How can I play an already uploaded video inside an Amazon S3 bucket? And how can I use the String Authentication on it?
I'm answering this, hoping I can help anyone else with the same problem.
If you're trying to play videos already uploaded to your S3 Amazon account, you won't find an appropriate Drupal Module to do so. (see this).
What I did is to get myself an Amazon Cloudfront account and protect the videos manually with an expiration date; then I pasted the video (using the player jwplayer), and I controlled the access to that node using any of the node access modules.