The site has an option to create and enforce acceptance of a site policy and other specific use policies on all users who access the site. If enabled and created, the policy will appear to any user the first time they arrive on the site and show them the HTML message you create and ask them to accept and record their acceptance with the date. I would suggest a site policy that is set to authenticated users. Add in the acceptance that they are confirming that they watched and understand the video presentation (or read the transcript).
You can read more about the policies tool at moodle.org39, http://docs.moodle.org/38/en_us/admin/tool/policy/editpolicydoc37