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Stabilizing Motion - Head Movements

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David Robertson
Stabilizing Motion - Head Movements
on Sep 22, 2009 at 2:32:04 pm

Hello,

I'm trying to standardise a set of talking head videos and have had a few goes at motion stabilization using some tutorials, but I can't do what I'm trying to do.

My films were filmed from a tripod, so there is no camera motion, but there is slight rotation and movement of the head while the people speak and I would like to minimize that, or remove it completely, to give a steady talking head without rotation or x,y movements. Unfortunately, I only have After Effects 7.0 with no prospects of an upgrade.

Is it possible to stabilize such motion using the AE motion stabilizer? If so, how?

Thanks.



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Dave LaRonde
Re: Stabilizing Motion - Head Movements
on Sep 22, 2009 at 3:57:14 pm

[David Robertson] "I'm trying to standardise a set of talking head videos... there is slight rotation and movement of the head while the people speak and I would like to minimize that..."

If there is no overwhelming reason for doing so, leave the footage alone and learn from any shooting errors that were made.

The phrase, "Well, I want to do this because I think it will look better," does NOT constitute an overwhelming reason.

My rationale is this: you shot 3D subjects and recorded them in video, a 2D medium. if there are indeed shots with subjects' rotation in them, how do you propose to re-invent the portions of the subjects' heads that are now concealed by the rotation, while eliminating the portions of their heads that were revealed by the rotation?

You could do it, but it's going to take a lot more hardware, software, knowledge and experience than either you or I have. Think about Gollum in the Lord of the Rings, and you have an idea of the processes involved.

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


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David Robertson
Re: Stabilizing Motion - Head Movements
on Sep 22, 2009 at 4:07:54 pm

I perhaps should have made it clearer... the motion I'm trying to eliminate is primarily x and y rotation/movement. No 3D problems.

I also have more reasons for doing it than "it will look better", it's part of my work.

I was just looking for suggestions on how to stabilize sideways or vertical movements.

Thanks anyway.



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Dave LaRonde
Re: Stabilizing Motion - Head Movements
on Sep 22, 2009 at 4:25:49 pm

[David Robertson] "..the motion I'm trying to eliminate is primarily x and y rotation/movement..."

Just so you know, it's beastly difficult to track facial features in AE... if it isn't downright impossible. you stand a fighting chance if the subject's wearing classes: you might be able to use the corners of the frames. How about eyes? Forget it: people blink, and there goes the track point.

It sounds like you're trying to stabilize the motion of an individual who slightly cocked his or her head to one side. To do that, AE's motion tracking -- if it can even track facial features at all -- will need to rotate the entire picture. This means that portions of the shot will rotate off the screen.

So: to present a full-screen picture, you will have to scale the picture up to fill the screen. Would you be okay with the resulting loss of crispness in such a shot?

If the answer's "no", you'll want to re-shoot. This time, you'll know the precise conditions you want your talent to meet, and you can control the circumstances better.


Dave's Stock Answer #2:

When you're out on a shoot, and you say, "we'll fix this in post" without knowing PRECISELY HOW you're going to fix it in post, don't shoot it! You'll only end up shooting it over again.

Since post typically costs three times the cost of production, fixing something in post is not a way to save money, but rather a way to spend more of it.

And, before you say "well fix it in post," always consider who's doing the work, especially if you're the one doing the editing.


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


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Stuart Elith
Re: Stabilizing Motion - Head Movements
on Sep 23, 2009 at 4:02:19 am

David, my advice is to listen to Dave!
I have recently been doing some work on something that sounds quite similar, with actors speaking to camera but moving around slightly because they were trying to get "into" their role... but it meant a lot of pain for us!

In my case, we had tracking dots on the nose and 2 on the temple/forehead, and even so, had mediocre results with stabilization - any facial movements seem to distort the face more that you might think... a smile makes the nose shift slightly, any eyebrow movements really affect the whole forehead, etc.
And I tried tracking the eyes but it was painful and still not a great result, even after I cleaned up the blinking frames etc.

If a reshoot is at all possible (and you can give instructions that will avoid your problems recurring) then push for that, I think.


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David Robertson
Re: Stabilizing Motion - Head Movements
on Sep 23, 2009 at 9:02:58 am

Thank you Dave and Stuart for your helpful comments.

The off-screen rotation won't be a problem, as I will be isolating the inner face features with an elliptical aperture mask and due to the relatively small presentation of the videos, any scaling I may do shouldn't cause a big problem.

I was having problems with one particular video (trying to track at or near the eyes) but had the blinking issues as you mentioned. I think I'm just going to have to go with the "best" results for him, rather than perfection. However, I tried tracking the corners of the glasses of another guy and it worked a treat, really excellent results despite quite a lot of head movement.

Shame they don't all have glasses.

Thanks a lot for the help.



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