load - If more then one html5 video on page ,they can not be load successfully

Question

In test page ,I write 5 html5 video file on the page ,like :

<video controls="controls"><source src="v1.m4v"></video>
<video controls="controls"><source src="v2.m4v"></video>
<video controls="controls"><source src="v3.m4v"></video>
<video controls="controls"><source src="v4.m4v"></video>
<video controls="controls"><source src="v5.m4v"></video>

But when open the page only the first video could be load. The other four is just black,or sometime the five are all black.When I there only one video on the page, it could be load successfully.

So I think maybe there is a limit on page load video file number?

My solution is put all video into a queue, only when the previous video load event completed, the next video load event is allow begin(using load()).But how can I know the previous video load event complete?