In the name In the name of of Allah Allah the compassionate, the merciful
Digital Digital Video Processing Video Processing S. Kasaei S. Kasaei Room: CE 307 Department of Computer Engineering Sharif University of T echnology E-Mail: skasaei@sharif edu E Mail: skasaei@sharif.edu Webpage: http://sharif.edu/~skasaei Lab. Website: http://ipl.ce.sharif.edu
Acknowledgment Acknowledgment Most of the slides used in this lecture have been provided by: Dr. DapengWu (University of Florida, Department of Electrical & Computer Engineering) based on the book: Video Processing & Communications written by: Yao Wang, Jom Ostermann, & Ya-Oin Zhang Prentice Hall, 1 st edition, 2001, ISBN: 0130175471. [SUT Code: TK 5105 .2 .W36 2001].
Chapter 15 Chapter 15 Streaming Video over the Internet
Outline Outline � Architecture for Video Streaming Systems Architecture for Video Streaming Systems � Video Compression � Application-Layer QoS Control for Streaming � Application Layer QoS Control for Streaming Video � Continuous Media Distribution Services Continuous Media Distribution Services � Streaming Services � Media Synchronization Media Synchronization � Protocols for Streaming Video � Streaming Video over Wireless IP Networks � Streaming Video over Wireless IP Networks Kasaei Kasaei 6
What is Video Streaming? What is Video Streaming? � Recent developments in computing p p g technology, compression technology, high- bandwidth storage devices, & high-speed g g p networks have made it feasible to provide real-time multimedia services over the Internet. � Video streaming refers to real-time transmission of stored video. Kasaei Kasaei 7
Video Streaming Video Streaming � Video streaming implies that the video content need to be downloaded in full, but it is being played out while parts of the content are being received & th t t b i i d & decoded. � Video streaming typically has bandwidth, delay, & loss requirements. y q Kasaei Kasaei 8
Outline 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 ed sy c o o ec s s – Protocols for streaming media • Summary • Summary Kasaei Kasaei 9
What is Video Streaming? g Receiver 1 Receiver 1 • Download mode: no delay bound. • Streaming mode: delay bound. g y Access Access SW SW SW SW Domain B Domain A Data path Domain C Access Access Access Access Internet Internet SW SW SW SW SW SW SW SW Source Source Sou ce Sou ce Receiver 2 Receiver 2 RealPlayer cnn.com Kasaei Kasaei 10
Time-Varying Available Bandwidth Receiver Receiver • No bandwidth reservation. Access Access SW SW Domain B R>=56 kb/s Domain A Data path Data path R<56 kb/s Access Access SW SW 56 kb/ 56 kb/s RealPlayer Source Source cnn.com Kasaei Kasaei 11
Time-Varying Delay Receiver Receiver Access Access SW SW R RealPlayer lPl Domain B Domain A Data path Data path Delayed packets regarded as lost. Access Access SW SW 56 kb/ 56 kb/s Source Source cnn.com Kasaei Kasaei 12
Effect of Packet Loss Receiver Receiver No packet loss. Access Access SW SW Domain B Domain A Data path Data path Access Access Loss of packets. SW SW N No retransmission. i i Source Source Kasaei Kasaei 13
Unicast vs. Multicast Unicast vs. Multicast Multicast Unicast (streaming media) ( g ) (email, file transfer, Web browsing) (email, file transfer, Web browsing) Pros and cons? Pros and cons? Kasaei Kasaei 14
Heterogeneity for Multicast Heterogeneity for Multicast • Network heterogeneity. Receiver 2 Receiver 2 256 kb/s 256 kb/s • Receiver heterogeneity. Access Access What Quality? SW SW Domain B Domain A Domain C Access Access Internet SW SW Gateway Gateway Ethernet Ethernet Telephone networks 1 Mb/s Source Source Receiver 1 Receiver 1 64 kb/s Receiver 3 Receiver 3 Receiver 3 Receiver 3 What Quality? Kasaei Kasaei 15
Outline 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 ed sy c o o ec s s – Protocols for streaming media • Summary • Summary Kasaei Kasaei 16
Architecture for Video Streaming Adapts bit streams according to network status & QoS requirements. Packetizes compressed bit streams. Kasaei Kasaei 17
Outline 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 ed sy c o o ec s s – Protocols for streaming media • Summary • Summary Kasaei Kasaei 18
Video Compression Schemes Video Compression Schemes � Scalable: Gracef ll copies � Scalable: Gracefully copies with the ith the bandwidth fluctuations of the Internet. � Non scalable � Non-scalable. Kasaei Kasaei 19
Video Compression Video Compression Layer 0 L L Layer 0 0 0 64 kb/s D Layer 1 Layer 1 256 kb/s + + D D Layer 2 Layer 2 1 Mb/s + D Layered video encoding/decoding. [ D denotes the decoder.] [ ] Kasaei Kasaei 20
Application of Layered Video Application of Layered Video Receiver 2 Receiver 2 256 kb/s • IP multicast. • IP multicast Access Access A 2 layers SW SW Domain B Domain A Domain C Access Access Internet SW SW Gateway Gateway Ethernet Telephone Telephone networks 1 Mb/s Source Source Receiver 1 Receiver 1 64 kb/s Receiver 3 Receiver 3 3 layers 1 layer Kasaei Kasaei 21
Outline 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 ed sy c o o ec s s – Protocols for streaming media • Summary • Summary Kasaei Kasaei 22
Application-Layer QoS Control Application-Layer QoS Control � T o cope with changing network p g g conditions & changing presentation quality requested by users. � T echniques include: Congestion control is employed to preserve � packet loss & reduce delay packet loss & reduce delay. Error control improves video presentation quality � in the presence of packet loss. � These are employed by the end systems. Th l d b h d Do not require QoS support from routers or � networks. networks. Kasaei Kasaei 23
Application-Layer QoS Control Application-Layer QoS Control � Congestion control (using rate control): ◦ Source-based requires: � rate-adaptive compression, or � rate shaping (forces the source to send at the rate dictated by the rate control algorithm). g ) ◦ Receiver-based. ◦ Hybrid. � Error control: ◦ Forward error correction (FEC). ◦ Retransmission. ◦ Error resilient compression. ◦ Error concealment. Kasaei Kasaei 24
Congestion Control Congestion Control • Window-based vs. rate control. (pros and cons?) Wi d Window-based control b d t l R t Rate control t l Kasaei Kasaei 25
Source-Based Rate Control Source-Based Rate Control Kasaei Kasaei 26
Video Multicast Video Multicast • How to extend source-based rate control to multicast? • Limitation of source-based rate control in multicast. • Trade-off between bandwidth efficiency & service fl flexibility. ibilit Trade-off between efficiency and flexibility. Kasaei Kasaei 27
Receiver-Based Rate Control Receiver-Based Rate Control • IP multicast for layered video. y Receiver 2 Receiver 2 256 kb/s Access Access 2 layers SW SW Domain B Domain A Domain C Domain C Access Access Internet SW SW Gateway Gateway Ethernet Telephone T l h networks 1 Mb/s Source Source Receiver 1 Receiver 1 64 kb/s Receiver 3 Receiver 3 1 layer 3 layers Kasaei Kasaei 28
Hybrid Rate Control Hybrid Rate Control � Under hybrid rate control: y ◦ Receiver regulates the receiving rate by adding & dropping channels, while ◦ Sender also adjusts transmission rate of each channel based on feedback from receivers. Kasaei Kasaei 29
Rate Shaping Rate Shaping � Is a technique through which the rate of Is a technique through which the rate of precompressed video bit streams are adapted to a target rate constraint. p g � Rate shaper is an interface (or filter) between: ◦ compression layer & network transport layer, or ◦ two network segments (with which the video k ( h h h h d stream can be matched to the available network bandwidth). bandwidth). Kasaei Kasaei 30
Error Control Error Control � Is classified into four categories: g ◦ Transport-level (FEC & delay-constrained retransmission). ◦ Encoder error-resilient coding. ◦ Decoder error concealment. ◦ Encoder-decoder interactive error control. Kasaei Kasaei 31
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