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Rotobrush jitteriness.

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Marius CrowneRotobrush jitteriness.
by on Jan 21, 2012 at 9:47:16 pm

I'm experiencing endless frustration with the rotobrush. All I am trying to do is isolate a character from my film (see image) from the background, so I can put a dark shadow across the top of the frame to help separate him from the background (it would cut behind his shoulders, hence why the entire figure isn't selected).

The character (and the shot) remain almost completely static, especially for the first 2 seconds where he doesn't move at all. HOWEVER, from the first frame to the second frame, there is already a jump with the selection despite the fact that I have the search radius relatively low (7) and Reduce Chatter all the way up (100%). This isn't all though, I've tried a whole slew of settings and strangely, they don't really seem to affect much.

I've read all of the documentation from Adobe on "Roto Brush and Refine Matte" and feel like I have a pretty solid grasp of the subject matter, but alas, something seems to be eluding me if the selection can't even stay still for one frame on a character (in a shot) that isn't moving.

Your help, as always, is much appreciated.

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Tudor "Ted" JelescuRe: Rotobrush jitteriness.
by on Jan 22, 2012 at 11:31:07 am

I admit, RotoBrush is not the most intuitive tool. It took a few tries to get things right. In your situation though I would go for traditional roto, since you said the character does not move much.

Tudor "Ted" Jelescu
Senior VFX Artist

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Dave LaRondeRe: Rotobrush jitteriness.
by on Jan 23, 2012 at 8:45:21 pm

I'll go out on a limb and say the is shot on a DSLR. If not, I'll say the footage is an HDV acquisition codec, MPEG1, MPEG2, AVCHD, mp4, mts, m2t, H.261 or H.264. In any case, a long-gop codec.

If the footage doesn't contain complete information for each an every frame -- and the ones mentioned above don't -- I'm not convinced that AE can play nicely with them using sophisticated features like Rotobrush or Warp Stabilizer.

The fix: change the codec of your footage to something lossless. I like Quicktime movies in either the Animation or PNG codecs.

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

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Marius CrowneRe: Rotobrush jitteriness.
by on Jan 23, 2012 at 9:02:40 pm

Hey there. Yes, the film was shot on a 5DMII, but I the footage is being edited as ProRes422.

I ended up just masking a mask for the beginning of the shot (where he isn't moving) and then using the roto brush when he starts moving. It worked surprisingly well all of the sudden after literally spending days trying to get the settings to something that worked well.

Here is a screenshot of my settings for anyone with similar issues. Thanks to both of you for your help.

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