<!DOCTYPE html>
<html lang="en-US">
<head>
<style>
video{
width:100%;
height:330px
}
</style>
</head>
<body>
<video controls>
<source src="/hawk.mp4" type="video/mp4">
</video>
<script>
var x = document.getElementsByTagName("video")[0];
function myFunction(){
alert("Video started loading");
}
x.addEventListener("loadstart", myFunction);
</script> </body>
</html>