Im trying to burn a DVD on my MAC?

Im using IMovie and for some reason I only burn 5 min of the total 21 min. I uploaded a personal video no prob from my video camera but I cant get the whole video on my DVD. I got it to work a few weeks ago. Im wondering if there is a problem lost in the translation in the conversion to mp4. I am not too sure I am just trying to figure this out. Any viable suggestions? Can you also leave a way to get a hold of you if I have any questions? Something like an e-mail would be awesome. Thanks for any help. I am just baffeled.