Fluid Responsive Videos
Works automatically for youtube and vimeo

just add the following code to a side html block or at the bottom of a page:

<script src="http://ecampus.nmit.ac.nz/moodle/pluginfile.php/348564/mod_folder/content/0/Course%20Specific%20Files/JS%20and%20CSS%20%282016%29%20-%20Alan%20PT/Fluidvids/fluidvids.js" type="text/javascript"></script>