CGTalk - Camera tracking pull down problems?

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jerm

01-17-2007, 06:40 AM

Hi - I recently shot some fx plates with an HVX200 at 720p24. Then I tracked the shots with good old icarus, and went about compositing in my CG elements. What I find is, there is some sort of pulldown sync issue with the footage and the rendered elements. There is a stutter between them, it's as if the pulldown on the footage and the pulldown on the CG are two frames out of sync. Which is funny, because if I'm not mistaken there should be no pulldown at all. The footage is 24p, viewed in a 24p sequence. And the CG is rendered frame by frame as well, without interlace. So what am I missing? What do I have to do to get rid of the stutter? Anyone run into this problem? How can I figure out if there is some weird pulldown scheme on my stuff?

basti

01-17-2007, 07:03 AM

hi

2 frames error sounds like a userr error (usually a frame shift).
so make sure your imported tracking starts with the same frame
your sequence starts.
and check your scene and compositing tools fps settings (maybe
it's set to 25fps somewhere)

some other possible reasons:

icarus:
icarus has some special camera parameters which cannot be exported
to a 3d package (what a great idea ;) ) you have to make your camera
exportable at first in icarus (this messes up the tracking most of the
time - another excellent idea from the programmers ;) )

motionblur:
when rendering with scenemotionblur in cinema you'll need to shift your
entire tracking some subframes according to your mb-strength. that's
because cinema is the only app on the market which samples in the wrong
direction (between current frame and the next frame - correct mb would
be between the last and the next frame)

basti

Simon Wicker

01-17-2007, 08:34 AM

don't forget that most apps consider frame 1 to be the first frame but cinema often prefers frame 0 to be the first frame.

for example if you have an animated background cinema only plays this back correctly if your project file starts at frame 0, if you start at frame 1 then you will be one frame out of sync.

cheers, simon w.

acid2002

01-17-2007, 10:05 AM

are you using 24 or 23.98 in C4D

Derek

acid2002

01-17-2007, 10:13 AM

Post a question here, it maybe that you have to remove the pulldown on you footage first.
here is the link http://www.lafcpug.org/phorum

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