Our video texture doesn’t support opacity. One way to achieve this is to create another mesh in front of the dome mesh and apply an opacity texture to it (or a diffuse texture with alpha). this texture will have to fit the sphere (or half dome) you put in front of the mesh.
Another way to achieve this would be to load the video using an HTML canvas and manipulating the canvas itself (applying the edges you wish to have on each frame). Since a 3D video mapping on the canvas is not the same as a standard “2D” video it might be a challenge to apply the edges correctly on the canvas itself.