Streaming Video over the Internet

Dapeng WuElectrical & Computer Engineering

University of Florida

2

What is Streaming Video?

AccessAccessSWSW

Data path

AccessAccessSWSW

Domain A

Domain B

Domain C

Internet

AccessAccessSWSW

SourceReceiver 2

Receiver 1•Download mode: no delay bound

•Streaming mode: delay bound

cnn.com RealPlayer

3

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

• Summary

4

Time-varying Available Bandwidth

Data path

AccessAccessSWSW

Domain A

Domain B

AccessAccessSWSW

Source

Receiver

56 kb/s

R>=56 kb/s

R<56 kb/s

cnn.com

RealPlayer

No bandwidth reservation

5

Time-varying Delay

Data path

AccessAccessSWSW

Domain A

Domain B

AccessAccessSWSW

Source

Receiver

56 kb/s

cnn.com

RealPlayer

Delayed packets regarded as lost

6

Effect of Packet Loss

Data path

AccessAccessSWSW

Domain A

Domain B

AccessAccessSWSW

Source

ReceiverNo packet loss

Loss of packetsNo retransmission

7

Unicast vs. Multicast

Unicast Multicast

Pros and cons?

8

Heterogeneity For Multicast

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

•Network heterogeneity

•Receiver heterogeneityWhat Quality?

What Quality?

9

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

• Summary

10

Architecture for Video Streaming

11

Video Compression

Lay

ered

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.

12

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

13

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

14

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

Window-based control Rate control

15

Source-based Rate Control

16

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

17

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

18

Error Control• FEC

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

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

19

Channel Coding

20

Delay-constrained Retransmission

21

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

• Summary

22

23

Continuous Media Distribution Services

• Content replication (caching & mirroring)

• Network filtering/shaping/thinning

• Application-level multicast (overlay networks)

24

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

25

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

• Summary

26

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

27

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

28

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

29

Protocol Stacks

30

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