I need to use avanced mask composing on kdenlive. I'd like use a video track (in grayscale) as mask for another video track. For example. I have two video clips and a video mask (with no alpha channel, only grayscale values). I'd like to use this video clip as a dynamic mask using an alpha value for opacity depending color value (luma or matte mask, I do not know exactly name).

I tried to put this video mask on the first track and a video on the second track using a "multiply" composite mode. This make all transparent white color and no transparent black color.

The problem is that I'd like use another clip as background of this composition, using the same video mask but with opposite alpha values (black as totally transparent and white no transparent).

Can you help me?

I do not believe this is possible yet.