exporting video with transparent background I have searched but not found an answer that exactly answers or works.

I have a rotating rendered head animation that I want to export with a transparent background so I can import into final cut pro x and lay over video footage or still imagery. I have tried saving as a blender render as quicktime .mov with alpha as transparent and as RGBA but doesnt work, a black BG. I have also tried as a cycles render but still black BG. Is there any particular file format that is better for this? H.264, MPEG, .mov? or something I am missing? thanks
Alpha and codecs don't behave terribly well. At last check, only the horrific QuickTime encoder on OSX permitted an alpha channel.

As with all good work practices, it is much more prudent to encode to a still format where plausible, and deal with encoding at the very tail end of a pipeline.