line-doublers vs 3:2 pull down

Discussion in 'Displays' started by Bob_M, Jul 15, 2003.

  1. Bob_M

    Bob_M Stunt Coordinator

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    Hello All,

    I am a little confused on a line-doublers VS reversing the 3:2 pull down process. MY understanding is DVD players reverse the 3:2 for progressive scan projectors. Why can't this be done for VHS or cable broadcast where I see a line-doublers are the recommended practice?

    Thanks Bob
     
  2. Michael TLV

    Michael TLV THX Video Instructor/Calibrator

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    Greetings

    Depends on the TV. Most current sets have line doublers that do 3:2 ... for film based material.

    Regards
     
  3. Bob_M

    Bob_M Stunt Coordinator

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    >that do 3:2 ... for film based material.<

    So if I was watching CNN then a line doubler would be the method of choice? How does it determine if it's film based or video?

    Thanks

    Bob
     
  4. Michael TLV

    Michael TLV THX Video Instructor/Calibrator

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    CNN is generally not filmed is it? So no 3:2 processing.

    There are flags in the signal that tell the processing when to kick in ...

    Setting a TV to film mode will cause it to apply processing to things that should not have it done as well ... hence degrading the image.

    Auto is usually the preferred setting.

    regards
     
  5. Bob_M

    Bob_M Stunt Coordinator

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    Michael,

    Do you think a time will come when reverse 3:2 is not needed. In others words the moveis on DVD will not have the processing applied in the first place. I guess that would have to wait until we all have progressive digital displays.

    Bob
     
  6. Michael TLV

    Michael TLV THX Video Instructor/Calibrator

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    3:2 will no longer be needed once we can get all film makers to stop shooting their films at 24 fps ... for theaters. This means changing all the projectors in the world ... and making every one shoot at 30 fps.

    Conversely, the entire TV world would have to stop shooting video at an equivalent of 30 fps and reduce it to 24 fps ... which means all the electronic equipment that everyone has will need to be replaced ...

    For a detailed discussion on 3:2 processing ... I recommend that you visit the secrets of home theater and hi fidelity site to read up on DVD technology.

    Regards
     
  7. Lew Crippen

    Lew Crippen Executive Producer

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  8. Allan Jayne

    Allan Jayne Cinematographer

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    Good doublers (de-interlacers) will need 3-2 pulldown sensing almost forever because there are so many DVD's out there that have 24 fps film source on them.

    HDTV 24 fps source will continue to proliferate with 3-2 pulldown applied at playback time. Actually film source DVD's are 24 fps also. The player (for DVD) and the HDTV box (for HDTV) convert the MPEG compressed video into video at (approx) 60 fields per second for 1080i or 480i or 60 frames per second for 720p or 480p and in so doing must create 3-2 pulldown.

    The best doublers automatically switch between "film mode" (3-2 pulldown preservation) and video mode as needed.

    Video hints:
    http://members.aol.com/ajaynejr/viddoubl.htm
     

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