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$.fn.showWhenScrolled=function(){
	var self = this;
	
	this.init = function(){
		self.each(function(){
			var self_top   = $(this).offset().top;
			var scroll_top = $(window).scrollTop();
			var win_height = $(window).height();
			var frame      = $(this).find('iframe');
			if(scroll_top > (self_top - win_height)){
				if(!frame.attr('src')){
					frame.attr({src:frame.attr('title')});
				}
			}
		});
	};
	
	$(window).scroll(function(){
		self.init();
	}).resize(function(){
		self.init();
	});
	
	self.init();
};

$('.youtube-container').showWhenScrolled();