Streaming Multimedia:Client Buffering client buffer constant variable fill drain from rate,x(t) rate,d to decompression network and playout buffered video Client-side buffering,playout delay compensate for network-added delay,delay jitter 7:Multimedia Networking 7-21
7: Multimedia Networking 7-21 Streaming Multimedia: Client Buffering Client-side buffering, playout delay compensate for network-added delay, delay jitter buffered video variable fill rate, x(t) constant drain rate, d
Streaming Multimedia:UDP or TCP? UDP server sends at rate appropriate for client (oblivious to network congestion ! o often send rate encoding rate=constant rate o then,fill rate constant rate-packet loss short playout delay(2-5 seconds)to compensate for network delay jitter error recover:time permitting TCP send at maximum possible rate under TCP fill rate fluctuates due to TCP congestion control larger playout delay:smooth TCP delivery rate HTTP/TCP passes more easily through firewalls 7:Multimedia Networking 7-22
7: Multimedia Networking 7-22 Streaming Multimedia: UDP or TCP? UDP server sends at rate appropriate for client (oblivious to network congestion !) often send rate = encoding rate = constant rate then, fill rate = constant rate - packet loss short playout delay (2-5 seconds) to compensate for network delay jitter error recover: time permitting TCP send at maximum possible rate under TCP fill rate fluctuates due to TCP congestion control larger playout delay: smooth TCP delivery rate HTTP/TCP passes more easily through firewalls
Streaming Multimedia:client rate(s) 1.5 Mbps encoding 28.8 Kbps encoding Q:how to handle different client receive rate capabilities? o 28.8 Kbps dialup o 100Mbps Ethernet A:server stores,transmits multiple copies of video,encoded at different rates 7:Multimedia Networking 7-23
7: Multimedia Networking 7-23 Streaming Multimedia: client rate(s) Q: how to handle different client receive rate capabilities? 28.8 Kbps dialup 100Mbps Ethernet A: server stores, transmits multiple copies of video, encoded at different rates 1.5 Mbps encoding 28.8 Kbps encoding
User Control of Streaming Media:RTSP HTTP What it doesn't do: Does not target multimedia ▣does not define how content audio/video is encapsulated ▣No commands for fast for streaming over network forward,etc. ▣does not restrict how RTSP:RFC 2326 streamed media is Client-server application transported;it can be layer protocol. transported over UDP or TCP For user to control display: rewind,fast forward, does not specify how the pause,resume, media player buffers repositioning,etc. audio/video 7:Multimedia Networking 7-24
7: Multimedia Networking 7-24 User Control of Streaming Media: RTSP HTTP Does not target multimedia content No commands for fast forward, etc. RTSP: RFC 2326 Client-server application layer protocol. For user to control display: rewind, fast forward, pause, resume, repositioning, etc. What it doesn’t do: does not define how audio/video is encapsulated for streaming over network does not restrict how streamed media is transported; it can be transported over UDP or TCP does not specify how the media player buffers audio/video
RTSP:out of band control FTP uses an "out-of-band" RTSP messages are also sent control channel: out-of-band: A file is transferred over ▣ RTSP control messages one TCP connection. use different port numbers ▣Control information than the media stream: (directory changes,file out-of-band. deletion,file renaming, o Port 554 etc.)is sent over a The media stream is separate TCP connection. considered "in-band". The "out-of-band"and "in- band"channels use different port numbers. 7:Multimedia Networking 7-25
7: Multimedia Networking 7-25 RTSP: out of band control FTP uses an “out-of-band” control channel: A file is transferred over one TCP connection. Control information (directory changes, file deletion, file renaming, etc.) is sent over a separate TCP connection. The “out-of-band” and “inband” channels use different port numbers. RTSP messages are also sent out-of-band: RTSP control messages use different port numbers than the media stream: out-of-band. Port 554 The media stream is considered “in-band