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Problem with Masking and Interpolation?

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Carleton Torpin
Problem with Masking and Interpolation?
on Nov 16, 2009 at 12:10:23 am

I've been working on a shot for several hours now and most of that has been rotoscope masking. It was going fine for a while, but then I decided to "improve the mask" by using "Smart Mask Interpolation". This at first seemed to make the mask and it's inbetween frames much smoother. After a while though I started to notice that it was acting kinda jerky and moving the inbetween frames all around between the actual keyframe that I set.

After a while trying to adjust the "Smart Mask" inbetween frames, I decided to just delete all frames that I didn't do myself. This took a while, but it worked for the most part.

On a ram preview set to full res, the clip looks just great and the mask stayed where I put it and matched the video just fine. Upon rendering the actual movie out via the Render Queue, I end up with a mask that jumps around all over the place between the keyframes I set. Each time it does a jump, it looks like only half a field is shown, which is off because it's supposed to be a 24 FPS progressive clip.

For reference, my settings are:

Source Footage - NikonD90 720P .mov file at 24 FPS

Sequence Settings: Width - 960, Height 720, Frame Rate 24 FPS

Can anyone tell me what I can to do alleviate the weird jumping on the mask? I am really hoping that I don't have to re-do all my masking again, as it took quite a few hours.

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Dave LaRonde
Re: Problem with Masking and Interpolation?
on Nov 16, 2009 at 3:54:05 pm

[Carleton Torpin] "Source Footage - NikonD90 720P .mov file at 24 FPS... Sequence Settings: Width - 960, Height 720, Frame Rate 24 FPS "

Are you ABSOLUTELY SURE your footage is 24 fps? Could it be 23.976? You'd better double-check.

If you're rendering with Open GL enabled, don't. It does more harm than good.

A .mov file is just a media container: a quicktime movie. The file within can be compressed any number of ways using a variety of codecs. So you need to find the codec's name in the project window, and you need to read this:

Dave's Stock Answer #1:

If the footage you imported into AE is any kind of the following -- footage in an HDV acquisition codec, MPEG1, MPEG2, mp4, m2t, H.261 or H.264 -- you need to convert it to a different codec.

These kinds of footage use temporal, or interframe compression. They have keyframes at regular intervals, containing complete frame information. However, the frames in between do NOT have complete information. Interframe codecs toss out duplicated information.

In order to maintain peak rendering efficiency, AE needs complete information for each and every frame. But because these kinds of footage contain only partial information, AE freaks out, resulting in a wide variety of problems.

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

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