Which template? which Gantry version? background or foreground video?
Please post in the correct template forum and always provide a link to your site and login details in secure tab of your post.
Regards, Mark.
Please search forums before posting. Please make sure your post includes the version of the CMS you are using and a link to the problem. Annotations on screenshots can also be helpful to explain problems/goals. Please use the "secure" tab for confidential information.