exporting alpha channel from Final Cut?

Hi,

I’m trying to export a sequence of TGA files from Final Cut, including an alpha channel.

The video clip is a shot of a presenter against a greenscreen, and the green has been keyed out using chromakey filters. This works fine inside FCP, but as soon as I export, the alpha channel disappears… I’ve tried exporting using the Quicktime Animation codec with Millions+ colours, as well as a sequence of TGA files, but I’m stumped…

Any suggestions? I don’t have AfterEffects, so can’t use that… And the Blender chromakey plugin wasn’t good enough for my poorly lit footage…