Loop HD stream? How...

Rothrock is right, you need to listen for the 'complete' event if using the FLVPlayback component, like so:
flvPlayer.addEventListener(VideoEvent.COMPLETE, videoDone);
function videoDone(e:VideoEvent):void{
// do something
};

If you're using a NetStream/NetConnect combo, you'd do something like so:
ntConnection.addEventListener(NetStatusEvent.NET_STATUS, getStatus);
function getStatus(e:NetStatusEvent):void{
switch(e.info.code){
case "NetStream.Buffer.Flush":
// do something when data has finished streaming
break;
};
};

I'm not all up on it in AS3, but in AS2 you would just listen for the Complete event and then do what ever you wanted. I don't have the AS3 docs handy at the moment, but I would suggest checking the NetStream (and related) class for a similar event. There should be a code example.