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Using a generic frame to mask out background

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Mark Jeater
Using a generic frame to mask out background
on Oct 18, 2016 at 2:34:12 pm

Hi,

I have a clip of a person walking into a fairly blank scene, there are a range of frames at the beginning with no subject in the image.

Therefore, would it be possible to use one of these frames to exclude the common objects (background) from the rest of the clip IE. end up with a cut-out of the person only. I could rotoscope it but I thought it might be easier this way.

I am quite new to AE so please be specific about how I would do this.

Thanks

Mark


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Michael Szalapski
Re: Using a generic frame to mask out background
on Oct 18, 2016 at 8:58:43 pm

You could use the Difference Matte effect. The problem is, unless the video was shot with a very high-end camera that captures relatively uncompressed (that is, not an MP4 or any other H.264 or MPEG compression flavor), you're going to have differences in color where you don't want them due to the compression and noise in your footage.

- The Great Szalam
(The 'Great' stands for 'Not So Great, in fact, Extremely Humble')

No trees were harmed in the creation of this message, but several thousand electrons were mildly inconvenienced.


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Mark Jeater
Re: Using a generic frame to mask out background
on Oct 19, 2016 at 11:01:52 am

Hi Michael,

I've tried the difference matte and it's close. The only thing is it is removing the moving person and not the background. Any ideas how I can reverse the matte to keep the person only?

Thanks

Mark


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Michael Szalapski
Re: Using a generic frame to mask out background
on Oct 19, 2016 at 6:26:10 pm

You can use invert to just invert the alpha instead of the RGB.
You can use Levels to do the same.
You can use that footage as an inverted alpha matte for a second copy of the layer.
You can use the Set Matte effect on a copy of the layer.

And there are probably several other ways to do it that I'm not thinking of off the top of my head.

- The Great Szalam
(The 'Great' stands for 'Not So Great, in fact, Extremely Humble')

No trees were harmed in the creation of this message, but several thousand electrons were mildly inconvenienced.


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