Tool for extracting only moving pixels?

[Mads Nybo jørgensen]

Hey Tyler,

Of the top of my head without applying brain-cells (apology in advance if this does not work):

If I was in a rush and had to find a “quick & dirty” solution, I would freeze frame the first frame, and then apply a “difference key” + maybe finding a way of reverting or isolating that.

But there are people here who knows A.E. better than I do.

Atb
Mads

[Gregory Mcgee]

Have you tried the “rotobrush” tool? If not, it’ll probably require a short tutorial. But it works great to git rid of the background. It creates a travelling matte, but you don’t have to go frame by frame and manually correct the matte on each frame. Rotobrush does it for you.
Here’s a pretty good tutorial.
Good Luck!
https://youtu.be/Tr1YIX_SZW4?<wbr>si=Ro2UbicoenGmS7H4

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[Tyler Mcneill]

Hi Mads, I was thinking of difference keying first but alas there was no clean plate to work with. I thought mathematically it probably wouldn’t be a problem to determine the movement of a pixel and turn that into a matte and that there is probably already a tool out there. But thank you anyways!

[Tyler Mcneill]

Hi Gregory,

Yes that was my solution to the problem too. But alas it is a complex scene with lots of moving parts and people. Rotobrush is doing a much better job than a few years before but it’s still very time consuming. But still thank you for your quick reply!

[Tom Morton]

+1 for Mads solution – I’ve tried to do exactly this in the past but even with a clean plate it’s difficult. Not to be pernickerty, but obviously the pixels themselves don’t “move”, they are static and just change color… so you can’t track pixel movement, you have to track changes to the pixel color… but unless you’re in highly controlled conditions – inside with no daylight leak, no moving shadow casts, static lighting etc – you’ll always have some change of color to a clean plate even if it’s a slight color cast or luma change… so then you need to add some margin of error into your difference key, which then leads to object edges having artifacts and losing clean edges…. I like the thinking and with some AI to help it out, it could be done i think…

Have you tried that magic mask in Davinci Resolve? Personally i think it does a better job then any of Adobe’s features.