Exporting with video that shows

I'm trying to export a animation with a video in the background but every time I do the background doesn't show. Apparently it's because the video's format H.642 wont work because of something with flash, and every time I try using a different format it either tells me it won't work unless it's the format that won't show after exporting or just export a single frame of the video like it's a picture. How do I import and export the background video!!!