What do you call this. Occasional frames duplicated.

Discussion in 'Digital Video' started by iHateMacs, Aug 27, 2011.

  1. iHateMacs, Aug 27, 2011
    Last edited: Aug 27, 2011

    iHateMacs macrumors 6502a

    iHateMacs

    Joined:
    Aug 13, 2008
    Location:
    Coventry, UK
    #1
    I am using FCPX thought I doubt the problem is restricted to this.

    I am trying to edit some footage from a VIO POV HD camera.

    It is recorded at 1080 30p

    I have imported the media and put a section onto an empty timeline. When I do this FCPX asks me to confirm the format of the video because it can't be sure. I tell it it's 1080P 30fps.

    If I step through the video frame by frame, about 4 times a second I see the same frame twice.

    If I watch the same source media in Quicktime and step through frame by frame, it works as you would expect. i.e. I press the arrow 30 times I see 30 different frames.

    What would cause this?

    EDIT: I have tried creating optimised media as it imports. This does not help at all, I still get the duplicated frames.
     
  2. cgbier macrumors 6502a

    Joined:
    Jun 6, 2011
    #2
    Pulldown.
    You sure your footage is 30, and not 24p?
     
  3. iHateMacs thread starter macrumors 6502a

    iHateMacs

    Joined:
    Aug 13, 2008
    Location:
    Coventry, UK
    #3
    Well the device is set to record at 30p


    Just before I see the duplicated frame I notice it has jumped one. Does this still sound like pulldown?
     
  4. MisterMe macrumors G4

    MisterMe

    Joined:
    Jul 17, 2002
    Location:
    USA
    #4
    It is a standard in videography for 30 fps to be recorded at at a true frame rate of 29.97 fps. This is a holdover from the analog days when it was necessary to account for dropped frames. If you force the recording to have a true 30 fps frame rate, then occasional duplicate frames must be added. It sounds like you are forcing your video to have a true 30 fps frame rate.
     
  5. iHateMacs thread starter macrumors 6502a

    iHateMacs

    Joined:
    Aug 13, 2008
    Location:
    Coventry, UK
    #5
    Thanks for the suggestion. I can see how doing that would cause the effect.

    But I have tried telling FCPX that it's 29.97 too. Nothing makes any difference.

    When I have a blank timeline and I add my first clip, I get the following message.

    [​IMG]

    I have tried 30P 29.97P.

    I must be missing something fundamental here. If FCPX cannot determine the properties of the clip, then doesn't it just see it as a series of frames? If I tell it it's 30p then wouldn't it believe me? If I tell it the same clip is 60p then would it not believe me again then play it back a double speed? It doesn't though. Whatever frame rate I tell FCPX the clip is, the duration on the timeline is always the same. So even though it says it cannot recognise the video properties, It must be getting something from there.
     

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