S3 works in this way :
It limits the time to load that resource on user's machine .
It loads the resource from s3 for the given duration after it stops loading the resource .So anybody who wants to download the video from the same link in the dom will not be able to do so after a certain duration .
But yes user can find the resource link afterall and to hide that we would need a special player that does not shows the resource link in dom like that of Jw player .
Second is vimeo .It does not allows users to right click and save the video but it still can be downloaded by inspect element and the finding the video url in source .