video alpha in Director - the answer

[Rob]

There's been tons of posts on this with no real answers. But there is
a solution, convoluted but it works.
Flash video. By storing an Alpha channeled FLV in an SWF you can do
it. For example I have chroma key video between graphics in Flash.
It's clumsy and takes a few steps but it works.

[Rob Wellington]

I have the steps here:
http://mmtipsntrix.blogspot.com/
and they work in Flash too of course