Simple Mpeg2 encoding question for all you smart guys

Discussion in 'Amateur Video Production' started by Sanman, Apr 21, 2004.

  1. Sanman

    Sanman Guest

    I know that encoding VHS to Half D1 for DVD is fine because the resolution
    of VHS is below or equal to that of Half D1. What about 8mm and Hi8? What
    are the resolutions of those two formats and will Half D1 harm them?

    Thanks

    Sanman
     
    Sanman, Apr 21, 2004
    #1
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  2. Sanman

    Mike Kujbida Guest


    I don't claim to be a smart guy but I can tell you that (aproximately) 8mm =
    VHS and Hi8 = SVHS. Therefore, I wouldn't expect half D1 to hurt 8mm but I
    would expect to see a quality hit from Hi8.

    Mike
     
    Mike Kujbida, Apr 21, 2004
    #2
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  3. Sanman

    Will Dormann Guest


    8mm is about 260 lines horizontal resolution, Hi8 around 400 lines.
    Each would look fine in Half D1 resolution, which is 352 horizontal.

    As discussed earlier, if you are using a low bitrate, it will look
    better in half D1 compared to full D1.


    -WD
     
    Will Dormann, Apr 21, 2004
    #3
  4. Sanman

    Dave Haynie Guest

    No. You're confusing "lines of horizontal resolution" with "pixels
    across the horizontal". For reference, DV has 540 lines of horizontal
    resolution (in 4:3 aspect ratio), but 720 pixels.

    The whole "lines of resolution" measurement goes way back into
    pre-digital optics, on film. It became a significant measurement for
    video, across the horizontal, since that was essentially a measurement
    of the system's bandwith, with the lens, imager (back in the vidicon
    tube days) and the horizontal all being analog in nature.

    In digital terms, the line resolution across the horizontal is the
    number of pixels (more or less) that run across the horizontal of the
    largest perfect circle you can inscribe in your visual field. In DV or
    DVD, in 4:3 aspect ratio, that's 720 * 3/4 = 540 (in 16:9 aspect
    ratio, that's 720 * 9/16 = 405).

    So flippimg back, if you're dealing with an analog format like Video8
    that's delivering 260 lines of horizontal resolution, you should be
    able to get a reasonable digital representation of that in ~350 pixels
    across the horizontal. So the 352 you get in Half-D1 does the job. For
    Hi8 or SVHS, something in the 400 line range, that's going to need
    about 540 pixels across to be well represented. You're going to want
    to run a full D1 capture to do justice to either of these.

    Keep in mind that digital sampling of an analog signal is ALWAYS an
    approximation, at best. The nature of analog is that a color can
    change anywhere along the horizontal. Professional titlers and other
    graphics, for analog broadcast, usually work in 1500-2000 pixel
    resolutions to deliver the kind of smooth graphics you see on the
    networks. The analog limit is bandwith, which doesn't say "you can
    only have changes here and there" (that's digital), but rather, "after
    you change something, you have to wait N-microseconds for the next
    change".
    Dave Haynie | Chief Toady, Frog Pond Media Consulting
    | Take Back Freedom! Bush no more in 2004!
    "Deathbed Vigil" now on DVD! See http://www.frogpondmedia.com
     
    Dave Haynie, Apr 21, 2004
    #4
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