For a number of reasons, I am not using Moodle. All information will be either posted on this website or shared via e-mail.
Ability to stream the video files directly depends on the specific software configuration on your device (browser, video player etc.). I expect you to download the files, not to stream them.
I use H.264 and MP3 for encoding so if you have problems still, that is what you should look into next. For playback, personally I use VLC.
First, there is no 'correct' way of playing Prisoner's Dilemma (or any game for that matter) in the absolute sense. It only makes sense to talk about it in reference to something. Perhaps the most popular reference is a rational agent, which we discussed in the first exercise session. Standard game theory analyzes the behavior of this rational agent. In experiments, we observe real people and some of them (potentially, most) are not 'rational' like that for various reasons.
It is only from the perspective of a rational agent that it makes no sense to cooperate because he is selfish and he thinks that everyone else is selfish, too. As long as someone has a different perspective, it may make a lot of sense to cooperate. Perhaps, the simplest case is when someone is a pure altruist. Not many people are like that but they do exist. Best response altruism or reputation buliding are other potential explanations that cover more cases.