-
Straight Alpha Channel on AVI
I’m trying to render some logo animation with feathered circle in the background. When I render the AVI I get the same results with straight and premultiplied. In Sony Vegas for example there is difference. If you select the straight alpha you get black feather on semi transparent edges, that is the effect I want to achieve.
-
4 Replies
-
When alpha is interpreted correctly, you don’t get fringing at all, whether you’re using premultiplied or straight. You DO get black fringing in transparent areas when you render with pre-multiplication, but interpret as straight alpha.
If you want to use this to creative effect, just use Interpret footage [link] to change the alpha interpretation.
Walter Soyka
Designer & Mad Scientist at Keen Live [link]
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
@keenlive | RenderBreak [blog] | Profile [LinkedIn] -
Yes, but when I render the AVI file with premultiplied alpha, I don’t get to choose the type of alpha channel in Premiere Pro when importing.
-
[Milos Ristoski] “Yes, but when I render the AVI file with premultiplied alpha, I don’t get to choose the type of alpha channel in Premiere Pro when importing.”
Premiere Pro has an Interpret Footage dialog you can use, but it’s a bit less flexible than Ae’s, so it’s not as easy to assign the incorrect alpha interpretation.
To get the “wrong-alpha fringe” from Ae to Pr, try rendering both an RGB pass (normal, premultiplied color) and a separate Alpha pass (add an output module and choose “Alpha” instead of “RGB” or “RGB+Alpha”). Import both movies into Premiere Pro and use Premiere’s Track Matte Key effect to to pull a luma matte from the alpha pass.
Walter Soyka
Designer & Mad Scientist at Keen Live [link]
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
@keenlive | RenderBreak [blog] | Profile [LinkedIn] -
Thank you, but I found a more simple solution. I rendered the animation in Targa sequence.
Reply to this Discussion! Login or Sign Up