What is 3:2 pulldown?

Discussion in 'Archived Threads 2001-2004' started by Meaux, Sep 17, 2001.

  1. Meaux

    Meaux Stunt Coordinator

    May 27, 2001
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    Hooked up my new 50H80 and don't see any mention of 3:2 pulldown in the Owners Manual. The TV works pretty good so far. I only did the 9pt. convergance for now, I'll have to read up on the 56 before I attempt that.
  2. Allan Jayne

    Allan Jayne Cinematographer

    Nov 1, 1998
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    Normal movies are shot and played back at 24 frames per second. NTSC video is 60 fields per second (regular) or 60 frames per second (progressive scan). Since 60 does not divide by 24 evenly the film is committed to video by repeating the first film frame 3 times, the next film frame twice, the next film frame 3 times, etc. (During editing or some scene changes, this 3-2 cadence might not be maintained perfectly).
    The significance with newer TV's and some DVD players is that progressive scan means combining two fields to make a complete video frame. For best results the player must identify odd and even video fields that were made from the same film frame as opposed to combining the odd scan lines that originated from one film frame and the even scan lines that come from the next film frame.
    Recognizing the 3-2 pulldown and then combining matching pairs of fields with a minimum of further pixel analysis is what we refer to as "3-2 pulldown" in a DVD player or TV.
    The video coming from the first stage of the DVD player (MPEG decoder) is usually flagged to help the second stage (de-interlacer) match up the fields but once in awhile (less than 1% of the time) the flags are incorrect or the cadence is lost. Then the better progressive scan players will analyze the video in terms of pixels to find the matching fields.
    For broadcast video and non-progressive DVD players and where the TV displays progressive scan, the TV does the job of combining fields into frames. The progressive scan TV cannot take advantage of flags in the DVD data but (better sets) can still recognize the 3-2 pulldown cadence by analyzing (taking hints from) the picture content.
    Non-progressive scan players and TV sets don't worry about the 3-2 cadence but simply handle the video fields one at a time as is.
    The visual difference between sensing the 3-2 pulldown and matching up fields and combining fields blindly so is subtle, but some videophiles find unmatched frames to be annoying.
    Other video hints: http://members.aol.com/ajaynejr/viddoubl.htm
    [Edited last by Allan Jayne on September 17, 2001 at 04:55 PM]

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