Considering that streaming media either uses UDP or RTSP traffic, I would start looking at top talkers on those protocols. Then I would look at the details of the conversations on the network. UDP traffic can mean a lot of different things.
Windows Media streaming uses TCP and UDP port 1755 to outbound, and UDP port 1024-5000 inbound.
UDP 6970-32,000, 1755 (MMS Windows Media resend requests)
I think realplayer uses RTSP.