Video Multicast over the Internet

Presented by: Liang-Yuh Wu

Lung-Yuan Wu

Hao-Hsiang Ku

12 / 6 / 2001

Bell Lab. And Georgia Institute of Technologies

IEEE Network · March/April 1999

Agenda

1. Abstract

2. Basic idea

3. Single-stream video multicast

4. Replicated-stream video multicast

5. Layered video multicast

6. Replicated vs. Layered

7. Error Control

8. Concluding Remarks

Abstract

Multicast of video / future network serviceVideo Conference

Distance Learning

Remote Presentation

Media-on-Demand ( MOD,VOD )

Lacks support for QoS assurance

Heterogeneity of the Internet transmission

Why?

Problem of “ Real time & Bandwidth ”

Base requires for Multicast video :

Mechanisms for Multicast data delivery

Ability to accommodate Real-time video

Focus on:

1.How real-time video can be accommodated

over Internet

2.Fairness

Focus & Discussion ??

Some general approaches and issue

(Real-time):

---Delay jitter, Data loss

1. Using QoS reserve resources

2. Using adaptive rate control “ Feedback

mechanism ”

3.Buffering

4.Change compression parameters

5.Error control technology

Video Bit-Rate adaptation

Adaptive Bit-Rate Video Multicast Options

1. Single Stream Adaptive Approach

2. Replicated Adaptive Streams Approach

3. Layered Video Streams Approach

Basic idea

Single-stream Video Multicast

The IVS Approach (in the H.261 encoder) Feedback information is based on packet loss measured at the receiver Packet loss is detected using RTP (Real-time Transport Control) RTP sends “reception reports” that provide feedback information

Single-stream Video Multicast(cont.)

Feedback implosion problemProbabilistic multicast technique Probing mechanism

Can’t provide fair treatment to multiple receiver in a heterogeneous environment

Tradeoff between multicast and unicast

Replicated-Stream Video Multicast

The DSG (Destination Set Grouping) Protocol

The goal of the DSG: To improve fairness over a single-group

feedback-controlled video multicast To address “scalability”

By transmitting video of differing quality and differing data rate on different multicast channels and allowing receivers to select the most appropriate one.

Replicated-Stream Video Multicast(cont.)

The DSG protocol has two main Components: Intra-stream protocol Inter-stream change protocol

A DSG experiment result : Fairness among receiver is improved

significantly over a single-group approach while incurring only a small additional bandwidth overhead.

Layered Video Multicast

Video layering can be supported by many video compression techniques EX: MPEG-2 supports layered encoding by

defining four scalable modes

Layered Video Multicast Protocol Receiver-driven Layered Multicast (RLM) Hierarchical Rate control (HRC)

Receiver-driven Layered Multicast

Receiver-based control Advantage:

burden of adaptation is moved from the sender to the receiver

Join-experiment result is successful result is failed

Receiver-driven Layered Multicast(cont.)

The key to scalability in layered multicast is “adding or dropping a layer” Shared Learning Advantage: Disadvantage:

unnecessary bandwidth and message processing overhead

Too much state information

Hierarchical Rate control (HRC)

Layered Video Multicast with retransmissions (LVMR) two key contributions:

retransmitting lost packets adapting to network congestion and

heterogeneity using HRCHierarchical Rate control (HRC) to distribute the information between the

sender, receivers, and some agents each entity maintains only the information

relevant to itself

Hierarchical Rate control (HRC)(cont.)

Comparing with RLM: allow receiver to maintain minimal state

information decrease control traffic on the multicast

session multiple experiments to be conducted

simultaneously drop the correct layer(s) during congestion in

most case

Hierarchical Rate control (HRC)(cont.)

In addition to avoid the above drawback of RLM Comprehensive group knowledge base Collaborative layer drop

decrease layer oscillation achieves more effective rate adaptation maintains better video reception quality

Add-layer experiment decrease unnecessary add-layer experiment provide smoother video quality

Replicated-stream VS. Layered video

For video multicast, layering is determined more by the coding requirements than by the bandwidth requirements

Replicated-stream VS Layered video: bandwidth economy Processing overhead

Error Control

1.Layered Video Multicast with Retransmission (LVMR)

2.Structure-Oriented Resilient Multicast (STORM)

3.Client-Server Architecture

The Key Idea In LVMR

Use a statically configured logical tree

Set Designated Receivers (DRs) at each level

Improve efficiency by no asking for retransmission

Improve response time by sending immediate message and multicast retransmissions

Use Buffers

Combine retransmission mechanisms

The Key Idea In STROM

Each receiver to dynamically select the best possible DR

Use a dynamically logical tree

Receiver decide the latency or reliability

The Steps of STORM

1.Build the recovery structure

2.Selection of Parent Nodes

3.Adapting the structure

The Key Idea In Client-Server Architecture

Separate the actual senders and receivers.Receiver either get the original or repaired video stream.The retransmit server and the repair server can be organized into LVMRUsing RTPRepair Buffer

Concluding Remarks

Network congestion lead to degrade the video quality.

Non-adaptive streams of video data don not share resource well in a best-effort network.

Future Work

To build a mechanisms which provide for the co-existence and resource sharing of video multicast stream .

Formalization of the notion of fairness

Understanding the effect of pricing on the behavior of receiver in a multicast video environment.

The End

Thank you so much!!