В прелоадере:

Код AS3:
//**********************
if (loaderInfo.parameters.stream) {
_soundLoader = new URLRequest(loaderInfo.parameters.stream);
trace ("flashVarStream is present")
}
else {
_soundLoader = new URLRequest("http://u14.di.fm:80/di_liquiddnb");
trace ("play builtin stream");
}
//************************
private function startup():void
{
var mainClass:Class = getDefinitionByName("MVCMain") as Class;
addChild(new mainClass(_soundLoader) as DisplayObject);
}