Charlie,
Here’s how to do this in FCP 7
Put the video you want to fade to white on video track 1
In the viewer click on the title generator button (bottom right looks like a film strip with an A in it) and select Matte -> Color Solid
Drag the video of a solid blue screen down to the Sequence on video track 2
Adjust the length of this slug to cover the video in track 1 from where you want the fade to start to the end
Double click the slug in the V2 track to edit the properties in the viewer
Select the Controls tab and click on the blue square, change to white with the color picker that pops up.
Now you need to matt the shape.
Select Effects -> Video Filters -> Mask shape, you should now have a white rectangle over your video
Go to the filters menu and change rectangle to oval
Drag the horizontal and vertical scale to 200 – this is your white out and should align with the end of the scene
click the keyframe button next to horizontal and vertical scale – it looks like a diamond in a circle with a left and right arrow either side
Now drag the playhead to the beginning of the slug
click the keyframe button next to horizontal and vertical scale again
You should see to the right of the keyframe buttons a green horizontal line with two black dots
Drag the horizontal and vertical scale to 0. This is where the fade to white starts. Note the green line now slopes upwards. The angle of the slope controls the speed the scale changes
Nearly there. You now have an expanding white oval that fills the screen over the video
To make it circular move the playhead to somewhere in the middle of the slug – you should now have a flat oval on the screen. Drag the right hand key frame for the vertical scale to the left until the oval becomes a circle, remembering to keep it at 200%. Basically what you’re doing here is getting the vertical scale to increase faster than the horizontal.
Render video and you’re done.
To adjust where the circle starts from adjust the centre control. to make it move around, keyframe the centre control
Hope that helps.
Dave