optimal frame dimensions for DV video?

Discussion in 'Professional Video Production' started by liu, May 2, 2011.

  1. liu

    liu Guest

    I use this as reference but wonder if I need to take DV's non-square
    pixels into consideration when converting it for web deployment?
    so instead of using 432 x 288 (maintaining the same aspect ratio of
    720:480), I should change 288 to 320 (= 288*10/9) by taking the 0.9
    vertical ratio?
    Also is video dimensions should be multiples of 16 still important
    nowadays. If I have to stick with it, I have just a few frame
    dimensions to use.

    liu, May 2, 2011
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  2. liu

    Frank Guest

    Nice chart but somewhat dated as encoding Flash video using either the
    On2 VP6 video codec or the Sorenson Spark video codec is a thing of
    the past. The Adobe Flash player has accepted files encoded with the
    ISO/IEC 14496-10 MPEG-4 Part 10 AVC / ITU-T Recommendation H.264 video
    codec (along with MPEG-4 ACC-LC audio) for several years now, and the
    file extension can be either .flv or .mp4, your choice.
    Yes, you do, unless you're posting raw DV files for consumption by a
    specially targeted audience.
    The square-pixel equivalent of NTSC video is 640 by 480. If you wish
    to use a smaller frame size, use 320 by 240. For truly
    postage-stamp-sized video, use 160 by 120.
    Different codecs have different requirements, and there are literally
    hundreds of video codecs in existence, although there are a few codecs
    which will produce frames of video of any arbitrary size. In general,
    if you stick to using frame sizes that correspond to those used for
    OTA (over-the-air) broadcast, or fractions thereof, you'll be okay.
    Hope this helps.
    Frank, May 2, 2011
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  3. liu

    liu Guest

    What is the math to get to these numbers? From my calculation.
    720 x 480 DV has 3:2 aspect ratio. Use that ratio on 640, it becomes:
    640 x 426.667. Then take the expand the v from 0.9 to 1, it becomes
    640 x 474.0741. Why is it 640 x 480 if I'd like to maintain the same
    aspect ratio?

    liu, May 2, 2011
  4. liu

    Bob Myers Guest

    Right there is your problem. You are assuming "square" pixels for 720 x
    480, and that's not the case. 720 x 480 video is intended to be shown
    as either 4:3 or 16:9 (to determine which it is, you have to check a
    flag bit).

    Bob M.
    Bob Myers, May 2, 2011
  5. liu

    Frank Guest

    No mathematics, just simple arithmetic.

    Keep the 480 scan lines as is, but multiply the width by the pixel
    aspect ratio of 0.888889 to 1 (720 times 0.888889 equals approximately
    The correct calculation is as given above.
    Since NTSC video has a display aspect ratio of 4 to 3 (4:3), the goal
    isn't to maintain the storage aspect ratio but to convert to the
    display aspect ratio. There are various methods to accomplish this.
    Here's a recommendation that Adobe used to give:

    "Practically speaking, you should use the D1 resolution for videotape
    and DVD; use a 4 x 3 ratio for computer playback.
    A standard conversion from D1 to 4 x 3 would begin as follows:

    1. Capture at 720 x 480 pixels.
    2. Deinterlace or inverse-telecine the video.
    3. Crop eight pixels from the left and right sides (so it's 704 x
    4. Resize the video to 640 x 480 pixels."

    And here's a link to the original announcement (dated August 20, 2007)
    about AVC/AAC support in Adobe Flash Player.

    kaourantin.net: What just happened to video on the web?
    Frank, May 2, 2011
  6. liu

    liu Guest

    Thank you so much for the helpful information, Frank and Bob.
    liu, May 3, 2011
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