Difference between Progressive and 3:2 pulldown?

Discussion in 'Archived Threads 2001-2004' started by jeff lam, Nov 12, 2001.

  1. jeff lam

    jeff lam Screenwriter

    Jun 4, 2001
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    San Jose, CA
    Real Name:
    Jeff Lam
    I'm new to the HDTV world and I am learning a lot. I understand interlaced and progressive now but what I don't understand is 3:2 pulldown. What is this and what's the difference between this and progressive? My local HIFI store calls the DVD's progressive, and TV's progressive image "Progressive". I thought the TV's line doubler was 3:2 pulldown. Isn't a line doubler the same as progressive? So where does 3:2 pulldown fit in?
  2. David West

    David West Auditioning

    Apr 3, 2001
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    A line doubler does just that, doubles the lines scanned on the screen in any given amount of time. Line doublers can result in either a progressive output (480i --> 480p) or interlaced output (480i --> 960i).
    Check this site out, it articulates what line doubling and inverse 3-2 pulldown are...
  3. Chris Vargas

    Chris Vargas Agent

    Oct 13, 2001
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    That article is excellent but intensive. Here's a quick, hopefully accurate, description of 3-2 pulldown.
    Movies run at 24 frames per second. Interlaced TV runs at 30 frames a second, 2 fields per frame. In order to pad 24 movie frames out to fit 60 video fields, if you do the math, you have to put 2 movie frames into 5 video fields. To do this, they duplicate movie frames. The first movie frame goes into 3 video fields, the next movie frame goes into 2 video fields, and so on. 3, then 2, therefore 3-2 pulldown (as in pulling down frames into video fields).
    Unfortunately, this means they end up having to split up some movie frames across separate video fields, and have a single video frame composed of two separate movie frames, one frame in one video field, one frame in the other. This can cause nasty visual artifacts.
    When you're viewing an HDTV, either the TV's line doubler or the progressive scan DVD player does an inverse 3-2 pulldown, attempting to reassemble the original frames of the movie from the interlaced fields. The quality of this reassembly, and the ability to recognize film sources vs video sources, is something to look at when comparing progressive scan DVD players.
    Hope that helps.
    [Edited last by Chris Vargas on November 13, 2001 at 12:06 PM]

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