Video Alpha Channel

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Video Alpha Channel

Postby genjutsu » Tue Sep 05, 2006 11:53 am

Hey everyone, it's been a while since I've been on here, but Ive been trying to master After Effects among other software. Can enyone tell me how I would go about creating an alpha channel for a video clip. I've seen videos with alpha channels and luma mattes but with all my reading I still havent been able to figure out how to do it on my own.
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Postby Zarxrax » Tue Sep 05, 2006 12:04 pm

From your question, it seems that there is likely a bit of confusion about what you are trying to do. Perhaps you could explain more thoroughly, exactly what it is that you are trying to do in after effects?
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Postby Gepetto » Wed Sep 06, 2006 5:07 pm

CHANNELS IN AN RGBA IMAGE:

Red: Stores information for the amount of red in each pixel.
Green: Stores information for the amount of green in each pixel.
Blue: Stores information for the amount of blue in each pixel.
Alpha: : Stores information for the opacity in each pixel.

Video editors that handle alpha treat every video file that does not come with an alpha channel as if it had a full-opaque alpha channel, and you can edit that. Image editors usually have an "add alpha" function, just look for it.

Also, it's unlikely that you've "seen" videos with alpha channels because no one distributes video in RGBA colorspace. It's a waste of kilobytes.

About EDITING/CHANGING/ALTERING the alpha channel, there's about a quarter million ways to do that, so you'd have to say what exactly you're going for.
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