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More Motion Key help Please.

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Allen ZagelMore Motion Key help Please.
by on Feb 14, 2010 at 11:49:01 pm

I decided to get the trial version for FCP instead of Vegas.

I have a situation that I can't figure out. Same video of the band playing and there's this fellow who walks diagonally up to the camera then heads away as he crosses left to right across the frame.

I tried keying him out. The first time I tried it I got ripples in the video following where I removed him. So I tried again only this time cutting the clip where I have to remove the guy. I didn't even have to set up the Motion Key as somehow it remembered the last time I tried and as soon as I dropped the key on the video clip he was gone, however there was a jump in the video at the I/O points where I made the cuts. I tried using a short transition but that really didn't help.

I'm having the problem because the person gets bigger as he approaches the camera and then smaller as he walks off screen. I adjusted the size of the tracking box, but I got those horrible ripples again.

Maybe I'm doing something wrong or just don't know the program, or this guy is too big to remove?

Can anyone offer any help?


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Boris YamnitskyRe: More Motion Key help Please.
by on Feb 19, 2010 at 1:45:15 pm

It sounds like you need to fine-tune the target area rectangles. The filter can only remove an object if there is enough image info in adjacent frames of video. Make sure to use preview mode with blue and red rectangles which tell you if the object can be completely removed. Make sure to read the pdf under the Help button. Watch this recent movie:

it's done in Avid but the main idea is the same.

In practice, successful removal can be done in clips where the object is moving with steady speed and direction and where the object itself is rather small (does not cover the entire screen). A person crossing the street or a car passing the intersection are the perfect examples.

Boris Yamnitsky

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Allen ZagelRe: More Motion Key help Please.
by on Feb 19, 2010 at 2:53:41 pm

Hi Boris

Thanks for your reply. I downloaded that video and watched it many times. That video was what prompted me to try the FX and motion keying.

Since it was done in Avid it threw me off a bit. I called Boris Tech Support and they told me in FCP I didn't have to duplicate the track like he did in Avid. I had to drop the clip from the browser into the well (which I didn't know).

I fine tuned the rectangle so the red was covering the person as well. I got 2 different kinds of results. In one try I used the blade and cut the clip so it became a separate clip. In that instance FX did remove the fellow completely but at the cut point the video has a small jump which I couldn't smooth out using a transition. The next try I left the clip whole and it also removed the fellow but you can see a ripple in the clip there the object would have been walking. He came toward the camera and got bigger, then walked away from the camera as he left the frame to the right. At one point he did cover quite a bit of the video. But this object was walking at a constant, steady speed. So I had a problem keying the size of the rectangle as well as the walking motion.

With my limited knowledge and experience I wasn't able to satisfactorily remove him. so I opted not to use that song (clip). (Music Video of a Polka Band).

The other object I wanted to remove was another fellow who was much smaller and walking straight across the screen. In a couple of songs he stopped and was bouncing his head. I believe he'd be easier to remove. But I didn't get far enough to try him. He's in quite a few clips.

Thanks for your help and information though. I appreciate it. I'll keep trying to work on it but my deadline to get this DVD out is fast approaching.


ASX Media Group, Inc.
MBP, iMac, Mac Pro
Final Cut Studio 2

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