I remember when I finally learned that you could make gradient masks in flash using code, I was so relieved to finally have, what I think should have been an option from the beginning. Well, recently I started a project where I wanted to do something a bit more interesting than what is built in. It got me to thinking of ways I could combine some of the bitmap effects I have been into, with the same principles behind how gradient masks are made.
The result; Video Masks! It may not be the most efficient, or processor friendly (though it worked much more efficiently than I expected), method to making a mask, but I needed something to fit my vision, and this was my mash-up result.
To give you a quick rundown of how it is done; You run a video like normal, write that to a bitmap in real-time as it runs, then use the bitmap method threshold to split the image up onto two separate bitmaps that you then use as the final mask. What is interesting is that you can also apply drop-shadows or blurs to those bitmaps so you can get a nice separation of depth between the two masks (if you want to really kill your users computer).
In the example I provided you will see it first transition using the ink video (which you will see in the top right), and then once that is done, you can click to see it transition using a random video I shot of a car. Not the greatest video for a transition, but it illustrates how it has the potential to be used with any video.