When exporting a video from iMovie it asks for a title. Upon saving the file you'll find it has named the file whatever you input for the title. Now if you rename that file in Finder then open it in QuickTime and show the Movie Inspector, you'll find that the video title is the old title - the title you input in iMovie. Unfortunately you can't edit the title here. It doesn't show the title in Finder's Get Info. So my question is how can you edit the video's title (not filename) without reexporting the movie from iMovie?
If you are running Mac OS X and find that some of your video files have metadata included, then it will have been set in Apple's iTunes. In iTunes you can add, edit or remove all metadata from video files. This is only applicable to certain video types, however, as they must be iTunes recognized filetypes. The file types supported by iTunes are the same as those supported by QuickTime, and so if you have QuickTime plugins installed, you will be able to utilize those as well.
Open iTunes on your Mac.
Click "Movies" or "TV Episodes" on the left.
Select the video you want to edit, right-click it and click "Get Info."
Click "Video." Highlight each field of data and press "Delete." Click "Info" and edit.
Or use free tool MetaZ ( http://griff.github.io/metaz/ )