Suppose that website is: http://www.mywebsite.com width Drupal Garland theme on all pages.
How to enable another theme and set it as default on a page like http://www.mywebsite.com/video ?
Blocks can be added on specific pages, but can templates done the same?
Take a look at the ThemeKey module.
From the module information:
ThemeKey is meant to be a generic theme switching module. It allows you to switch the theme for different paths and based on object properties (e.g. node field values). It can also be easily extended to support additional paths or properties as exposed by other modules.