function OverlayScreen(vis, options) {
  // Pass true to gray out screen, false to ungray
  // options are optional.  This is a JSON object with the following (optional) properties
  // opacity:0-100         // Lower number = less grayout higher = more of a blackout 
  // zindex: #             // HTML elements with a higher zindex appear on top of the gray out
  // bgcolor: (#xxxxxx)    // Standard RGB Hex color code
  // grayOut(true, {'zindex':'50', 'bgcolor':'#0000FF', 'opacity':'70'});
  // Because options is JSON opacity/zindex/bgcolor are all optional and can appear
  // in any order.  Pass only the properties you need to set.
  var options = options || {}; 
  var zindex = options.zindex || 100;
  var opacity = options.opacity || 70;
  var opaque = (opacity / 100);
  var bgcolor = options.bgcolor || '#000000';
  var dark=document.getElementById('darkenScreenObject');
  if (!dark) {
    // The dark layer doesn't exist, it's never been created.  So we'll
    // create it here and apply some basic styles.
    // If you are getting errors in IE see: http://support.microsoft.com/default.aspx/kb/927917
    var tbody = document.getElementsByTagName("body")[0];
    var tnode = document.createElement('div');           // Create the layer.
        tnode.style.position='absolute';                 // Position absolutely
        tnode.style.top='0px';                           // In the top
        tnode.style.left='0px';                          // Left corner of the page
        tnode.style.overflow='hidden';                   // Try to avoid making scroll bars            
        tnode.style.display='none';                      // Start out Hidden
        tnode.id='darkenScreenObject';                   // Name it so we can find it later
    tbody.appendChild(tnode);                            // Add it to the web page
    dark=document.getElementById('darkenScreenObject');  // Get the object.
  }
  if (vis) {
    // Calculate the page width and height 
    if( document.body && ( document.body.scrollWidth || document.body.scrollHeight ) ) {
        var pageWidth = document.body.scrollWidth+'px';
        var pageHeight = document.body.scrollHeight+'px';
    } else if( document.body.offsetWidth ) {
      var pageWidth = document.body.offsetWidth+'px';
      var pageHeight = document.body.offsetHeight+'px';
    } else {
       var pageWidth='100%';
       var pageHeight='100%';
    }   
    //set the shader to cover the entire page and make it visible.

	var d = detectMacXFF2(); // detect ff2 on mac and solve for opacity issue
	if (d) {
	  //osx ff2 css opacity + flash wmode transparent doesn't work
	  dark.style.backgroundImage= "url(images/overlay.png)";
	  dark.style.backgroundRepeat="repeat";
	} else {
	    dark.style.backgroundColor=bgcolor;  
	    dark.style.opacity=opaque;                      
	    dark.style.MozOpacity=opaque;                   
	    dark.style.filter='alpha(opacity='+opacity+')'; 
	}
    dark.style.zIndex=zindex;        
    dark.style.width= pageWidth;
    dark.style.height= pageHeight;
    dark.style.display='block';                          
  } else {
     dark.style.display='none';
  }
}

function VideoOverlay(video_name){

	OverlayScreen(true);
	
	var myMovie = swf.movie('standalone.swf?speaker_id=' + video_name, 775, 367, 8, getObj('noswf').cloneNode(true));
	myMovie.setParam('wmode','transparent');
	myMovie.setParam('bgcolor','#000000');
	myMovie = getObj("FlashLayerFLASH").appendChild(myMovie);
	document.getElementById("FlashLayer").style.visibility = "visible";
	document.getElementById("FlashLayerFLASH").style.visibility = "visible";

}
function VideoOverlay_Off(){
	OverlayScreen(false);
	document.getElementById("FlashLayerFLASH").innerHTML = "";
	document.getElementById("FlashLayer").style.visibility = "hidden";	
	document.getElementById("FlashLayerFLASH").style.visibility = "hidden";	
}
function closeSpeaker(){
	VideoOverlay_Off();	
}

function detectMacXFF2() {
  var userAgent = navigator.userAgent.toLowerCase();
  if (/firefox[\/\s](\d+\.\d+)/.test(userAgent)) {
    var ffversion = new Number(RegExp.$1);
    if (ffversion < 3 && userAgent.indexOf('mac') != -1) {
      return true;
    }
  }
}