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How Streaming Media Works
Bilguun GinjbaatarIT 665Nov 14, 2006
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Outline
• Introduction: What’s Streaming?• Source Material for Streaming• Streaming Technology• Streaming Servers• Media Players• Streaming Audio• Streaming Video• Bandwidth• How Does Edinboro University broadcast?• Protocols
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Playing compressed video or sound in real time as it is downloaded over the internet
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Streaming AudioStreaming Audio
1.1. Capture Audio SourceCapture Audio Source
-Microphone
-CD
2.2. Optimizing the Audio SourceOptimizing the Audio Source
-Use sound editor
3. Encoding the streaming audio Encoding the streaming audio clipclip
-choose streaming format
-choose one or several streaming bandwidth
4. Deliver the streaming audio clipDeliver the streaming audio clip
-broadcast is available through website
-If combined with another streaming clip, create SMIL file.
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Streaming Audio Bit RatesStreaming Audio Bit Rates
Internet Radio=56 Kbps, Talk show=32 Kbps, Stereo & CD Quality=256 Kbps
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Streaming Bandwidth and StorageStreaming Bandwidth and Storage
• Usual Video window size: 320 x 240• Streaming Media Storage Size
– Megabytes– Gigabytes– Terabytes
• What’s the Storage Size for 1 hour of video, encoded at 300kb/s?
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Streaming Video (Webcast)
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How does EUP broadcast the Commencement Ceremony?
Firewire
http://147.64.32.6
Windows 2003 Server
http://147.64.32.8: Port 1185
Ross Hall
Windows Media Encoder
64Kbps
256 Kbps
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Protocols• User Datagram Protocol
(UDP)• Real-Time Streaming Protocol
(RTSP)• Real Data Transport
(RDT)• Real-time Transport Protocol
(RTP)• Real-Time Transfer Control Protocol
(RTCP)• Resource ReSerVation Protocol
(RSVP)
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UDP
• Sends media as series of small packets
• Provides connectionless & best-effort message service
• Simple & efficient
• Packets are liable to be lost or corrupted
• Client may use Error Correction to recover data or Drop Out
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RTSP• Developed in 1998 as RFC-2326• Allows client remotely control: play, pause, next• Clients: RealPlayer, VideoLAN, MPlayer, Windows MP, Quicktime
• Session ID is used to keep track– No permanent TCP connection needed
• RTSP requests based on HTTP– DESCRIBE: includes rtsp://…– SETUP: request specifies how a single media stream must be
transported – PLAY: request will cause one or all media streams to be played – RECORD: used to send a stream to the server for storage – TEARDWON: used to terminate the session
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RDT• Real Data Transport proprietary transport protocol for
audio/video• Developed by RealNetworks in 1990’s.• Tolerant to loss.• Works in companion with RTSP.• Uses ports: 16384 – 32767
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RTP
• Real-time Transport Protocol• Provides end-to-end delivery interactive audio/video over
the internet.• Can be used for VOIP applications: Skype, VoipCheap• 1996: RFC 1889 => 2003: RFC 3550• Does not have standard TCP or UDP port to communicate• UDP connections are done only via an 2n port.• 2n+1 port is used for RTCP communications.
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RTP Packet
Real-time Transport Protocol
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RTCP• Sister protocol of Real-time Transport Protocol (RTP)• Defined in RFC 3550• Partners with RTP in delivery of multimedia data• DOES NOT transport any data itself• Monitors participating packets in steaming multimedia session.
– Sends control packet to get feedback on QoS– Gathers stat info on: bytes sent, bytes received, lost packets, jitter,
roundtrip delay
• Types of RTCP:– Sender Report Packet– Receiver Report Packet– Source Description RTCP packet– Goodbye RTCP packet
• SRTCP (Secure) is used for encryption, authentication, and integrity
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RSVP• Transport Layer protocol designed to reserve resources across the
Internet
• Described in RFC 3936 (Oct 2004)
• Can be used by HOSTS or ROUTERS
• Delivers specific QoS for data streams
• RSVP is not a routing a protocol, but works with other routing procols.
• Notice: RSVP is rarely deployed by tele-com networks today
• Traffice Engineering RSVP (RSVP-TE) is available now.
• RSVP requests resources for simplex flows: a traffic stream in only one direction from sender to one or more receivers.
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Conclusion• Streaming is used widely everywhere• To stream a media you will need: camera, firewire, encoder, server,
and a high speed internet connection• Media Players: Adobe Flash Player, Windows Media Player.• How Streaming Audio & Video works.• Streaming Bit Rates differ: higher the bit rate the better quality.• The Protocols used:
– User Datagram Protocol (UDP)– Real-Time Streaming Protocol (RTSP)– Real Data Transport (RDT)– Real-time Transport Protocol (RTP)– Real-Time Transfer Control Protocol (RTCP)– Resource ReSerVation Protocol (RSVP)
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Reference
• www.google.com• www.microsoft.com• www.realnetworks.com• www.RealNetworks.com• www.ShoutCast.com• www.StreamCast.com• www.wikipedia.org
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