how to export a file that's already an H.264

Why do you have H.264 clips in FCP to begin with? FCP doesn't work with H.264 natively.

-DH

Want to edit H.264 native? Don't use FCP. Adobe Premiere works with this natively. If you want to edit it in FCP, you need to transcode it to ProRes. And no, you won't notice the difference between the ProRes files and H.264 originals. ProRes is a good codec designed for high quality. And yes, you will convert back to H.264. How compressed it looks depends on the settings.

Again, want native. Use Adobe.

Actually fcp will work with h264 material, just not dependably.

Dependability is everything.

I agree, but people are always complaining when we tell them not to work in h264, that it's always worked before...

I actually have a peculiar workflow in which I bring in an xml sequence from premiere into fcp which remains linked to the h264 media, and do a media manage to prores. It's worked flawlessly (so far - not sure I would recommend it to anyone).

You and I seem to have a basic philosophical difference of opinion. You seem to want to only give people the information that they should have, while I think people should be allowed to make their own mistakes. If they choose to ignore my advice.... Not sure my way is the right way, and I know I can be a pain by nitpicking this stuff.

And the OP probably tuned out a long time ago.