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Alpha Matte question
I am attempting, with no luck so far, to make an AVI file with a Alpha matte on it. So far the only format that I have been able to make an alpha work on is Quicktime…what am I doing wrong?
thanks for any help you can give
-Dave -
4 Replies
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Probably nothing
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Quicktime is a suite of codecs. Some of those codecs support an Alpha channel like IFF, TIFF, PNG, Animation, while most do not. You need to find an AVI codec that does support an alpha channel. I can’t recommend one because I’ve never used an AVI before.
Chris Smith
https://www.sugarfilmproduction.com -
From what I know, AVI does not support alpha channels (we use QT whenever we do alphas). However, perhaps there is a codec that supports this.
Can’t you use QT?
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Dave –
You can’t make an .avi file with an alpha channel embedded. The workaround is to output the fill and the matte separately. We receive animations on tape all the time using this method. The fill clip has the part of the animation that will be seen; the matte clip has the alpha channel as luminance (white and black). It’s a simple matter to line the clips up in After Effects (or whatever you’re compositing with) and use the matte clip to cut out the areas that will be transparent. In AE, you put the matte clip on top of the fill clip, then select “luma matte” in the fill clip’s Track Matte pulldown, next to the Mode selector in the timeline box.
Joe Bourke
Art Director / WMUR-TV
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