I am using:
$("#vid1").src += "&autoplay=1";
Give this a try
var newSource = $("#vid1").attr('src').replace("&autoplay=1", "&autoplay=0"); $("#vid1").attr('src', newSource );
A few things to note:
The  isn't needed. You're selecting an ID and it should only appear once. If you were selecting a class that could appear more than once you'd use
This will only work if you've already appended the
&autoplay=1 to the src. If this is a problem add a check to see if it's there or not.