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Progressive/interlaced frame rate confusion

Discussion in 'Archived Threads 2001-2004' started by Dave_M, Jul 26, 2002.

  1. Dave_M

    Dave_M Agent

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    Location:
    Minneapolis, MN
    Real Name:
    David Martin
    First of all, I realize the answer to my question will be: "Use whatever looks good to you", but here it is anyway: As I understand it, one of the main considerations with progressive players is how they handle the difference between video and film frame rates. Since I have both interlaced and progressive players, are there some discs that that simply won't (or aren't designed to) look any better on a progressive player? I'm thinking more along the lines of TV shows on DVD and extras on movie discs(stuff shot on video). Or is progressive scan supposed to be universal and give better image quality with any type of source? My Panasonic CP-67 has a section where you can change from video/film to film to video only. Is this necessary? Do I need to know the frame rate that each feature is shot in to know what to select? And finally, what types of things/artifacts happen when the correct rate is not selected? So many questions....Thanks.

    Dave
     
  2. itai

    itai Stunt Coordinator

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    dave, i dont have a prog-scan tv or dvd player, but as i understand it, its the same frame rate for both techniqes.
    one is projecting the frame with a single progressive scan across the frame(top to bottom, a line at a time), the other, inter-lacing two half rez images, one line each, at the same frame.
    the thing with video, is that its ability to present two discreet frames at the same time (same frame), gives it the ability to "squeeze" more frmaes per second.
    if normal ntsc is 30fps, than you actually can have 60 frames, but due to the video's nature of showing two interlaced frames together, it "folds" them together to one frame, thus staying at the original fps. (phew!..)
    the by product of this ability is smoother motion, you have double "temporal" (time) resolution to resolve the moving things, like pans for instance.
    in movies, where the fps is 24, you can see stroby pans, not as smooth as video.
    where was i? whats the question??[​IMG] ...
    movie material is 24fps, single frame (no interlacing needed here thank you), so when transfered to our dvd players it needs to change a bit.
    1 - in order to stay correct in a 30fps world (ntsc), it goes through a process called 3:2 pull down, that repackages the frames in a way that, shown in ntsc, the movie will look correct (timing wise).
    2 - it is obvious that film doesnt need interlacing(also known as fields), so progressive scan is there to help.
    with hdtv, the world of video is getting away from interlacing and that "cheap" video look.
    new, 480p, 720p, 1080p material, will need the compatible dvd and tv that have prog-scan.
    regular scan equipment, will just interlieve the prog-scan image as two images i guess.
    hmm...intresting question! :b
    hope this helps!
     
  3. Allan Jayne

    Allan Jayne Cinematographer

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    >>> one of the main considerations with progressive players is how they handle the difference between video and film frame rates
    No, one of the main considerations with progressive players is how they handle the difference between video and film interlaced field content.
    Currently the first stage (MPEG decoder) of the DVD player electronics always delivers interlaced video. If it is from a film source (possesses the 3-2 pulldown pattern coming out of the first stage) the strategy for making progressive scan out of it is different from if it is not from a film source (subject motion may occur between every two fields). For the second stage (de-interlacing) almost all progressive players handle film source correctly, the quality of non-film source (e.g. live video) handling is more difficult to achieve and varies widely. The player must fall back on its non-film source handling if the 3-2 cadence in film source video comes out of the first stage corrupted every now and then which happens.
    Video hints:
    http://members.aol.com/ajaynejr/viddoubl.htm
     
  4. itai

    itai Stunt Coordinator

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    thanks, allan, for correcting me.[​IMG]
     

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