AS3 - check if flv has video in it

I'm a n00b @ AS but I have managed to put together a video player using NetStream that suits my needs perfectly. The thing I'd like to add is that it would display a certain image if t开发者_如何学Gohe streamed .flv clip only has audio track in it (mp3 converted flv).

Q: is there a way to check if the .flv I'm streaming has video in it?

OK, I think I found the solution. Using info from "onMetaData" I can check for video codec (videocodecid) and it seems to return "undefined", if the .flv only contains audio.