3:2 Vs 2:3 pull down

Discussion in 'Archived Threads 2001-2004' started by Michael Hudson, Aug 19, 2001.

  1. Michael Hudson

    Michael Hudson Stunt Coordinator

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    I got my new issue of Sound and Vision yesterday the September issue and in three different places they say that DVD players have 2:3 pull down. In each of the three places it correct the 3:2 and says 2:3 is more accurate. Any idea why they are wanting to change the lingo ?
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  2. Don Black

    Don Black Screenwriter

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    Possibly because every two film frames (e.g., 24fps) are being upconverted to 3 NTSC frames (e.g., 30fps) instead of vice-versa?
     
  3. Eugene Hsieh

    Eugene Hsieh Supporting Actor

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    I've often thought the 3:2 pulldown terminology didn't make sense, like S&V, but then shouldn't that be 2:3 push up instead then? [​IMG]
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  4. Darryl_B

    Darryl_B Stunt Coordinator

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    My understanding is that 3-2 Pulldown (or telecine) is the frame-rate conversion scheme used for converting film material (24fps) to interlaced video (30fps).
    I think S&V is finally trying to correct themselves from misusing the term by using the term 2-3 Pulldown instead - meaning "inverse telecine". 2-3 Pulldown would probably be a more appropriate description of what technique most progressive-scan players use to actually recreate the progressive frames of film-sourced material.
    I've always thought the term "3-2 Pulldown" was used incorrectly very often. Many say the phrase "I want a Progressive-scan DVD player that has 3-2 Pulldown", which I think more correctly should be said as "I want a Progressive-scan DVD player that has some form of 3-2 Pulldown Detection" to recognize film-sourced material appart from video-sourced material. Once the film-sourced material is recognized, the player should be able to employ 2-3 Pulldown to appropriately reassemble the progressive frames.
     
  5. Steve Schaffer

    Steve Schaffer Producer

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    Maybe it should be called 2/3 pullUP instead of 3/2 pulldown? (just trying to be funny.)
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  6. Allan Jayne

    Allan Jayne Cinematographer

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    3:2 vs. 2:3 pulldown -- exactly the same thing.
    The terminology should be something like "3:2 pulldown detection and optimizing". Coming out of the MPEG decoder 24 fps film source video is interlaced with 3-2 pulldown. The de-interlacing stages following need to recognize this and construct the appropriate progressive scan frames using matching fields. The best progressive DVD players fall back on using hints from the video content to assemble the full frames if the white flags normally used for the purpose are missing or not correctly positioned.
    Other video hints: http://members.aol.com/ajaynejr/video.htm
    [Edited last by Allan Jayne on August 19, 2001 at 04:13 PM]
     
  7. Mark Fontana

    Mark Fontana Stunt Coordinator

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    For home theater purposes, they are the same thing, and the ratio notation (when not referring to a ratio but rather a sequence) confuses people.
    But for technical folks, there is actually a slight difference.
    2-3 pulldown means that for four film frames (A,B,C,D) spread over 5 video frames, A and C last 2 video fields and B and D last 3 fields.
    3-2 pulldown is the opposite; A and C last 3 video fields and B and D last 2 fields.
    So in 2-3 pulldown, the first film frame in a stream lasts 2 fields, whereas in 3-2 pulldown, the first film frame lasts 3 fields.
    Having the first film frame last 2 fields is more common, so 2-3 pulldown is probably the most correct term.
    The difference only becomes an issue when you're doing a telecine transfer and trying to match the pulldown sequence at the start of an insert edit, etc.
     
  8. RyanDinan

    RyanDinan Stunt Coordinator

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    Mark nailed it on the head -
    I also agree that the term 3-2 pulldown gets misused (like Darryl mentioned). ALL dvd players use 3-2 pulldown - Simply because there's no one way to encode a DVD. You can have the data stored as 24 full frames, 60 fields (3-2 pulldown allready applied), 48 fields (the redundant field removed), etc. The MPEG decoder must make sure that it gets 60 fields per second - even the progressive scan players (with the exception of the JVC player). So if the data is stored as 24 frames, the MPEG decoder applies 3-2 pulldown to get 60 fields. If the data is allready stored as 60 fields, it passes the data on through. If the data is 48 fields, is must repeat a field every other frame. Progressive scan players (ones that have a film mode), once they have their 60 fields per second, de-interlace the image by either detecting the cadence, or by reading the flag data encoded with the video.
    So the feature should always be called "3-2 pulldown detection"
    -Ryan Dinan
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