Streaming Video over the Internet

Dapeng Wu Electrical & Computer Engineering University of Florida

What is Streaming Video?

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

Access SW

Receiver 1

Domain B Access SW Domain A

Data path Internet Source cnn.com

RealPlayer

Domain C Access SW

Receiver 2 2

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 3

Time-varying Available Bandwidth Receiver No bandwidth reservation

Access SW Domain B

R>=56 kb/s

Domain A

Data path

Access SW

56 kb/s R<56 kb/s RealPlayer Source cnn.com

4

Time-varying Delay Receiver

Access SW

RealPlayer

Domain B Domain A Access SW

56 kb/s Source Data path cnn.com

Delayed packets regarded as lost 5

Effect of Packet Loss Receiver No packet loss

Access SW Domain B Access SW Domain A

Data path Source Loss of packets No retransmission 6

Unicast vs. Multicast Unicast Pros and cons?

Multicast 7

Heterogeneity For Multicast • Network heterogeneity • Receiver heterogeneity 256 kb/s

Access SW

Receiver 2 What Quality?

Domain B

Source

Domain A Access SW

Ethernet Internet

Domain C

1 Mb/s Receiver 1

Gateway

Telephone networks What Quality?

64 kb/s Receiver 3 8

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 9

Architecture for Video Streaming 10

Video Compression

Layer 0 Layer 1 + Layer 2 64 kb/s D 256 kb/s D + 1 Mb/s D Layered video encoding/decoding.

D

denotes the decoder.

11

Application of Layered Video

IP multicast 256 kb/s

Access SW

Receiver 2

Domain B

Source

Domain A Access SW

Ethernet Internet

Domain C

1 Mb/s Receiver 1

Gateway

Telephone networks 64 kb/s Receiver 3 12

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 13

Congestion Control

• Window-based vs. rate control (pros and cons?) Window-based control Rate control 14

Source-based Rate Control

15

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 16

Receiver-based Rate Control

IP multicast for layered video 256 kb/s

Access SW

Receiver 2

Domain B

Source

Domain A Access SW

Ethernet Internet

Domain C

1 Mb/s Receiver 1

Gateway

Telephone networks 64 kb/s Receiver 3 17

Error Control

• • • • FEC – Channel coding – Source coding-based FEC – Joint source/channel coding Delay-constrained retransmission Error resilient compression Error concealment 18

Channel Coding

19

Delay-constrained Retransmission 20

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 21

22

Continuous Media Distribution Services • • • Content replication (caching & mirroring) Network filtering/shaping/thinning Application-level multicast (overlay networks) 23

Caching

• • • What is caching? Why using caching? WWW means World Wide Wait?

Pros and cons? 24

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 25

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 26

Media Synchronization

• • Why media synchronization?

Example: lip-synchronization (video/audio) 27

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 28

Protocol Stacks 29

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 30