Are digicam pixels non-square? PAL 5:4 -> VGA 4:3

Discussion in 'Amateur Video Production' started by Marian Stary Zgred, Jan 21, 2004.

  1. Hello!

    A standard computer monitor has 4:3 display (640x480, 800x600,
    1024x768...). A video material transferred from a PAL DV digicam has
    720x576 pixels, which gives 5:4 pixel aspect.

    I want to convert such video to a DivX file, targetting computer
    playback. Does it mean that I have to shrink whole movie to 93,75% its
    heigth, so that non-square pixels from a digicam would convert to square
    VGA pixels?

    Thank you...
     
    Marian Stary Zgred, Jan 21, 2004
    #1
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  2. Marian Stary Zgred

    Jukka Aho Guest

    Then again, there are commonly used modes with non-square pixels,
    such as 1280x1024, 320x200 and 640x200. (Well, the last two are
    not so common any longer, but all SVGA cards still support them.)

    Having square pixels on a computer monitor is just a (modern)
    convention. The display hardware can usually be programmed to
    output very exotic modes with various oddball pixel aspect
    ratios if one wanted to. The 8-bit and 16-bit home computers
    used to have non-square pixel graphics modes as a general rule.
    Close, but no cigar. The actual 4:3 area is 702x576 in "PAL"
    DV pixels, even though the frame size is 720x576. (This
    702x576 area is the middle part of the 720x576 area.)

    See this page for more information:

    <http://www.iki.fi/znark/video/conversion/>

    Also note that if you scale the frame vertically, you will
    usually get problems with interlacing (unless you are using
    a camcorder that allows shooting in so-called "progressive
    frames" mode.) That is yet another kettle of fish, and I
    would recommend reading

    <http://www.lurkertech.com/lg/fields/fields.html>

    to get a firm grasp of the problem. (Then go googling for
    "VirtualDub", "AviSynth" and Donald Graft's "Smart Deinterlacer")
     
    Jukka Aho, Jan 22, 2004
    #2
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