It has some aliasing artefacts around the edge of the circle, you can see it very clearly during the fade-in. When the video is playing you don't really notice

It has some aliasing artefacts around the edge of the circle, you can see it very clearly during the fade-in. When the video is playing you don't really notice it. My guess is that this is caused by the way the mask is created. I can't try it out right now, but it could probably be solved by setting the RGB channels of the mask image to black.