There are many research projects that detail methods for adapting layered multicast transmissions to network conditions.  For an overview oflayered multicast see, Layered Transmission and Caching  for the Multicast Session Directory Service .

Several of these projects concern the compatability of layered multicast with TCP/IP,  as with approaches to inter and intra multicast, network monitoring, for multi source environments.  A key conclusion that is relevant to VLab's implementation, is that network performance is more stable when the layered streams are encoded as constant bit rate streams.

Some of these projects describe coding schemes to adapt the data rate or composition of the component streams.  The adaptation can occur at the reciever end or through feed back at the sender end, resulting in a prioritized transmission.  The primary means for the scaling of the video streams are; rate control, a scaling of a video frames spatial content, and transformations of the data such as temporal or frequency based filters that transcode the video streams.   Liu and Li, in, "Adaptive Video Multicast Over the Internet",  propose a coding scheme that relates to the decomposition of the information with in the streams, while noting that this approach has not yet been extensively developed.  An architecture for content or object scalability is supported in MPEG 4 where objects may be independent.

Liu and Li offer that;

"Simulcast has already been advocated in many commercial video-streaming systems. For example, RealNetworks’ RealSystem G2 supports simulcast under the name of SureStream, which generates a fixed number of streams at prescribed rates, and a receiver can dynamically choose a stream commensurate with its bandwidth.
Bandwidth redundancy caused by replication remains a drawback of simulcast.

A more attractive solution involves information decomposition. A commonly used decomposition scheme is cumulative layering, in which a raw video sequence is compressed into some nonoverlapped streams, or layers. There’s a base layer, which contains the data representing the most important features of the video. Additional
layers, called enhancement layers, contain data that progressively refine the reconstructed video quality."

Cumulative Layered transmission is a primary use of multicast on the internet today, as implemented with forward error correction in reliable multicast.  Reliable transmission is primarily used for bulk data transfer, Cisco and Digital Fountain are two key venors in this area.   Another approach to stream decomposition has been developed by Digital Fountain, this technique codes the data so that each packet contains error correction that relates to the complete data set.  See; Byers, Luby,et al.  "Fine Grained Layered Multicast"

VLab's system makes use of non cumulative layered transmissions to offer an end user a degree of interactivity with multicast.  An end user is able to pan accross fields of view.  The video data is encoded to optimize the overall use of bandwidth; regions of the image field may be transmitted with priority according to feedback from the end users.  This is an architecture that provides a foundation that leads towards object based prioritized streaming.

Layered Session Announcement Protocol Referrence

In the research paper, "Layered Transmission and Caching  for the Multicast Session Directory Service" (link) Swan, McCanne, and Rowe, present a method by which to synchronize layered multicast channels using the Session Description Protocol.

From their paper:

"Although SDP has provisions for describing layered sessions, it cannot be used to describe layered sessions in which all layers are not transmitted within the same scope."
 

"The bandwidth for SAP announcements sent to the global MBone is limited to 200 bits per second. Assuming 25 global sessions with an average message size of 500 bytes, the bandwidth constraint leads to an announcement interval of 10 minutes or so. Coupled with unreliable delivery of multicast traffic, a user running a session directory tool often has to wait upwards of 10-20 minutes to see a particular session announcement. "

A ``session directory forwarding agent'', or sdfor.

"This split architecture has been previously proposed but , to the best of our knowledge, has not appeared in the research literature. Moreover, our system is the first complete design and working implementation. This program is run as a background process and performs the following tasks:

Layered Session Completion
As described above, the agent listens to all SAP announcements. When a layered session with missing layers is detected, it locally allocates and re-advertises addresses for the missing layers. This task is discussed in greater detail in the next section.

Caching
As part of the SAP announce-listen protocol, the agent maintains a cache of the sessions currently being advertised. Thus, when a session directly client starts up, it can consult the cache expediently to reduce the waiting time for all announcements to be received.

Proxy Announcement
A user who wishes to announce a session may configure his or her session directory tool to contact the agent and have it announce the session on its behalf. As long as the agent process is kept running reliably by a system administrator, the user need not continuously run a session directory tool to ensure that the persistence of the advertisement"
 

Links

Rate control

A tutorial on Low-cost rate control algorithm development

Forward Error Correction and Compression Bibliography
http://chen.htm

References:
 

Jiangchuan Liu, Bo Li eta al.

Dynamic Layering and Bandwidth Allocation for Multi-Session
Video Broadcasting with General Utility Functions

Brett J. Vickers, Célio Albuquerque and Tatsuya Suda

Adaptive Multicast of Multi-Layered Video: Rate-Based and Credit-Based Approaches
 

A Distributed Max•Min Flow Control Algorithm for Multi•rate Multicast Flows

W.Tan, E.Chang, A. Zakhor

A RealTime Software Implementation of Scaleable Video Codec

Chen-Khong Tham, Yung-Sze Gan, Yuming Jiang

Congestion Adaptation and Layer Prioritization in Multicast Scaleable Video Delivery Systems

Andrew Swan, Steven McCanne, Lawrence A. Rowe

Layered Transmission and Caching  for the Multicast Session Directory Service

ACM Multimedia 98 - Electronic Proceedings

Anthony Vetro

"Mpeg-4 Rate Control for Multiple Video Objects"

IEEE Transactions On Circuits And Systems For Video Technology, Vol. 9,1999

Qian Zhang, Wenwu Zhu, and Ya-Qin Zhang ,

“Network-Adaptive rate control with TCP-friendly protocol for multiple video objects,”

IEEE International Conference on Multimedia and Expo, New York, July 30 - August 2, 2000

Lifeng Zhao, Jitae Shin, JongWon Kim, and C.-C. Jay Kuo,

"FGS MPEG-4 video streaming with constant quality rate adaptation, prioritized packetization and differentiated forward,"

in Proc. SPIE ITCOM `2001: Video Technologies for Multimedia Applications, Denver, CO, Aug. 2001.

J. Chakareski and B. Girod,

"Rate-Distortion Optimized Video Streaming with Rich Acknowledgments,"

Proc. SPIE Visual Communications and Image Processing (VCIP-04), Santa Clara, CA, January 2004

J. Chakareski, S. Han, and B. Girod,

"Layered Coding vs. Multiple Descriptions for Video Streaming Over Multiple Paths,"

Proc. ACM Multimedia 2003, Berkeley, CA, Nov. 2003

B. Girod, J. Chakareski, M. Kalman, Y. J. Liang, E. Setton, and R. Zhang,

"Advances in Network-adaptive Video Streaming",

Proc. 2002 Tyrrhenian International Workshop on Digital Communications (IWDC 2002), Capri, Italy, pp. 1-8, Sept. 2002.

B. Girod, N. Farber,

"Wireless Video,"

in A. Reibman, M.-T. Sun (eds.), Compressed Video over Networks, Marcel Dekker, 2000.

B. Girod, M. Kalman, Y. Liang, and R. Zhang,

"Advances in Channel-adaptive Video Streaming,"

Wireless Communications and Mobile Computing, vol. 2, no. 6, pp. 549-552, September 2002

M. Kalman, E. Steinbach, and B. Girod,

"Adaptive Media Playout for Low Delay Video Streaming over Error-Prone Channels,"

IEEE Transactions on Circuits and Systems for Video Technology 2001
 

U. Horn, K. Stuhlmuller, M. Link, and B. Girod,

"Robust Internet Video Transmission Based on Scalable Coding and Unequal Error Protection,"

Image Communication, vol. 15, no. 1-2, pp. 77-94, Sept. 1999

Andres Albanese, Johannes Blomer, Jeff Edmonds, Michael Luby,

"Priority Encoding Transmission"
 

Andres Albanese, Johannes Blomer, Jeff Edmonds, Michael Luby, and Madhu Sudan

"Priority Encoding Transmission",

Transaction on Information Theory, 1996
 

Bernd Lamparter, and Malik Kalfanc,

"The implementation of PET",
 

Christian Leicher,

"Hierarchical Encoding of MPEG Sequences using Priority Encoding Transmission"
 

Rainer Storn,

"Modeling and Optimization of PET-Redundancy Assignment for MPEG Sequences"
 

J. Bolot, T. Turletti, and I. Wakeman,

“Scalable Feedback Control for Multicast Video Distribution in the Internet,”

Computer Comm. Review, vol. 24,
no. 4, Oct. 1994, pp. 58-67.

S. Cheung, M. Ammar, and X. Li,

“On the Use of Destination Set Grouping to Improve Fairness in Multicast Video Distribution,”

Proc. Ann. Joint Conf.
IEEE Comptuer and Comm. Soc. (Infocom 96), IEEE Press, 1996, pp. 553-560.

X. Li and M. Ammar,

“Bandwidth Control for Replicated-Stream Multicast Video,”

Proc. High Performance Distributed Computing (HPDC 96), IEEE CS Press, 1996.
 

T. Jiang, E. Zegura, and M. Ammar,

“Interreceiver Fair Multicast Communication over the Internet,”

Proc. Network and Operating System Support for
Digital Audio and Video (NOSSDAV 99), 1999, pp.103-114, http://www.nossdav.org.

S. McCanne, V. Jacobson, and M. Vetterli,

“Receiver-Driven Layered Multicast,”

Proc. ACM Sigcomm Conf., ACM Press, 1996, pp. 117-130.

L. Wu, R. Sharma, and B. Smith,

“Thinstreams: An Architecture for Multicast Layered Video,”

Proc.Network and Operating System Support for Digital
Audio and Video (NOSSDAV 97), 1997, pp. 173-
182, http://www.nossdav.org.

L. Vicisano, and J. Crowcroft,

“TCP-Like Congestion Control for Layered Multicast Data Transfer,”

Proc. Ann. Joint Conf. IEEE Comptuer and
Comm. Soc. (Infocom 98), IEEE Press, 1998, pp.996-1003.  [ref]

S. Bajaj, L. Breslau, and S. Shenker,

“Uniform Versus Priority Dropping for Layered Video,”

Proc. ACM Sigcomm Conf., ACM Press, Sept. 1998, pp. 131-143.

D. Rubenstein, J. Kurose, and D. Towsley,

“The Impact of Multicast Layering on Network Fairness,”

Proc. ACM Sigcomm Conf., ACM Press, 1999, pp. 27-38.
 

R. Gopalakrishnan et al.,

“Stability and Fairness Issues in Layered Multicast,”

Proc. Network and Operating System Support for Digital Audio and Video
(NOSSDAV 99), 1999, http://www.nossdav.org.

A. Legout and E.W. Biersack,

“Pathological Behaviors for RLM and RLC,”

Proc. Network and Operating System Support for Digital Audio and Video
(NOSSDAV 00), 2000, http://www.nossdav.org.

D. Sisalem and A. Wolisz,

“MLDA: A TCP-Friendly Congestion Control Framework for Heterogeneous Multicast Environments,”

Proc. 8th Int’l Workshop on Quality of Service (IWQoS), IEEE Press, 2000, pp. 65-74.

B. Vickers, C. Albuquerque, and T. Suda,

“Source Adaptive Multi-Layered Multicast Algorithms for Real-Time Video Distribution,”

IEEE/ACM Trans. Networking, vol. 8, no. 6, 2000, pp. 720-733.

J. Liu, B. Li, and Y.-Q. Zhang,

“A Hybrid Adaptation Protocol for TCP-Friendly Layered Multicast and Its Optimal Rate Allocation,”

Proc. Ann. Joint Conf. IEEE Comptuer and Comm. Soc. (Infocom 02), IEEE Press, 2002, pp. 1520-1530.

T. Kim and M. H. Ammar,

“A Comparison of Layering and Stream Replication Video Multicast Schemes,”

Proc. Network and Operating System Support for Digital Audio and Video (NOSSDAV 01),
2001, pp. 63-72, http://www.nossdav.org.

S. Sarkar and L. Tassiulas,

“Fair Allocation of Discrete Bandwidth Layers in Multicast Networks,”

Proc. Ann. Joint Conf. IEEE Comptuer and Comm. Soc.
(Infocom 00), IEEE Press, 2000.

N. Yeadon et al.,

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IEEE J. Selected Areas in Comm., vol. 14, no. 7, 1996, pp. 1245- 1262.

I. Kouvelas, V. Hardman, and J. Crowcroft,

“Network Adaptive Continuous-Media Applications Through Self Organised Transcoding,”

Proc. Network and Operating System Support for Digital Audio and Video (NOSSDAV 98), 1998,
http://www.nossdav.org.
 

E. Amir, S. McCanne, and R. Katz,

“An Active Service Framework and Its Application to Real-Time Multimedia Transcoding,”

Proc. ACM Sigcomm
 

B. J. Vickers, M. Lee and T. Suda.

“Feedback Control Mechanisms for Real-Time Multipoint Video Services.”

IEEE J. Select. Areas Comm., 15(3), Apr. 1997.

 A. Legout and E. W. Biersack,

“PLM: Fast Convergence for Cumulative Layered Multicast Transmission Schemes”,

in Proc. ACM SIGMETRICS ’00, Santa Clara, CA, June 2000

S. McCanne, V. Jacobson, and M. Vetterli,

“Low-complexity Video Coding for Receiver-driven Layered Multicast”,

in IEEE Journal on Selected Areas in Communications, vol. 16, no. 6, Aug. 1997, pp. 983-1001

S. Sakar and L. Tassiulas.

"Distributed algorithms for computation of fair rates in multirate multicast trees."

In Proc. of IEEE INFOCOM '00, pages 52{61. IEEE, 2000.

D. Wu, Y.T. Hou, and Y.-Q. Zhang,

“Scalable video coding and transport over broadband wireless networks,”

Proceedings of the IEEE, vol. 89, no. 1, pp. 6-20, January 2001.

P. de Cuetos, D. Saparilla, and K. W. Ross,

“Adaptive streaming of stored video in a TCP-friendly context: multiple versions or multiple layers,”

in Proceedings of International Packet Video\Workshop, April 2001.

K. Kar, S. Sarkar, and L. Tassiulas,

“Optimization based rate control for multirate multicast sessions,”

in Proceedings of IEEE INFOCOM’01, April 2001.

 J. Liu, B. Li, and Y.-Q. Zhang,

“An end-to-end adaptation protocol for layered multicast using optimal rate allocation,”

to appear in IEEE Transactions on Multimedia.

X. Sun, F. Wu, S. Li, W. Gao and Y.-Q Zhang,

“Seamless switching of scalable video bitstreams for efficient streaming,”

in Proceedings of IEEE ISCAS’02, May 2002.

References relevant  to Digital Fountain

 M. Luby, J. Gemmell, L. Vicisano, L. Rizzo, J. Crowcroft, and B Luecken-hoff.

"Asynchronous layered coding: A scalable reliable multicast protocol."

Technical report, Work in progress presented in the IETF, Adelaide, Australia, March 2000.

V. K Goyal

"Multiple Description Coding: Compression Meets the Network"

 IEEE Signal Processing Mag., vol. 18, no. 5, pp. 74-93, Sept. 2001.

[Ref]

The difficulties associated with coordinating join and leave attempts motivated Vicisano, Rizzo and Crowcroft to propose their Receiver-driven Layered Congestion Control (RLC) algorithm. Their approach called for synchronized join experiments, where the sender would temporarily increase the sending rate on a layer and the receiver would join a higher layer only if there was no packet loss during this experiment. One goal of this approach  was to avoid the problem of long IGMP leave latencies by ensur-ing that a receiver joined a higher layer only if there appeared to be sufficient available bandwidth in the system. Their work also
demonstrates that under the idealized conditions seen in simula-tion their algorithm is TCP-friendly.