video in indesign project When exported in epub fixed layor get the wrong size in epub file

Pretty much what Bob says. EPUB's single great flaw is that it's completely dependent on the reader used, and there are no completely standard, bug-free readers available... especially for fixed-page, FXL EPUBs. FXL is a complicated, problematic format and because of that, is very difficult to tweak or repair after export. (You either get it right, or start over.)

It is possible that some CSS statements applied to the video frame/<div> at the time of export could correct size issues, but that would take a fair amount of expert experimentation. But the place to start is with a reasonably reliable reader; I recommend Calibre for many reasons even though it's not 'perfect.'

The rule is pretty simple: if you want fixed pages, use PDF (and Acrobat to read it). If you want an e-book, use reflowable EPUB. There's no good third choice except pure HTML, which doesn't make very good "books."

Fixed layout EPUB depends entirely on the EPUB Reader application. Beyond Books on Mac and Thorium Reader they're all substandard and the format itself is so bad, that while I was once very excited about it, I can no longer recommend it for much of anything.