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Stabilize + chroma footage with Mocha and AE

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Ivan CastellStabilize + chroma footage with Mocha and AE
by on Mar 8, 2010 at 3:29:23 pm

Hi,

Let's see if someone can point me in the right direction :)

I'm trying to stabilize a shot of a mobile being hand-held in front of a camera. These is a for a typical product promo review. The screen has a green picture that I'll replace with another clean video footage (let's call this "screen") using a chroma.

That's what I'm doing:

1) Track the phone with Mocha (all options enabled: translation rotation, scale, shear and perspective).
2) Open a new composition in AE, in a layer the phone, underneath these layer, the video footage "screen".
3) Using mochaimport script, I move the "screen" layer according to the phone data.
4) Make a chroma to replace the green with the "screen" layer.

Now the footage looks great and the screen has been replaced correctly.

The problem is now I also want to stabilize the whole composition, so it doesn't move and jitter (stabilize hand-held mobile), but something I'm doing must be wrong because it looks weird. What I do is the following:

5) Precomp the composition and apply the tracking data from mocha to stabilize the whole comp (screen + mobile).

The shot gets stabilized, BUT the "screen" layer looks weird. It's not moving fully according to the tracking data.

I've tried to export the comp as a movie and even track again this clip. But the effect it's the same. The screen footage (only the screen footage) get somehow corrected by the tracker and it doesn't integrate correctly.

I must be doing something really wrong so any advise, tip, etc.. will be greatly appreciated.

Thanks folks.


Indie filmmaker
http://ivancastell.org


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Ivan CastellRe: Stabilize + chroma footage with Mocha and AE
by on Mar 9, 2010 at 2:30:50 pm

Ok, I think the problem is related to the perspective and shear data not being transfered to AE, so the screen is not properly "corrected" (it has changes in perspective). I could do a corner pin to use this data, but we are touching the screen with the finger, and I'll have to rotoscope...

Indie filmmaker
http://ivancastell.org


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Dave LaRondeRe: Stabilize + chroma footage with Mocha and AE
by on Mar 9, 2010 at 11:07:07 pm

You know, the way they get stable product shots like this is to stabilize the subject. Build a rig to hold the smart phone steady, then the talent holds onto it, thus hiding the rig.

Very simple, very effective.....

Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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Ivan CastellRe: Stabilize + chroma footage with Mocha and AE
by on Mar 9, 2010 at 11:41:14 pm

Dave,

Thanks for the info. Is there any example out there of this kind of rigs? Lately we're doing a lot of product reviews, so it'll be great to build one of this.

Indie filmmaker
http://ivancastell.org


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Dave LaRondeRe: Stabilize + chroma footage with Mocha and AE
by on Mar 10, 2010 at 5:22:18 pm

The only place I've seen one recently is on a Geico spot. It's a demonstration of how easy their online service is to use.

When the announcer says, "...so easy a cave man can do it," the hand model walks away in disgust, leaving the phone in the rig.

You might be able to find the spot on the Geico web site. Don't get sidetracked and buy insurance.

Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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