RTP, RTCP, and RTSP

Transcript

[slide79] We're gonna focus on RTP and RTCP. And we'll also mention RTSP, and RTSP was the streaming version. So why do we put RTSP on top of either TCP or UDP? What's the advantage? Okay, so let's start with the basic, why do we put RTP on top of UDP in the first place? [student answers: Because it's not important if you lose a packet.] Right, so we just saw we could lose an individual packet, and we don't have time to ask for a retransmission of it. So we just live with it. That's the perfect thing for UDP. But if we have pre-recorded media, what can we do? Well, if we lose it, we can go and fetch it from the source again, because we're not having to play it out in real time. So therefore, we can put that on top of TCP if we want. So today, if you use something like Apple Streaming Media, what does it really do? It sends you the audio or video and audio content about 100 kilobytes at a time. So it sends you bunches of little files. If you're missing one, what do you do? You go and fetch it again, okay?