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Roto Brush - increase analyzed time span

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Marc NiborRoto Brush - increase analyzed time span
by on Dec 1, 2015 at 4:51:44 pm

I need to seperate a persons face and hair from the background. The clip is 02.30 minutes long.
Normally I would try to key it, since the background is basically just a gradient. The problem is that the background color is almost skin tone, so I thought I try to go with the roto brush.

The Roto Brush does a very good job with finding the edges.... but the problem is that it wants me to re-sample the area about every 25 frames...

So my question is.... is there any way to make the roto brush analyze more than just those approx. 25 frames?

I actually thought it would automatically chew it's way through to the end of the footage unless it's stopped. Kinda like the tracker...



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Steve BrameRe: Roto Brush - increase analyzed time span
by on Dec 1, 2015 at 6:00:54 pm

The lighter grey bar with the left and right pointing chevrons is the area to analyze. Simply click and drag the edges of this area to lengthen or shorten that area. You can drag it all the way to the end of your clip if you want.



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Marc NiborRe: Roto Brush - increase analyzed time span
by on Dec 1, 2015 at 7:21:22 pm

Thank you Steve. That was some very helpful information - exactly what I was looking for!
Actually I went through several lengthy tutorials about the Roto Brush before I posted this question. Surprisingly none of them mentioned this bit of information.



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Steve BrameRe: Roto Brush - increase analyzed time span
by on Dec 1, 2015 at 7:27:02 pm

It's an available technique, but I'll second what Dave says - the conditions where you can successfully extend the analysis area past the default would be rare. I'm in the process of doing 40+ interviews where I'm replacing the background with Rotobrush, and I've only had one clip where it worked. In that particular clip, the foregound subject's color and luminance was so drastically different from the background, that Rotobrush was able to analyze from beginning to end without any interim cleanup. Not so for the others.

Asus P6X58D Premium * Core i7 950 * 24GB RAM * nVidia GeForce GTX 770 * Windows 7 Premium 64bit * System Drive - WD Caviar Black 500GB * 2nd Drive(Pagefile, Previews) - WD Velociraptor 10K drive 600GB * Media Drive - 2TB RAID0 (4 - WD Caviar Black 500GB drive) * Matrox MX02 Mini * Adobe CC * QuickTime 7.7.5
-------------------------------------------
"98% of all computer issues can be solved by simply pressing 'F1'."
Steve Brame
creative illusions Productions


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Dave LaRondeRe: Roto Brush - increase analyzed time span
by on Dec 1, 2015 at 6:20:03 pm

Actually, 25 frames is pretty good for Rotobrush. Remember, it's a tool that helps make Rotoscoping less painful... not effortless. I'd check out some of the training materials to see how to extend the span. Since Rotobrush use is not at all intuitive, it doesn't lend itself well to "here's how you fix it" posts in a forum.

Dave LaRonde
Promotion Producer
KGAN (CBS) & KFXA (Fox) Cedar Rapids, IA


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