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  1. Member
    Join Date
    Mar 2014
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    nice try...
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    This thread might end up being a Non Sequitur, but I'd still appreciate some answers if they exist.

    As you all know, back when television was entirely in analog, nobody knew what a pixel was, let along a square pixel, and nobody had any reason to make their television systems easily translatable to square pixels. Even in the DVD era, said DVDs were authored with resolutions that use non-square pixels, like 720x480. These resolutions are apparently stretched to appear correctly with monitors that use square pixels, in this case let's say 640x480 for a 4:3 aspect ratio.

    Here's where things get crazy. I'm going to talk about late era DOS gaming, which used resolutions like 320x200 and 640x400. Square pixel wise these were 16:10 resolutions, but the images generated are supposed to have a 4:3 aspect ratio. It has been discovered that by doing a nearest neighbor upscale of 320x200 to 1600x1200 (and likewise 640x400 to 3200x2400) you could get an image which looks identical to what the 320x200 and 640x400 images would look on an analog monitor supporting non-square pixels in 4:3.

    Of course, part of the reason the upscaling is relatively straightforward is that the game graphics were made digitally to begin with. SMPTE RP 187 apparently gives rather crazy pixel aspect ratios for exact images. From Wikipedia: "SMPTE RP 187 further attempted to standardize the pixel aspect ratio values for 480i and 576i. It designated 177:160 for 480i or 1035:1132 for 576i. However, due to significant difference with practices in effect by industry and the computational load that they imposed upon the involved hardware, SMPTE RP 187 was simply ignored."

    I would like to know what all this means, and what the equivalent "perfect" square pixel resolutions of various analog tv non-square resolutions are (like for DVD, VHS, Laserdisc etc). Am I overthinking all this? Can anybody with better knowledge explain everything for me?
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  2. Normal analog SD TV (broadcast, VHS, laserdisc...) was all 4:3 DAR. There were no pixels of course. And in reality nobody saw a perfect 4:3 image -- analog TVs were very bad at keeping the aspect ratio. It varied with adjustments, age, temperature, nearby magnetic sources...

    When digitizing:

    https://forum.doom9.org/showpost.php?p=1058927&postcount=11
    Last edited by jagabo; 8th Jun 2018 at 20:10.
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  3. Member
    Join Date
    Aug 2010
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    San Francisco, California
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    There are no pixels on an analog display, only scan lines. Whatever the logical pixel format, a digital-to-analog converter must turn it into a scanning signal which is supported by the display. The display does not know pixel aspect ratio from a hole in the ground.
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  4. Here's a post with a sample animation that shows how a CRT scans the screen:

    https://forum.videohelp.com/threads/334839-interlace-help/page7#post2083644
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