MP4 as a link to download or are you trying to make a player?
To play the video in live stream like youtube.
I use this code on one of my sites to display a fullwidth video.
<video id="video_background" preload="auto" autoplay="true" loop="loop" volume="100">
<source src=" /VIDEO-URL-HERE.mp4" type="video/mp4"> Video not supported
This requires that you upload the video file.
That is one file format and HTML5 so you have limited browser access with that.
Another option is always to add the MP4 as a Media Download (Modules > Media Downloads > Add Media Download > Select MP4 (Streaming) from drop down Menu)
1) Add MP4 (Streaming)
2) Follow BCTHOR's example above.
-- Optional --
1) Add Media to webpage as a module or content holder.
2) iFrame media download to autoplay on page
a) You can also set _target to be New Window so video pops up in new tab/window
The upside to adding MP4 as a Media Download is customer insight. You are able to add this media link in a webpage, email or any other hyperlink, and track media downloads or views by a particular customer. You're welcome to message me if this needs further explanation.
Hope this helps.