FCP crashes for me too, try exporting with x264 through compressor, it will work, but I got qualitybroblem with the x264-codec, anyone else? It’s like the edges of things in the video get pixelated,even though I have a resolution of 1280×720 and high bitrate
To fix h264 to mp4:
open the h264-file in quicktime>export>movie to MPEG-4>then in videoformat choose “pass”(I thing it is, I dont have English Quicktime…)
then it will just change the container of the file, it goes fast.