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alpha channel in dv avi
here’s something I’ve never really understood:
Suppose I have some material on the timeline with an Alpha channel (for example: footage with a chromakey filter applied, or some generaated media with one transparent color). There is nothing underneath it, so the transparent parts will show as black.
When I render to a dv avi the transparent parts allways look black in the rendered clip. Changing the alpha channel properties of the rendered clip (settings like: “premultiplied” or “straight”, which I never understood either) doesn’t change this.
Is the alpha information allways lost after rendering? -
6 Replies
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It’s just that DV avi doesn’t support alpha channel. Try rendering as uncompressed instead. Same for still images; jpeg won’t do alpha channel, png will.
Gary
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But uncompressed takes a lot of diskspace. Isn’t there any compressed videoformat that supports alpha channel?
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It requires a 32 bit file- the “extra” 8 bits are for the alpha channel.
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It looks to me like there are a couple of quicktime codecs that might work. Animation codec is one of them.
Rob Mack
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It works indeed, very nice. You have to set the alpha channel in the rendered clip though (I set it to ‘straight’).
Do you know if that’s the standard format for working with animation? I’m working with an animator now; he gives me .png files with alpha channel, a seperate file for every frame seems not to be the fastest solution. -
I don’t know if that codec is a standard for animation or not. That’s just it’s name. I assume there are other codecs available that are compressed but add alpha, I just don’t know what they are.
When you think about it, a lossy codec would smudge up your transparent areas, so you’d want to use a codec that was as nearly lossless as possible. That’s why the uncompressed AVI codec has alpha but the Sony YUV codecc doesn’t.
I had read about the animation codec here:
https://codecs.onerivermedia.com/Looking around, it seems like Huffyuv might also support alpha.
Rob Mack
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