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How Streaming Media Works

Bilguun GinjbaatarIT 665

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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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ApplicationsApplications

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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.bilguun.net • www.ShoutCast.com • www.StreamCast.com • www.wikipedia.org