardless of the resolution of the input signal the picture is formed from individual spots of fixed size say 1/640;th the screen width and in fixed positions say 1/640'th, 2/640'th., etc. from the left edge. If two (or more) pixels worth of input line up with a given pixel on the digital display, that spot on the screen should be of a compromise shading.
    Input vertical resolution is the number of scan lines or rows of pixels represented by the input signal. Display vertical resolution is the number of scan lines or rows of pixels on the display. If they don't match one of two things must happen (requiring special electronics):
    1. scaling, involving doubleing, skipping or blending of a few lines here and there, or
    2. Cropping the firsst few and last few scan lines if the input has more than the display, or leaving unused black areas on top and bottom of the display if the input has fewer than the display.
    If the number of scan lines (and the number of frames per second) is the same for input and display, no scaling electronics is needed even if the number of pixels horizontally, express or implied, is different for input and display.
    Other video hints: http://members.aol.com/ajaynejr/video.htm
    [Edited last by Allan Jayne on August 16, 2001 at 10:15 PM]

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