Here i have tried as follows:
HTML
<iframe id="player" style="position: relative; height: 220px; width: 400px" src="http://www.youtube.com/embed/7a_CVFRqYv4?rel=0&enablejsapi=1"></iframe>
Script
var player;
function onYouTubePlayerAPIReady() {player = new YT.Player('player');}
Here i want to such action like when the player timing reaches 6 seconds,i want to change the src of the iframe.