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." Highlight each field of data and press "Delete."