streaming video over the internet · streaming video over the internet dr. dapeng wu university of...

Streaming Video over the Internet

Dr. Dapeng WuUniversity of Florida

Department of Electrical and Computer Engineering

What is Streaming Video?

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AccessAccessSWSW

Data path

AccessAccessSWSW

Domain A

Domain B

Domain C

Internet

AccessAccessSWSW

Receiver 1•Download mode: no delay bound •Streaming mode: delay bound

SourceReceiver 2RealPlayercnn.com

Outline• Challenges for quality video transport• An architecture for video streaming

– Video compression– Application-layer QoS control– Continuous media distribution services– Streaming server– Media synchronization mechanisms– Protocols for streaming media

• Summary3

Time-varying Available Bandwidth

Data path

AccessAccessSWSW

Domain A

Domain B

AccessAccessSWSW

Receiver

56 kb/s

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Source

R>=56 kb/s

R<56 kb/s

No bandwidth reservation

RealPlayer

cnn.com

Time-varying Delay

Data path

AccessAccessSWSW

Domain A

Domain B

AccessAccessSWSW

Receiver

56 kb/s

RealPlayer

Delayed packets regarded as lost

Source

cnn.com5

Effect of Packet Loss

Data path

AccessAccessSWSW

Domain A

Domain B

AccessAccessSWSW

Source

ReceiverNo packet loss

Loss of packetsNo retransmission

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Unicast vs. Multicast

MulticastUnicast

Pros and cons?7

Heterogeneity For Multicast

Domain A

Domain B

Domain C

Internet

Source

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Receiver 1

Receiver 2

AccessAccessSWSW

AccessAccessSWSW

GatewayGateway

EthernetTelephonenetworks

Receiver 364 kb/s

1 Mb/s

256 kb/s

•Network heterogeneity

•Receiver heterogeneityWhat Quality?

What Quality?

Outline• Challenges for quality video transport• An architecture for video streaming

– Video compression– Application-layer QoS control– Continuous media distribution services– Streaming server– Media synchronization mechanisms– Protocols for streaming media

• Summary9

Architecture for Video Streaming

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Video Compression

Laye

red

Cod

er D

D

D

+

+

Layer 0

Layer 1

Layer 2 1 Mb/s

256 kb/s

64 kb/s

Layered video encoding/decoding. D denotes the decoder.

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Application of Layered Video

Domain A

Domain B

Domain C

Internet

Source Receiver 1

Receiver 2

AccessAccessSWSW

AccessAccessSWSW

GatewayGateway

EthernetTelephonenetworks

Receiver 364 kb/s

1 Mb/s

256 kb/s

IP multicast

Application-layer QoS Control• Congestion control (using rate control):

– Source-based, requires• rate-adaptive compression or • rate shaping

– Receiver-based– Hybrid

• Error control:– Forward error correction (FEC)– Retransmission– Error resilient compression– Error concealment

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Congestion Control• Window-based vs. rate control (pros and cons?)

Window-based control Rate control14

Source-based Rate Control

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Video Multicast• How to extend source-based rate control to multicast?• Limitation of source-based rate control in multicast• Trade-off between bandwidth efficiency and service

flexibility

Receiver-based Rate Control

Domain A

Domain B

Domain C

Internet

Source Receiver 1

Receiver 2

AccessAccessSWSW

AccessAccessSWSW

GatewayGateway

EthernetTelephonenetworks

Receiver 364 kb/s

1 Mb/s

256 kb/sIP multicast for layered video

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Error Control• FEC

– Channel coding– Source coding-based FEC– Joint source/channel coding

• Delay-constrained retransmission• Error resilient compression• Error concealment

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Channel Coding

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Delay-constrained Retransmission

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Outline• Challenges for quality video transport• An architecture for video streaming

– Video compression– Application-layer QoS control– Continuous media distribution services– Streaming server– Media synchronization mechanisms– Protocols for streaming media

• Summary21

Continuous Media Distribution Services

• Content replication (caching & mirroring)• Network filtering/shaping/thinning• Application-level multicast (overlay networks)

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Caching• What is caching? • Why using caching? WWW means World Wide Wait?• Pros and cons?

Outline• Challenges for quality video transport• An architecture for video streaming

– Video compression– Application-layer QoS control– Continuous media distribution services– Streaming server– Media synchronization mechanisms– Protocols for streaming media

• Summary24

Streaming Server• Different from a web server

– Timing constraints– Video-cassette-recorder (VCR) functions (e.g.,

fast forward/backward, random access, and pause/resume).

• Design of streaming servers– Real-time operating system– Special disk scheduling schemes

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Media Synchronization• Why media synchronization?• Example: lip-synchronization (video/audio)

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Protocols for Streaming Video• Network-layer protocol: Internet Protocol (IP) • Transport protocol:

– Lower layer: UDP & TCP– Upper layer: Real-time Transport Protocol (RTP) &

Real-Time Control Protocol (RTCP)• Session control protocol:

– Real-Time Streaming Protocol (RTSP): RealPlayer– Session Initiation Protocol (SIP): Microsoft

Windows MediaPlayer; Internet telephony

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Protocol Stacks

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Summary• Challenges for quality video transport

– Time-varying available bandwidth– Time-varying delay– Packet loss

• An architecture for video streaming– Video compression– Application-layer QoS control– Continuous media distribution services– Streaming server– Media synchronization mechanisms– Protocols for streaming media

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Homework

• Reading assignment: Chap. 15

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