Extract the swf url from an embed tag at screencast.com: http://www.screencast.com/users/jlewin/folders/Jing/media/fb0eb212-aab2-44fa-a3e1-f3de484ba5c0

extractContentUrlFromFlashVars.js

function extractContentUrlFromFlashVars(){
  var segments = $('#scPlayer param[name=flashVars]').attr('value').split('&'),
      flashVars = {},
      segment,
      index;

  for (var i = 0; i < segments.length; i++)
  {
     segment = segments[i];
     index = segment.indexOf('=');
   
     flashVars[segment.substring(0, index)] = segment.substring(index + 1);
  }

  return flashVars.content
}

extractContentUrlFromFlashVars();