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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!!